Help! Power and limit lights solid red, nothing plugged in. Yamaha B100-115III

SkyFarmer007

SkyFarmer007

Oct 15, 2024
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#1
Yamaha B100-115III
When I turn it on zero sound or hum, then a few seconds and there's a click in the cab (muting switch?). No sound. I disconnected the speaker and pulled it out of the cab. Nothing looks burnt. Lights staying on with it disconnected from the speaker as well. Any help would be appreciated!

Attached but here are links just in case:
Repair Manual: https://medias.audiofanzine.com/files/yamaha-b100-115-469907.pdf

User Manual: https://fr.yamaha.com/files/download/other_assets/7/313727/b100115iii_en.pdf
 

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#2
Unfortunately this would be indicator of one of several serious (and non-user repairable) faults, though a QUALIFIED (and experienced in older school solid state amps) service tech should have no problem diagnosing and repairing it.

That said, the schematic you attached does not match your amp, I think you actually have a B 100 iii version and are misunderstanding the lights above the level controls for the PEQ sections which are indicators that the PEQ sections are engaged (foot switchable). There are no limit LEDs on any B 100 that I have seen.

On the iii version, try jumping from the preamp out jack to the power amp in jack with a short patch cord and see if your problem resolves. If so, it's just an intermittent jack normalling switch contact, cycling a plug into the power amp in jack a few times should resolve it.
 
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#3
Hooked up a different speaker and it works. Tested the EVM-15B speaker inside and it's completely dead. Those "peak lights" were actually parametric EQ indicators not limit lights. I just acquired this amp so I was unfamiliar with it and made assumptions, and those assumptions proved to do their job lol.

Now just to figure out if that EV speaker is worth repairing. Looks like a solid platform.

Hope this thread helps someone in the future!
 
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#4
agedhorse said:
Unfortunately this would be indicator of one of several serious (and non-user repairable) faults, though a QUALIFIED (and experienced in older school solid state amps) service tech should have no problem diagnosing and repairing it.

That said, the schematic you attached does not match your amp, I think you actually have a B 100 iii version and are misunderstanding the lights above the level controls for the PEQ sections which are indicators that the PEQ sections are engaged (foot switchable). There are no limit LEDs on any B 100 that I have seen.

On the iii version, try jumping from the preamp out jack to the power amp in jack with a short patch cord and see if your problem resolves. If so, it's just an intermittent jack normalling switch contact, cycling a plug into the power amp in jack a few times should resolve it.
Click to expand...
Thanks for the quick reply. I jumped the gun... it was a dead speaker.
 
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#5
The EVM-15B is a great high performance old school driver. An experienced recone shop will have access to the best aftermarket parts available since the original parts have been discontinued by the factory.
 
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#6
I believe you can have a 15B reconed as a 15L, which will give you a little more brights. I've had both and prefer the L.
I had a 15B reconed a few years ago. If you are near Boston, I can recommend a great reconer.
 
#7
Stewie said:
I believe you can have a 15B reconed as a 15L, which will give you a little more brights. I've had both and prefer the L.
I had a 15B reconed a few years ago. If you are near Boston, I can recommend a great reconer.
Click to expand...
This is correct.
 
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