Pioneer SA-9500 II stays in protection mode

[tosicus]

I just finished recoping my pioneer sa-9500 II. Everything went smooth, no fireworks or blown fuses. However, the pioneer stays in the protection mode.

I did check all transistors and diodes, and they all are good. Then, I took measurement on every transistor's pin, all are good except 4 on the AWS-109 board. All these transistors are part of the protection mode circuit.

Here they are:

transistor - - - - - - - - - circuit param - - - - - - -my readings

AWS-109 Q3 2SC945 - - - 0v, 0.6v, 19.4v - - - - - 0v, -0.6v, 20.55v
AWS-109 Q6 2SC945 - - - 0v, -1.8v, 8.8v - - - - - 0v, -1.58v, 0.55mV
AWS-109 Q7 2SC1384 - - -8.2v, 8.3v, 7.6v - - - - 115mV, 36.9v, 0v
AWS-109 Q15 2SC945 - - -8.8v, 8.3v, 8.2v - - - - 055mV, 36.9v, 155mv


What should I do next to find why these transistor's voltage is wrong?

Any suggestions and help will be greatly appreciated!!!!

tos

 

[montecarlossfan]

I just finished recoping my pioneer sa-9500 II. Everything went smooth, no fireworks or blown fuses. However, the pioneer stays in the protection mode.

I did check all transistors and diodes, and they all are good. Then, I took measurement on every transistor's pin, all are good except 4 on the AWS-109 board. All these transistors are part of the protection mode circuit.

Here they are:

transistor - - - - - - - - - circuit param - - - - - - -my readings

AWS-109 Q3 2SC945 - - - 0v, 0.6v, 19.4v - - - - - 0v, -0.6v, 20.55v
AWS-109 Q6 2SC945 - - - 0v, -1.8v, 8.8v - - - - - 0v, -1.58v, 0.55mV
AWS-109 Q7 2SC1384 - - -8.2v, 8.3v, 7.6v - - - - 115mV, 36.9v, 0v
AWS-109 Q15 2SC945 - - -8.8v, 8.3v, 8.2v - - - - 055mV, 36.9v, 155mv


What should I do next to find why these transistor's voltage is wrong?

Any suggestions and help will be greatly appreciated!!!!

tos

Stupid question, but was it working before you did all this work on it?

 

[tosicus]

Yes, it was.

 

[montecarlossfan]

Id make sure my c13(timing cap) was in properly, Give q14 a check although I believe it is going to check out good, 39v at the collectors of q7,15 looks like just the voltage of q14 passing through something is pulling down the 8.8v at q6...(possible dud transistor e-c short would do that since emitter is 0v) If the 8.8 is not present on the base of q15 will not get the 8.2v for both q15 and 7 base to emitter drop of .7v is what is expected....I would also check d24 the anti spiking diode to make sure it is not conducting both ways(out of circuit)

I didn't really analyze the circuit in depth but this should get some things figured out and narrowed down.

 

[tosicus]

Id make sure my c13(timing cap) was in properly, Give q14 a check although I believe it is going to check out good, 39v at the collectors of q7,15 looks like just the voltage of q14 passing through something is pulling down the 8.8v at q6...(possible dud transistor e-c short would do that since emitter is 0v) If the 8.8 is not present on the base of q15 will not get the 8.2v for both q15 and 7 base to emitter drop of .7v is what is expected....I would also check d24 the anti spiking diode to make sure it is not conducting both ways(out of circuit)

I didn't really analyze the circuit in depth but this should get some things figured out and narrowed down.

Thank you for your reply.

C13 is brand new.
Q14 checked, is good. e 36.6v, c 48.6v, b 37.2v
D24 checked, is good, anyway was replaced with 1N448

tos

 

[markthefixer]

I just finished recoping my pioneer sa-9500 II. Everything went smooth, no fireworks or blown fuses. However, the pioneer stays in the protection mode.

I did check all transistors and diodes, and they all are good. Then, I took measurement on every transistor's pin, all are good except 4 on the AWS-109 board. All these transistors are part of the protection mode circuit.

Here they are:

transistor - - - - - - - - - circuit param - - - - - - -my readings

AWS-109 Q3 2SC945 - - - 0v, 0.6v, 19.4v - - - - - 0v, -0.6v, 20.55v
AWS-109 Q6 2SC945 - - - 0v, -1.8v, 8.8v - - - - - 0v, -1.58v, 0.55mV
AWS-109 Q7 2SC1384 - - -8.2v, 8.3v, 7.6v - - - - 115mV, 36.9v, 0v
AWS-109 Q15 2SC945 - - -8.8v, 8.3v, 8.2v - - - - 055mV, 36.9v, 155mv


What should I do next to find why these transistor's voltage is wrong?

Any suggestions and help will be greatly appreciated!!!!

tos

this IS the "standard" protection circuit.

pin 4 of the 109 board is a ground!!!

what are the anode and cathode voltages of d24? right now i don't see the 36 volt power after the relay coil....

then:

voltages on pins 40 and 41 of the 109 board?
d21, d22, d23 anode and cathode voltages? this means SIX voltage readings!

 

[tosicus]

this IS the "standard" protection circuit.

pin 4 of the 109 board is a ground!!!

what are the anode and cathode voltages of d24? right now i don't see the 36 volt power after the relay coil....

then:

voltages on pins 40 and 41 of the 109 board?
d21, d22, d23 anode and cathode voltages? this means SIX voltage readings!

Pin 4 is grounded.

D24 - a 36.4v, c 36.4v

pin 40 - 0v (not constant, 2mV - -1mV)
pin 41 - 0v (not constant, 1mV - 0v)

D21 - a 16.94v, c 16.61v
D22 - a 16.94v, c 16.43v
D23 - a 16.94v, c 24.80v


tos

 

[markthefixer]

your labeling of the transistor voltages is inconsistent,
the two Pioneer schematics have different voltages on them, Pipneer's error...
assumptions:
AWS-109 Q3 2SC945 - - - 0v, 0.6v, 19.4v - - - - - 0v, -0.6v, 20.55v ebc
AWS-109 Q6 2SC945 - - - 0v, -1.8v, 8.8v - - - - - 0v, -1.58v, 0.55mV ebc
AWS-109 Q7 2SC1384 - - - +8.2v, 8.3v, 7.6v - - - - 115mV, 36.9v, 0v ecb
AWS-109 Q15 2SC945 - - - +8.8v, 8.3v, 8.2v - - - - 055mV, 36.9v, 155mv ecb


unscrambling:

AWS-109 Q3 2SC945 ecb - - - -0.6v, 19.4v, 0.0v - - - - - -0.6v, 20.55v, 0.0v ebc good

aws-109 q5 2sa733 ecb - - - 18v, -1.8v, 20v
AWS-109 Q6 2SC945 ecb - - - 0v, 8.8v, -1.8v - - - - - 0v, 0.55mV, -1.58v ebc good
AWS-109 Q7 2SC1384 ecb - - - 7.6v, 8.3v, 8.2v - - - - 0v, 36.9v, 115mV ecb
AWS-109 Q15 2SC945 ecb - - - 8.2v, 8.3v, 8.8v - - - - 155mv, 36.9v, 055mV ecb
Pin 4 is grounded. good

D24 - a 36.4v, c 36.4v good

pin 40 - 0v (not constant, 2mV - -1mV) good DC balance for this channel
pin 41 - 0v (not constant, 1mV - 0v) good DC balance for this channel

D21 - a 16.94v, c 16.61v good, the over current is not triggering it
D22 - a 16.94v, c 16.43v good, the dc protect is not triggering it
D23 - a 16.94v, c 24.80v good, the dc protect is not triggering it

the dc protect is not triggering it
the over current is not triggering it

q6 collector is pulled low?, remove q6 and see if (c13 charges and) the relay pulls in, if not C13 may be shorted or backwards, because R42 should be trying to charge C13
if so, q6 is shorted, this transistor is marginal in this function, and a beefier transistor with a better safe operating area for pulse currents used.


THIS POST IS NOT FINISHED AND MAY CONTAIN ERRORS, I AM BEING INTERRUPTED TO DO PHYSICAL THERAPY HERE IN THE HOSPITAL!!!

 

[tosicus]

your labeling of the transistor voltages is inconsistent,
the two Pioneer schematics have different voltages on them, Pipneer's error...
assumptions:
AWS-109 Q3 2SC945 - - - 0v, 0.6v, 19.4v - - - - - 0v, -0.6v, 20.55v ebc
AWS-109 Q6 2SC945 - - - 0v, -1.8v, 8.8v - - - - - 0v, -1.58v, 0.55mV ebc
AWS-109 Q7 2SC1384 - - - +8.2v, 8.3v, 7.6v - - - - 115mV, 36.9v, 0v ecb
AWS-109 Q15 2SC945 - - - +8.8v, 8.3v, 8.2v - - - - 055mV, 36.9v, 155mv ecb


unscrambling:

AWS-109 Q3 2SC945 ecb - - - -0.6v, 19.4v, 0.0v - - - - - -0.6v, 20.55v, 0.0v ebc good

aws-109 q5 2sa733 ecb - - - 18v, -1.8v, 20v
AWS-109 Q6 2SC945 ecb - - - 0v, 8.8v, -1.8v - - - - - 0v, 0.55mV, -1.58v ebc good
AWS-109 Q7 2SC1384 ecb - - - 7.6v, 8.3v, 8.2v - - - - 0v, 36.9v, 115mV ecb
AWS-109 Q15 2SC945 ecb - - - 8.2v, 8.3v, 8.8v - - - - 155mv, 36.9v, 055mV ecb
Pin 4 is grounded. good

D24 - a 36.4v, c 36.4v good

pin 40 - 0v (not constant, 2mV - -1mV) good DC balance for this channel
pin 41 - 0v (not constant, 1mV - 0v) good DC balance for this channel

D21 - a 16.94v, c 16.61v good, the over current is not triggering it
D22 - a 16.94v, c 16.43v good, the dc protect is not triggering it
D23 - a 16.94v, c 24.80v good, the dc protect is not triggering it

the dc protect is not triggering it
the over current is not triggering it

q6 collector is pulled low?, remove q6 and see if (c13 charges and) the relay pulls in, if not C13 may be shorted or backwards, because R42 should be trying to charge C13
if so, q6 is shorted, this transistor is marginal in this function, and a beefier transistor with a better safe operating area for pulse currents used.


THIS POST IS NOT FINISHED AND MAY CONTAIN ERRORS, I AM BEING INTERRUPTED TO DO PHYSICAL THERAPY HERE IN THE HOSPITAL!!!

Mark, thank you for your help.


I'm sorry for the confusing. I got new readings:

Q3: b -9.2mV, c 16.37v, e -0.57v
Q5: b 16.94v, c -1.31v, e 17.56v
Q6: b -1.31v, c 29.0v, e 0v
Q7: b 82mV, c 36.8v, e 0v
Q15: b 29mV, c 36.8v, e 82mV

The relay coil has 36.8v on both pins.

When I apply 16v on the relay coil, it clicks.

Also, the relay coil has 650 kOhm reading on the board (didn't pull it out from the board).


Added after your post was edited:

Removed Q6 and the relay pulls in in a few seconds.



tos

 

[markthefixer]

get a NEW q6, the first time it turned off, the new c13 was too much for it.

do NOT use any 2sc945's of any type.

use 512-KSD1616AGBU

 

[tosicus]

get a NEW q6, the first time it turned off, the new c13 was too much for it.

do NOT use any 2sc945's of any type.

use 512-KSD1616AGBU

Replaced Q6 with 512-KSD1616AGBU (I bought all transistors for the 109 board).

No changes. Still in the protection mode.


tos

 

[markthefixer]

Replaced Q6 with 512-KSD1616AGBU (I bought all transistors for the 109 board).

No changes. Still in the protection mode.


tos

Removed Q6 and the relay pulls in in a few seconds.

this exonerates C13, r43, r42, q7, q15 and R44

remove q6 and read the emitter base and collector voltages where it would be connected.
also (keep q5 IN) read Q5's voltages.

also check D25 / c14 minus for minus 5.5 volts

d25 is a candidate for replacement, 1n4004 has been used successfully in the past.

reassure me that you have installed the transistors correctly, and have looked up each and every transistor's pinout, as well as recognize the transistor symbol printed on the pc board.

 

[tosicus]

this exonerates C13, r43, r42, q7, q15 and R44

remove q6 and read the emitter base and collector voltages where it would be connected.
also (keep q5 IN) read Q5's voltages.

also check D25 / c14 minus for minus 5.5 volts

d25 is a candidate for replacement, 1n4004 has been used successfully in the past.

reassure me that you have installed the transistors correctly, and have looked up each and every transistor's pinout, as well as recognize the transistor symbol printed on the pc board.

D25 replaced with 1n4004.
C14 replaced with 647-UKL1HR22KDDANA.

Q6 removed readings:

Q6: b -65mV, e 0v, c 9.8v
Q5: b 16.05v, e 16.67v, c 12mV
D25: a -2.09v, c 2.12v
C14: +side 1.6mV, -side -2.08v
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Q6 IN readings:

D25: a -2.66v, c 2.07v
C14: +side 0v, -side -2.66v

Q1-Q7, Q15 checked, installed correctly.



tos

 

[markthefixer]

Check the voltage on both sides of R38. we are looking for the -13v, check the +/- 64 raw dc and the +/- 48 and +/- 30 regulated power supplies as well.

I don't like that D25/-c14 voltage, too low in either case.

 

[tosicus]

Check the voltage on both sides of R38. we are looking for the -13v, check the +/- 64 raw dc and the +/- 48 and +/- 30 regulated power supplies as well.

I don't like that D25/-c14 voltage, too low in either case.

R38 checked, 46.6k
R38 -13.25v, -1.30v on Q5 side

raw dc +74.5v, -74.5v

pin 66: +48.6v
pin 62: -48.8v

pin 69: +30.3v
pin 65: -30.6v


tos

 

[tosicus]

I'm adding two images of the protection circuit with standard parameters and my readings. The red ones are standard and the blue are mine. Hope this helps to see where is the problem.

tos

 

[markthefixer]

Check the voltage on both sides of R38. we are looking for the -13v, check the +/- 64 raw dc and the +/- 48 and +/- 30 regulated power supplies as well.

I don't like that D25/-c14 voltage, too low in either case.

the raw and regulated voltages are ok.
the -13v is ok

until the C14: +side 0v, -side -2.66v is correct at -5.5v all bets are off.

the problem is that removing q6 allows the timer circuit to work, while not correcting the c14 minus voltage.

pictures for checking that circuit are indicated. look for foil solder shorts.

 

[tosicus]

the raw and regulated voltages are ok.
the -13v is ok

until the C14: +side 0v, -side -2.66v is correct at -5.5v all bets are off.

the problem is that removing q6 allows the timer circuit to work, while not correcting the c14 minus voltage.

pictures for checking that circuit are indicated. look for foil solder shorts.

My pioneer works again! Mark, thank you very much for your help!

Replaced C14 with the old one and the relay pulls in... (weird)

However, when I turn the volume knob about 30% (-37db) it goes to protection again.

Also, on the power board AWH-052 is a capacitor C15 1uF 50v CEANL which I didn't replaced because the new one is ceramic (667-ECQ-V1J105JM) and it's bipolar. Should I replace it too? Will it improve the sound?



tos

 

[markthefixer]

C15 being changed to an ecq is very good thing.

protect could be several things, up to C9,C10 Q1, Q2 over current sense

BUT FIRST

does it do it when the amp is both quiet AND carrying music?
does cutting out the tone controls make any difference?


measure the DC voltage at the speaker terminals while turning up the volume knob to -37db with no audio. on this amp there is no dc offset adjust...
see if the dc voltage changes with tone control in and out, as well as various volume control settings.
we are looking for DC going into the power amp AND the input caps (c1q,C15L / R ??) leaking and letting it in.

if it does it on music only
then q1,q2,c9,c10 bear replacement. this is more likely.

 

[montecarlossfan]

I'm adding two images of the protection circuit with standard parameters and my readings. The red ones are standard and the blue are mine. Hope this helps to see where is the problem.

tos

Is it me or is d21 acting like a wire and not a diode.....16.9 both sides....and 16.4 after d23 which shows that is dropping voltage....