Any Ideas on How to find a Radio Shack MPA@250 amp shematic?
- Thread starter crispycircuit
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I've found a parts list but no schematic. One question - is it a 250 or a 250A or 250B. The MPA250 has analog meters, the 250A and B have digital displays. As far as I can tell, the A and B versions are the same except B is black front. One possible problem with the A or B is that the heat sinks tend to pull on the boards in shipping,and can cause cracks at the other end of the board around the mounting screws.
Sorry but even if you find who actually made them, OEM factories do NOT talk to the end supplier , your only bet is Radio Shack itself or *maybe* some Authorized Service guy , although obviously he'll prefer you send the dead amp to him.
Of course, if you are experienced and have a well stuffed Lab you can service them anyway without schematic, by applying "general purpose" diagnostic and service procedures, such as checking for presence of correct rail voltages, shorted power and driver transistors, dead PSU diodes , open or missing or unsoldered filter caps, etc.
Living in Argentina I have to do it all day long.
Probably many who live outside USA have a similar experience, working without schematics and lacking access to original parts.
Oh well.
Of course, if you are experienced and have a well stuffed Lab you can service them anyway without schematic, by applying "general purpose" diagnostic and service procedures, such as checking for presence of correct rail voltages, shorted power and driver transistors, dead PSU diodes , open or missing or unsoldered filter caps, etc.
Living in Argentina I have to do it all day long.
Probably many who live outside USA have a similar experience, working without schematics and lacking access to original parts.
Oh well.
I was given one of these amps - the one with analog VU meters, because it was not working. The bridge rectifier was shot. I replaced it and the amp works fine and sounds better than I expected. The fan is a little noisy (not a very good fan), but I unplugged it. Even at half throttle, the heat sink is cool to the touch. I think the fan is there in case the amp is rack mounted.
I still have not found a schematic for the amp. I like that it has Toshiba 2SA1302 power transistors.
Adam
I still have not found a schematic for the amp. I like that it has Toshiba 2SA1302 power transistors.
Adam
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