Replacing the AL-80A Bandswitch

The AL-80B bandswitch, compared to the existing switch shaft.

With my wallet being $115 lighter, the AL-80B bandswitch arrived within a week. Now, it isn't the same as the original AL-80A bandswitch.

There are two key differences. First, as you can see from the picture, the shaft layout is different. In the original AL-80A bandswitch has the input network switch wafter in front of the bandswitch, whereas the AL-80B has it behind the bandswitch.

This means you can't just replace the AL-80A switch with the AL-80B switch. The best you can do is to unstack the wafers and put them on the original AL-80A switch shaft.

AL-80B switch with AL-80A wafers.

The second difference has to do with the switch wafers. Electrically, they are identical. The AL-80B switch has the 160m padder cap and the Pi-L network wafers reverse. Since we're going to re-stack the wafers anyway, this doesn't matter.

The Pi-L wafer is positioned differently. The contacts are two positions counter clockwise (as viewed from the front of the shaft) from the AL-80A. This means that a bit of re-wiring is necessary to make the connections.

Wafer-less switch.

Removing the switch wafers isn't a big deal, since I have done this earlier. The rear wafer comes off with all the coils attached, and the padding caps unscrewed, there being only one wire that needs to be unsoldered, and it slips off. The middle wafer has a similar wire to be unsoldered, and it comes off as well. The front wafer has one wire to the padder cap, and it comes off as well.

With all the wafers off, the new switch wafers are stacked on. Because the Pi-L wafer has contacts rotated two positions, they are a little harder to access between the switch and the loading capacitor.

New wafers in place.

Once all the wafters are on and screwed down, the next step is to re-solder all of the connections. I took lots of pictures before unsoldering the old wafers, so I had a pretty good idea of what goes where.

Front switch wafer anchors the coax shield, and adds the 160m padder cap. The Pi-L switch wafer was the only one that gave me trouble. Since the contacts are rotated from the original, this required a bit of extra wire to make the required connections. The rear switch wafter has five connections tot he coil assembly. It took a bit of work to unsolder. This sort of thing is best not rushed and done with great care, to avoid damaging the coils. Everything goes in the same place on this last switch wafer, which was easy once I got all the coil wires into the right positions in the narrow switch contact lugs.

The finished product. Reassembled with new switch wafers.

Sounds easy, eh? But realistically, it was nearly three hours on the workbench.

Moved it back to the operating desk and tested for full output into a dummy load on all bands. No problem on 160, 80, 40, 20, 15 and 10m.

For 17m and 12m, I proceeded more cautiously. The AL-80A is designed to operate on 12m using the 10m switch position. It works on 17m using the 20m switch position. But it has often been on 17 or 12m that I've had the most issues with arcing in the PA circuit.

For this reason, I've decided to reduce drive to about 30 watts for 17 and 12m. It's a little less output power, but also less of a chance of burning up a $115 bandswitch.

With the testing done, it was time to button up the amp. Took me about 20 minutes to find 10 of the 13 screws that hold the cabinet top on. I had removed them a year and a half before, but finally found them in a neat pile on the workbench.

The AL-80A is back up and running on all bands!

Digging back into the AL-80A....

Front switch wafer - showing contacts burned
completely away.

Back in July of 2018, I was chasing the KH1/KH7Z expedition on 17m, and the AL-80A stopped producing any output. I dug into enough to find that the Pi-L output switch contacts had arced and burned. So, I jumpered the switch so the amp was only usable on 40m and above. And it has worked OK since then - but not on 80 or 160m.

It's way past time to fix this, so I recently got started. I figured that I just needed to replace a switch contact or two like I've done before.

Back side front switch wafer showing more
contacts completely burned away.

Once I got the lid off and removed the switch wafers, well, the photographs tell the sad story.

Middle switch wafer. You can see my jumper
between the to contacts on right. There was not
enough material on the switch wedge to make
contact with the 40m contact.

Replacing the contacts won't be enough. Plenty of the switch wiper was gone on the Pi-L (middle) switch wafer -- especially the corner that used to short out the Pi-L coil on 40m. And the 160m padder capacitor (front) switch wafer isn't any better.

No, this means I'll have to replace the switch entirely. I've ordered one from Ameritron, with shipping it came to $115! This is the AL-80B switch, which is similar, but not identical.

The Station Notebook

When I originally set up my station as a novice, I didn't make a lot of notes. I wrote a few things on the back-side of my logbook pages: radios I used, antennas I put up. But, for the most part, I freely made changes to my setup without a lot of documentation.

Some years later, I had a small steno-style notebook lying around, and I used it to record certain information. Like the exact color-code of the RS-232 cables I wired up for my computer. That sort of thing was handy to have written down, because it saved a lot of reverse-engineering later I went to make another cable. But that was about it.

Perhaps a dozen years ago, I read a couple of articles about James Lawson, W2PV, and how he kept copious notebooks about his station. He even solved a sticky problem during a contest, because he kept notes about his antenna installation.

After that, I started writing more things down in my little Steno notebook. Most of it was changes I made to the station -- radios or antenna modifications. Or if something big happened -- like I blew up the amplifier. I recorded a lot more details, and I put dates on everything.

But when I began to spend most of my time out in Floyd County it put my little steno notebook out of reach. I had a new station and I still wanted to keep notes. My solution was dead simple -- I created a text document using TextEdit. I called it Floyd County Station Log.

Looking at it today, it's more like a diary. Each month, I put in a new heading: March 2017. And below that I record anything interesting that I do. I record the things that work, and I also record the things that don't work! If I don't do anything that month, I'll just change the heading to the next month.

The bottom of this document has a list of projects to be worked on. Silly now, since I'm no longer at that QTH: 6m antenna, K9AY controller, 20m and 30m traps for the dipole, tribander-Moxon  times 3 (now that's an interesting project I'll need to write about some day!), remote antenna switch, etc.

This method worked so well, in May 2015, I adopted it for my main station log. Not only did I make new entries, but I also entered all the data from the steno notebook. Plus, I went back through all of my contest comment submissions and recorded all the changes I had made to the station from November 1994 to date.

Today the Gwinnett County Station Log is a reasonably complete record of all the things I've done with the station for the last 22+ years. It has six pages of project notes at the end. Lots of stuff to work on! And, yes, I also have a smaller document for the Walton County Station Log.

I guess my point is that having a station notebook is extremely valuable. It doesn't matter if you use a small steno notebook, a spiral-bound notebook, a composition book with graph paper, a loose-leaf notebook, or a computer document. The important thing is to find a style that works for you to keep notes. After a while, there's just too much to try to remember. So keep good notes.

Ameritron AL-80A - Fixed!

AL-80A re-assembled, needing just 3-500Z and cover.

As I wrote previously, my AL-80A needed a repair. The plate choke was burned, with several windings melted, the protective diode and capacitor on the B- rail to ground had gone open, and I'd found that the amp would not tune on 160m -- due to some melted switch contacts.

I thought it might be a while before I could get around to doing this -- considering the last repair took about a year. However, since I had some parts on hand, I put the amplifier on the bench and got started.

1N5308 diode next to glitch
resistor on rectifier board. And
the replaced capacitor below.

First order of business was to fix the protective circuits on the B- rail. I removed the 1N4007 I had installed earlier. I tested it and found it to be completely open. Which is pretty much what I expected, given that the capacitor had opened destructively....

I replaced the capacitor with a fresh part, and installed a 1N5308 diode, as recommended by W8JI. And I mounted it on top of the board this time.

Next part to arrive was the Ameritron Plate Choke (Part Number 10-15197). It was a thing of beauty, and despite the package having a nice accordion dent in one corner, was intact.

Replacing the choke was actually pretty easy. I figured out I had to unsolder the wire to the parasitic suppressor and plate cap connector, and then the two blocking capacitors. This was much easier with the tube removed. (I put the tube inside the plate choke's packing box). I then removed the mounting screw and unsoldered the high voltage and the bypass cap.

Beautiful new choke installed.

Oh! Did I mention that you need to unplug the amplifier and make sure the plate circuit is completely discharged before sticking your hands into the amplifier? No? Gosh, that would be dumb. Of course, you do that first.

The old choke had a teflon washer under the ceramic, but it completely disintegrated when I removed the choke. I decided it wasn't required, and mounted the new choke directly to the sheet metal base.

The new choke had a slightly different geometry with respect to the lugs at the base and top. I decided to loosen the lug on the top and rotate it about 100 degrees. Otherwise, the blocking caps were not going to reach. To move the lug, I first had to unwind the top end of the winding and re-wind it to the lug. I think the choke wire ends were unsoldered for this reason.

Once in position, the lugs were easy to solder.

The final task replaces the melted switch contacts. I must say I got a lot of positive answers from the Amps email reflector (amps@contesting.com). Their diagnosis of my issues was spot on, and I got a lot of helpful advice.

Vic Rosenthal 4X6GP sent a link to an article about band-switch arcing on the Heathkit SB-1000, which essentially was a clone of the AL-80A. He suggested I should add the corona washer, which would help prevent more melted switch contacts. From what I can tell, my AL-80A is a very early model, and it did not have this modification. George Hall N2CG also sent me an email with pictures of the washer.

A huge thank you to goes to Louis Parascondolas, who not only wrote to me with suggestions on how to replace the switch contacts, but mailed me six contact elements (I needed four), plus the brass 2-56 hardware needed to secure them. Thank you, Louis!

Switch wafers disassembled. This was the hard part.
On left is the wafer where the contacts were replaced,
shown with contacts removed, and glued.

Replacing a switch contact isn't a huge deal. The first step is to remove the switch wafer. That took some doing. I deduced I could accomplish this without doing a lot of desoldering and re-wiring. The rear bandswitch wafer is basically connected to the coils and a couple of padding capacitors. One end of each coil was fastened to the capacitor studs, which simply required removing a couple of nuts. The larger coil had two small phillips screws holding it to plastic mounting blocks. The padder capacitors could also be unscrewed from their lugs. Easy right?

Not so fast! a single wire needed to be unsoldered connecting to the loading cap, and the rear switch wafer slid off with both coils attached.

The second wafer just had three connections, easily desoldered: coax and coil end, coil tap, and the cap. Once those were removed, it slid off.

The third wafer is the one we are after. I unscrewed the connection to the plate padder cap, and slid it off with the coax connection in place. That made it easier to unsolder the coax.

Once you get these wafers off, you have to handle them very gingerly! They are delicate ceramic and can easily shatter. The tricky part is to remove the old contacts. I recommend a drill press and very small drill bits to drill out the rivets holding the contacts in place. Gradually go to larger bits until you have removed all of the rivet material. Go very slowly because you don't want to break the ceramic switch wafer.

This is what I told myself, and I managed to get the contacts off with no trouble. I still had the shell of the rivet, which I carefully drilled out of the first hole. The last hole, of course, was a problem. I broke the switch wafer.

New switch contacts engaged for 160m.

I apparently said something aloud which brought my younger daughter into the basement to see if I was OK. (I was) The wafer was now in three pieces. What to do? I decided that I could glue the three pieces together, and it should hold. Superglue to the rescue! The glue took easily to the ceramic, and soon I couldn't tell where the split was.

I cleaned as much of the burnt contact debris off the two switch wafers as I could. When I was done, you could not see any discoloration of the L network (second) wafer, but there was still a little in the contact well of the 160m padder (third) wafer. The contacted would cover that up.

Adding the four contacts to the switch wafer was really easy.

Getting all the switch wafers re-assembled was the hard bit. I added the coax ground connection to the 160m padder (third) wafer, but I held off on the padder capacitor connection until the very end, so I could place the corona washer.

The L network (second) wafer was a bit problematic. I couldn't remember the orientation of the switching portion of this wafer, as there are two ways to put it on. Then I couldn't remember which wires went where. More pictures before disassembly would have been helpful. Studying the schematic made it clear which way things went.

Corona washer in place.

The bandswitch (first) wafer was easier. The tricky bit was soldering the connections to the loading capacitor.

Last bit was to install the corona washer to the padder cap. A brass washer was specified, but I didn't have one in the junk box. I made do with a steel washer and a lot of solder. I verified the continuity of the connection with an ohmmeter. Perhaps I'll redo this the next time I have to fix the amp. (which I hope may be a while)

After any fix like this, there's always the moment of truth. No sparks turning it on, and a quick test on a dummy load proved it tuned up with no surprises on 160, 80, 40, 20, 15, 10, 12, and 17m.

Ten minutes later, I had replaced all 13 cover screws and was already using the amp to chase DX on 40, 20 and 17m.

Working great again!

Pursuit of 5BDXCC IV - 80m

Shunt-feed wires rise up the side of the tower.

For the last three years, near the end of summer, I have written about converging on 5BDXCC. I wasn't close when I only had thirty countries to confirm on 80m. The next year, I had inched a little closer, but taking the proposition a bit more seriously. And last year,  I made some serious progress, and was hopeful I was within striking distance.

Let's review the numbers, shall we? Last year I stood at 89/88, right? Well, turns out, this was slightly off. I discovered that a confirmation of CP1FF on 15m Phone was credited to 80m. This has since been corrected, so I was really at 88/87.

Today, I hold 91/90. Yes! At least down to the last ten confirmations. Not a lot of progress from last year, but at least progress.

I do have paper QSL confirmations for a couple more entities on 80m. According to ClubLog, I've worked 103 countries on 80m. Looking at the data, perhaps a couple of those have busted calls on one end or the other.

This leaves me with two methods of achieving this goal: I can pursue getting paper confirmations from contacts I've already made, or I can strive to make more contacts and get LoTW confirmations from them.

Let's look at the latter.

Last year, I ran into a few obstacles trying to work DX on 80m. Since moving from Floyd County to Walton County, I had to take down the 80/40m dipole and also the very effective 160/80/40m Inverted-L. The 80/40m dipole is up at the Walton County QTH, but the low height and local noise limits its usefulness. With the Gwinnett County QTH just minutes away, I've been more tempted to operate from there, when I can. The 160/80/40m Inverted-L and all the 30 lbs of radials are still sitting in a box. I don't really have a location to put it up right now.

That leaves me with the shunt-feed tower for 80m. I ran into a number of issues last fall with the shunt-feed matching network. The 80m cap had to be replaced. I also found that the shunt isn't as effective as it might have been. Certain times of the early evening, the 80m dipole was much more effective.

Plus, I'm seeing some RFI-related issues when using the shunt-fed tower. These didn't affect the Elecraft K2/100 or the Kenwood TS-430S, but they sure make a mess of the Elecraft K3/100.

I also wanted to put up the K9AY loops with a new loop controller. The new loop controller didn't work properly, and even using the old mechanical switch, I discovered I had other RFI feedback from the K9AY loop feed line.

So, It's clear to me I need to take care of a number of things before fall begins:

• Fix the Shunt-feed network. To improve matching on 80m, I'll add a relay and an extra variable capacitor, which would give me settings for 160m, 80m and 75m. I'll also bypass the control lines to prevent RFI ingress. Decoupling on the feed line couldn't hurt, either. 

• Add Radials. The 29 or so radials for the shunt-fed tower may have deteriorated in the last 15 years, and a few of them have been damaged. I have about 2,000 feet of surplus cloth-covered copper wire, and my plan is to put it ALL down as radials. 

• 80m Dipole. I'm working on a design for a trap 80/40/20m dipole, which may double as a second-radio antenna. That should go back up where the old 80/40m was.

• Amplifier. One benefit of the 80m dipole is I can use the amplifier. The shunt-feed network can't handle much more than 100 watts. 

• K9AY Loops. Fix the controller. Re-route the feed line to avoid RFI pick-up. 

Once all that is done, there's the small matter of being there. I guess I should start operating more from Walton County. Perhaps plan to work a few DX contests on 80m. Perhaps the ARRL DX contest would be good.

How about the former? I've already used ClubLog and OQRS to request paper QSLs for a couple of the contacts for which I have matching information. Those should come eventually.

Plus, I need to go through my batch of QSLs and see if I have anything matching on 80m. I think I did this exercise last year, but I've gotten some new QSLs from the bureau that I haven't processed yet.

The final step is to use ClubLog to identify some of those contacts I've worked and not confirmed and request paper QSLs. Those may take a while to arrive, but at least I don't have to fix antennas or wait for propagation to get that done.

Uh-Oh.

There's that moment -- that moment of pure clarity. The pure clarity that occurs when you realize you've done something really stupid -- something stupid you can't take back.

This happened yesterday. You see, I got off work early and thought I'd spend the afternoon chasing a little DX. I managed to work VP6J on 12m CW, and later they moved down to 17m RTTY. I've never worked Pitcairn using RTTY, so I was watching their frequency closely. They weren't strong, but I went ahead and set up the amplifier on a clear nearby frequency. The day was waning, and I figured if they ever came up a bit so I could get clear print, I'd want to give it my best shot.

In the meantime, I moved down to 30m and worked some other stations. Of course, I switched the AL-80A to standby, and cranked up to 100 watts.

Everything was fine. Until later I went back to 17m to see how VP6J was doing. Their signal had come up a bit, and I could actually read the print well enough to try for a contact. I reached over and flipped the amplifier to operate, and clicked the button to send my call.

That's when I had my moment of clarity.

There was a loud noise from the RF compartment of the AL-80A, along with several sparks, and abruptly, it went dark. An acrid burning smell hung loosely in the air. Certainly, something had gone wrong.

I knew right away what I had done. I had transmitted 100 watts into an amplifier designed to take only 50 watts input.. An amplifier whose original design had not included 17m, and was happier with 40 watts on that band.

Roasted plate choke in AL-80A.

I switched the amp off and then back on, still dark. Clearly, I've blown a fuse. A quick check verified that one of the two 10A fuses had blown. It was replaced, and the amp came back to life. But as it turned on, there was a tiny arc coming from the plate choke. I switched it back off, turned the meter to the HV setting, and briefly switched it on again. The High Voltage looked fine, but I was going to have to get the amp on the workbench to see what was wrong with the choke.

Once I got the cover off, it was easy to see the problem. The plate choke has a black burnt mark. Looking closer, the turns of the choke had melted and separated. The choke would need to be replaced. From the location of the burn, it looks like it had arced from the end of a screw on the plate tuning capacitor to the choke.

I took the tube out and gave it a quick check with an ohmmeter. No grid to cathode or grid to plate shorts, which was good. The Taylor 3-500Z is pretty darn tough, and likely shrugged off the abuse I had just put it through.

Low voltage cap blown to protect meter.

While I had the amp on the bench, I checked out a couple of other things. Looks like one of the protective caps I placed on the B- rail to ground failed. Probably helped to protect the meter movements.

I'll be replacing that cap, along with the 1N4007 rectifier, since it must have gone open for the capacitor to fail. I'll replace it with the recommend 1N5408 rectifier, which can handle a whole lot more surge current.

Melted switch contacts.

Another mystery of this AL-80A I solved -- why it wouldn't tune up on 160m. An inspection of the front switch wafer shows that the switch contacts for the additional plate tuning cap have completely melted away. Since I've never used the amp on 160m, this was not me -- this was an existing problem. The switch contacts, or perhaps the wafer will need to be replaced to restore service on that band.

I ordered a replacement plate choke from Ameritron. They don't carry the original AL-80A part, but instead use a single choke (Part number 10-15197) for virtually all their amplifiers, including the more modern AL-80B. I've read this part avoids resonances on 17m which may be present in the original single-winding choke.

In the meantime, I'll have to chase DX without an amplifier for a while. Perhaps there won't be as many fireworks.

Update: I've been told that part of the problem with the 160m switch contacts is the lack of a corona washer. The picture clearly shows an absence of this part. I'll be adding one when I make the repair.

Fixing the Ameritron AL-80A. Again.

If you remember from last August, I repaired my AL-80A. Well, that fix lasted little more than a month before I once again had an arc while tuning and it started acting weird. Grid meter would drift up when the amp was keyed, and would pin hard against the right stop when RF was applied.

Surprisingly, though, it was working -- only the metering seemed to be affected. Sadly, my lust for DX overcame my caution, and I occasionally used it even though the metering was weird. While the amplifier continued to work as designed, the grid current meter pounded so heavily against the right stop that eventually the needle broke off. 

Blown 1.5 ohm 3 W resistor on left.
Proper-looking spares on right.

I finally pulled the rig over to the workbench and took it apart. What I found wasn't pretty. Yes, the same 1.5 ohm 3 watt resistor had disintegrated. The metal foil had been blasted away from the resistor form. It was completely open. It was no wonder that the grid meter acted so strange -- it had no shunt!

I also found a article by Tom Rauch, W8JI on proper amplifier metering. It talked about a very simple circuit change that would likely prevent this sort of damage in the future. 

Indeed, after doing some research, I found that this protective circuit to be part of several Ameritron amplifiers, include the AL-811, AL-80B, AL-82 and AL-572. Unfortunately, it wasn't included in the AL-80A.

Small caps added across the B- rail.
Added ground lug visible on rectifier board.

No matter, very simple to add. I placed two small capacitors on the B- rail to ground, right on the capacitor board. The glitch diode took a little more doing. I already had a glitch resistor mounted to the rectifier board, and it seemed logical to place the diode there. I added a ground lug to give me a good ground connection, and placed the diode underneath the board. 

Tom recommends a 1N540x diode, but I didn't happen to have any. I did have plenty of 1N4007 diodes -- which don't offer nearly as much protection. However, I figured that some protection was better than none at all.

I still had the problem that the grid current meter had no needle. The broken needle was still in the meter face, so I used a tiny drop of superglue to re-bond it to the post. So far, it is holding, although I don't know how long that will last. 

1N4007 on bottom of rectifier board.
Note the picture has it installed backwards,
something I have since corrected.

Buttoning it all up, I thought this would be an easy victory. Well, the multi-function meter seemed to be operating correctly now, but the grid meter behavior hadn't changed. It was still pinning with the least bit of RF. Something was still not right. 

It was a few days before I had a chance to pull the amp back to the workbench. Off came the thirteen screws holding the cover. Then the eight screws holding on the front panel, plus all the knobs and indicators. Pulled the meters, and then the meter board out where I could see it.

Placing an ohmmeter across the grid current meter showed that the shunt wasn't in place, since it read about 450 ohms. The resistor itself was OK. Looking at the meter board, I found that there was a open in one of the traces. Apparently, the glitch was strong enough that part of the board acted like a fuse! A bit of solder and a piece of bare wire bridged this open.

Buttoning it up again, it once again works as it should. Now I can enjoy chasing DX without the guilt. Indeed, I worked XR0YS on Easter Island just as soon as the amplifier was repaired.

BAM! - AL-80A Broken Again

Well, crap. The AL-80A is broken again. Yup. I was on 17m chasing a bit of DX, when I decided I needed more than 100 watts. I hit the A->B button, then A/B, then tuned a bit away from the DX frequency (never tune up on DX - ever), dialed in 50 watts, switched the amp to operate and hit the Tune button.

Heard something go POP! as I turned the plate tuning knob, and immediately the grid current meter pegged. Not good.

A little diagnoses -- with no RF, keying the amplifier the grid current meter reads about 100 mA. Even with about 20 watts, the grid current meter pegs. Seeing the output meter peg, too.

At the worst, I may have fried my tube. I suspect I may have blown more of the metering circuitry.

This amplifier is very picky about 17m....

Pursuit of 5BDXCC III - 80m

I wrote of this dream first two years ago. Back then, I thought it would be an easy thing, perhaps to work (and confirm) nearly 30 countries on 80m in a single winter. Boy, was I naive. I only added six confirmations on 80m the entire year.

Can this shunt-fed tower put me over the top?

The next  year, I at least had the sense to understand the difficulty of the proposition. I enumerated things I might do that year. In the end, I only did a couple of them. I did not add more radials to the Inverted-L, I did not bring the amplifier up to Floyd county, I never did finish the new K9AY controller. 

However, I was there a lot. I spent a lot of time on 80m. As a result, I now stand at 89/88 confirmations - I added a dozen over the year. That's twice as productive as the previous year. 

If I can pull it off again this year with a dozen confirmations, I should be able to meet all the requirements of 5BDXCC.

It's going to be interesting. At the moment, the Inverted L, with over 30 lbs of radials, is sitting in a box. I'm still trying to figure out if I can put it somewhere where I can lay down those radials safely. My only 80m DX antenna is the shunt-fed tower in Gwinnett county. 

Wish me luck.

AL-80A Repairs

AL-80A back in the operating position

Hard to believe, but it has been 10 years since I purchased the AL-80A. Archie, K4GA owned it before me, and it has served me well since that time. I added a step-start circuit a few years ago, and it's been doing well until April 2014.

I wrote earlier this year that the AL-80A had a failure that I traced down to an open 1.5 ohm 3 watt resistor on the meter board.

I finally got a replacement part from a source in China. (Well, it was cheap, but not fast) Installing the resistor was the easy part. While I had the amplifier away from the operating position, I decided I needed to do a couple of other updates.

Back in 2009, I added a glitch resistor, but I installed it on the wrong side of the B- line. It was between the capacitor bank and the rectifier, where it wasn't doing any good. I moved it into the B- line between the capacitor bank and the meter board.

Glitch resistor on the rectifier board.

My AL-80A rectifier board had a number of unused lands (likely for full-wave rectifier bridges in other amplifier designs), two of which were perfect for the glitch resistor. If you look carefully at the photo, you'll see a darker brown wire going from the capacitor bank land near the middle back to up the board. This goes to the far end of the glitch resistor.

The near end is hooked up to the brown wire that disappears off the bottom of the capacitor board, heading to the meter board. 

This made for a neat installation, and now that is is on the right side, it will actually do some good.

The other issue I addressed was the meter lighting. Because of a bad trip to Barbados long ago, the two grain of wheat bulbs were not affixed to the grid meter. One of them had been destroyed, and one other bulb on the multi-meter had burned out.

Grain of wheat bulbs like this are nearly impossible to find these days, plus I didn't want to have to fool with changing them when they burn out. So, I took a tip from the internet and replaced them with white LEDs. The LEDs were ones I had bought some time ago from Mouser.com. (Mouser part # 593-VAOL-5LWY4 - 4000 mcd standard white / clear LED -- these are still in stock, although you can get way brighter ones (35,000 mcd!) for less money) At 5mm (T 1-3/4) they were the perfect replacements for the old bulbs. 

The Grid Current meter did not have the holes drilled for the lamps. I held my breath and did this, using a very slow drill speed and working slowly. I didn't want to mess up the meters. Since the lamps are run from the internal 12 volts supply (actually about 13.5 volts), a 1.5 kiloohm resistor was wired in series to set the current at about 9 mA.

LEDs being glued in place on the meters.

The LEDs are glued to the back of the meter faces. Superglue would have been perfect, but unfortunately, I was out. I ended up using 30 minute epoxy, but this particular stuff is so old it was more like 240 minute epoxy.

I re-used the blue leads from the defunct grain of wheat bulb to wire in the negative terminal of the LEDs, and picked out some red wire for the positive side. I mounted the LEDs so the negative and positive corresponded to the terminals on the meter. Less chance of screwing something up.

Toughest part of this exercise was wrestling the meter board back into place. After buttoning it all up, it was time for the moment of truth.

Lighted meter faces.

Et voila, it works! The LEDs are not quite as diffuse a light as the grain of wheat bulbs, but they do a respectable job of indicating that the amplifier is turned on. 

It might be nice to get some more even illumination, but I'm pretty satisfied. Perhaps I might add some reflection inside the meters next time I need to open the box -- which hopefully, won't be for a while. Maybe in another five or six years.

Fixed the AL-80A (Sorta)

My AL-80A amplifier has been busted for a while now. I think it was back in April of 2014 that I was chasing some DX, trying to quickly tune up the amplifier and something went ZAP! inside the box.

After that, the grid meter was reading all funny, like registering about 60 milliamps even with no RF. That's not right.

I put it on the workbench, and at some point disassembled it. I had pulled the front faceplate off, then pulled the meters and meter switch board out through the meter holes. But I never got around to fixing it. It sat like that, taking up much space on the workbench for months. Until today.

I had determined that the 3-500Z tube was likely OK. No indication of shorts or other damage. I figured the problem must be on the meter switch board -- one of the components there must have gotten damaged. Sure enough, a little probing around found that the 1.5 ohm 3w 1% resistor in the grid current network was showing as completely open.

I also figured out that the 10 ohm 20w "glitch" resistor I put into my amp was wired in incorrectly. The resistor needs to go in the B- circuit on the same side as the capacitor bank. I had placed it before, were it wasn't doing any good.

It's quite possible a glitch took out the 1.5 ohm 3w 1% resistor. This is not a typical value that I have lying around in the junk box. However, I did have a 1.5 ohm 1w 10% resistor. That would do at least for a proof of concept fix.

Wired the resistor in, put the switch board, meters back in place and put the front panel and covers back on.

Moved it over to the operating position, and behold, it amplifies! Well mostly. I got it to work on 80-10m, but I wasn't getting much of any output on 160m. Not sure what's wrong there. That fix will have to wait a bit.

However, I don't have any antennas for 160m that can take more than 100 watts anyway. Seems like the AL-80A should be good to use for a while, at least until I can get the proper resistor and troubleshoot 160m.

Pursuit of 5BDXCC II - 80m

As I wrote last year, I have DXCC awarded on 40, 20, and 15m, and have more than enough credits for 10m. I'll probably submit for 10m this year. For Five-Band DXCC, that leaves 80m.

Last year, I had 71/70 confirmed on 80m. Today, that stands at 77/76. So, in the entire winter season I only added six additional confirmations. That was only about one fifth of my goal.

The 160/80/40m inverted L has been a great antenna. I've been working the W1AW-portable operations since February. I really don't have much of a problem busting through on these bands even with just 100 watts. In fact, this antenna has really been my ONLY antenna since April, when the 80/40m trap dipole fell down.

So, why did I fail to work 30 entities? Well, part of the problem is that people just can't hear my 100 watts. I had many instances where really loud DX stations could not hear me, even after calling and calling.

I'm once again thinking of the things I can do to push toward that magical 100 on 80m, before fall gets here:

• Inverted L - currently, it has 24 radials - Eight 125 feet long, and sixteen 62.5 feet long. That's 1500 feet of wire, and at about $45 for a 500 foot spool, it wasn't cheap. Could be that this is my last winter at the Floyd County QTH, so it might be worth putting down a couple of more spools for 32 more 62.5 foot radials.

• K9AY - I talked last year about building a push-button controller. I've got that about half-way complete. Perhaps I can get that finished. The K9AY loops themselves will likely be suspended under a magnolia tree in the front yard. This would be close to the power lines, so I'll have to test to make sure I'm not picking up noise there.

• Amplifier - At the moment, the AL-80A is busted. Something went pop and now the grid current meter reads funny. I've determined that the tube appears to be OK - no shorts. I think something in the metering circuit is toast, although it isn't obvious. However, since it is on the bench, maybe I can re-wire it for 120 volts.

• Being There - While I've been active on the air much more this year than in the past, I don't think I concentrated enough on looking for 80m DX at the right time. I'll try to remedy that this fall. I really didn't make a habit of this last year.

• Contests - I did work the ARRL DX CW as 80m single band. I've done that before, and I wouldn't be surprised if I win a certificate for my low-power token effort. I may do that again this year, if I don't wind up at NQ4I's multi-multi. Even if I go the all-band route, I do plan to emphasize some 80m operating time. 

Fall is always a very busy time. Wish me luck. If nothing else, I hope to get closer this year.

Schematic for the Step-start

Dennis N2RIT wrote to ask me about the schematic for the Step-start circuit. Well, Dennis, it's pretty simple. I used the design posted by Rich Measures AG6K here. For the AL-80A, I used the +12 volt supply, which is about 15 volts unregulated. The coil of the relay I used is about 360 ohms, so to get the voltage about right, I used a 100 ohm dropping resistor.

I also added a 1n4148 diode across the relay coil to absorb the back EMF when the relay opens. Probably not needed, but it seemed like cheap protection. 

Step-start for the Ameritron AL-80A

For many years, I did not own an amplifier. I ran barefoot at 100 watts. You can work a lot of stations with just 100 watts. When I contest, I generally enjoy competing in the 100 watt category. But, a four years ago, I bought a used amplifier.

It had been owned by one of my fellow contest club members, K4GA. I didn't know Archie that well, aside from the e-mails we exchanged on the club reflector. After he passed away, his widow wanted his radio equipment to find a good home. I made an offer on the amplifier, and it was mine.

K4BAI later told me that this Amplifier had a bad trip to Barbados once -- it had been damaged in shipping, but had been repaired by insurance. When I got it, it needed a little TLC. The cover was on backwards, and several of the cover screws were missing. The meter switch had been replaced with one that had a shaft about an inch too long. 

I fixed the meter switch with a few minutes work with a hacksaw. I bought all new screws and put the cover on the right way. The meter reading for the high-voltage was a bit low -- this turned out to be a problem with one of the divider resistors. I had much higher-quality replacements in my junk box. That fixed, the meter for high voltage read exactly as it should. The open-frame antenna relay would sometimes leave the receiver antenna disconnected. This was easily taken care of with a little contact cleaner.

This amplifier has given good service in the last four years. I've used it pretty heavily in RTTY contests, running about 400-500 watts out. I've had only a couple of complaints.

One was the jarring THUMP that would sound when I switched the power on. It didn't happen every time, but often. All that inrush current couldn't be good for the power supply components. It didn't take long to figure out I needed a step-start circuit.

Step-start is simple. Low-value resistors are placed on the main power leads. They limit the inrush current when the unit is switched on. Once the capacitors charge to a certain point, the resistors are shorted out by a relay. For the AL-80A, this is easily accomplished with two 10-ohm 10-watt resistors. Selecting the relay was a little trickier. I found a nice 12 volt relay, an Omron G2RL-24. This is a DPDT relay with contacts that can carry 8A at 250 volts. This sealed relay was only about $3.00 from Mouser Electronics. 

I designed a simple circuit board for this project. It was also my first experience with TEC-200 film. The first

 version of the board didn't come out too well, as I tried to flood-fill to leave as much copper in place as possible. The result was pretty ugly, because all that toner didn't stick well to the board. I probably didn't have the heat setting right. I redesigned the board without the flood-fill, and I also beefed up the size of all the traces. Getting the TEC-200 film to transfer the toner with just an iron is going to take more practice, but I'm pleased with the results.

Note from the design -- I layed out this board in 2007, but I didn't get a chance to build it until recently. I will admit that I drilled some of the component holes a little large. I'll have to remember to use the smallest of my numbered drill bits next time I make a circuit board.

The one nice thing about designing your own board -- it's guaranteed to fit your parts. There's only five components on this board, and it goes together with a few minutes of soldering.

Getting the board in the AL-80A took more doing. For one thing, it is heavy. Moving it around is not easy, and must be done with great care to avoid damage to the amplifier and also to myself.

The next problem was getting in to wire the board up. The power connections are on a barrier strip that's close to the power transformer. Fortunately, one can remove the screws and unsolder a few connections and the back panel lays down flat. 

Figuring out how to connect the board was tricky. Like I said, this AL-80A had a bad trip to Barbados. The original transformer had been replaced with an AL-80BX transformer -- which also has buck/boost windings. 

I ended up hooking the board from the connections from the fuses to the barrier strip. 12 volt power from the auxiliary jack drives the relay. 

While I had the amplifier open on the workbench, I also added a glitch resistor to the B- lead from the rectifier stack. This is a 10-ohm 20-watt resistor. If the tube were to become gassy and short out, the glitch resistor will help dissipate the energy stored in the capacitor bank. I borrowed a couple of unused lands on the rectifier board in order to mount the glitch resistor.

Buttoning it all back up, then came the smoke test. Fortunately, I kept the smoke in. Step-start works great. No more loud thump.