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-   -   Punch 40DSM no output on either channel ( 23rd June 2010 02:36 AM

Punch 40DSM no output on either channel
What is the best way to attack these amps. Right now I have no output on either channel, but I have a clean signal leaving the input board. I pulled the output fets so I wouldn't have to worry about them shorting. I did find one transistor shorted on the driver card, believe it was a PNP (3B) BC856. Could a 2G transistor be sub'd for this?

I have two of these amps and both have the same problem. The 10uF caps have all been changed, if they needed it or not.


Perry Babin 23rd June 2010 04:26 AM

2 Attachment(s)
The MMBTA56 should be a good sub.

With the outputs out of the circuit, you can't do much troubleshooting of the audio section with the amp powered up. Do you have a clean signal on pin 1 and no signal on pin 2 of the left channel and the reverse for the right channel?

Beyond that, virtually everything is in the feedback loop and depends on the feedback from the outputs to determine the voltage on the various components.

The attached images show the most common components to fail on the driver boards (assuming that you have this version of the driver boards). 23rd June 2010 01:02 PM

I have a clean signal for both channels, took me forever to figure out one channel fed into pin 1 and the other to pin 2.

The transistor in the upper right had failed shorted. I will put the outputs back in, and look for other problems. 24th June 2010 04:14 PM

1 Attachment(s)
Messing around in paint with the pics Perry posted, I am mapping the input signal from pins 1 and 2.

If this turns out to help I will do the same for the output side.

What is W3, dual transistor? I can't find any data on it.

Perry Babin 24th June 2010 05:04 PM

Paint should be outlawed. Download Open Office (free). It has a 'Draw' application that's infinitely better than Paint.

Email me before you do any more on this board. 24th June 2010 06:21 PM

Sent an email.

I use Gimp normally, used open office prior to getting MS Office for a class.

Perry Babin 24th June 2010 09:19 PM

Is the TOC line going to -15v on the audio driver board? 25th June 2010 02:19 AM

The 40 has +-12 supplies and yes it is going to -12(pin4).

The swf file uses shockwave? I have just used windows explorer to see it, not sure if I am missing anything by doing this.

Perry Babin 25th June 2010 02:41 AM

Generally, you'd use your internet browser. 25th June 2010 03:13 AM

Any logic in removing the protection diodes? I have done this in the past to eliminate that part of the circuit. It looks to be D112 and D109?

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