Dave Posted October 30, 2008 Share Posted October 30, 2008 Sorry this is a duplicate post, but I just realised my question might fit better in this area of the forum (and the more help I can get the better): Hi everyone. Before you ask I did attempt a search on this topic and didn't find anything directly relevant to my query. Basically I have a couple of old Marshall bass amps with scratchy/crackly (actual words?) pots and I want to get this sorted. After searching this site I did find out about a product called Servisol, and someone else mentioned getting some Maplin Switch Cleaner to spray on the pots, but I'd still like a little more info. If I purchase one of these products do I simply spray them on the outside of the volume/EQ knobs (should I try to remove the plastic knobs first before using) or do I actually need to do something internally to get rid of the problem? I also read how the dust/dirt can build up from lack of use (I have a feeling these amps were stored unused for long periods of time), and some people have simply twisted the knobs frequently to get rid of the crackling sound. Does this really work? I'd be happy to remove the knobs if this would allow better access and lead to improved results, though I'm not sure if I should simply try to pull them off or not (I'm somewhat worried about damaging them)? Any suggestions as to how I can make my playing/adjusting less crackle-y would be (as ever) GREATLY appreciated! If you think I need to seek a professional to sort out this problem, then any recommendations would also be appreciated (I'm based in the Midlands/Birmingham area). Cheers! Quote Link to comment Share on other sites More sharing options...
bremen Posted October 30, 2008 Share Posted October 30, 2008 [quote name='Dave' post='318227' date='Oct 30 2008, 11:00 AM']Sorry this is a duplicate post, but I just realised my question might fit better in this area of the forum (and the more help I can get the better): Hi everyone. Before you ask I did attempt a search on this topic and didn't find anything directly relevant to my query. Basically I have a couple of old Marshall bass amps with scratchy/crackly (actual words?) pots and I want to get this sorted. After searching this site I did find out about a product called Servisol, and someone else mentioned getting some Maplin Switch Cleaner to spray on the pots, but I'd still like a little more info. If I purchase one of these products do I simply spray them on the outside of the volume/EQ knobs (should I try to remove the plastic knobs first before using) or do I actually need to do something internally to get rid of the problem? I also read how the dust/dirt can build up from lack of use (I have a feeling these amps were stored unused for long periods of time), and some people have simply twisted the knobs frequently to get rid of the crackling sound. Does this really work? I'd be happy to remove the knobs if this would allow better access and lead to improved results, though I'm not sure if I should simply try to pull them off or not (I'm somewhat worried about damaging them)? Any suggestions as to how I can make my playing/adjusting less crackle-y would be (as ever) GREATLY appreciated! If you think I need to seek a professional to sort out this problem, then any recommendations would also be appreciated (I'm based in the Midlands/Birmingham area). Cheers![/quote] You'll need to get inside the chassis and at the actual pots. Once you're in there you'll be able to see where the active parts of the pots are. Just squirt a bit of Servisol inside and turn the knobs a couple of times. Yes, sometimes just twiddling the knobs can help. Quote Link to comment Share on other sites More sharing options...
Bilbo Posted October 30, 2008 Share Posted October 30, 2008 Bugger that, mate. Get some WD40 on it. It's always worked for me! Squirt a little tiny bit on the pot on the outside of the amp and then turm it all of the way back and forth several times. The crackle will quickly reduce and then stop in matter of seconds. I would guess that the Maplins stuff is chemically the same but don't know that for a fact. Quote Link to comment Share on other sites More sharing options...
bremen Posted October 30, 2008 Share Posted October 30, 2008 [quote name='bilbo230763' post='318235' date='Oct 30 2008, 11:09 AM']Bugger that, mate. Get some WD40 on it. It's always worked for me! Squirt a little tiny bit on the pot on the outside of the amp and then turm it all of the way back and forth several times. The crackle will quickly reduce and then stop in matter of seconds. I would guess that the Maplins stuff is chemically the same but don't know that for a fact.[/quote] More likely to be isopropyl alcohol. Quote Link to comment Share on other sites More sharing options...
BOD2 Posted October 30, 2008 Share Posted October 30, 2008 The "correct" way (i.e. the method an amp technician would use) to clean the pots would be to open up the amp so that you can see the pots from the inside of the chassis. If it's a Marshall valve amp then the whole chassis slides out of the wooden sleeve once a few bolts are removed. The bottom of the chassis is completely open and you can see all of the components from there. NOTE: Valve amps contain potentially lethal voltages. To avoid any problems disconnect the amp from the mains and leave for 24 hours before opening, and then avoid touching any components while the amp is open. Once you can see the pots locate the open front of the pot (where the 3 connectors are) or often there is a little pressed "notch" in the pot casing that gives access to the insides. Attach the "straw" that comes with the Servisol spray to the tin and direct a couple of short burst into the inside of the pot. Leave the pot for a minute of so then rotate it fully backwards and forwards several times. Reassemble, switch on and test. If it's not a valve amp it will probably still be very similar, with an open-bottom metal chassis. Quote Link to comment Share on other sites More sharing options...
BigBadBassman Posted October 30, 2008 Share Posted October 30, 2008 WD40 is a light oil based water dispersent with a solvent carrier - hence "WD" It does not clean pots properly as it coats everything with a coating of oil which causes dust etc. to collect on the surface you're trying to clean Servisol is the stuff to use and is isopropyl as Bremen suggests Tim Quote Link to comment Share on other sites More sharing options...
Bilbo Posted October 30, 2008 Share Posted October 30, 2008 Well now I know! Quote Link to comment Share on other sites More sharing options...
Dave Posted October 30, 2008 Author Share Posted October 30, 2008 Thanks again Basschatters, as always you are a whirlwind of information! I've done some more internet searching and found quite a wide variety of ideas, but I think BOD2 seems to have supplied exactly what I was looking for (sorry, no prize). One of the Marshalls is a valve amp, and the other is solid state, so I guess I'll have fun playing/dismantling one of each. I wouldn't say I was overly adept with electronics, but am always willing to give it a go (and I don't think I need to worry about voiding the warranties on these) so I guess that's what I'm going to do. I work in a lab so have access to isopropanol, but think I may go for the more expensive can of compressed cleaner as I assume this will work better (will get inside the pots more easily). Looking forward to some crackle-free knob twisting! (I hope). Cheers! Quote Link to comment Share on other sites More sharing options...
BOD2 Posted October 31, 2008 Share Posted October 31, 2008 [quote name='Dave' post='318304' date='Oct 30 2008, 12:40 PM']..... I wouldn't say I was overly adept with electronics, but am always willing to give it a go ...[/quote] There's no electronic knowledge required. You just need to be able to figure out how to get the chassis out and then identify where the pots are (which is easy enough). An aerosol spray with a "drinking straw" attachment is easiest for getting into any awkward to reach areas. While you're in there you should also give any jack sockets and switches a squirt as well - saves having to open it up again and do it later. It also won't do any harm to remove the valves and spray the contacts in the valve bases. If you remove one at a time, spray the base, then put the valve back you can't go far wrong. Note that the valves have a notch or missing pin that must be correctly aligned before it will fit in the valve base so it's not possible to put the valve back in the wrong place. Quote Link to comment Share on other sites More sharing options...
Dave Posted October 31, 2008 Author Share Posted October 31, 2008 Cheers BOD2, I've bought some Servisol Switch Cleaner from fleabay with the straw attachment, so I'll definitely be giving that a go. I had a bit of a play with the solid state Marshall last night and there is NO WAY simply turning the knobs back and forth will be fixing anything (I think they are quite dirty). I have also been playing around with different valve types in the other Marshall, but the pots on that one aren't nearly as bad, so will have a go at cleaning the bad ones and maybe try your valve base cleaning method as well. I guess I just have to be sure everything is completely dry before I switch it on again. If this doesn't work then I assume I may need to sort out some new pots, and I will probably need to find a decent amp repair specialist for that (hopefully not necessary). Thanks for all the advice (everyone), very helpful indeed! Quote Link to comment Share on other sites More sharing options...
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