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Post by angelofdeath on Jan 23, 2007 17:21:58 GMT -5
i just bought an ampeg amp and i believe one of the pots needs to be replaced. its the lead channel volume pot. it only works when i have it turned up to full. so as you can imagine its rather annoying going from a nice volume clean to loud as crap distortion. i guess my question is can you put 500k pots in an amp? or do i need to find specific amplifier pots or something? any help would be greatly appreciated.
chris
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Post by vonFrenchie on Jan 23, 2007 17:35:28 GMT -5
There are no special amplifier pots. Some companies my sell them like they are... but there arent. There are two main types of pots. Rheostats and potentiometers. Rheostats are big... very big. Potentiometers are small in comparison.
the 500k stands for 500 kilo ohms at its maximum. When the pot is turned the other direction (in this case increasing the volume) the resistance decreases until it is eventually around 0 ohms.
First thing you need to do is determine if the pot is actually bad or if its just the wiring.
Second thing you need to do is determine the value of the pot. Easiest way to do this is talk to ampeg or look on their site for info about your amp.
Third thing you need to do is purchase the right type (wattage, value, size, taper). Lots of amps have a notch in the pots so they stop at 50 percent (like SWRs) Im not sure about ampeg but its easy to find out. If you want it like that make sure you buy that specific type of pot.
Then the final step is to wire it up.
If you're unsure about it the easiest thing to do is take it into the local music shop. You may not know but something else might be wrong with your amp aswell. That happened to me a few times.
Good luck with your amp.
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Post by angelofdeath on Jan 23, 2007 17:37:45 GMT -5
ok...thanks for the help. I'm takin it apart here in a little bit to see.
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Post by UnklMickey on Jan 23, 2007 18:09:07 GMT -5
i just bought an ampeg amp and i believe one of the pots needs to be replaced. ... 1 -- if that's a tube amp, be extra careful. Ampeg uses ridiculously high voltages in their amps. 2 -- many Ampeg amps use linear pots for volume control. i think this is silly, so, i personally, would use an audio pot as replacement. however, if it is a 2 channel amp, if you don't replace both volume controls, the new one will be a higher setting when they are both at the same volume. BTW, Chris, Welcome (belatedly) to GuitarNuts2. unk |
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Post by sumgai on Jan 23, 2007 18:53:02 GMT -5
chris, Another Chris, the Moderater kind, will be along in a short while to move this topic over to the correct forum, so don't be surprised to see it land in, where else, Amps.  Even so,  to these here fun-time forums! vF has the gist of it, there are no special pots in your amp. But you have described a scenario where a good cleaning just might be the ticket. Snag up some contact cleaner that is the non-lubricating type - lubricant based cleaners leave trace residue that will attract dust and other gunk, and just crap-out your pots all the more quickly. Radio Shack has both kinds, read the labels carefully. unklmickey also has it right, you really wanna pay attention to what he said. I'll repeat it for you: DANGER! Severly high voltage present! If you don't use caution, you will be using a doctor..... or worse.Even just for de-crappifying the pots, wait a few minutes after turning the amp off and unplugging it before you remove the chassis from the cabinet. And for criminy's sake, use a wooden stick to poke wires out of the way as you insert the plastic pipe into the pot's opening. If you're gonna replace a pot, do you have soldering experience? If not, the stop right there, check your emotions at the door, and step back behind the line. Become fully aware that if you blow a solder joint inside your guitar, all you lose will be the signal. If you blow a solder joint inside your amp, you may cause a great amount environmental damage (smoke, meet house), and a lot of anguished phone conversations with your insurance agent. Bottom line for the inexperienced: which is cheaper, the professional repairman, or your insurance deductible?  One more thing, now that I've raised your Chinese laundry bill, do you have a multimeter, of any flavor? Like John Belushi said in Animal House: "You can't fly with GN2 eagles if you're equipped like a turkey." ;D Or words to that effect!  HTH sumgai |
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Post by angelofdeath on Jan 23, 2007 20:19:31 GMT -5
i have a multimeter somewhere. i took it apart(which was way more difficult than i thought it would be) and looked at the pot in question. it seems to slide completely free till you turn it all the way up. its almost like its not making contact with anything till i turn it up to the max. i didnt realize the pots would be soldered into one giant computer chip thing. i dont feel comfortable soldering that since my experience extends to soldering guitars. so i will most likely take it to someone if that contact spray doesnt work. this isnt a tube amp. its an ampeg SS70C. its fairly old.
p.s.-sorry about posting this in the wrong area, my bad
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Post by ChrisK on Jan 23, 2007 20:51:21 GMT -5
I have the Aspen Pittman Tube Amp book with over 850 schematics on CD.
Tell me the exact amp model and the exact pot (?Rxx) and maybe I can tell you what it should be.
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Post by sumgai on Jan 24, 2007 22:39:30 GMT -5
Chris, Somehow you missed '.... this isn't a tube amp. its an ampeg SS70C.' I have this funny feeling that Aspen wouldn't have included that particular little jewel in his Tube Data Book. ;D Saw one go through the shop here about a year or so ago. Didn't take a copy of the schematic, it was pasted inside the top of the chassis, figured it'll be there if I need it again. ~!~!~!~ Chris (the other Chris!), If you haven't put that meter back together, then forget it and go down to Radidio Slack and get a $30 or $50 meter. Time better spent, and it'll have a warranty.  sumgai |
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Post by UnklMickey on Jan 24, 2007 22:53:08 GMT -5
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Post by sumgai on Jan 25, 2007 5:51:53 GMT -5
unk,
Good find, but it doesn't do capacitance. Seems like a good thing to have around, for those times when you buy an assortment of unmarked caps. ;D
sumgai
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Post by vonFrenchie on Feb 13, 2007 21:24:30 GMT -5
Those DMMs are nice. They have transistor testers built in (my engineering school has a BUNCH of those)
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