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SA-8100 : low volume right channel problem (RESOLVED)

Wyatt Weeks

Wyatt Weeks

Member
EDIT: the initial problem with idle current has been resolved (thanks to MTF!) - see post #14 for a description of the The ‘low volume right channel’ issue I’m now having... EDIT: The low volume in right channel problem is also now resolved.

Hi - I recently acquired and rebuilt a SA-8100. After rebuilding, it comes out of protection normally, all voltages are close to spec, and i have set the bias on both sides to zero. BUT, the idle current is hovering around zero, and it does not change on either side throughout the full range of the trimmers.

The amp worked before i did anything to it, though with sounds of dirty pots and failing transistors. I replaced all transistors, e-caps, and diodes. Also, replaced the relay. I did not replace the original Sanken outputs, as they all tested OK. I did recheck all transistor, diode, and cap orientations.

I'm hoping to get some ideas on troubleshooting this issue of zero idle current. Perhaps a mismatched replacement part? I'm out of ideas, myself. This is only the 3rd unit i've added to my collection and worked on myself, so i'm far from an expert!

Voltages and parts lists below.

power amp AWH-022
pin voltage specifiedVoltage
5 47.8 50
21 47.8 50
27 36.3 38
36 36.3 38

protect circuit AWM-027
6 -12.6 13
17 7.2 7.5 (ac)
16 33.3 35

power supply AWR-030
4 -36.5 -38
5 36.2 38
9 47.5 50
12 -39.4 -42
13 -22.2 -24
14 -19 -18
15 -12.6 -13
16 12.7 13
17 19.8 18
18 23.7 24
19 33.3 35

filter assy AWK-020
7 19.8 18
8 -19 -18

Control Amp AWG-017
3 -19.7 -18
4 19.7 18
7 19.7 18
8 -19.7 -18

EQ Amp AWF-006
1 -22.1 -24
8 23.6 24

Parts list in next post...
 
Last edited:
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Here are the parts i used:

Board BoardName location OEM Part# uF Volts type replacementuF ReplacementVolts MouserPart#
AWF-006 EQUALIZER AMP c1 2.2 25 cssa 2.2 50 647-UKL1H2R2MDDANA
AWF-006 EQUALIZER AMP c10 100 6 cea 100 10 647-UPW1A101MDD
AWF-006 EQUALIZER AMP c11 2.2 25 cssa 2.2 50 647-UKL1H2R2MDDANA
AWF-006 EQUALIZER AMP c12 2.2 25 cssa 2.2 50 647-UKL1H2R2MDDANA
AWF-006 EQUALIZER AMP c19 100 25 cea 100 25 647-UPJ1E101MED
AWF-006 EQUALIZER AMP c2 2.2 25 cssa 2.2 50 647-UKL1H2R2MDDANA
AWF-006 EQUALIZER AMP c20 100 25 cea 100 25 647-UPJ1E101MED
AWF-006 EQUALIZER AMP c21 220 16 cea 220 16 647-UPW1C221MPD1TA
AWF-006 EQUALIZER AMP c5 470 6 cea 470 10 647-UPW1A471MPD
AWF-006 EQUALIZER AMP c6 470 6 cea 470 10 647-UPW1A471MPD
AWF-006 EQUALIZER AMP c9 100 6 cea 100 10 647-UPW1A101MDD
AWF-006 EQUALIZER AMP Q1 2SA774 512-KSA992FBU
AWF-006 EQUALIZER AMP Q2 2SA774 512-KSA992FBU
AWF-006 EQUALIZER AMP Q3 2SA774 512-KSA992FBU
AWF-006 EQUALIZER AMP Q4 2SA774 512-KSA992FBU
AWF-006 EQUALIZER AMP Q5 2SC1345 512-KSC1845FTA
AWF-006 EQUALIZER AMP Q6 2SC1345 512-KSC1845FTA
AWF-006 EQUALIZER AMP Q7 2SC1345 512-KSC1845FTA
AWF-006 EQUALIZER AMP Q8 2SC1345 512-KSC1845FTA
AWG-017 CONTROL AMP c11 220 6 cea 220 10 647-UPW1A221MED
AWG-017 CONTROL AMP c12 220 6 cea 220 10 647-UPW1A221MED
AWG-017 CONTROL AMP c15 100 6 cea 100 10 647-UPW1A101MDD
AWG-017 CONTROL AMP c16 100 6 cea 100 10 647-UPW1A101MDD
AWG-017 CONTROL AMP c17 4.7 25 cssa 4.7 25 647-UKL1E4R7KDDANA
AWG-017 CONTROL AMP c18 4.7 25 cssa 4.7 25 647-UKL1E4R7KDDANA
AWG-017 CONTROL AMP Q1 2SC1478 512-KSC1845FTA
AWG-017 CONTROL AMP Q2 2SC1478 512-KSC1845FTA
AWG-017 CONTROL AMP Q3 2SC1478 512-KSC1845FTA
AWG-017 CONTROL AMP Q4 2SC1478 512-KSC1845FTA
AWG-017 CONTROL AMP Q5 2SA726 512-KSA992FBU
AWG-017 CONTROL AMP Q6 2SA726 512-KSA992FBU
AWG-017 CONTROL AMP Q7 2SC1345 512-KSC1845FTA
AWG-017 CONTROL AMP Q8 2SC1345 512-KSC1845FTA
AWH-022 POWER AMP c1 0.22 25 cssa 0.22 63 505-MKS2C032201BKI00
AWH-022 POWER AMP c10 47 10 cea 47 10 647-UPW1A470MDD
AWH-022 POWER AMP c11 330 10 cea 330 10 647-UPM1A331MPD
AWH-022 POWER AMP c12 330 10 cea 330 10 647-UPM1A331MPD
AWH-022 POWER AMP c17 47 50 cea 47 50 647-UPW1H470MED
AWH-022 POWER AMP c18 47 50 cea 47 50 647-UPW1H470MED
AWH-022 POWER AMP c19 47 50 cea 47 63 647-UPW1J470MPD
AWH-022 POWER AMP c2 0.22 25 cssa 0.22 63 505-MKS2C032201BKI00
AWH-022 POWER AMP c20 47 50 cea 47 63 647-UPW1J470MPD
AWH-022 POWER AMP c21 22 10 cea 22 10 647-UPW1A220MDD
AWH-022 POWER AMP c22 22 10 cea 22 10 647-UPW1A220MDD
AWH-022 POWER AMP c3 0.47 25 cssa 0.47 100 505-MKS2D034701E00JS
AWH-022 POWER AMP c4 0.47 25 cssa 0.47 100 505-MKS2D034701E00JS
AWH-022 POWER AMP c9 47 10 cea 47 10 647-UPW1A470MDD
AWH-022 POWER AMP D1 1S2473 512-1n4148
AWH-022 POWER AMP D10 1S2471 512-1n4148
AWH-022 POWER AMP D11 1S2471 512-1n4148
AWH-022 POWER AMP D12 1S2471 512-1n4148
AWH-022 POWER AMP D13 1S2471 512-1n4148
AWH-022 POWER AMP D2 1S2473 512-1n4148
AWH-022 POWER AMP D3 1S2473 512-1n4148
AWH-022 POWER AMP D4 1S2473 512-1n4148
AWH-022 POWER AMP D5 1S2473 512-1n4148
AWH-022 POWER AMP D8 1S2471 512-1n4148
AWH-022 POWER AMP D9 1S2471 512-1n4148
AWH-022 POWER AMP Q1 2SA726 512-KSA992FBU
AWH-022 POWER AMP Q10 2SC1451 512-KSC3503DSTU
AWH-022 POWER AMP Q11 2SD357 512-KSC2690AYS
AWH-022 POWER AMP Q12 2SD357 512-KSC2690AYS
AWH-022 POWER AMP Q13 2SB527 512-KSA1220AYS
AWH-022 POWER AMP Q14 2SB527 512-KSA1220AYS
AWH-022 POWER AMP Q15 2SD370 863-MJ21194G
AWH-022 POWER AMP Q16 2SD370 863-MJ21194G
AWH-022 POWER AMP Q17 2SB530 863-MJ21193G
AWH-022 POWER AMP Q18 2SB530 863-MJ21193G
AWH-022 POWER AMP Q2 2SA726 512-KSA992FBU
AWH-022 POWER AMP Q3 2SA726 512-KSA992FBU
AWH-022 POWER AMP Q4 2SA726 512-KSA992FBU
AWH-022 POWER AMP Q5 2SC869 512-KSC2383YTA
AWH-022 POWER AMP Q6 2SC869 512-KSC2383YTA
AWH-022 POWER AMP Q7 2SA628A 512-KSA1013YBU
AWH-022 POWER AMP Q8 2SA628A 512-KSA1013YBU
AWH-022 POWER AMP Q9 2SC1451 512-KSC3503DSTU
AWH-022 POWER AMP VR1 TRIMMER 10K 652-3296Y-1-103LF
AWH-022 POWER AMP VR2 TRIMMER 10K 652-3296Y-1-103LF
AWH-022 POWER AMP VR3 TRIMMER 100ohm 652-3296Y-1-101LF
AWH-022 POWER AMP VR3 TRIMMER 100ohm 652-3296Y-1-101LF
AWK-020 FILTER AMP c1 1 50 cea 1 50 647-UPJ1H010MDD1TD
AWK-020 FILTER AMP c10 330 25 cea 330 25 647-UPW1E331MPD6
AWK-020 FILTER AMP c2 1 50 cea 1 50 647-UPJ1H010MDD1TD
AWK-020 FILTER AMP c7 10 16 cea 10 16 647-UPW1C100MDD1TD
AWK-020 FILTER AMP c8 10 16 cea 10 16 647-UPW1C100MDD1TD
AWK-020 FILTER AMP c9 330 25 cea 330 25 647-UPW1E331MPD6
AWK-020 FILTER AMP Q1 2SC1345 512-KSC1845FTA
AWK-020 FILTER AMP Q2 2SC1345 512-KSC1845FTA
AWM-027 PROTECTION UNIT c3 330 6 cea 330 10 647-UPM1A331MPD
AWM-027 PROTECTION UNIT c4 330 6 cea 330 10 647-UPM1A331MPD
AWM-027 PROTECTION UNIT c5 4.7 25 cea 4.7 25 647-UKL1E4R7KDDANA
AWM-027 PROTECTION UNIT c6 100 16 cea 100 16 647-UPM1C101MED1TD
AWM-027 PROTECTION UNIT D1 1S2472 512-1n4148
AWM-027 PROTECTION UNIT D2 1S2472 512-1n4148
AWM-027 PROTECTION UNIT D3 1S2472 512-1n4148
AWM-027 PROTECTION UNIT D4 1S2472 512-1n4148
AWM-027 PROTECTION UNIT D5 1S2472 512-1n4148
AWM-027 PROTECTION UNIT D6 1S2473 512-1n4148
AWM-027 PROTECTION UNIT D7 1S2473 512-1n4148
AWM-027 PROTECTION UNIT D8 1S2473 512-1n4148
AWM-027 PROTECTION UNIT Q1 2SC857K-A 512-KSC1845FTA
AWM-027 PROTECTION UNIT Q2 2SC857K-A 512-KSC1845FTA
AWM-027 PROTECTION UNIT Q3 2SC945 512-KSC1845FTA
AWM-027 PROTECTION UNIT Q4 2SC945 512-KSC1845FTA
AWM-027 PROTECTION UNIT Q5 2SA733 512-KSA992FBU
AWM-027 PROTECTION UNIT Q6 2SC945 512-KSC2383YTA
AWM-027 PROTECTION UNIT Q7 2SA1384 512-KSC2690AYS
AWR-030 POWER SUPPLY c10 100 50 cea 100 63 647-UPW1J101MPD1TD
AWR-030 POWER SUPPLY c11 100 50 cea 100 63 647-UPW1J101MPD1TD
AWR-030 POWER SUPPLY c12 10 16 cea 10 35 647-UPW1V100MDD1TD
AWR-030 POWER SUPPLY c13 10 16 cea 10 35 647-UPW1V100MDD1TD
AWR-030 POWER SUPPLY c16 330 35 cea 330 50 647-UPM1H331MPD
AWR-030 POWER SUPPLY c17 220 50 cea 220 63 647-UPW1J221MPD
AWR-030 POWER SUPPLY c6 220 50 cea 220 63 647-UPW1J221MPD
AWR-030 POWER SUPPLY c7 220 50 cea 220 63 647-UPW1J221MPD
AWR-030 POWER SUPPLY c8 220 50 cea 220 63 647-UPW1J221MPD
AWR-030 POWER SUPPLY c9 220 50 cea 220 63 647-UPW1J221MPD
AWR-030 POWER SUPPLY Q1 2SD313 512-KSC2073TU
AWR-030 POWER SUPPLY Q2 2SB507 512-KSA940TU
AWR-030 POWER SUPPLY Q3 2SC945 512-KSC2383YTA
AWR-030 POWER SUPPLY Q4 2SA733 512-KSA1013YBU
AWS-035 SWITCH UNIT B C1 1 50 cea 1 50 647-UPJ1H010MDD1TD
AWS-035 SWITCH UNIT B C2 1 50 cea 1 50 647-UPJ1H010MDD1TD
AWS-035 SWITCH UNIT B C3 10 16 cea 10 16 647-UPW1C100MDD1TD
AWS-035 SWITCH UNIT B C4 10 16 cea 10 16 647-UPW1C100MDD1TD
AWS-035 SWITCH UNIT A c5 0.47 25 cssa 0.47 50 505-MKS2.47/50/10T
AWS-035 SWITCH UNIT A c6 0.47 25 cssa 0.47 50 505-MKS2.47/50/10T
AWS-035 SWITCH UNIT A c7 0.47 25 cssa 0.47 50 505-MKS2.47/50/10T
AWS-035 SWITCH UNIT A c8 0.47 25 cssa 0.47 50 505-MKS2.47/50/10T
AWS-035 SWITCH UNIT B Q1 2SC1345 512-KSC1845FTA
AWS-035 SWITCH UNIT B Q2 2SC1345 512-KSC1845FTA
CHASSIS RELAY ASR-003-0 653-MY4F-DC24
CHASSIS FILTER CAPS 10000 50 10000 63 647-LKG1H103MESCBK
CHASSIS FILTER CAPS 10000 50 10000 63 647-LKG1H103MESCBK
CHASSIS FLYBACK DIODE 863-1N4004RLG
 
one more thought on the parts list: is mouser part# diode 512-1n4148 an acceptable replacement for diodes 1S2473, 1S2472, and 1S2471?
 
Update: for the heck of it, I replaced the outputs (because i had them). No change.
Also, checked the placement, orientation, and solder connections of every component. Didn't find any issues there either.
The mystery continues...
I know this certainly isn't an 'easy one', but any advice would be appreciated!
 
My SA8100 suffered very alike.

In the end, the problem was an oscillation. Also this was after replacing transistors.

I would not have found the problem without the oscilloscope.

I took the oscilloscope after the voltages I measured in the power amp output circuit did not make sense trying to figure out why bias setting would not work properly.



You can find the SA8100 refurb on my webpage, including a schematic with two added little 15 pF capacitors at the first transistors base to collector of the three-stage current amp (btw I did state b-e in the schematic but this must be b-c ....).

I tried to slow down the circuit by using those caps. I lowered the capacitances until it looked overshooting/unstable applying a test square wave, and then doubled or tripled the capacitance again....that is how I ended up using 15 pF
http://members.quicknet.nl/gerard.slikker/pioneer-sa8100.htm
 
the description in the manual for those measurement procedures is execrable.

please describe exactly how YOU did the DC Offset and Idle Current measurements.

Let's stick with the left channel until we solve it.


uh oh - that's NOT my transistor list for the amplifier!!!!!!!!!!!!!!!!!!!!!!
edit - oh ****!!! IT IS!!!!!!!!!!!! how did I screw THAT up!!!

The 2sb527 & 2sd357 4mhz drivers were replaced by TO-126 rip snorting 175 MHz hot rods.

q1 q2 q3 q4 2sa774 first diff pair bce 35v .05a .15w 540hfe 65mhz
512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

q5 q6 2sc869 second diff pair ecb 160v .03a .2w 90hfe ?mhz
512-KSC1845EBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

q7 Q8 2sa628 second diff pair current source ecb 25v .1a .15w 55-800hfe 100mhz
512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

q9 q10 2sc1451 bias string current source ebc 150v .05a .7w 150hfe 130mhz
512-KSC3503estu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.28 ea


q11 q12 2sd357 npn driver bce to-126?? 130v .8a 1/10w 55-300hfe
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54
NOT
AWH-022 POWER AMP Q11 Q12 2SD357 512-KSC2690AYS to-126 ecb 120/a160 1.2a 1.2w/20w 175mhz 35-320hfe

q13 q14 2sb527 pnp driver bce to-126?? 130v .8a 1/10w 55-300hfe
512-KSA940TU_Q pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54
NOT!!!!!!!!!
AWH-022 POWER AMP Q13 Q14 2SB527 512-KSA1220AYS to-126 ecb 120/a160 1.2a 1.2w/20w 175mhz 35-320hfe

..... 534-4672 to-220 mica insulators $0.12 each...........


q15 q16 2sd370 npn output to-3 100v 8a 80w 40hfe 8mhz?
863-MJ21194G npn to-3 250v 16A 250W 4mhz 8-75hfe $3.83

q17 q18 2sb530 pnp output to-3 100v 8a 80w 40hfe 8mhz?
863-MJ21193G pnp to-3 250v 16A 250W 4mhz 8-75hfe $3.83
........534-4662 to-3 mica insulators $0.16 each.................
 
Last edited:
Mark - Here's how i did the DC offset and Idle Current adjustments (which i've also done on an SX-939):

1) I did not terminate input terminals terminals of the power amp with 4.7kohm resistance - i've read here that it's not necessary to do so.
2) No speakers connected, volume to zero, input to AUX1, loudness off, muting off, all other pots set to neutral
3) first fired up on DBT and let amp warm up 10min
4) DMM connected to terminals 1 & 2 and set to DC - for idle current measurement - initial reading 0
5) adjusted VR3 through the full range of adjustment - no change from zero (plus or minus a couple of tenths of a mV)
6) immediately switched to DC offset (bias / neutral potential) measurement for same channel - connected DMM to pin 3 and ground
7) initial reading was 60ish V - adjusted VR1, bringing to 0V
8) switched back to pins 1 & 2, still reading zero
9) cycled thru the VR3 adjustment range again - no change
10) tried the same as above on wall power - same behavior

is the 4.7kohm resistance actually needed for this procedure? I hope it's that simple!

Wyatt
 
thank you for the tip gslikker. I may try restoring Q9 / Q10 with the originals, but will probably keep that in my back pocket for now, until I can troubleshoot further.
 
As you can see, further investigation has kept me hopping all this time.

Q11, Q12, Q13 and Q14 were mis-specified with too fast transistors. MY BAD - I'm NOT ducking it....
If the originals pass the EchoWars 6 way diode test you can try re-installling them, or if you have a940 and c2073 transistors
you can swap them in.

Do NOT put the Q9 / Q10 2sc1451 transistors back replacing the c3503 transistors, those C3503's are ENTIRELY CORRECT!!!

I wouldn't power up the amp until this is corrected.

Gslikker has a reasonable correction, seeing that Q13 and Q14 each already have 82 pF capacitors connected from it's Collector to it's Base.
He killed the RF gain at Q7. Might still be appropriate.
Gslikker only:
As a test, 82 pF capacitors could be added to Q11 and Q12 , each capacitor connected from that transistor's Collector to it's Base. For RF stability. If you retain those hot rod transistors...

is the 4.7kohm resistance actually needed for this procedure?
Click to expand...
NO
 
thank you Mark! I'll give your recommendations a try. I don't have the a940's and c2073's on-hand, so i'll test the originals and make an order if they don't pass. I'll report back... thanks again!!
 
well, that did the trick. we are back in the music business. the original Q11,Q12,Q13,Q14's (2sd357 / 2sb527) tested ok, so i put them back in and idle current was online. adjusted bias and idle currents - and she sounds great. i'll order the a940 and c2073 transistors and eventually get those originals replaced for posterity.

Thanks so much Mark.
 
Is there any general thinking as to whether the original Sanken outputs or the On-Semi replacements are preferred (for sound quality)? or does it not make a difference?

Also, if I have further troubleshooting questions on this unit, should I start a new thread, or add to this one? (Guess I should have thought a about that when i named the thread!)
 
One problem solved (thanks again Mark!), and another one encountered: Low right channel volume. not distorted at all, just low. about half the volume of the left channel. It is somewhere in the preamp, as both channels are equal when i run another source into the SA-8100 power amp inputs. Yes, i did run the unit through the standard de-oxit and faderlube procedures as outlined in the 'idiot's guide' post here and post procedure, none of the controls produce any audible noise in the output when manipulating.

Also, the low right channel volume is not affected by:
- changing speakers to run off of 'B' outputs, vs. 'A' outputs
- switching left/right speakers (i.e. it's not the speakers)
- testing with input to AUX1 vs. AUX2
- changing to mono, or reverse stereo
- changing, wiggling, etc, any of the unit's controls (treble, bass, muting, tape, etc)

Voltages are all similar to the values posted earlier in this thread, and bias/idle have been set to spec.

So, this must be an issue in the EQ, Filter, or Control Amp boards, correct? Any pointers on where to start? i already checked for wires i might have knocked loose during refurb, and for bridged solder pads, or anything else visually out of whack with these boards. Also, reflowed a couple of solder connections that looked questionable.
 
Last edited:
i de-oxit'tized the unit again. no change. i'm starting to think that rather than low volume in the right channel, this might be high volume in the left channel.

I've been listening to the amp with the balance adjusted to even the speaker output (about 3'oclock on the balance dial), and based on where the volume knob is positioned, the output seems reasonable.

Any ideas where in the preamp section i might go about checking the output strength of each channel? I have the service manual, but am struggling to figure out what i'm looking for. i'd post the schematic, but it's too big to attach.
 
ok - i had a couple of beers and think i'm starting to figure out the schematic. so the signal goes EQ amp -> control amp -> filter amp -> power amp (which is powered by the power amp assy, and protected by the protect assy), i think... + a bunch of switches at various points of the signal path (pre-power amp).

i see an in1/in2 & out1/out2 on each board, so i think i'm measuring those to get left/right signal in mA... or at least that's my guess. so if i get a difference (between 1/2) on the outs from a board, then the problem lies within that board. if i get a difference in the ins for a board, than the problem lies between that board and the upstream board (assuming the previous board outs were roughly equal).

and i'm assuming i must do all this with a signal coming through the selected input and a load (speakers) connected to the output.

That's my armchair electrical engineering guess, and i figure i can't really hurt anything by taking these measurements (using mini-grabbers and cutting the power before changing pin locations). is this a valid approach?
 
First check if the difference is there when using the tape monitor selection. This definately bypasses the equalizer amp.
 
I found it. while checking voltages and quadruple checking components placement and orientation, i discovered one of the 1845's in the filter amp was installed incorrectly. can't believe i missed this in previous checks. Regardless, she's re-assembled with a new, properly installed transistor in the filter amp, and signing again - with equal volume/output on both channels. Done and Done!

Thanks to all who contributed, in helping keep me on the right path to resolution.
 
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