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Repurposing a broken Rumble 200

R

RitterSport

Apr 20, 2020
460
431
#1
Continuing from this thread (Adding a cabinet to a Fender Rumble 200), I bought a used, broken Fender Rumble. The seller said it powered on, but the electronics were shot. My hope was that the pre-amp was broken, but I could still use the FX return with the amp to get some extra oomph.

No luck. When I switch it on, the light goes on, but nothing works, not even the fan comes on. So, my next thought is to rewire the speakers to one of the inputs and use it essentially has a Fender 115 cab.

Is that something that seems feasible? I have some soldering skills, but I'm no expert. I'm hoping for some thoughts, advice, and guidance.
 
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#9
RitterSport said:
Looking at the block diagram, it looks like two wires going from the amp to the speakers, so my guess is that there's a passive crossover, and the tweeter on/off switch is also passive.
Click to expand...
The block diagram is very simplified.

The crossover is passive, but iirc it’s located inside the amp chassis. It’s been quite a while since I’ve seen one.
 
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#13
Not on the amp itself unless everything that’s connected to this jack is disconnected. The Rumble’s amp’s output stage can present a short circuit and therefore must be thoroughly isolated from the jack.
 
#14
RitterSport said:
If I can figure out the wiring, can I reuse the external speaker jack? Seems like it should be the right capacity, impedance, etc.
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If the jack socket is on a circuit board then for what you save - a few quid/dollars maybe - it doesn't seem worth the complication and risk. Much better to disconnect or remove all the electrics and start with a clean sheet, then you can be quite confident its safe. For similar reasons I wouldn't bother with the tweeter and just wire the woofer straight to the new jack socket. As its a second cab you'll probably find you get enough tweeter from the main amp.

Looking at photos of R200s I think I'd be inclined to completely remove the old electronics, and seal any apertures into the speaker enclosure. If someone were to "helpfully" plug your good amp into a socket on the broken one bad things could happen, and with road gear it always seems to me the best way to avoid mistakes is to make them impossible.
 
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#16
What JimChjones said above. Remove the amp entirely. You can replace it with a two wooden panels fixed at right angles. It can even be dressed in tolex and screwed in place of the amp. You can make for the volume of the head with a piece of foam or leave it empty. Disconnect the twitter, but leave it in place. Mount a 1/4" female connector to the new panel and connect the leads from the woofer directly to it, observing polarity. If the cab sounds too dull without the twitter, you can make a simple CO and connect the twitter to it. It could be as simple as just 1 capacitor. Alternatively, you may try to locate the original CO and extract it from the amp.
It could be a fun project. If you don't have the tools to cut and drill wood, I'm sure someone can do it for a few bucks.
 
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#18
If there are more than 2 wires going to the cabinet from the amp, the crossover is in the amp. If only 2 wires, than it is in the cab. the crossover MAY be mounted to the jacks on a PCB - that makes things more difficult. Just be aware. ALSO -be sure to check the cab with a multimeter, etc to be sure that something in the cab didn't short out and blow the amp.
 
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#19
This is what I would probably do. I would disconnect the 15 completely from the old electronics. Then I'd run new wires to the 15, connect them to a new jack and run it as extension 15. You will be forfeiting the tweeter but you already have one in your main amp. This should give you roughly 6db more headroom if things are in phase.
 
#20
Hurricane Jimmie said:
So Anyway, unless you're planning on repairing the amp/electronics someday, I'd pull the amp out and just use the Rumble chassis as a speaker cab.
I did the same thing with a Fender Frontman 100, and I have no electrical experience.

Good Luck to you.
Click to expand...
The Rumble is different than the Frontman, that’s why we are discussing the challenge of dealing with the crossover.
 

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