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Pioneer SA-9800 - what to do?

I honestly don't know. I did not measure any of them and none of them were bulging or leaking. I replaced them since i knew what difference it would do to the sound and I can say that my thoughts were right. Original vs. restored is no match at all.
 
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So, restored sounds much better with the shotgun recap?

elektronror said:
I honestly don't know. I did not measure any of them and none of them were bulging or leaking. I replaced them since i knew what difference it would do to the sound and I can say that my thoughts were right. Original vs. restored is no match at all.
Click to expand...

So, restored sounds much better with the shotgun recap? I am still replacing transistors
 
Hurray! Yahoo! Many Many thanks to Elektronror

The Pioneer SA9800 GWF116 equalizer board is totally functional! MC phono works on both L and R channels. MM phono works on both L and R channels. Tuner works on both L and R channels. This would not be possible if it were not for Elektronror. 25 transistors out of a possible 73 transistors were replaced in the same unit (also did a shotgun rebuild of the power supply). Is this not an Audiokarma record for the Pioneer SA9800?
 
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Very glad to hear you got her functional. I'm just a little stunned that all of those transistors failed. Maybe there was a spike in the wall outlet or something?
 
Yes, you also had a grounding problem

Yes, I am stunned also. 25 transistors is a lot to replace. Actually just 10 transistors were used for the "shotgun" power supply rebuild, but that means 15 more for the MC phono and MM phono stages. You would think that the 60ma on both the positive and negative 32 volt supplies would not generate enough heat to fry the transistors. However, we did have a lightening strike that fried a tree and garage door opener along with the router. There were at least 5 or 6 surge suppressors in the Pioneer SA9800 room however. Hard to know for sure, just speculation.
 
Stunned

Yes, furthermore, the Sencore Cricket will diagnose a bad transistor even when it passes signal with no gain. So we have increased sensitivity to a bad transistor even when it tests good with the conventional diode tests. The cricket can also check those pesky 2SA725 and 2SA726 PNP transistors; when they start making noise, I noticed that the gain is very very low, likely unity. These pesky transistors will slip under the radar because you will not suspect the transistor unless it does not pass signal.
 
Well, I routinely replace ALL of the a725 and a726 transistors. The fixer's lair is the end of the line for them. A black hole I guess... :D

p.s. also the c1451 and it's cousin the a809.
 
Mark the fixer's genius and wisdom

The more I study and learn about Pioneer vintage gear, the more I stand in awe of Mark the fixer's genius and wisdom. Such profound knowledge and experience is truly a huge gift to Audiokarma! Thanks for any and all opionions, Mark! I will try to learn more about the A809
 
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ITS FIXED! 34 out of 73 transistors replaced!

backmd said:
The more I study and learn about Pioneer vintage gear, the more I stand in awe of Mark the fixer's genius and wisdom. Such profound knowledge and experience is truly a huge gift to Audiokarma! Thanks for any and all opionions, Mark! I will try to learn more about the A809
Click to expand...

Test point Voltage spec measured value with respect to chassis ground
Base of Q1 0.6 0.50
Emitter of Q1 0.0 0.70
Base of Q5 -0.6 0.14
R37 29.0 23
Base of Q13 0.8 19.5
Base of Q15 -0.8 19.0
R27 -29.0 -1.4!
R39 -32.0 -2.8! See if pins 10 and 11 on power supply are
–32volts; no it’s –2.8!
Therefore check Q12; no gain! 32volts/178ohms=180ma;excessive current?
NTE2667 BCE soldered in, connections verified.

C10 is next c10 47uf 63v cea 47 100 647-UPW2A470MPD1TD
Connections verified and capacitance is in spec
C9 is next c9 47uf 63v cea 47 100 647-UPW2A470MPD1TD
Connections verified and capacitance is in spec
OK the positive supply has 204ma (burning 6.5 watts) and the negative supply has 83ma (burning 2.66 watts); spec is 60ma for both supplies.
R side MC works L does not.
R side phono works, L does not.
Tuner works on both channels.
27 volts positive and negative volts; within 15 percent
Cautiously reconnect the positive and negative rails.
Yellow to pin 6; orange to pin 10. Double-checked.
Check C17 (99.2uf) and C21 (unable to measure but not shorted)!
The power supply is best illustrated on pages 48 and 49 of the 54 pages in the service manual.
So likely Q12 is fried again. I knew this might happen again and it was an NTE2667 that fried.
First repair Q12 on the AWR194 board with the last remaining NTE2667 and then replace both Q13 and Q14 on the GFW116 board. Note we still have the MJE15033G PnP in reserve as the last replacement for the Q12 on AWR194 board.
NTE2667 BCE soldered in, connections verified. If the 1980 Q12 was the first Q12, we are on our 5th Q12
Pins 10&11 -32v spec, –32.8 measured
Note both Q12 transistors failed in the same manner; infinite resistance between all of the junctions.
The equalizer board (GFW116) is best illustrated on pages 27 and 30 of the 54 pages in the service manual.
Q14 bad 2SC1735 (NTE31); soldered in and all connections verified
Q13 bad 2SC1735 (NTE31); soldered in and all connections verified
One transistor had 6 ohms from Emitter to collector; essentially a short!
The other bad transistor had open circuit between the junctions.
The PC board showed scorching at the transistor mounting positions.
Q5 bad 2SA978 (NTE234);
Q7 2SA1114 (NTE234);
Q11 2SC1919 (NTE199)
Q15 2SA850 replaced with NTE290 PNP
Q6 bad 2SA978 (NTE234);
Q8 2SA1114 NTE234;
Q12 2SC1919 NTE199
Q16 2SA850

Q27 2SC1919 NTE199 10 for 8.50 on ebay
Q31 2SA850

Q28 2SC1919 NTE199
Q32 2SA850
Q15 tests good on two ranges; albeit lots of leakage, this was replaced with NTE290;
Replaced with NTE32 PNP, which is rated at 160 volts soldered in and all connections verified!
Test point Voltage spec measured value with respect to chassis ground
Input of Q17 0.0 -0.011
Base of Q25 29.0 27.0
Base of Q29 yellow 0.8 27.0
Base of Q27 -29.0 -29.0
Base of Q31 red -0.8 25.0
Emitters of Q19 big red black 5.0 5.0 and 5.0
So clearly Q29 (2SC1735)and Q31 (2SA850 or KSA1220AYS or NTE32) may have issues, now we have targets! These transistors formerly tested well. Note: I have a PNP high voltage in stock, NTE32
Q31 soldered in and all connections verified
Furthermore the analogous Q32 had gain on two settings! After the transistor is removed, all tests well? Passive component issues ie caps?
Emitter of Q29 is 26.4 volts
TP17 is 25.9 volts
Check C35, R81,C33, C37, R87, R89, C41, R95, R83, R85, R91, R93, C39, C43
OK works on tuner, R phono MM, R phono MC.

Signal injection techniques, loud output when injection occurs at Q17, no output when injection occurs at Q25 or Q29!
Test Q17, Q19, Q21, and Q23; Q21 (2SA995 and NTE45), it checked good before, and Q23 (2SA726 and NTE234), replaced before, measure badly.

Need NTE45 and NTE234 Ordered both on ebay 4-8-14; probably take 5 days!

Use matched pairs of single transistors for each device per avionic regarding the 2SA995.
2sa725 = ksa992 per anderslober

The NTE234 versus the KSA992; they both have 120 volt breakdown voltages but the NTE handles 100ma versus the KSA handles 50ma. Still it is worth a shot. The same issue exists for the NTE45, which handles 100ma versus 50ma for the KSA.

The NTE234, 2SA726, and KSA992 all have identical pinouts ECB

Q23 soldered in and all connections verified!

KSA992 matched to within 1.1 percent! Fabricated a Q21 out of two matched KSA992s WITH a common base (advanced soldering techniques).

Q21 soldered in and all connections verified!

Hooray, the tuner, the MM phono, the MC phono work on both channels!

Pin number Spec Measured
15 red 0 .005 was -4.9
16 yellow 0 .002-3.4
17 green 0 .005 was 14.9
18 blue 0 -0.1 was –10.4

Observing TP 15,16,17, and 18it may be important to adjust VR1, VR2, VR3 and VR4 respectively.
 
The recapped one is now broken. I was going to listen to my headphones but when the relay clicked i just got a loud hiss. Turning up the volume decreased the hiss.

Fired it up with a bulb and the noise was gone. Fired it up connected directly to the wall and the hiss was back. The noise is coming from the preamp but i have no idea what to look for. I'm really not fond of powering it up in case something more brakes.

What could have happen? I haven't done anything with it, not even moved it.
 
Looks like the power supply is fried. Had +70v and -3v to the tone controls. I can only imagine how much damage is done. :tears:
 
Did you not rebuild the power supply recently?

elektronror said:
Looks like the power supply is fried. Had +70v and -3v to the tone controls. I can only imagine how much damage is done. :tears:
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I am getting older, but I seem to recall that you rebuilt the power supply recently in the Pioneer SA 9800?
 
I sure did. Everything except for the resistors are new.

Iv'e only done some minor testings and so far i haven't found anything wrong, not even a shorted transistor.
 
70 volts and -3 volts on the tone control assembly

elektronror said:
I sure did. Everything except for the resistors are new.

Iv'e only done some minor testings and so far i haven't found anything wrong, not even a shorted transistor.
Click to expand...

Boy that is not good at all. I looked up the normal values and the tone controls use the good old 32 volt positive and 32 volt negative. Unfortunately I have experience with 34 blown transistors on this amp, some many times. The power supply is real real easy to have transistors develop problems. If we have a collector emitter short on Q11 we can develop 50 volts but you have 70 volts. If Q12 opens then we can have 0 volts or maybe even explain a negative 3 volts if Q12 conducts almost like an open circuit.

Do you have a variac with an integral ammeter and voltmeter. I have a 1 amp fuse in my homemade variac with an integral ammeter and voltmeter as an add on box in series with my loads and a switch. That way any huge amounts of power will be detected. Do you have a transistor tester that can check gain. Sometimes transistors will PASS the diode test and still be faulty.

I am fearful of having abnormal voltages on the power amp. Do we have the requisite 55 volts plus and minus on the power amp? Aha, just as I thought, we need to have a balanced plus and minus 52 volts to control the bias circuits of the power amp, so we risk an uncontrolled power amp if certain voltages are incorrect. These positive and negative 52 volts come from Q1 and Q2 on the power supply.

I would hate to make a mistake and cost you your power amp. The above things are my current thoughts. I am pretty darn sure that at least you would have to shotgun the power supply again even though I tried not to do that, I learned my lessons from others on Audiokarma.
 
What if we isolated the power supply

I have a hair brained idea. What if we disconnected the main power amp from current; ie disconnect the 55 volt balanced plus and minus supplies which are not from the AWR194 board or the AWR191 board. And what if we also disconnected the 52 volt balanced plus and minus supplies. That way all the high current would no longer be connected to the power amp and there also would be no bias at all. Therefore if everything that could burn up in the power amp was disconnected, nothing bad could happen power amp wise. Someone with experience should double check my logic.

OK then I would also disconnect the positive and negative 32 volt supplies from their loads. So to recap, the 32 volt supplies and the 52 volt supplies no longer will have loads. Could we not then measure the voltages at these supplies and with this important data conclude whether or not we have a bad power supply or a bad load ie partial short? Furthermore the compulsive Pioneer SA9800 manual also denotes the normal current flow. When rebuilding the preamp circuits sometimes there was triple the current flow due to just a few bad transistors.
 
Check the preamp boards!

elektronror said:
The recapped one is now broken. I was going to listen to my headphones but when the relay clicked i just got a loud hiss. Turning up the volume decreased the hiss.

Fired it up with a bulb and the noise was gone. Fired it up connected directly to the wall and the hiss was back. The noise is coming from the preamp but i have no idea what to look for. I'm really not fond of powering it up in case something more brakes.

What could have happen? I haven't done anything with it, not even moved it.
Click to expand...

Pin number Spec Measured
15 0
16 0
17 0
18 0

Observing TP 15,16,17, and 18it may be important to adjust VR1, VR2, VR3 and VR4 respectively.
However I strongly suspect that none will be close to zero, in which case some transistors are likely leaky at the very least or shorted at the CE junctions at the worst case scenario
 
Iv'e only read your posts briefly since i haven't got the time to fix it for the moment. I do however appreciate your help and i will read it thoroughly and look in to it.
 
These are okay:
5,6
3,4
10,11

These are not okay:
1,2 (-74v)

Collector of Q12 that should be -48v is also -74v.

This means that the positive rail is good and that the -32 circuit is good. Something is wrong with the -52v circuit.

Q6 was bad so that is replaced. Rest of the transistors are okay. Not shorted or open. Same thing with capacitors and resistors.
 
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