Help! Fender Rumble won’t turn on

Exile777777

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Hey all I have a fender rumble 500 which is only a few years old and has never been pushed very hard. A few days ago during band practice it just suddenly had no power. We played about 20min it was working fine, took a 5min break (amp was never turned off) and suddenly nothing. Flipped it on and off, tried a new power cord, different outlet, even opened it up and tried a new fuse… still nothing! The strange thing is I’ll flip the power switch on and nothing happens, no light comes on, no sound, but a few seconds after I switch it off the light will quickly blink on and off once or twice - and sometimes a faint noise/sound from the amp for a split second. Anyone know if this might indicate what is wrong with it?? It would be a huge help to save some time trying to figure this thing out! Thanks in advance.
 

Peegoo

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Most likely cause: the power supply in the amp has failed.

If you can solder, you can probably fix it. Unplug it, pop it open, drain all the filter caps, and look for leaky electrolytic polarized caps in the power supply section of the board. They'll look like this:

Bad-Capacitors.jpg


Read the specs on each bad cap and order new ones. Ideally, you'll get the same physical sizes (as well as identical specs). The white goop in the pic above is not leaky stuff; it's added to prevent movement and vibration of larger/heavier components on the board.

Desolder the bad caps and install the new ones. Mind the polarity.
 

Exile777777

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Thanks for the reply and images! I was afraid it would be more than just swapping out the power switch or something like that. When I swapped out the fuse everything looked like new on the board, but I’ll inspect the caps more closely.
 

dsutton24

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Capacitors do fail, but unless the fuse is blowing bad caps aren't likely to cause the problem you describe. It is possible the problem might be a bad power switch or the like, but replacing things at random will only throw money away. You need to do some troubleshooting.

Do you have a meter, and are you comfortable sing it? How well do you solder? Many beginning or intermediate techies struggle when making repairs to p.c. board based amps. You can cause permanent and / or expensive, not to mention unneccessary damage to your amp.

Based on the questions you asked, I believe that you'd be far better off getting a pro to repair this amp.
 

Peegoo

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Thanks for the reply and images! I was afraid it would be more than just swapping out the power switch or something like that. When I swapped out the fuse everything looked like new on the board, but I’ll inspect the caps more closely.

Closely inspect the entire top and bottom of the board, under bright light with magnification. Look for burned resistors, cooked traces, etc.
 

Exile777777

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Capacitors do fail, but unless the fuse is blowing bad caps aren't likely to cause the problem you describe. It is possible the problem might be a bad power switch or the like, but replacing things at random will only throw money away. You need to do some troubleshooting.

Do you have a meter, and are you comfortable sing it? How well do you solder? Many beginning or intermediate techies struggle when making repairs to p.c. board based amps. You can cause permanent and / or expensive, not to mention unneccessary damage to your amp.

Based on the questions you asked, I believe that you'd be far better off getting a pro to repair this amp.
I have a few decent multi meters and have done a lot of soldering but mostly on cables. Not a pro but I feel fairly comfortable with it. My initial thought after trouble shooting the fuse was maybe a bad switch. I’m going to do a more thorough inspection of the caps and test the switch. Holding it’s a cheap fix. Thanks for the advice!
 

lylelwr

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Sadly, these new Fender amps are not really designed to be repaired. If it's in warranty, they give you another one. If it's out of warranty the cost of replacing the circuit board and the labor is going to be hundreds of $$ so you would probably just buy another amp to get the warranty again.
 

RetiredUnit1

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Sounds like a loose wire, or quick disconnect. LOADS of vibration in bass amps can shake those loose. Pic is what I'm talking about. Used for the power switch as well as some transformer connections on new fenders
1660243506984.png
 

Milspec

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I have rarely seen a full failure without some warning signs leading up to it. Static, volume loss, smoke, burning plastic smells, visible arcing, etc. If it did none of that, I would not expect it to be with anything on the board, but rather with the switch or cord. You said you tried a different cord already, so look at the switch.

Switches are cheap.
 




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