Hi,
I am trying to fix a problem with this amp. With the "Direct" button ON, the Direct Led lits up and there is sound on both sides. As indicated with Direct ON, the Bass, Treble and Balance does not work. When I OFF the Direct button, there is totally no sound at all, I checked the transistors, diodes, resistors on the Tone Board and they are OK. I replaced the Tone IC (M5220) with MC33078N as the M5220 is not available, but still no sound. I am confused as what can be the problem. Can someone please help.
Thanks
Carlos
I am trying to fix a problem with this amp. With the "Direct" button ON, the Direct Led lits up and there is sound on both sides. As indicated with Direct ON, the Bass, Treble and Balance does not work. When I OFF the Direct button, there is totally no sound at all, I checked the transistors, diodes, resistors on the Tone Board and they are OK. I replaced the Tone IC (M5220) with MC33078N as the M5220 is not available, but still no sound. I am confused as what can be the problem. Can someone please help.
Thanks
Carlos
Wire bridges on ADPT2 missing?
Otherwise, probably a case for a signal tracer (which essentially is a fancy floating amplified speaker with clip leads on its input).
Otherwise, probably a case for a signal tracer (which essentially is a fancy floating amplified speaker with clip leads on its input).
Hi Carlos,
The "Direct" button bypasses tone controls, so that is completely normal. The new op amp wouldn't have fixed your problem.
Check that the "pre out" and "main in" jumpers are installed. If they are missing, you can replace them with a short RCA patch cord. Before touching that connection, either turn the power off (preferred) or turn the speakers off. The "main in" jacks got directly into the amplifier with no volume control, so even touching that connection can be loud in the speakers.
One question. Does the speaker relay go "click" 3 ~ 5 sec after you turn the amplifier on, or not?
-Chris
The "Direct" button bypasses tone controls, so that is completely normal. The new op amp wouldn't have fixed your problem.
Check that the "pre out" and "main in" jumpers are installed. If they are missing, you can replace them with a short RCA patch cord. Before touching that connection, either turn the power off (preferred) or turn the speakers off. The "main in" jacks got directly into the amplifier with no volume control, so even touching that connection can be loud in the speakers.
One question. Does the speaker relay go "click" 3 ~ 5 sec after you turn the amplifier on, or not?
-Chris
Yes, I dont remember seeing any wire bridges at the back of the amp. I will take a close look at these mentioned issues.
Thanks alot guys
Carlos
I always start with the dumbest possible cause.
The direct switch defeats the tone control board, so if components on tone control board are ok, and no sound is heard while running through the tone control board, then either one of the ribbon cables may be damaged or the connector at either end is bad eg cold solder joint.
The direct switch defeats the tone control board, so if components on tone control board are ok, and no sound is heard while running through the tone control board, then either one of the ribbon cables may be damaged or the connector at either end is bad eg cold solder joint.
You kinda need to clean the direct switch(es, actually, there are two individual switches in parallel) for like an hour, pretty much. It gets super corroded, and won't pass any sort of signal whatsoever. Best would be to open it up and grind off the corrosion, but doing this will ruin the switch because you'll never get it back together. Not to mention, actually reaching the switch is virtually impossible.
There are no pre/main links on the back.
There are no pre/main links on the back.
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As mentioned, there was no wire bridge across ADPT2. I bridged the ADPT2 terminals and then the bass, treble, balance and loudness are all working fine. Thanks alot all you guys for your help. You are all GREAT!
Carlos
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