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Post by silencer006 on Mar 13, 2016 10:24:08 GMT -5
Hi guys. I have a Laney LC 50w tube amp that has been working fine except for the spring reverb. It hasn't worked since I've owned it and the previous owner didn't know what was wrong with it. Last week I cleaned my pots with some Deoxit and I had a wild idea that maybe the issue with the reverb was the audio cables (the little tank is connected to the board via black and red audio cables). So I found some cables this week. And last night decided to change them. Though, it's been about a week since I actually turned the amp on, I don't expect that anything was wrong with it prior to last night. So, I took it apart and changed the cables. I am not sure, but maybe the new cable's connection seemed a *little bit* smaller, but ... they still fit. I put everything back together and tried it out. No sound. Just a hum-like buzz. Maybe I plugged the audio cables in the reverb tank up wrong (the ones on the board are color coded, and had the red go to the red plugin, black to white. On the reverb tank, it was just white-white, although they say IN and OUT. Anyway. I take the amp apart again and decide to plug the old audio cable up thinking I did something wrong. And now when I turn it on, there's still no sound! I am absolutely certain I plugged the cables in correctly on the board, I wasn't so sure on the tank again (being paranoid) so I switched them out. No difference. There is an audible change in sound if I turn the gain channel on where you can kinda hear the hum better, and then I turn the reverb knob up all the way...the hum gets a little bit louder. Turn it down, the hum dissapears.
Save for wondering what's wrong with it, I also would like to know if by changing audio cables (if they weren't the "correct" ones) could I have screwed the amp up somehow? Also, can I disconnect the reverb tank and take the audio cables out and turn the amp on to see if it work, without anything happening to the amp?
I have checked the tubes to the best of my knowledge, and they are all glowing like they should. The speaker cable seems to be attached good. I don't *think* there's any metal pieces laying about shorting something out. I have also jumped the fx loop; No change. I do have a cheap multi meter if I need to check something, but I'm not really sure how to use it on an amp.
Thanks for any info. Sorry for the long post, just trying to get as much info in as I can.
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Post by sumgai on Mar 13, 2016 17:48:46 GMT -5
agent 006,
First, no reverb tank means no harm to the amp itself, so don't worry on that score.
Second, wiggle the tubes in their respective sockets. By that I mean, pull a tube out just a tiny bit, tip it to one side a few degrees, then to the opposite side a few degrees, then to one of the sides between your first two, then the remaining side. Now go around in a circle once or twice, in that tipped condition, and plug the tube fully back into the socket. Do this for all of the tubes, and see what happens. Sometimes a tube will be seated such that it lights up, but one of the elements' pin might have built up a bit of crud (oxidation), and moving the tube in and out of the socket will usually break apart that crud.
Third, pull the jumper from the Effects loop, it shouldn't be necessary. However, keep the jumper nearby, we may need it yet.
Fourth, if there are any footswitches plugged in, unplug them and test. Now, plug in the footswitch(s), and retest, in both/all states (on/off for each switch). For both footswitch and Effects loop jacks, the same thing happens as what I said for the tube sockets - crud builds up, and the friction of motion pretty much cleans them up.
Fifth, and sadly, the most important, if the above hints don't help: Deoxit is a connection cleaner, not a control cleaner. The chemicals found therein actually contain a lubricant, and such compounds can, and sometimes do, cause a bridge to form between electrical points, what we call a short (or a shunt, for you Britishers). This short is exactly what we don't want, we only wanted the crud to disappear. That can be done without any lubrication, so the next time you look for a contact cleaner, make sure the label does not say "contains lubricant" or anything similar.
I can't be sure this the problem in your case of course, but the next thing I'd do is to find a good source of high pressure air (60-70psi), and blow out the innards of every control - you want them good and dry inside. In fact, I'd do this anyways, regardless if the amp is working properly or not, just to get rid of any possibility of future problems. Then use a proper contact cleaner.
Report back with your results.
HTH
sumgai
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Post by silencer006 on Mar 13, 2016 18:09:58 GMT -5
Thanks sumgai!
I will try the helpful tips you provided, but before I do i just wanted to reply with two things:
First, I didn't know that about the deoxit. I did pretty extensive research before I bought it (for scratchy pots) and ended up reading many testimonials of people using it, many also said you *wanted* one with lubricant because the other one (without lube) could freeze up the controls. After using deoxit, I used the amp for about a week or so without issue. Could things have affected the pots this late after the fact? I'm not questioning your answer like so, I'm just trying to understand better.
Second, since you say that unplugging the reverb tank wouldn't affect that amp, could I assume (and thus calm down) that I didn't damage the, say output transformer or something else, by using *wrong* audio cables when I tested the other pair I had?
Much appreciated. I'll post more later as I get to trying your tips!
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Post by sumgai on Mar 14, 2016 17:37:14 GMT -5
agent 006,
Again, you haven't caused any damage to the amp... at least, not from what you've described so far.
As to Deoxit, and others saying that lubrication is good, I have to stand back and say "I'm happy with my 55 years of experience in servicing all manner of electrical and electronic equipment". While lubricants may make a control feel good to operate, just remember, anything that does lubricate also attracts cruft, such as dirt, cat hair, dryer lint, you name it, whatever can float in the air and be "caught" by some kind of high-surface-tension coating (such as nearly all lubricants), then it'll get caught by the lubricant, and therefore it will get into your controls, and ruin your day.
Trust me, better to have the control be two percent harder to operate and it wears out naturally, than to have it super-easy to operate and find it all worn out prematurely.
HTH
sumgai
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Post by silencer006 on Mar 15, 2016 20:07:04 GMT -5
Hi sumgai, and thanks for the replies again.
I have performed the actions you've suggested; wiggled the tubes a bit and checked the inputs. Sadly, no change.
The only difference I noticed is that when I plug the footswitch into it's slot there's a bit of a pop from the speaker, which I believe wasn't there before. I don't know if that matters or not. The reverb control is the only thing that seems to bring out any sound of the amp still, that hum, the more it's turned up.
I forgot to mention I checked the fuse the other day and it's good, if that matters.
The only can of air I have doesn't have any psi listed. Would that be ok to try?
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swingarm
Apprentice Shielder
Posts: 40
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Post by swingarm on Jan 29, 2017 21:09:33 GMT -5
You did'nt just break up with your girlfriend did you? These creatures have been known to spray lacquer on your input jacks when they are angry check this out and remember to keep in mind you can use computer speakers. LOL this thread is old, did'nt notice
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Post by sumgai on Jan 31, 2017 0:27:54 GMT -5
LOL this thread is old, did'nt notice Well, that makes two of us that missed it. I really dropped the ball on this one, hard.
silencer006, if you're still out there, let us know, and I'll pick up the ball again with you.
sumgai
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swingarm
Apprentice Shielder
Posts: 40
Likes: 0
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Post by swingarm on Jan 31, 2017 1:04:27 GMT -5
Sumgai, you were timely, it was me that messed up however i guess this area does not get much use. I started looking at the rest of the threads and they are mostly all quite old.
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Post by sumgai on Jan 31, 2017 14:01:11 GMT -5
swinger,
Well, yes, not very many players come here for answers/advice/etc. about amps. Lots of other sites on the WWW can do that as well, or better. I think the greater number of threads here are started by those who are already members, and trust us to issue reasonable advice without getting too technical, or otherwise making a person feel uncomfortable.
About the only thing we harp on, as a group of Nutz, is safety, an idea which it looks like you're also on board with. If someone is turned off by the safety aspect of amp repair, then I'm not particularly fond of trying to keep them in the fold, so to speak. I'll bet you understand, amiright?
sumgai
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