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All static in left channel

Johnnm,
I can get the photos later today. I'm not home right now.
Now that I've played with this a little more I'd like to update the sypmtoms. The static is 100% now. I have not been able to get sound by playing with the volume. It did work for maybe a minute or so last night (prior to the deoxit treatment), but as I played it the left channel faded to static and I've not been able to get a clear signal since.

Looked at both links above. Not sure where those points are where he is measuring voltage. I'm assuming those measurements are while it is on (as dumb as that sounds)?

I've printed off the diode/transistor article and when I get home I'll see if my meter has a diode setting.

Frankly this all seems a bit over my head. Any one know of a tech near Columbus OH or Fredericktown, OH? I live in St. Louis but do business with a company in OH and have access to "free" shipping on a delivery truck.
 
johnnm said:
avionic: Why would they only glue one side? I feel like I've seen select components glued before (and not necessarily the largest ones).
Click to expand...

The boards could have been assembled by different people, one of whom went a little nutty with the glue. If it is glue, I bet the other board has some under the caps.
 
Still don't understand the glue. These caps have a clamp around them that mounts to a metal part of the chassis. Where are they going to go?
 
Back home now.

Previous owner confirms this is glue as many have stated.

Also tried the headphones and they are the doing the same. Static in the left.

Turned down the volume and cycled the A speaker switch about 20x’s. Then turned to low volume and the static dropped from 100% to about 90%. I could actually hear some faint music through the static. So that did something.

Took the bottom of the amp off and see 3 clear relays. 2 are together and 1 is alone. My guess is the 2 are for the speakers. Don’t know Afrom B though. Also not sure how to remove the covers. Both also have some sort of white tape wrapped around them.

My guess is clean the contacts on the relays. I’m going to need instruction on removing the clear covers and what about this tape? Is it OK to remove it?

I'll get the other photos requested in a few minutes.
 
The capacitors appear to all have the same markings. B 15,000 uF A Blank C Blank
Can't see the 4th label because it is turned such that I can't see the writing.

See photos of speaker relays. There is a white tape around them. Can these be cleaned? Can the tape be removed? If so how hard it this to do.

Is it similar to the "paper" cleaning process that was described in the deoxit article for cleaning the relays? Or 2000 grit sand paper?

Johnnm
best shots I could get of the amp boards. only shot 1 side, can't get focus past the front edge on the back. What is it you want to see and maybe I can check it out?
 

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Adhesive is used in the assembly process to stabilize the larger(heavier) components so they stay in place while the printed circuit board passes over a wave solder fountain.This wave soldering, solders the majority of the components all at once.Very common manufacturing process. Depending on the enviorment,age,heat the glue darkens and hardens.Unfortunately the glue also tends to trap moisture,which reacts with the glue and excelerates corrosion in the local area of the glue.
 
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Is that masking tape? If it's tape and not some sort of thermal insulator, I'd remove it. It's not holding the physical relay closed, is it?
Do you hear the relay engage when you turn the amp on? When you first turn it on there should be no sound coming out until you hear a "click!" from the relay engaging.
 
Both relays click (A and B seperate of course). The relay on the right is the problem, I can see the wires from the speaker outputs back to the relay.

The tape looks like its from the factory. There are little rectangular objects on the side of the clear plastic housing. There is no way the tape could have been put on after the relays were installed.

Not sure what the little grey rectangular object are. They do not have any wires coming out of them, they are on both sides of both relays. Between the 2 relays they touch with the exception of the tape between them. I removed the tape on the right relay and it was VERY tight between these grey objects. Got it out but can't get the covers off. I've tried flexing the plastic to allow it to get over the tabs, but no luck. I don't want to pull too hard since it is mounted to the PCB. I'll try some more. They look like they could have some writing on the face of them, but can't get in there to see.

By the way it is not masking tape nor white electrical tape. It was very strong though and had to cut it with a razor knife.
 
You may or may not be able to remove those relay covers. Good luck, but if you feel like you're going to break it, then let it be. I'll do some more thinking and write up some easy detailed instructions you can follow tomorrow.
 
Got the relay cover off. By the way the gray rectangles on the sides of the covers are rare earth magnets. Not sure what they do. Slipped thin strips of paper between the contact about 10 times each side. Applied light pressure to the contact and pulled the paper out. No residue or grabbing, the paper moved smoothly. Seemed clean.

Then I powered back up. Still static. So I lifted the case with the rack handles to make sure nothing was touch the relay and suddenly with the slightest twist of the chassis there was clear sound. So I flexed the chassis a little and I could make the static appear and disappear at will.

So while running and lowest possible volume I started gently pushing on major components to see if a bad solder joint was the cause. Nothing on top, but on the bottom when I pushed on the main PCB it was there and gone with each push /flex. So what does that mean, broken solder joint?

Any one know how to get a look at the back side of this board or does that get into de soldering? If that's what I should be doing.

Could not seem to isolate it to one component. Seemed like the slightest pressure anywhere in the center of the board cause the static to come and go.
 
avionic said:
Adhesive is used in the assembly process to stabilize the larger(heavier) components so they stay in place while the printed circuit board passes over a wave solder fountain.This wave soldering, solders the majority of the components all at once.Very common manufacturing process. Depending on the enviorment,age,heat the glue darkens and hardens.Unfortunately the glue also tends to trap moisture,which reacts with the glue and excelerates corrosion in the local area of the glue.
Click to expand...

I've heard that some of it has a nasty habit of turning conductive enough to cause problems, too.
 
Sam Cogley said:
I've heard that some of it has a nasty habit of turning conductive enough to cause problems, too.
Click to expand...

Anything is possible I guess.I have found mostly bad green corrosion on resistor leads almost completely corroded away.
 
There is a transistor that I will try soldering tonight. It doesn't look like the solder is fractured, but it is hard to get me head into the space close enough to see the joints closely. I is one that if the bottom of the amp got slammed could have taken a blow and fractured the joint? It's worth a try. After that I'm lost. Really I'm lost already, with the exception that I don't think it is a relay anymore.
If I'm doing something stupid, please someone tell me!
I'm going to get a bite to eat and try the solder tonight.
 
Sorry I sound like I'm confused, but seems that anywhere you push on the center of the main circuit board causes change in the static. I really don't have a clue.
A and B have their own relay and both have the problem so I don't think it is the relay itself. Could there be a fracture on the circuit board itself?
 
avionic said:
Anything is possible I guess.I have found mostly bad green corrosion on resistor leads almost completely corroded away.
Click to expand...

I mostly see that with leaked electrolyte. One place I've seen that was a series of early 90s Mitsubishi-built automotive engine computers that were notorious for having the caps dump their electrolyte and corrode away the circuit traces underneath.
 
Nikkoholic said:
Sorry I sound like I'm confused, but seems that anywhere you push on the center of the main circuit board causes change in the static. I really don't have a clue.
A and B have their own relay and both have the problem so I don't think it is the relay itself. Could there be a fracture on the circuit board itself?
Click to expand...

Look around for broken ground connections especially around RCA jacks.
 
You likely should R&R the speaker relay. It is likely a part of your problem.

I hate that design anyway; it it totally needless.

The rest of your problem stems from corporate greed and the need to save money; solder costs money, and your "wave-soldered" gem was likely run through on a thin feed, and needs to have solder applied lovingly by you or your field technician to put there what should-a been there in the first place.

Welcome to economics 101! :thmbsp:
 
Nikko Alpha 450 - static

Hi guys - I am the member who sold this amp to Nikkoholic. I have been talking to him and I hope my 2 cents worth may help diagnose the problem.

Firstly, let me say that the caps looked fine to me - noticed nothing leaking. The board seems clean as a whistle. The substance seen is only glue as most of you know is used to secure the caps.

With regards to the static - while I had the amp, I did experience static in one channel (I mentioned this before selling). I took the cover off, sprayed the rear gain controls and voila - sound was crystal clear again. I did not have a problem afterwards. Also, the problem first appeared after I adjusted the gain controls (which had not been moved in quite a while)

Now I could have gotten lucky - perhaps just turning off the power caused the speaker relays to just engage in a different position.

This 50 lb amp was shipped a long distance - Newfoundland, Canada to St. Louis.

T
 
Forgot to mention - the fact that the static went away when the volume was increased, usually indicates a dirty volume control???

Also, listening through headphones makes no difference. Does the signal to the headphones go through the speaker relays??
 
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