I am working on a Galaxy 600 amplifier and am having no luck getting it going. the amp has good plate voltage (850 or so) on the tubes and is keying when excited with RF. The problem is no RF is getting into the driver tube. The RF goes away when keyed and the SWR on the radio goes very high. There is no signs of anytime burned a once in a while the amp will tuneup. The original problem was a blown power supply filter cap, they were replaced and the diodes as well. the tubes check ok, however one of them seems a little gassy and glows blue from time to time. Thanks for any advice.
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Galaxy 600 rf amplifier not working
- Thread starter A1dxop
- Start date
If you have no RF getting to the driver tube i'd suspect the relay.The contacts for the input RF side could be bad or not making a good connection when engaged.
If the problem is intermittent, it's most likely the relay. If you can't get it to make power after checking the relay, it could be a blown driver tube. It is very common for the fusible cathode link inside a sweep tube to pop open when over loaded. If you know what to look for inside the base of the tube, it's easy to spot too.
Well guys thanks so far for the help, but nothing is working. The t/r relay was cleaned and still when keyed the radio swr goes high and output signal goes through the amplifier. When the stanby swith is in the off position radio rf goes through the amp fine. When the amp is switched on the rf goes somewhere. the plate voltage (920 volts) is good on the plates and solder joints appear good.
Pull out the 6KD6 driver tube. Locate pin 2 and follow it with your eye inside the tube. It will connect through a thin silver colored metal strip to the cathode towards the center of the tube. Carefully inspect this strip to see if it looks like a blown fuse. Your problem could very well be this tube.
Pin #2 on the 6kd6 checks okay. One of the 8908 finals is bad and I don't have another to plug in, however the amp should put out power with one final tube shouldn't it? The filaments are wired in parallel. There seems to be something open in the rf input path.
Hi,
I know I'm resurrecting an old thread, but I have a 600 that's doing basically the same thing. When I got it, the keying circuit was all messed up. All that is working now. It had the wrong tubes in it, so I put 36KD6's in it. It had 31JS6C in it. I've cleaned the contacts in the relay. When in standby RF will pass through, but when you key it up, SWR goes sky high and you get no RF out. Any suggestions?
Thanks,
Stuart
I know I'm resurrecting an old thread, but I have a 600 that's doing basically the same thing. When I got it, the keying circuit was all messed up. All that is working now. It had the wrong tubes in it, so I put 36KD6's in it. It had 31JS6C in it. I've cleaned the contacts in the relay. When in standby RF will pass through, but when you key it up, SWR goes sky high and you get no RF out. Any suggestions?
Thanks,
Stuart
I would start with testing the tubes. More than one way to get this fault, but the tubes can fail and cause this. There's a post up above asking about the tube's "cathode fuse". No, it's not meant to be a fuse, just acts like one. Operating at high power with the output tuned wrong seems to be the best way to blow this fuse.
Here's one example.
73
Here's one example.
73
Hi Nomad,
All the tubes are good. It will key up, but I get high input SWR and no power out.
Stuart
All the tubes are good. It will key up, but I get high input SWR and no power out.
Stuart
The Galaxy 1000 in this diagram is definitely different on the inside from your 600. But there's a family resemblance. Just to start, the tubes have 6.3-Volt heaters in parallel on this diagram. Yours apparently has the tube heaters wired in series to power directly from the 120-Volt line. What I would do starts with a current-limited variable DC bench supply. Doesn't need to be bigger than 1 Amp. It gets set to 12 Volts and clips to the standby switch and ground, to operate the relay circuit without the hazard of the high voltage. I'd key it and follow the signal from the antenna socket with a 'scope, into and then out of the relay and on to the driver tube's cathode. A high SWR on the input suggests that something has disrupted the signal path from the relay's input side to the driver tube's cathode pin.
I attached a later diagram, made after they started using the russki 6p45 tubes and marking them "8975". Still won't be the same as yours, but can't hurt. This is the one from the cb tricks web site. The people who made the Galaxy tube base amplifiers were opportunists. They would shop for a quantity buy of a tube for as cheap as possible, and build that year's Galaxy linears with that tube. Lost track of all the different types they used.
73
I attached a later diagram, made after they started using the russki 6p45 tubes and marking them "8975". Still won't be the same as yours, but can't hurt. This is the one from the cb tricks web site. The people who made the Galaxy tube base amplifiers were opportunists. They would shop for a quantity buy of a tube for as cheap as possible, and build that year's Galaxy linears with that tube. Lost track of all the different types they used.
73
