Temporally jump across the relay contacts.That is correct. But when it’s on the relay kicks in and no wattage passes through. All the drive watts disappear when it’s on.
They may be closing but damaged and not making contact.
73
Jeff
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XForce 1KW supply voltage.
- Thread starter BJ radionut
- Start date
They may be closing but damaged and not making contact.
73
Jeff
Transistors that run the fans...
Are you sure they are transistors and not voltage regulators to keep the fans running at a steady speed?
Can you read the part numbers? 7808 8volt 7812 12 volt these are positive regulators, the "79's- 7908 7912 are negative regulators.
Sorry, I didn't read through all the posts before posting.
There are to-3 can voltage regulators too that can run 3 amps and not have to use three 1 amp regulators.
So the way that I'm reading this, it sounds like the bypass works when the box is off. But when you put the on switch on the relay automatically comes on and you no longer have a bypass and it's going into the amplifier correct? If that's the case then your keying circuit is bad. The relay should not click on until it's keyedThat is correct. But when it’s on the relay kicks in and no wattage passes through. All the drive watts disappear when it’s on.
I’ll try to be as clear as I can. Radio on driver amp on and main amp off. I get 200 watts through the main amp. Turn on the main amp and key up the relay pulls in and 0 wats out of the main amp. The tuning capacitor is soldered directly to the relay. So jumping the pins on the relay is nearly impossible without removing the tuning capacitor.
The next step in diagnosis is going to be to remove connections on the relay except for the one to the jacks, and start using a meter to check for continuity in and out of the relay keyed and unkeyed to make sure the signal is getting through the relay
Thanks brother. I figured as much. Just hate the thoughts of removing the tuning capacitor. I’ll mark it with a sharpie before I remove it.
Finally got some time to remove the tuning capacitor to test the relay. Results, I have continuity with the relay pulled in. Tested from input coax all the way to the input transformers. Also tested from the output transformers to the antenna socket. Every thing on the relay checks out. What should be the next step? About all that’s left there is the capacitors on the transformers and transistors.
Again thanks for your most helpful advice.
Again thanks for your most helpful advice.
At this point you might contact https://carlbuilt.net/ He is the one who built your amp and has probably seen this before.
Roger that. I sent him a email just waiting for him to respond. Other feed back is ok. I’ll take what I can get.
Getting 64 transistors to all run within a 2-watt balance of each other and not heat this resistor, is a difficult task. I've seen a different builder use 100,000 ohm resistors rather than 100 ohm resistors. When I asked him why, he said they don't smoke...
I would suspect those three dipped silver Mica capacitors across the input coil. You might want to remove them and test them. Another way to confirm this as a possibility would be to drive the amplifier with just the radio and see what the input SWR is. Don't key it for long, in the event I'm wrong and there happens to be a short on the output. If I'm right, you will have a very high input SWR and when you put your finger on top of any of the transistors when your keyed, there will be no change in temperature, because no drive power is arriving at the transistors.
The same type of short could be happening inside of the brass tube capacitor on the output, if the Teflon insulator has been punched through with an RF Arc. That will cause the transistors to get hot when you are keyed and all of the output power would be shorted across the brass tube capacitor. A very difficult condition for the transistors.