A Peek Under The Kilt
- Thread starter LBPete
- Start date
Now, here's the question of the day. How do you clean this type of pot? I don't see any way to get the de-oxit nozzle into the four gangs on this thing. It looks like if it were unsoldered and removed from the circuit board, it could be disassembled, but that seems pretty risky. Any suggestions?
- Pete
- Pete
It is an Alps pot and it is clearly high grade. One of the issues I'm having with this unit is that there is low sound from both speakers with the volume turned all the way down. The volume control pot seems like a good place to start.
The unit had a thick layer of house hold type dust on all the exposed horizontal surfaces. There is no evidence of nicotine contamination or any kind of garage, workshop or greasy kitchen dirt. The construction of this pot should have keept it pretty clean, but the rest of the switches are showing intermittant and scratchy operation.
- Pete
The unit had a thick layer of house hold type dust on all the exposed horizontal surfaces. There is no evidence of nicotine contamination or any kind of garage, workshop or greasy kitchen dirt. The construction of this pot should have keept it pretty clean, but the rest of the switches are showing intermittant and scratchy operation.
- Pete
BeatleFred
Super Member
Well, hopefully the one thats on Ebay now is working problem-free, its bidding for some good money:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=50596&item=5700033090&rd=1
B/F
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=50596&item=5700033090&rd=1
B/F
Originally posted by THOR
"low sound from both speakers with the volume turned all the way down"
Umm geez sounds like the volume is working fine to me
Thor, You got me thinking,
So I tested some other receivers and here's what turned up:
The 8080 I use as a benchmark has zero audio output when the volume control is turned all the way down.
The 9090DB I'm using as a daily driver has low audio from the left channel when the volume is turned all the way down.
My sweet little Pioneer SX-780 has low audio from both channels when the volume is turned all the way down. This low volume is not affected by turning the balance control one way or the other.
A little Lafayette LR100 has low audio from both channels, and a POS digital control JVC RX505V doesn't realy go close to zero audio on either channel with the volume turned all the way down.
So maybe it's normal to have some output with the volume down. It also may be the 8080 is exceptional.
Anyone care to check what ever they are listening to and report the findings?
- Pete
CDFixer
Number 1 USC Trojan Fan
It has been my experiance that the volume pot normally is connected with the input on one end, ground on the other and the output on the wiper. If you have sound when the control is turned all the way down it indicates that the control is not going all the way to ground, or the ground connection to the pot has some resistance.
Pete, I had a 9090DB that had that problem and was corrected by replacing the volume control with another. When tested the control would not go to a full short on one channel when turned all the way down.
Pete, I had a 9090DB that had that problem and was corrected by replacing the volume control with another. When tested the control would not go to a full short on one channel when turned all the way down.
CD, welcome back, long time no post. The 9090DB volume control that you changed out, was it damaged or was it just poorly made? I agree with DanTana. Its reasonable to expect the volume to go to zero but from this small sample of receivers, there are just a few that truly do go to zero.
Anyone else care to check their equipment?
By the way DanTana, did the pictures make you wet your self in a good way, like an puppy glad to be home or in a bad way like that first drop on a roller coaster? I hope to have it all back together this weekend and hopefully I won't wet myself if I find a few "extra" parts.
- Pete
Anyone else care to check their equipment?
By the way DanTana, did the pictures make you wet your self in a good way, like an puppy glad to be home or in a bad way like that first drop on a roller coaster? I hope to have it all back together this weekend and hopefully I won't wet myself if I find a few "extra" parts.
- Pete
Still Distorted
I’m ready to throw in the towel. The G-20000 still has distorted output from the right channel.
Last weekend I finished cleaning the switches and pots and reassembling the pre-amp/tuner unit. Over the course of the previous week, I gave the controls four cleaning cycles, two with DeOxit-5 and two with Pro-Gold. The chassis went back together without any drama. I was a little concerned about restringing the dial cord but it was pretty straight forward. The service manual has a clear and detailed diagram for the dial cord. (I just wish the schematics were that clear).
With great optimism I hooked everything up and turned it on. The left channel sounded great but the right channel was severely distorted. Worked all the switches to no avail. The distortion was very consistent. All of the previous erratic operation was gone and there was no scratchiness from any of the switches or pots. But the right channel was consistently distorted. I switched the leads that connect the audio output from the pre-amp/tuner to the Amp to see if the problem was in the pre-amp/tuner or the amp unit. When switched, the distortion remained in the speaker connected to the right channel. Damn.
That was last Sunday. This week, I tore back into the amp. The power supply boards, which have the output relays, also have three of the infamous fuse resistors. All three fuse resistors on the right side power supply board were over spec. One by a magnitude of 5. Could it be this simple? I replaced all of them on both power supply boards.
I also wanted to check the output relays again. It is interesting how the output relays are wired, each power supply board has two, DPST relays. One for the “Speaker A” output and one for the “Speaker B” output. The two poles of each relay are connected in series so the output signal is routed through both sets of contacts. I carefully checked the continuity of the signal though it’s entire path including all the solder joints for the relay. Clean as a whistle. Hooked everything back up and have the same distortion in the right channel.
That’s where it stands now. Left channel blasting the blues courtesy the Long Beach Jazz station, KKJZ and the right channel sucking wind.
If I can’t come up with anything else, I’m ready to pack it up and seek professional help. Northridge Electronics is about an hour’s drive to the north or Mike Zuccaro is about an hour and a half drive to the south.
- Pete
I’m ready to throw in the towel. The G-20000 still has distorted output from the right channel.
Last weekend I finished cleaning the switches and pots and reassembling the pre-amp/tuner unit. Over the course of the previous week, I gave the controls four cleaning cycles, two with DeOxit-5 and two with Pro-Gold. The chassis went back together without any drama. I was a little concerned about restringing the dial cord but it was pretty straight forward. The service manual has a clear and detailed diagram for the dial cord. (I just wish the schematics were that clear).
With great optimism I hooked everything up and turned it on. The left channel sounded great but the right channel was severely distorted. Worked all the switches to no avail. The distortion was very consistent. All of the previous erratic operation was gone and there was no scratchiness from any of the switches or pots. But the right channel was consistently distorted. I switched the leads that connect the audio output from the pre-amp/tuner to the Amp to see if the problem was in the pre-amp/tuner or the amp unit. When switched, the distortion remained in the speaker connected to the right channel. Damn.
That was last Sunday. This week, I tore back into the amp. The power supply boards, which have the output relays, also have three of the infamous fuse resistors. All three fuse resistors on the right side power supply board were over spec. One by a magnitude of 5. Could it be this simple? I replaced all of them on both power supply boards.
I also wanted to check the output relays again. It is interesting how the output relays are wired, each power supply board has two, DPST relays. One for the “Speaker A” output and one for the “Speaker B” output. The two poles of each relay are connected in series so the output signal is routed through both sets of contacts. I carefully checked the continuity of the signal though it’s entire path including all the solder joints for the relay. Clean as a whistle. Hooked everything back up and have the same distortion in the right channel.
That’s where it stands now. Left channel blasting the blues courtesy the Long Beach Jazz station, KKJZ and the right channel sucking wind.
If I can’t come up with anything else, I’m ready to pack it up and seek professional help. Northridge Electronics is about an hour’s drive to the north or Mike Zuccaro is about an hour and a half drive to the south.
- Pete
DanTana,
You got me thinking. I hadn't checked it since before I took the pre-amp/tuner apart. Originally it had almost half a volt on the right side but with a little help from EchoWars it adjusted down to next to nothing.
So I checked it again tonight. The left channel is 0.010v and the right channel is now 0.000 and doesn't change much if the trimmer is bumped one way or the other. Looks pretty fishy.
- Pete
You got me thinking. I hadn't checked it since before I took the pre-amp/tuner apart. Originally it had almost half a volt on the right side but with a little help from EchoWars it adjusted down to next to nothing.
So I checked it again tonight. The left channel is 0.010v and the right channel is now 0.000 and doesn't change much if the trimmer is bumped one way or the other. Looks pretty fishy.
- Pete
Hi Jim,
That’s a very generous offer. I don’t know if you realize what you are getting into. This thing is a monster. With its guts splayed out, it is consuming just about every horizontal surface in my garage. It’s not something that can be easily moved. I’ve sent you scans of the amp schematic. Please take a look at them first. I’m still hoping for something easy that I’m overlooking.
- Pete
That’s a very generous offer. I don’t know if you realize what you are getting into. This thing is a monster. With its guts splayed out, it is consuming just about every horizontal surface in my garage. It’s not something that can be easily moved. I’ve sent you scans of the amp schematic. Please take a look at them first. I’m still hoping for something easy that I’m overlooking.
- Pete
This weeks update
The distortion is fixed. After some careful inspection and some valuable advice from CDFixer and Echo Wars, the problem was isolated to an open diode on the right side driver board. The details are in a couple of threads in the DIY forum. After getting a couple of other minor problems sorted out I had a chance today to crank it up. Music, sweet music, at volumes high enough to twice make my wife come out to the garage to complain. Life is good!
Thanks to everyone that pitched in.
- Pete
The distortion is fixed. After some careful inspection and some valuable advice from CDFixer and Echo Wars, the problem was isolated to an open diode on the right side driver board. The details are in a couple of threads in the DIY forum. After getting a couple of other minor problems sorted out I had a chance today to crank it up. Music, sweet music, at volumes high enough to twice make my wife come out to the garage to complain. Life is good!
Thanks to everyone that pitched in.
- Pete
