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Hi, everyone--
I just received a Fender Rumble 25 Bass Version 3 solid state amp that has a somewhat common problem of ultra-low output that sometimes kicks in ultra loud*.
Fender no longer sends out the schematic upon request.
Brad the Guitologist on YouTube somehow got the schematic and shows parts of it in this video:
https://www.youtube.com/watch?v=xiBbvl4vQZc
But in the comments, when people asked him where he got the schematic, he said to Google/DuckDuckGo it.
So far, Google/DuckDuckGo/Bing only return the Rev. A schematic, which is a bit too different from Rev. C (especially test point values).
Could someone post either the schematic or the service manual for the Fender Rumble 25 Bass Version 3 (aka Revision C)?
Thanks very much in advance!
* It's not the headphone jack having cold solder joints and causing the complete speaker cut-off. I hear audio on the speaker and all the controls work properly--it's just really low volume. There are a couple of similar discussion threads out there on other forums that describe the same symptom, and it seems a few people know what it is. They claim the TL074 IC (not sure which one of the two, U1 or U3) fails prematurely and must be replaced. I figure it's U3 they are referring to, since the AUX IN is also very quiet, and AUX IN is after U1 in the block diagram. It might also be U2, an LM13700M used in a limiter circuit that could be drastically suppressing the input to the power amp. I'd need the test point values on the schematic to isolate the problem.
I just received a Fender Rumble 25 Bass Version 3 solid state amp that has a somewhat common problem of ultra-low output that sometimes kicks in ultra loud*.
Fender no longer sends out the schematic upon request.
Brad the Guitologist on YouTube somehow got the schematic and shows parts of it in this video:
https://www.youtube.com/watch?v=xiBbvl4vQZc
But in the comments, when people asked him where he got the schematic, he said to Google/DuckDuckGo it.
So far, Google/DuckDuckGo/Bing only return the Rev. A schematic, which is a bit too different from Rev. C (especially test point values).
Could someone post either the schematic or the service manual for the Fender Rumble 25 Bass Version 3 (aka Revision C)?
Thanks very much in advance!
* It's not the headphone jack having cold solder joints and causing the complete speaker cut-off. I hear audio on the speaker and all the controls work properly--it's just really low volume. There are a couple of similar discussion threads out there on other forums that describe the same symptom, and it seems a few people know what it is. They claim the TL074 IC (not sure which one of the two, U1 or U3) fails prematurely and must be replaced. I figure it's U3 they are referring to, since the AUX IN is also very quiet, and AUX IN is after U1 in the block diagram. It might also be U2, an LM13700M used in a limiter circuit that could be drastically suppressing the input to the power amp. I'd need the test point values on the schematic to isolate the problem.
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