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Fender Rumble 100 V3 - blown cap.

D

Devs Ad

May 23, 2020
14
13
#1
Hi.
Son's FR 100 is 'dead'. Opened it up and found an exploded surface-mounted capacitor - C357. Thanks to another thread on here with a link to a schematic, it appears to be 0.015 and 630V. http://www.fmicassets.com/Damroot/Original/10002/Rumble 100 V3 Schematics-Diagrams.pdf

Before I replace the cap (with a non-SMT type), I'd appreciate any thoughts on this, such as what the likely cause could have been? Is it likely there will be other damaged components? Would the amp appear completely 'dead' from just this component having blown? Oh, and what is the actual value of '0.015'?! Is it 0.015F or what?

Many thanks :-)

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#3
No, you have something else that has failed that caused this.

troubleshooting SMPS requires a knowledge of high voltage safety as well a high frequency non-linear electronics, a scope, and a fair amount of understanding of electronics.
 
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#5
The power supply/power amp module is not supported even for service center repairs. It's a replacement item that is generally not available outside the Fender service network.

Those are snubber caps for the high voltage DC bus. When this fails, it's almost guaranteed that the line frequency bridge has failed, and possibly the HV bus bulk caps and whatever collateral damage may have happened.

Give your authorized Fender (electronics) service center a call, before paying for diagnostics be sure that they can get the replacement module otherwise diagnostics are pointless.
 
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#8
agedhorse said:
The power supply/power amp module is not supported even for service center repairs. It's a replacement item that is generally not available outside the Fender service network.

Those are snubber caps for the high voltage DC bus. When this fails, it's almost guaranteed that the line frequency bridge has failed, and possibly the HV bus bulk caps and whatever collateral damage may have happened.

Give your authorized Fender (electronics) service center a call, before paying for diagnostics be sure that they can get the replacement module otherwise diagnostics are pointless.
Click to expand...

Thanks again.

If I go 'Fender', I suspect it'll be prohibitively costly. I don't suppose you have any idea of ballpark figures for that board?

I'm thinking the only sensible options are to either pass it on for someone else who can take on the repair, or hang around for a dropped and smashed item to come up on eBay, but with good electronics inside!

Do you happen to know if the boards are shared with any other Rumble, say the '200'?

Thanks.

(Or, the boards might not be 'generally' available, but are there any other sources for these, say from the Far East?)
 
#10
Devs Ad said:
Thanks again.

If I go 'Fender', I suspect it'll be prohibitively costly. I don't suppose you have any idea of ballpark figures for that board?

I'm thinking the only sensible options are to either pass it on for someone else who can take on the repair, or hang around for a dropped and smashed item to come up on eBay, but with good electronics inside!

Do you happen to know if the boards are shared with any other Rumble, say the '200'?

Thanks.

(Or, the boards might not be 'generally' available, but are there any other sources for these, say from the Far East?)
Click to expand...
The boards are exclusive to the Rumble 100.

Contact a Fender authorized service center and see if they can get you the current service information on availability.
 
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#11
Having worked on SMPS, both as a repair tech, and later on in life as an engineer developing them, they can be real PITA to work on.

It is sorta possible that the capacitor simply shorted and burned the foil on the circuit board. That theory is easy to test, just remove all four of the rectifier snubbers, repair the circuit board traces, check over the rest of the components with an ohmmeter and see what happens (recommend slow bring up and current limiter). If you're really, really lucky, that's all that happened.

But chances are there's a lot more bad happened and killed the power supply. Also, there are safety considerations to keep in mind. I'd recommend not trying to repair it. (and I'm the kind of idiot with the know-how and the tools to dig into it...)

Best bet, as mentioned in the thread, is see what it would take to replace the entire module. It might not be that bad to replace it outright, but only an authorized service center would have access to the part. Although, such parts do turn up on eBay and so on from time to time.
 
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#12
Thanks all.

I am quite familiar with soldering, so would find it straight-forward to replace the rectifier, and mount a standard cap where the defunct SMT one is. I'd happily try this if there was a decent chance that's all that's wrong! But since there's probably a greater chance that more is amiss, I'd rather sell it on as an untampered-with amp, as it's in otherwise such good order.

I'm emailing as many amp repair folk as I can easily find, asking for quotes either for a repair or a new board. I'll keep the thread updated.

Cheers.
 
#13
Not much luck at getting an affordable repair - typical rates are £95 per hour min.
Time to pass it on to someone with the skills :-(

Curious - looking at the schematic diagram, if it is 'just' the power supply part that's failed, would an option for someone else (not me) be to install a third-party supply and bypass the existing? It 'looks' straight-forward.
 

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  • Screenshot 2023-09-19 at 09-55-06 p_n 2315300020 120V - Rumble 100 V3 Schematics-Diagrams.pdf.png
    Screenshot 2023-09-19 at 09-55-06 p_n 2315300020 120V - Rumble 100 V3 Schematics-Diagrams.pdf.png
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#15
Thanks, BC. Yes, always an option - it certainly won't be scrapped.

But, looking at the schematic, the PSU section is quite separate from the amp part on the same board, literally joined by two 'wires'. So, any reason why a perfectly valid solution wouldn't be to install a separate PSU to supply the amp?

If the amp was in tatty condition, I'd explore doing this myself, although I'd need to have the required info on voltages and stuff. But since the amp is little-used and immaculate, I think I'll sell it on as 'spares or repair' to a more tech-savvy home, and hope it can be brought back to life.
 
#16
Devs Ad said:
Not much luck at getting an affordable repair - typical rates are £95 per hour min.
Time to pass it on to someone with the skills :-(

Curious - looking at the schematic diagram, if it is 'just' the power supply part that's failed, would an option for someone else (not me) be to install a third-party supply and bypass the existing? It 'looks' straight-forward.
Click to expand...
No, that's not practical. It might seem so until you dig in farther.
 
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#18
I think you will find it to be way more complicated than it looks, especially the part about finding a suitable replacement supply.

Then there's the little issue of EMC and safety certifications.
 
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