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June 30, 2022, 05:41:51 AM

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Ss guitar amp volume ouput weak reverb screeching when turned up

Started by Billythekid, April 11, 2018, 02:40:16 PM

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Billythekid

Can anyone throw me some Pointers on where to begin to het my amp back in good condition?

Jazz P Bass


Billythekid

Well i bought a new multimeter. Lost the old one. Built a signal tracer. Started tracing but unsure about where to and how. Bought one 2n3055 output transistor. Match the speakers they are 16ohm 10 inch Chicago telephone speakers two per box. total of two boxes with two tens in each box. The fuses were all different so i bought the 5 amp 250volt slow blow fuses the amp schematic called for ans now im waiting for some advice and finepoints. I can send schematics videos of the amps sound and insides inner workings whater i am told to do but really want this amp back in shape you know even if its a slow process. Any advice???

phatt

Measure the 2 voltages at fuses 1&2 of DC supplies. **What do they read?**
(Neg probe on Common or ground which is the junction of C5 & C6)

Next check for any DC voltage at speaker output,, should be well under 1/2 a volt DC. ideally around 50~100mV DC.

If both supply rails are close to same i.e. +30VDC and -30VDC
and zero on speaker then break the signal input to power amp.
Then insert an MP3 player or some audio signal at the junction of c1 and R5. You should have a good strong signal out the speakers. If that checks out then you will have to work back through the Reverb, Vibrato and preamp boards.

Regards the Vibrato board; IF any stray light is reaching the LDR's it will reduce the volume and that maybe the case even if the Vibirato is OFF. 8|

ed; adding,LDR is called Photo cell on the schemo
Phil.