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 Post subject: help with project/one mark 440
PostPosted: Feb Sat 22, 2020 8:39 am 
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Joined: Feb Sat 22, 2020 8:29 am
Posts: 1
OK guys I need help I recently found what was considered a rare find for me, I found a project/one mark 440 and everything seemed to work but when I hooked my speakers up they worked only on very low volume once I turned it up a little they started to distort what might cause this? I'm new to all this and have tried everything I possibly could think of.

 Post subject: Re: help with project/one mark 440
PostPosted: Feb Sat 22, 2020 4:25 pm 

Joined: Feb Sat 12, 2011 2:29 pm
Posts: 595
Location: Smithfield, Pa. 15478
Without knowing some voltage readings it would be hard to say. First guess is output transistors blown, but again that is just a guess. I WOULD NOT turn it up though until you confirm no shorted output leads as that could take out the outputs if uncorrected.

Begin by verifying all voltages around the output stages are correct. If not you will need to obtain schematic and troubleshoot accordingly. If voltages are good, begin by applying low audio signal and confirming no excess changes occur. (Possible emitter resistors are open, that will show up as signal causes current increase through them.) Beyond that I would only be speculating without knowing more details on readings.

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