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Another 55v no xmit
- Thread starter Hawkeye351
- Start date
Great job on getting it going Hawkeye! I expected no less from you and you delivered.
Update:
Replaced driver and final (2166/1969), got full output back. Swings around 25w PEP (without tuning) and RF power seems to function properly.
Only keyed it a few times briefly to check for RF power function and modulation. Want to go back over my work again and check voltages and check for any heat issues.
Thank you Brandon and Cable, this site is the best.
For those just jumping in:
I came to the conclusion that this radio had went through a voltage spike, lightening strike or power backup while transmitting and blew out the entire RF output section and regulator section. Catastrophic failure.
Passthrough regulator replaced
AF regulator replaced
Modulation trans replaced (TR49)
VR13 replaced
Pre-driver replaced
Driver replaced (3 times)
Final replaced (twice)
R220 replaced
R221 replaced
C175 replaced
22uh bias inductors replaced
Other caps checked and replaced if needed
Driver, final, Passthrough insulators all were cracked, so I replaced those also.
Replaced driver and final (2166/1969), got full output back. Swings around 25w PEP (without tuning) and RF power seems to function properly.
Only keyed it a few times briefly to check for RF power function and modulation. Want to go back over my work again and check voltages and check for any heat issues.
Thank you Brandon and Cable, this site is the best.
For those just jumping in:
I came to the conclusion that this radio had went through a voltage spike, lightening strike or power backup while transmitting and blew out the entire RF output section and regulator section. Catastrophic failure.
Passthrough regulator replaced
AF regulator replaced
Modulation trans replaced (TR49)
VR13 replaced
Pre-driver replaced
Driver replaced (3 times)
Final replaced (twice)
R220 replaced
R221 replaced
C175 replaced
22uh bias inductors replaced
Other caps checked and replaced if needed
Driver, final, Passthrough insulators all were cracked, so I replaced those also.
I missed all the good stuff. I have family visiting so I have had little time to get online. Great job!
This one radio is gonna be the death of me. Hooked it back up, turned it back on to finish up with alignment, immediately wouldn't key up. It would make the sound of keying up momentarily but would still be receiving while ptt was pressed. Picked radio up, shook it a few times, still no key up, shook some wires, still no key up, lifted it 6in off the desk and dropped it, immediately it keyed back up and has been keying up every since. Thinking either a cracked solder joint or a connection not soldered good. I hate tracing gremlins like this down.
Yep, been there. Check over the shields, lift them a little. Then, reheat all joints along the regulator side of the rail.
But the rx while TX is somewhat of an indicator. Does the light change? I guess no.
Keep an eye on that hot potato resistor from earlier, if it goes nuclear again you got a ground issue. All I can say is hit every joint you can and scrutinize every wire.
I'm thinking mic cable connection or a dirty PTT switch. You probably heard the one side of the PTT switch disconnecting the audio, while the other half of the PTT switch didn't pull down the comparator to activate TX. Wiggle the mic cable at the connector and the PTT switch to try to reproduce the problem.
Couldn't get it to reproduce the issue. Pryed on parts using my ceramic tuning driver, pushed around on all the IFT cans, shut it off for several hours and tried several times. Just can't get it to do it again. Guarantee it will do it again immediately upon the owner trying it out.
Hey, I have gotten reports on it. They say the audio is booming loud but yet crystal clear and the signal is strong and steady. They are about 8 miles away.
I have tuned the output (even went back over RF stage IFT's (4)) for cleanest signal on the spectrum. It looks great. Carrier level set to 1w all the way down to 4.5w all the way up. It swings to 25w PEP (around 18w peak). I did place a 22k resistor across the AMC Timing Capacitor to force more average swing. No swing mods whatsoever and all limiters are still intact.
I tried my best last night to run it hot by hammering on it pretty hard. Nothing would get hot, only warm, and that's after about 20 minutes of a constant tone with RF power wide open.
But, more than likely it will drop the transmit immediately when they try it out.
Oh, signal looks great on our local ham operators SDR, both the spectrum portion and waterfall portion.
For those that have our local ham operators SDR to listen to my locals, we now stay on channel 1 (26.965mhz).
Hey, I have gotten reports on it. They say the audio is booming loud but yet crystal clear and the signal is strong and steady. They are about 8 miles away.
I have tuned the output (even went back over RF stage IFT's (4)) for cleanest signal on the spectrum. It looks great. Carrier level set to 1w all the way down to 4.5w all the way up. It swings to 25w PEP (around 18w peak). I did place a 22k resistor across the AMC Timing Capacitor to force more average swing. No swing mods whatsoever and all limiters are still intact.
I tried my best last night to run it hot by hammering on it pretty hard. Nothing would get hot, only warm, and that's after about 20 minutes of a constant tone with RF power wide open.
But, more than likely it will drop the transmit immediately when they try it out.
Oh, signal looks great on our local ham operators SDR, both the spectrum portion and waterfall portion.
For those that have our local ham operators SDR to listen to my locals, we now stay on channel 1 (26.965mhz).
You could put it in the freezer for a few hours to see if that breaks the contact, then if nothing is found, heat gun around the op-amp and keying diode while its still cold just to be sure.
Maybe pull the mirror board, tape the key down, then really mess with it one piece at a time while watching for a flicker in the TX/RX LED.
Touched up ALL solder joints on the entire board. Still hasn't done it since Sunday morning.
Anyway, finished it up. Works great, just like new.
The owner is on his way to get it and I informed him of the gremlin. He said he would get back with me immediately if it does it again.
Thank you guys..
Anyway, finished it up. Works great, just like new.
The owner is on his way to get it and I informed him of the gremlin. He said he would get back with me immediately if it does it again.
Thank you guys..