TEAC X-10R R2R right channel noise issue

O. Friend

O. Friend

Member
Hi all, I’m having an issue with my TEAC X-10R. Quick recap: (pun intended)
I was having some noise on the signal output, using a test tape the sine wave would have random jags on it. Not sure what particular transistor might be going bad, I decided to go ahead and recap the REC AND PLAY AMPL ASSEMBLY board. I used Nichicon UKL series for most of the caps, since I had a bunch handy. I also replaced the transistors that I had either exact matches for or known good substitutes. The few that I didn’t have, I just left in place.

I was very meticulous on this one, doing one item at a time, checking the new parts and part being removed on the tester to make sure I had the proper uf and polarity, as well as ECB position as well. I’ve rechecked since and everything looks good. No caps or transistors tested bad, but about 1.2 of the old caps were over 20% off, as would be expected. On each transistor, after I soldered them in I would put the meter on to make sure there were no shorts and that each leg was electrically connected with something on the same trace. No issues there.

After finishing, the unit seemed to work fine, with a clean sine wave now. However, when I started fine tuning the pots for input level, meters, output level, bias etc, I noticed that when I turned the volume up, the right channel would CLICK when it hit a certain level in the music. I’ve attached a video that shows this.

It’s possible I could have just messed up a pot while adjusting, since there was at least twice I was turning one and found out I had the wrong one, but I can’t be sure.

The CLICK sound comes through the headphones and through the line out, but it does NOT get recorded. At low volume position, click is gone, but as I move volume up, it kicks in and gets worse with more volume.

I moved this tape with this recording to my X3 and it plays with no clicks. Also, there are no clicks when just listening to the line IN through the unit. So it would SEEM to be in the amp section from the HEADS onward. But, my schematic skills aren’t the best so….

Question is, based on the schematic I’m attaching and the other info here, where should I being to start troubleshooting this? (I just put new caps in the output board, no help there.) I've included schematic, board detail and transistor list for this. The transistors in yellow are the ones I replaced.

Anyway, thanks in advance for any advice!

Video link:
 

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I've pulled this unit back off the shelf to give it another go. I've retraced my steps and have looked at the orientation of the transistors I replaced, and those look good. Could it maybe be a capacitor instead? It's only on the Right channel, and only on playback, as described above.
Thanks for any help, I want to get this one back up and running!
 
Post a photo or video of what this noise/distortion looks like on your scope. Scope connected to both line outputs and with you playing a test tape with sine waves.
 
Does the noise happen only when playing a tape or does it also happen with deck in SOURCE mode and a sine wave signal applied to LINE IN?
 
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tapetech said:
Does the noise happen only when playing a tape or does it also happen with deck in SOURCE mode and a sine wave signal applied to LINE IN?
Click to expand...
It happens only on tape playback, as far as I can tell. The 1st video here shows the scope with a tape playing (you might be able to see the sharp "pop" transient every now and then but it's so fast it doesn't register well) then I hit source to go to the sine wave input, and it's clean.
Also, if I record this sine wave the playback while it's recording (monitoring TAPE) will have the pops, but the recorded tape will not when played back on another deck.


 
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Have you tried cleaning these three slide switches (S307, S308, S309) with contact cleaner or Deoxit? They switch between FWD and REV.

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dankik said:
Have you tried cleaning these three slide switches (S307, S308, S309)? They switch between FWD and REV.

View attachment 3448963

View attachment 3448965
Click to expand...
I will try that now. The unit was working fine, just some slightly dull recording and a bit of noise - which is why I thought I could recap and replace transistors to optimize that. The left side seems fine, just right. I am getting confused about what transistors are on the RIGHT side based on the schematic.
But I'll get the D5 and give it a shot, thanks!
 
dankik said:
Have you tried cleaning these three slide switches (S307, S308, S309) with contact cleaner or Deoxit? They switch between FWD and REV.

View attachment 3448963

View attachment 3448965
Click to expand...
Ok, I cleaned them well with D5 and exercised them a bunch. No change (except those are clean now!).
If anyone could clue me in to what components are in the RIGHT channel based on that schematic, that would help a lot. I could start isolating those transistors and see what's bad. I'm assuming it's somewhere late in the schematic, maybe right after the record head but before the amp section, since the signal records to tape fine, and the line in monitors fine. Thanks for any hints.
 
See post 5. What does the deck output look like (on your scope) when playing a test tape tone? Tone should be 185 or 250 nWb/m flux level and a 1K, 500Hz or 400Hz tone
 
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What is the flux level of the test tape you used in the above videos?

And the noise you see on the lower trace is in FWD play and REV play?

And if you just play a blank tape you still see that noise on the lower trace?. And you can hear the left channel noise on speakers?

And when you play the test tape the channels have equal volume?
 
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185. FWD at 7.5ips.
Blank tape has the same noise proportionally, on right only.
The volume is different by about 40%, Right lower.
 
dankik said:
Have you tried cleaning these three slide switches (S307, S308, S309) with contact cleaner or Deoxit? They switch between FWD and REV.

View attachment 3448963

View attachment 3448965
Click to expand...
Are you able to figure out if the Right channel is the EVEN or ODD component numbers (Q301/Q302 etc)? (EDIT: Looking closer maybe it's just a RANGE of transistors that are on the L and R, not odd even? EDIT AGAIN: And I just noticed the note at the bottom of the schematic that says it's for the LEFT channel, that makes sense now.)
I have time tonight to poke around on that board, just wanted to cut the workload in half, haha.
Thanks for any help!
 
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O. Friend said:
Are you able to figure out if the Right channel is the EVEN or ODD component numbers (Q301/Q302 etc)?
I have time tonight to poke around on that board, just wanted to cut the workload in half, haha.
Thanks for any help!
Click to expand...
The service manual for an X-1000r calibration indicated adjusting L channel first and it was always an odd number while the R was even. The schematic lists odd/even transistors but I'm not 'positive' if the odd/even always indicates L and R channel transistors. Guessing, I guess so.... :)
 
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Looking at the schematic, all components on the LEFT channel (yellow) are odd reference numbers. All even numbers (green) are on the RIGHT channel (not shown on the schematic, but same as the LEFT channel).

EDIT: If you have been looking at the ODD components with your scope, you are looking at the LEFT channel. If the Right channel has the noise, then you need to look at the EVEN parts (for the most part).
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Here is how the board is partitioned into L & R sectioned areas.

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Here are the Playback and Record (Line In) signal paths. They become common at the Tape/Source switch.
If the channel sounds good when you monitor the source, then the blue path is OK.
When you monitor the tape, you hear problems.

The problem is with the Right channel so you should be looking at the EVEN numbered components.
Use your scope to look at the signals going into and out of each transistor (even number) in the path and see if you can find the culprit.
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Blank tape has the same noise proportionally, on right only.
The volume is different by about 40%, Right lower.
Click to expand...
So you have a noise problem in right play amp as well as the level is several dB lower (you should always indicate how many dB lower the right channel is from left). It was a bit odd that your scope photos did not show any level differences between channels.

So you need to signal trace and that will tell you where the defect is. All you do is start at the input of the play amp and compare both channels with your scope probe. Playing your test tape both channels should have the same level and same noise. When you get to the point in the circuit where left and right DON'T have same level and same noise then you have found the defect.
 
dankik said:
Here is how the board is partitioned into L & R sectioned areas.

View attachment 3449981

Here are the Playback and Record (Line In) signal paths. They become common at the Tape/Source switch.
If the channel sounds good when you monitor the source, then the blue path is OK.
When you monitor the tape, you hear problems.

The problem is with the Right channel so you should be looking at the EVEN numbered components.
Use your scope to look at the signals going into and out of each transistor (even number) in the path and see if you can find the culprit.
View attachment 3450059
Click to expand...
Awesome, that helps a lot!
 
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