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Just a final post on this issue. Amplifier idle is dialed in perfectly on both channels after replacing same transistors and trimmer pots on left channel board. Speaker outputs on scope with Signal Generator show identical wave patterns on both channels. Thanks again Mark for all your help on...

Well, you can shoot me now Mark!!! I swapped Q33 and Q34 and as you suspected, the issue did not move. (I also noticed a fine dust hair across the 3 legs of Q34 when I pulled it). But...checking idle voltage, I no longer have major up/down fluctuations! Just minor changes. So I removed solder...

OK, will take these steps if issue doesn't follow swapped drivers. Will post an update on Saturday.

Re-measured Output and Driver Vbe's. Left Outputs: Q10 .635 Q8 .628 Q2 .629 - .587 flutter up/down Q4 .630 When Q2 dropped to .587 and continued flutter (after about a minute of warmup), the left outputs measured: Q10 .589 Q8 .587 Q2 .587 - .610 flutter up/down Q4 .591 Right Outputs (initial...

Hmm. I looked at what I wrote down for "Q24-Q22 Collectors climb to 1.774mV and steady after a minute" and it was -1.774 Just checked these: On Q14, monitor the collector to emitter voltage, looking for flutter and it was .686mV and steady On Q18, monitor the collector to emitter voltage...

All 3 measurements are steady. Note these measurements were taken with Q26, Q28, Q30 & Q32 still removed. R48 climbs to -2.204mV after a minute and stays steady. R54 climbs to 2.172mV after a minute and stays steady. Q24-Q22 Collectors climb to 1.774mV and steady after a minute. I'll go back...

Checked R44 and it is fluttering a bit -62.8mV up to -64 back and forth. Unfortunately, with the 4 transistors (all original a733 and c945) removed, I still get idle current flutter 35mV up to 80mV, up and down with VR4 and VR6 fully counter-clockwise.

I'm pretty sure everything in this amp was all original when I got it, but I will double-check. Also, 2 of those transistors, Q28 and Q30 have film capacitors marked B 472K solder to the legs of the Base and Emitters on the solder side of the board (same as left channel). do I reinstall those...

D10 is 1.138mV after 2 minutes. VR4 at .6mV fully counter clockwise. D6 is 2.503mV after 2 minutes R30 2.157mV I found flutter in the following as well: R34 -3.234mV up to 3.309, up and down D28 1.981mV up to 2.013 back down to 1.99, up and down D30 1.424mV down to 1.39 up to 1.443, up and...

Yesterday after installing new components, I did check D10 and it appeared steady after brief measurement, nearly same voltage as left side D9. I will check it again for longer time period. I'll also recheck other voltages today and report back. The idle current flutter is constant back and...

Hi Mark, sorry for the long pause. We were out of town for a bit. Parts came in and replaced the following: Q8 w ksa1013 Q10 w ksa992 D8 w 1N4148 Results appear to be the same with fluctuating idle current at pins 18 and 20. I don't have any D6 6.1v zener diodes, so will have to order them...

I watched D10 and voltage across it went from 1.176, dropping .001 ever 5-7 seconds. It was at 1.082 at 15 minutes. I compared that to the left channel D9 which started at 1.106 and dropped to 1.096 and appeared steady after 3 minutes. Voltage across VR4 (new Bourne's trimmer) was 9.6, steady...

Measured Q8 Base for 10 minutes. 2.728 up to 2.734 in first 10 seconds, then drops to 2.716 at 2 mins. About every minute it drops .001 and at 10 min it seems to stabilize at 2.709.

Across R30: starts at 2.02 and creeps up to 2.082 after a minute or so and stays steady there. Across R24: -1.127 and steady. Q8 Base: starts at 2.728 up to 2.730 (30 sec) then down to 2.721 after 1 min and 2.717 after 2 min where it seems to stabilize. I don't have any of the Q8 substitutes...

B-B fluctuates up and down between 2.55 - 2.68 in first 30 seconds. E-E fluctuates up and down between 1.3 - 1.333 in first 30. Never stabilizes.

After setting VR4 to 56mV (fluctuating) and then VR6 to 70mV (fluctuating), both Q34 and Q35 Vbe change over time. Q34: +.592 to .587 after 3 minutes to .586 after 5 minutes Q36: -.601 to -.579 after 20 sec to -.583 after 2 min to -.584 after 5 min Took a couple of readings with similar...

Took some Vbe. Drivers: Q34: .596v Q36: .601v With the Outputs still connected: Q10: .648 Q8: .648 Q2: .638 Q4: .644 In order to do as you say "Those you can get away with just disconnecting the collector and the base drive one transistor of each pair at a time.", I'm not sure how to do that...

One other thing to add...the unit plays equally loud out of both channels, and the static/distortion I was hearing on right channel was initially attributed to a dirty balance control, but then after some Deoxit on all pots and diving deeper with the Idle Balance, it appears not.

Hi Mark, thank you for chiming in. I noticed these comments on another post that I'm going to look to address first before diving into the drivers and outputs. The amp (each channel) has a mandatory replace transistor: 2sa726... ksa992 (Q9 & Q10, emitter follower buffer) and IF you go straight...

When setting Idle Current, I can dial in left channel no problem. But with right channel, when trying to set Idle #1 adjustment to 56mV, the voltage fluctuates constantly from 54mV to 60mV. It doesn't settle down, even after being on for 5-10 minutes. I replaced electrolytic capacitors, and that...

I know this is an old thread, but I just want to mention that with the 525 I recently worked on, I tried using the TIP outputs and could not get bias down to 30 mV (lowest I could get to was about 70 mV). With the KSB596 and KSD526 pairs, both channels dialed in easily at 30 mV.

Hi all. I've put my MA 5100 on the bench to address a balance issue (left channel louder than right) and want to clean all pots and switches first. I found this thread and have some ideas. I was able to squeeze the crimped end of one of the original rods (they are hollow) so that I could stick a...

Same relay. I found all 3 parts on Digi-key and have placed an order. Thanks!

Hi everyone, I realize this post is over a year old, but wanted to get your thoughts on replacing the relay in my TR 2080. Looking at the markings, the TR 2080 has the same relay. But I've not yet checked the schematics to compare and verify that wiring pin outs are the same. Though I do see...

I’m getting 4.92v to pin 2 on AWX-124 and after the first cleaning of the tuning shaft and the Deoxit dried (no spray on fins), the QL has stopped going erratic when changing input selections. Looks like all is good. Thanks guys.