rotary volume knob crackle

[obsolete?]

I have an older Technics (I think GX910) receiver that I recently added a center channel speaker to - now when I adjust the volume I get crackling through all of the speakers and muted volume - taping the knob just right seems to "equalize" and "un-mute" the volume - it sounds similar to what I would expect a short to sound like. Its unlikely that the knob has suffered mechanical damage from being hit. Anyone know the likely cause? - do the internals of rotary knobs oxidize or something else that requires replacement over years - or could the center channel speaker itself be the problem - it may be a very power hungry speaker for the somewhat limited center channel power output of the receiver?

Thanks for your thoughts.

 

[3db]

I have an older Technics (I think GX910) receiver that I recently added a center channel speaker to - now when I adjust the volume I get crackling through all of the speakers and muted volume - taping the knob just right seems to "equalize" and "un-mute" the volume - it sounds similar to what I would expect a short to sound like. Its unlikely that the knob has suffered mechanical damage from being hit. Anyone know the likely cause? - do the internals of rotary knobs oxidize or something else that requires replacement over years - or could the center channel speaker itself be the problem - it may be a very power hungry speaker for the somewhat limited center channel power output of the receiver?

Thanks for your thoughts.

Does the crackle sound still appear when the center channel is disconnected? If so, I beleive your dealing with oxidized contacts on the volume control.

 

[Midcow2]

Clean the contacts /remove oxidation

You might try and Electrical Cleaner and Lubricating spray, example:

http://www.globalindustrial.com/gcs/prod/30149942/i/productInfo.web?utm_source=google_pr&utm_medium=cpc&utm_campaign=Cleaners/Degreas-google_pr

Good Luck!

MidCow2

 

[TLS Guy]

I have an older Technics (I think GX910) receiver that I recently added a center channel speaker to - now when I adjust the volume I get crackling through all of the speakers and muted volume - taping the knob just right seems to "equalize" and "un-mute" the volume - it sounds similar to what I would expect a short to sound like. Its unlikely that the knob has suffered mechanical damage from being hit. Anyone know the likely cause? - do the internals of rotary knobs oxidize or something else that requires replacement over years - or could the center channel speaker itself be the problem - it may be a very power hungry speaker for the somewhat limited center channel power output of the receiver?

Thanks for your thoughts.

I'm unable to find any details of that receiver. Do you know if the volume control is analog or digital? It sounds as if it may be analog. Analog variable resistors, are prone to dirt causing the problem you describe, however eventually the control wears down. If that is the case, it has to be replaced. If it is analog it will not be possible as those type of controls are no longer manufactured. If it is a digital control you still may be in trouble, as these have a high rate of obsolescence.

I can't find anyone who has a schematic for that receiver. How old is it?

 

[obsolete?]

model is the SA-GX910, I believe manufactured in 91 & 92; it was Technics top of the line surround receiver at the time.

Thanks for the suggestions; I'll muck around with it a little after work today - wow - the analog control is no longer manufactured!?

 

[TLS Guy]

model is the SA-GX910, I believe manufactured in 91 & 92; it was Technics top of the line surround receiver at the time.

Thanks for the suggestions; I'll muck around with it a little after work today - wow - the analog control is no longer manufactured!?

Controls have become a huge problem restoring and repairing older gear.

I suspect your receiver at that date is a prologic receiver and not Dolby Digital, so it is really a two channel receiver with the other channels synthesized. It is not won't putting any money into.

Analog controls, single channel, are readily available. Ganged two and up are now mostly special order with minimums of 1500 units. There are some small ganged potentiometers available, but you never seem to get what you want off the shelf.

That unit is of a date, where the control is likely mounted and soldered to the board. Older units used point to point wiring for the control which gives you a chance. The problem with the direct mounted control, is that not only do you have to have a control of the same value, but it has to have the same physical dimensions. This makes it impossible, unless you are prepared to move the control slightly and drill a new mounting hole.

I have built up a reasonable stash of older analog controls. I have also made some by carefully combining some single controls.

If you can post a photograph of the inside of the unit showing the control, I can be more certain of your options.

 

[obsolete?]

seems to be there even when the center channel disconnected, but is exasberated by the center channel - but it doesn't seem to just be more audible b/c of the center channel, the problem seems overall worse when the center channel is hooked up. The puzzle is that it has never been an issue before hooking this into the tv and introducing the centre channel - my new LCD is getting more expensive by the month !

your right, it is pro-logic; I suspect I'll use the receiver for a second system in a different room - and muck with the knob when I find a replacement receiver The problem seems only at the first quarter of travel - which is where the knob has gotten the most use over the years - its too bad because otherwise I have no reason to shell out for a new receiver - but maybe I just don't know what I'm missing!

 

[TLS Guy]

seems to be there even when the center channel disconnected, but is exasberated by the center channel - but it doesn't seem to just be more audible b/c of the center channel, the problem seems overall worse when the center channel is hooked up. The puzzle is that it has never been an issue before hooking this into the tv and introducing the centre channel - my new LCD is getting more expensive by the month !

your right, it is pro-logic; I suspect I'll use the receiver for a second system in a different room - and muck with the knob when I find a replacement receiver The problem seems only at the first quarter of travel - which is where the knob has gotten the most use over the years - its too bad because otherwise I have no reason to shell out for a new receiver - but maybe I just don't know what I'm missing!

I suspect there is a fader for every channel. The center channel has not been used before, but I suspect that wore down more than the others for some reason. You are certainly not going to find one of those controls anymore.

Really using prologic for movies is pretty "old hat". It is time for you to move on and help stimulate the economy.

 

[scooterp7]

I'm not sure if this would help your vintage of receiver or not. but I got the following advice from the now deceased Steve Zipster of Sunshine Stereo Re: my Yamaha CR-2040. he advised me to go to RadioShack, buy a can of tuner cleaner. He then told me to take off the top and spray the living **** out of the volume, balance and tuner controls. After I was done, it worked like new. of course, this would depend on whether or not your receiver is analog or digital. a search of Google groups of "CR 2040" would yield the correspondence.

Ahh hell,here it is:
http://tinyurl.com/ag8hw5

 

[yettitheman]

I'm not sure if this would help your vintage of receiver or not. but I got the following advice from the now deceased Steve Zipster of Sunshine Stereo Re: my Yamaha CR-2040. he advised me to go to RadioShack, buy a can of tuner cleaner. He then told me to take off the top and spray the living **** out of the volume, balance and tuner controls. After I was done, it worked like new. of course, this would depend on whether or not your receiver is analog or digital. a search of Google groups of "CR 2040" would yield the correspondence.

Ahh hell,here it is:
http://tinyurl.com/ag8hw5

Gotta be careful with it though. I've used that stuff for a long time, with no ill effect, BUT, you still need to make sure you spray it where it counts!
Simply spraying on top of the pot will not get it! It's possible to waste an entire can and not hit the wipers if you don't know what you are doing!

Like in my DSP-A1000, the pre-amp volume is motor driven as well as potentiometer controlled. Cleaning it requires removing a bent metal guard that sucks to remove, and sucks even more putting it back on. You really have to make sure you don't bend it as it will make the input shaft wobble and bind.

Really obscure pots, you might even have to drill two holes in the cover of the wiper assembly to get the cleaner in. You really risk damaging it with that method. Fortunately, I have not ran into this problem very much. It's been a long time since I've done a "closed" pot, and I can't remember or tell you what I found it in.