subwoofer problems

But it did work fine for 3 years, now it does it, that is why i thought it was maybe in the receiver...

Allo Indianjjy

Several questions first....

1} Assuming you have the power-plugs hooked into a 'multi-way' power strip, have you plugged any new equipment into the same power strip???

2} Have you recently changed the physical position/location of any of the speakers/receiver???

The usual source of speaker 'hums', is an 'Ground' or 'Earth' loop. (The jargon varies from country to country ) Having a 'Ground/Earth on the same circuit or a different circuit can cause it, along with having a broken Ground/Earth loop. It's a tricky problem as it varies from system to system.

As an example, with my home stereo system, the CD player-amplifier-radio work fine on the same power strip, but the record deck causes it to hum if it's in the same strip. If I connect an earth/ground lead from the deck to the amplifier, the hum goes away!!! If I connect the record deck to a different power socket and disconnect the earth/ground lead, it doesn't hum!!! I got splinters in my fingertips from scratching my head over that

Check that ALL the various leads and connections are firmly pushed in, and check the the cables aren't trapped under anything. Having a trapped cable can cause the internal wires to short out or break. It's remote, but possible and known to have happened.

I have installed a new ATT U verse box for my TV on the same circuit. the receiver and U verse box are in a power strip, the subwoofer is 25 feet away plugged into the wall but is probably the same circuit. Right now I have 2 cheap rca cables going to the subwoofer but I have purchased a 30 ft. monster cable and I will try that. I will also try replugging the receiver as well as the U Verse box at different locations. Does that sound like a good idea? Thank all for the info, I am just a 58 year old burnt out hippie that is getting ready to retire but I do really love my 5.1 system, My subwoofer is a JBL and I figure that JBL has always been quality in my opinion. Would a 12 volt converter plugged into the wall next to the subwoofer have anything to do with it?

It certainly can't harm to try the receiver and 'u verse' plugs in different locations. Did the humming start when you plugged in the new box???

Yep, JBL do make good speakers, especially in guitar amps. They give a lovely rich, warm sound

It's strange how us old hippies love our sound-systems

I just made a custom gutar amp, 3 12ax7 preamp tubes, 2 el84 power tubes,15 watts with a Eminence 12 inch 150 watt Swamp Thang speaker.IMHO Eminence is the king of guitar amp speakers, Celestions have no bottom end. But to get back to my sub problem, I even had the hum when I tried another subwoofer. I will try this out in the morning and get back with you. As info I have a 335 epiphone and practice mostly blues now. I am not very good but it keeps me out of the bars.

indianjjy wrote:

I just made a custom gutar amp, 3 12ax7 preamp tubes, 2 el84 power tubes,15 watts with a Eminence 12 inch 150 watt Swamp Thang speaker.IMHO Eminence is the king of guitar amp speakers, Celestions have no bottom end. But to get back to my sub problem, I even had the hum when I tried another subwoofer. I will try this out in the morning and get back with you. As info I have a 335 epiphone and practice mostly blues now. I am not very good but it keeps me out of the bars.

I'm not sure that (in red) is a good thing. Some of lifes fondest memories can be traced back to one bar or another.

But about the hum,,,,, that's usually a grounding problem. It may be in the cables themselves or in the jacks on the speakers or PC.

I have a JBL Sub Woofer that I paid over $100 for several years back. Almost since day one it's had a bad input jack. I took it apart and found a cracked solder joint where the input jack fastens to the little circuit board.

I suspect that somewhere in the mix, you're loosing ground.

That homemade amp sounds like a real buttkicker.

Good Luck,
The Doctor

To all, I just bought a well abused guitar amp,70's solid state but it is a MOSFET style. Is there any special instructions on cleaning this curcuit board ? It is very dusty and dirty,pots are very scratchy, but it does perform well. As info it is a RANDALL RG90A commander 2. Any help on this matter is greatly appreciated. Everyone on here has helped me alot. I must have lost alittle too much grey matter in the 60's. Thanx

For the circuitry, a stiffish brush and a can of compressed air should clean most of that dust out. I seem to remember that MOSFET transistors were particularly susceptible to static electric zapping them, so take care when handling the component side of the circuitry. It might be one of the few instances where I'd recommend wearing an 'Earth/Grounding strap' round you wrist.

Unfortunately, there isn't a great deal that can be done for scratchy pots, apart from replacing them. For a short-term cure, a quick squit of 'WD40' works wonders for getting rid of scratchiness, but it doesn't last long.

If you have a component store nearby (or can order them online), they're not too difficult to replace, just make a quick diagram of which wire to what terminal. The hardest part of the job will likely be actually getting them off the mounting panel .

Some amps were a joy to work inside, everything was easily accessible, others were pigs, seeming to need every last nut & bolt removing to do anything.

I'm not familiar with 'Randall' amps, but from your description and the fact it's working good, it'll be worth spending the few $$$'s in getting it up to scratch.


Edit: I've locked this thread sd the question is duplicated in this sub-forum - WereBo