Tascam PA-20 mkII

[Michael Doncaster]

Hi,

Anyone familiar with the PA-20 mkII?

I have one which has a fault, on power up the speaker relay does not trip in, I have tested the relay with a battery, and it pulls in no problem.

Does anyone have a schematic? I can't find any schematics online anywhere.

 

[SkywaveTDR]

It is most likely not the relay itself as they are highly reliable in general. The problem is either the sense circuit or that there is something wrong in the amp as it might have DC at the output which is what the relay is suppose to prevent.

 

[Michael Doncaster]

Hi Sam,

Yes, the relay is fine, if I trip it manually with a 9v battery I get clean sound out of the speakers.

 

[SkywaveTDR]

Oh there you go a STK flat pack. These amps always promise more than they can develop. On top of that I have removed some failed packs to only find the most smallest amount of heat sink past applied to them. This then causes them to overheat and fail early and the paste isn't even the good stuff but the cheapest zinc Oxide that they can find. The solder legs of these amps also seem to unsolder themself. Determine the output pins and make DC measurements to see if they are putting out DC where they should not- that may be what is causing the relay to not trip on.
The days of the well built product are long gone and in this case you should take the bull by the horns and fix and improve the unit on your own. I would first take the chip off the heat sink and make sure it was properly applied to the sink- most the time they are not. All metal interface of the IC should have paste on it and be well mounted to the heat sink. Then look over the wave soldering that always is problem I find with units. I looked for a service manual and I did not find one.