CT28v preamp problem

[Shamrock 2]

Hey guys

I have a problem with this preamp in that it has a really weak output, as in full volume through my av806x amplifier just to be heard. I have another preamp that works fine with this amp.

 

Dont know where to start looking, I was going to check the adjusting pots as these are a candidate to go bad but I don't want to do this without a service manual (which I can't find anywhere)

 

Any suggestions on common problems ,where to start troubleshooting or where to find a service manual?

[weitrhino 1,443]

We don't have the service manual for this model in the library presently. However this might help. Alternatively this manual appears to be available for purchase here.

[Shamrock 2]

Service manuals for ct27v ct28v and ct29v don't seem to exist on the net. I have the owners manual but that's no help. All there is out there is paying 10 bucks for schematic drawings which seller says are hard to make out (thanks for the link btw). It kinda sucks

[kve777 6,888]

First thing I'd do is hit every switch, pot and connector with DeOxit and articulate them vigorously. Dirty tape monitor switches, balance pots, etc can almost eliminate the output. The least used ones are most suspect as they can build up a layer of crud that will not conduct. Oxidation on connector pins inside will do this, too. Hint: take pics if you are going to unplug a lot of connectors. Some will fit in multiple sockets. Clean the input/output jacks, too. Let us know if this helps.

[Shamrock 2]

 

 

First thing I'd do is hit every switch, pot and connector with DeOxit and articulate them vigorously. Dirty tape monitor switches, balance pots, etc can almost eliminate the output. The least used ones are most suspect as they can build up a layer of crud that will not conduct. Oxidation on connector pins inside will do this, too. Hint: take pics if you are going to unplug a lot of connectors. Some will fit in multiple sockets. Clean the input/output jacks, too. Let us know if this helps.

 

Thanks that sounds like very good advice. I used deoxit on the pots and connectors that I could get at, I'll take photos then disassemble the boards from the unit so I can get at everything and check for bad solder joints while I'm at it. I'll let you know how I get on

[Shamrock 2]

Removed every board deoxit on all controls and connectors , the only trimmers are on the tuner board and i didnt want to mess with those without a manual , inspected pc boards for cracked or dry joints too , reflowed a few. Reassembled it all but it still performs the same , weak sound level and what's there sounds pretty tinny