Fender Rumble 40 Power PCB capacitors blown

Switchy

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Just adding some photos for the tech geeks and the idly curious:
 

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Switchy

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Replaced the 2 small 35v capactitors on the power amp PCB, and the power LED cycles on and off as before.
I suspect the power supply has a problem, and am waiting for the TWO 1000uF 35V filter capacitors. :(

*Note: onboard button fuse is still OK
 
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Replaced the 2 small 35v capactitors on the power amp PCB, and the power LED cycles on and off as before.
I suspect the power supply has a problem, and am waiting for the TWO 1000uF 35V filter capacitors. :(

*Note: onboard button fuse is still OK
if need be you could replace the 2 caps with 1000UF 50 volt , fender uses some cheaper parts in their amps made out of country , I just did a full recap on a fender BF twin reissue for a client recently the QC on that amp was deplorable , I took my own amp ( a BFRI twin) apart but I had none of the issues of the amp I repaired, cold so;dered connections , bad component placement ( connectors were not properly soldered in place ETC) , so check out the amp carefully caps dont blow unless there is a reason , and it may even be cheap caps in the first place, I always use F&T caps made in germany , they rock!
 

Switchy

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if need be you could replace the 2 caps with 1000UF 50 volt , fender uses some cheaper parts in their amps made out of country , I just did a full recap on a fender BF twin reissue for a client recently the QC on that amp was deplorable , I took my own amp ( a BFRI twin) apart but I had none of the issues of the amp I repaired, cold so;dered connections , bad component placement ( connectors were not properly soldered in place ETC) , so check out the amp carefully caps dont blow unless there is a reason , and it may even be cheap caps in the first place, I always use F&T caps made in germany , they rock!


I'm hoping it's the 2 main caps. The problem I'm having is that everything looks good on the board. But I'll test more parts once I receive the replacement caps.
 

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I know this covers the Rumble 40, but this was the type of issues I found in the Twin BFRI I worked on, he is verbose so scoot ahead the the repair portion and he shows some bad solder joints , this may help you , look at the circuit board and the connectors for continuity , before you replace the caps .....just in case



BTW I have a rumble 100 that I use (I experimented with it and it makes a great sounding guitar amp )
 

Switchy

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I know this covers the Rumble 40, but this was the type of issues I found in the Twin BFRI I worked on, he is verbose so scoot ahead the the repair portion and he shows some bad solder joints , this may help you , look at the circuit board and the connectors for continuity , before you replace the caps .....just in case



BTW I have a rumble 100 that I use (I experimented with it and it makes a great sounding guitar amp )



Yeah, when you open up the 40 and 25, it's quite apparent that they are made cheaply! :eek: There's very little inside.
Which works in my benefit, making it a little easier to work on.
 

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Yeah, when you open up the 40 and 25, it's quite apparent that they are made cheaply! :eek: There's very little inside.
Which works in my benefit, making it a little easier to work on.

My twin BFRI had none of those issues , I guess I got lucky , but the unit i worked on ,whew!

Hope its an easy repair for you!
 

Switchy

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I switched out the two capacitors, but no dice. Still the same. LED power cycles on and off. Kinda blinked twice this time, and the speaker let out a little pop.
My last hope is to switch out the larger 330uf 200v capacitors, because one looks just slightly bit fat on the top.
 

Switchy

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I'm a little confused because the schematics don't exactly match the board, but any how...
Is this solder crossover EVER supposed to happen???? :eek:



305 detail 2.jpg
 

EsquireOK

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$200 asking price amp, and often can be haggled down a bit, brand new – $100 to $150 used. If you paid anything at all for it, it’s not worth any more than an hour of your time. If you got it for free, maybe two hours.

I would give up on the amplifier, and just convert the cab into an extension cabinet for a brand new one. The working one will sound significantly better that way anyhow, and the whole rig will still weigh practically nothing. Add some interior padding and port tubes while you’re in there too. These are popular and well researched mods; look ‘em up online.
 

Switchy

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$200 asking price amp, and often can be haggled down a bit, brand new – $100 to $150 used. If you paid anything at all for it, it’s not worth any more than an hour of your time. If you got it for free, maybe two hours.

I would give up on the amplifier, and just convert the cab into an extension cabinet for a brand new one. The working one will sound significantly better that way anyhow, and the whole rig will still weigh practically nothing. Add some interior padding and port tubes while you’re in there too. These are popular and well researched mods; look ‘em up online.


I totally get this, but, some people buy puzzles to relax in their free time, I like solving things. I personally enjoy learning now things work, and fix them if I can. It's quite a rush if I can figure it out.
 

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I'm a little confused because the schematics don't exactly match the board, but any how...
Is this solder crossover EVER supposed to happen???? :eek:



View attachment 726594
I would reflow that connection, do those two components connect in the schematic?

but thats the stuff like i was refering to

heres some pic of the sloppy construction of the BFRI twin
OI000317.JPG
-2.jpg


as well as all the caps were replaced
 

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looking at your pics something dawned on me , tou have a lot of SMD devices on your board ( surface mounted caps and resistors) look very carefully at these items as well, look for Bad, or cold soldered connections or deviced that have lifted as well
 

Switchy

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looking at your pics something dawned on me , tou have a lot of SMD devices on your board ( surface mounted caps and resistors) look very carefully at these items as well, look for Bad, or cold soldered connections or deviced that have lifted as well

Yeah! Tell me about it. When looking close up, the soldering on a lot of the SMP components look crappy.
The consensus is that these are made cheaply, and yeah, I agree.
 

Switchy

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Well, all the big caps were switched out. No improvement. LED cycles on and off.

It is currently out of my scope of repair skills. :(

Symptom I found in a troubleshooting list on the internet:

Periodic power cycling, tweet-tweet, flub-flub, blinking power light - shorted semiconductors, faulty over voltage or over current sensing components, bad controller.

Something I read:

From experience, over 90% of power cycling problem was caused by
bad components in the secondary section. It could be a shorted
secondary diode, bad filter capacitors, and faulty components in the
regulation circuits i.e. Sampling, Error Detection and Feedback
Optoisolator IC
 
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Switchy

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For what it's worth, I took another look, as I am determined.
I managed to find a diode (D311) which seems to be shorted, and has continuity in both directions.
There is another on the board which I could compare it to, so this one is not as it should be. Seems to be a 1n4148, pretty common, but not in SMP form factor, I may just scavenge something comparable.

Diode 20200602_140924.jpg
 

Telecastoff1

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The button fuse on my Rumble 40 was acting up, intermittently. I removed it and installed an inline 1.5 amp fuse in its place and it works great!
 

tuubes

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For what it's worth, I took another look, as I am determined.
I managed to find a diode (D311) which seems to be shorted, and has continuity in both directions.
There is another on the board which I could compare it to, so this one is not as it should be. Seems to be a 1n4148, pretty common, but not in SMP form factor, I may just scavenge something comparable.

View attachment 727592
a Diode X a resistor 330 ohm WILL read in both directions, the resistance path is wayy smaller is why
 




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