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Author Topic: signal tracing  (Read 6702 times)

Crich

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signal tracing
« on: December 06, 2019, 10:34:07 PM »
Trying to repair a fender FM15 DSP that blows the F2 fuse. Trying to use an audio probe but can't read schematics. very well. Need to trace signal from input to out put. Can anyone help me? I also think the problem could be in the DSP board but not sure the schematic even shows it. Would like to know how to bypass it if possible.  This is a learning project for me so don't need to buy another amp Thanks.I

g1

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Re: signal tracing
« Reply #1 on: December 07, 2019, 02:06:07 PM »
You can't signal trace til you fix the fuse blowing problem.
The first step would be to build a lamp limiter so you can troubleshoot without blowing fuses repeatedly.
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Crich

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Re: signal tracing
« Reply #2 on: December 07, 2019, 07:43:20 PM »
Thanks I will look into it.

joecool85

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Re: signal tracing
« Reply #3 on: December 09, 2019, 01:57:35 PM »
Trying to repair a fender FM15 DSP that blows the F2 fuse. Trying to use an audio probe but can't read schematics. very well. Need to trace signal from input to out put. Can anyone help me? I also think the problem could be in the DSP board but not sure the schematic even shows it. Would like to know how to bypass it if possible.  This is a learning project for me so don't need to buy another amp Thanks.I

It shows the plug going to DSP.  I believe you can unplug this and use the amp without any DSP.  It's been a while since I've been inside my 25 DSP, but I think this is the case.
Life is what you make it.
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Crich

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Re: signal tracing
« Reply #4 on: December 09, 2019, 11:52:01 PM »
I will disconnect the power at P9 and P10 see what happens. F2 fuse is connected to P9. Fuse not blowing right away amp works awhile then blows. Wondering if dsp board over heating. If I jumper pins L in to L out plus or minus I  have power at R20 & R22 but nothing at Q1 transistor and beyond. I need to know what pins to jumper at P11 connect. The attached Princeton 65 DSP is close but connector P6 different but dsp board I think is identical. Any help appreciated. Thanks

g1

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Re: signal tracing
« Reply #5 on: December 10, 2019, 02:26:30 PM »
To run with DSP disconnected, I'd think you jumper Lin to Lout+ and ground Lout-.

U6 on the main board is also running off the 5V (F2) line.

Crich

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Re: signal tracing
« Reply #6 on: December 17, 2019, 09:41:40 PM »
Sorry for taking so long to thank you for the suggestion. I haven't had a chance to get back to the amp. I will post results.