Safety must come first. Some modifications are a risk to life.
Introduction
If you are the owner of a Kenwood TL-922 linear amplifier, or considering picking up one from a ham fest, or a mate, and it looks like it is in reasonable condition, it can be a good deal. They are an attractive and a relatively compact amplifier. Although there are some potential design issues, it’s not hard to rectify and you will end up with a really stable and powerful desktop amplifier.
I don’t know how many TL-922’s were sold by Kenwood since its introduction in circa 1980, but it’s safe to say that it was very popular, because it seems that this is one most talked about older amplifiers on the internet. As a result it is the easiest to find a wealth of information from hams that have used, modified and loved this old amplifier over the decades. With the pair of 3-500Z’s you can join the group of amateurs who far prefer an amp with warm red glowing tubes, than designs utilising 3 legged fuses. I understand that it takes all sorts, and some like 3 legged fuse’s. That’s cool. Each their own and power to them.
In a TL-922 review on eHam.net posted in November of 2009, the reviewer had this to say (blue text), and I have taken the liberty of adding some text in red by way of comments (open the down arrows to view my comments).
I agree, it might have a bit of a cult following … in much of the same way that a Ford enthusiast loves the look of his 1939 Coupe. Truth be told … that old Ford had massive body roll, a gutless V8 engine, prone to overheating and rear axles that could easily break if driven hard. A very marginal car by today’s standards. I would sooo love to own one. That old side-valve V8 engine … even though it was gutless, it was reliable, sounded great, and is totally awesome! For many, the TL-922 is a bit like that old Ford that never dies!
Yet… The price that old Ford realises today, is based on beauty, styling and what you can do to make it into something that is just pure art to the restorer or the hot rodder. That’s how many hams might view the TL-922.
The many faults include, Poor RF design (in some ways yes, but really easy to correct)
Poorly rated RF parts (not so sure I concur, but I encourage you to make you own judgements)
Poor or NO protection circuits(Well, it did have two HT interlocks to keep one safe if you took the covers off. True, no glitch resister, but that is a super easy fix. A couple of minor mods could protect the filament transformer and the meters in a catastrophic tube short, but, point taken)
Lots of trouble with parasitic problems. (Possibly. But perhaps due to other issues rather than parasitics, more on that later)
No spare parts available. (really? eBay has lots popping up all the time. Hideously expensive mind you!)
Tubes that are getting expensive. (That’s true to a degree. My purchase of two new 3-500Z’s cost me US$476.00 purchased March 2026, and this included DHL International delivery and bank currency exchange charges and 10% government tax on import)
If you ran this amp in a contest you will probably burn it out. (Yep. It is a really good idea to change out the antenna change over relay)
I absolutely agree that a soft start will be a great addition so that you never loose your power switch, but new power switches are still available)
https://harbachelectronics.com/
The band switch is a very good item to replace. I think these are still available from Multi-Tech. The new switch improves reliability even when being miss-tuned and generating excessive RF voltages in the tank circuit due to operator error etc. Or more likely the antenna change over relay disconnected the antenna before drive was removed. I have changed my band switch) https://www.facebook.com/MTIINC1/
The load C spacing is marginal, if you even try and tune it into a moderate 2:1. VSWR you will ARC this crappy capacitor. (mine seems to work fine, but that is not necessarily disagreeing. The load Cap is a close spaced variable, and of course that lowers the breakdown voltage. If the tank circuit is miss-tuned and we have high RF voltages present, arc over is possible. Can I just say that in my limited experience the problem of arching is more common due to antenna change over relay issues than any other reason and that arching is more likely on the plate tuning Cap and sometimes the band switch. (especially on the higher bands)
The relay switching is slow and will damage newer model radios. No inrush limiting and many other design failings. (As mentioned earlier, new antenna change over relays are a highly recommended modification to do, and we can certainly make it work with modern rigs and their lower voltage control requirement)
Just do a google on the TL922 and you will come across several pages on “mods” to try and correct its many design failings. (That’s one of the greatest benefits of the TL-922. You will never be short of ways to get the best from your classic amplifier)
I like buying blown up TL922’s and converting them to 6 meters. However on HF I would only recommend the TL922 to my worst enemy. If you have one keep it, however I would not invest money in such a marginal amplifier. (Can I be your worst enemy? The TL-922 is a perfect base for building, modifying, improving or even changing to 6m if desired. JH2CLV added 6m to his. So he has all HF bands plus 6m. That’s a very cool undertaking. Tatsumi-san even has a 3-500Z running on 2m. That is a higher frequency than Eimac mentions on the 3-500 data-sheet. His fellow JA ham’s thought he was crazy to even try, but he built a really neat amplifier. It’s on his web site. https://www5a.biglobe.ne.jp/~jh2clv/pdf/3-500z2m.pdf I would love to copy his design some day, and my parts collection to do so, is underway)
This AL-1500 you mention, It’s the one with the really low cost 8877 / 3CX1500A7 tube right? Penta Labs has these tubes for U$1,350.00, DX Engineering has them for U$1,699.99, and a 2nd hand “pull” from RF Parts has them at U$1,189.90. All these prices were current in March 2026, + freight and taxes as applicable. Remember my two new 3-500Z’s cost U$476.00. That’s a tad more attractive from a dollar perspective.
“Bottom line” …. the purpose of this web site, is;
If you want a vintage TL-922 to really hum, then I hope you find this to be of assistance to you. Not being an RF engineer or expert. I look at what others have done, and try to discern and filter what I have found, read, and discovered, and come up with some of the things I want to apply to my TL-922. I get more fun working on the gear than I probably do using it. When I see that I can achieve a really good result from this vintage amplifier, a reliable amplifier that works as it should … that’s exactly what I want. In the case of the TL-922, it’s the thrill of a classic amplifier that just hoots. To me this is the definition of amateur radio. I am the amateur, and this is my radio (amplifier).
Lets look into this “cult following” and see why it’s loved. (for the most part)
At the top of the page there are links to specific mods that you might find useful.
Image credits: IU8NQI and rmsothebys.com