KLM 2M Amp Help - Elmers Forum at eHam.net

$\'\'$

$\'\'$

$\'\'$

eHam.net Forum : Elmers : KLM 2M Amp Help

Forum Help

1-3 of 3 messages

Page 1 of 1

KLM 2M Amp Help	Reply
by WB2PJH on April 5, 2005	Mail this to a friend!
My KLM 2 meter amp, model PA 10-80 BL, has suddenly quit. I am using an old TS-700 to drive it, and it stopped working right in the middle of a CW contact. There was no overheating, smoke, or other signs of self-destruction. The amp simply stopped being keyed. I took it apart and checked the relay (OK) and made sure that the unit was getting power (it was). I don't have a schematic for this unit and would appreciate any advice on what has likely failed so that I can troubleshoot and fix it - perhaps other folks here have had a similar problem. Thanks, Dave WB2PJH

RE: KLM 2M Amp Help	Reply
by WB2WIK on April 5, 2005	Mail this to a friend!
When you say, "stopped being keyed," do you mean keyed by the RF signal, or hard (direct) keyed by a key line output from the exciter or other source? Where to look to find the problem depends a lot on this answer. How did you determine the relay was still okay? I've rebuilt a lot of these old KLM amps and the things that fail most often are: -The relay -The output/feedback network components -And those components can unsolder themselves from the PCB traces (microstrip) because the parts get hotter than the melting temperature of solder! Sometimes, the parts themselves are still good, they're just not connected any more. Another place to look is the collector lead of the PA transistor, which can also get hotter than 230C (solder's reflow temperature) and make this connection crystallized and high-resistance, to the point where there's just no connection -- although it might "look" fine. WB2WIK/6

RE: KLM 2M Amp Help	Reply
by WB2PJH on April 9, 2005	Mail this to a friend!
Thanks for taking the time to reply. The amp is RF keyed, and it just stopped (in the middle of a QSO). I did get the unit apart and checked the relay coil and found 200 ohms of resistance. There was a diode that appeared to be open, so I jumped it with another small signal diode but the unit was still broken. I will check it carefully for bad solder connections - the unit has never run particularly hot but it is old and I have no idea how the previous owner treated it. If you have any other suggestions, I will appreciate them - running 10W on 2 meters is a challenge! --Dave WB2PJH

Page 1 of 1

Next Topic: Why Enameled Wire?
Previous Topic: Ameritron AL-811

Email Subscription
You are not subscribed to this topic.

Check our help page for help using Forum, or send questions, comments, or suggestions to the Forum Manager.

$\'\'$