I'm experiencing an odd issue on the right channel in all quad modes (signal passing through the quad boards). I'm getting distortion on the right channel only at certain frequencies (seems like mostly mid-range). It is more pronounced in the rear than front channel. However, this is only the case with a source connected to external inputs. I do not notice distortion when the source is the tuner, which had me scratching my head. Try as I might with different stations, different kinds of music, I can't hear the distortion with the tuner as the source. This left me wondering about the signal level of the source and if that was having an effect. So, I connected my computer through the headphones jack to AUX input - no distortion! Tried the same with a cassette player with variable output, and again no distortion. I know CD players have much higher output voltage than tape players and the headphone jack of a computer.
Other background info:
1. No distortion is heard when the quad circuit is bypassed (putting speaker selector in 2 channel mode, or using a 4 channel source and the Direct setting on the receiver). So, this narrows down the source of distortion to the quad section.
2. Swapped known good quad boards (F-2087 and F2088) from a QSD-2 I have and distortion from the quad section does not change.
3. Cleaned all connector pins on F-2634 that the quad boards plug into.
4. All pass throughs on the F-2634 were pinned and re-soldered a couple of years ago. Have not had issues until this distortion problem surfaced recently.
5. Some "popping/static bursts" can be heard in all channels in quad mode after initial power on.
6. When I pinned the F-2634 board I also replaced all transistors on F-2087, which was loaded with 2SA726 and 2SC1312; however, as mentioned in #2, swapping quad boards with those from a QSD-2 had no effect on distortion. At that time I also recapped F-2639 (pre-PS board).
7. Driver boards were restored shortly after I got the receiver several years ago.
8. Output transistors replaced with MJ21194G and MJ21193G and PS board (F2638) re-capped last fall, just before I started noticing some static in the rear channels, at which time I removed the 8001 from my main system to have a look at it later. So, it's been sitting idle on a shelf until last week.
8. If I connect the QSD-2 to the 8001 (tape 1 out connected to QSD-2 input, 4 channel output of the QSD-2 connected to tape 2 input) I can use the QSD-2 for all quad modes and set the 8001 to tape 2, 4 channel. I get no distortion for any source using the QSD-2 for quad processing.
My thought is there must be some component on the R channel on F-2634 that is "over-driving" or somehow does not like a higher voltage input, but I can't figure out what it might be. On the 8001 version of 2634 there are no transistors on that board, which would be my first thing to suspect. I've been troubleshooting this for about a week trying different tests/configurations, and pouring over the schematic & SM, but can not come up with answers. Any suggestions would be appreciated.
Other background info:
1. No distortion is heard when the quad circuit is bypassed (putting speaker selector in 2 channel mode, or using a 4 channel source and the Direct setting on the receiver). So, this narrows down the source of distortion to the quad section.
2. Swapped known good quad boards (F-2087 and F2088) from a QSD-2 I have and distortion from the quad section does not change.
3. Cleaned all connector pins on F-2634 that the quad boards plug into.
4. All pass throughs on the F-2634 were pinned and re-soldered a couple of years ago. Have not had issues until this distortion problem surfaced recently.
5. Some "popping/static bursts" can be heard in all channels in quad mode after initial power on.
6. When I pinned the F-2634 board I also replaced all transistors on F-2087, which was loaded with 2SA726 and 2SC1312; however, as mentioned in #2, swapping quad boards with those from a QSD-2 had no effect on distortion. At that time I also recapped F-2639 (pre-PS board).
7. Driver boards were restored shortly after I got the receiver several years ago.
8. Output transistors replaced with MJ21194G and MJ21193G and PS board (F2638) re-capped last fall, just before I started noticing some static in the rear channels, at which time I removed the 8001 from my main system to have a look at it later. So, it's been sitting idle on a shelf until last week.
8. If I connect the QSD-2 to the 8001 (tape 1 out connected to QSD-2 input, 4 channel output of the QSD-2 connected to tape 2 input) I can use the QSD-2 for all quad modes and set the 8001 to tape 2, 4 channel. I get no distortion for any source using the QSD-2 for quad processing.
My thought is there must be some component on the R channel on F-2634 that is "over-driving" or somehow does not like a higher voltage input, but I can't figure out what it might be. On the 8001 version of 2634 there are no transistors on that board, which would be my first thing to suspect. I've been troubleshooting this for about a week trying different tests/configurations, and pouring over the schematic & SM, but can not come up with answers. Any suggestions would be appreciated.
