Sony TA-FE230 Amplifier 120W

Hi
I have a Sony DVP-SR760 Amplifier and when I connected it to my Turntable (with the volume on zero) then I just had to move the volume control nob slightly and the volume was just about right, I just thought it strange that I only had to move the volume such a small amount, anyway that was fine, the next time I switched the Amp on there was loud craking coming out of the speakers, that was with the volume at zero, they were very loud, I switched to Aux, then CD, then Phono, still loud cracking, then there was nothing coming out of the Amp., checked speakers and they are showing 6hms, so they seem not to of blown !
So the question is how do I test a Amps audio output ?.
Attached Service Manual.
cheers

Spike
You need a small filter what keeps ur noise down that’s all
 

MisterBill2

Joined Jan 23, 2018
18,167
Hi
Is it these coils as pictured, getting 22.2v from each one !.
OK, YES, it is those coils. From the circuit attached to post #12 we see that those coils are connected to the amplifier module pin 12, which is the output, AND the notation is that the voltage should be zero, or very close to zero. So this is why the relay is not operating, because that would damage the speakers.
Since the same voltage is present on both outputs that implies that the negative supply voltage is not present, indicating some sort of failure in the negative part of the power supply.

It appears that we do not have that circuit, which may be on sheet 20. I will investigate the manual attachment that I see toward the first posts of this thread.
What I see is that there are two power transformers shown and that there is a dual voltage regulator circuit, and it is not easy to follow the +45 and -45 volt supplies on my screen.
But based on the +22 volts on the output of the amplifier modules, the failure is in the negative 45 volt supply, and the protection IC is doing what it should do. There should be a -45 ormaybe -47.5, volts on pin 16 of the amplifier modules. THAT is what is missing. So the problem seems to be in the power supply section. That is on page 19, sheet 20, in the service manual attached to post #1. Somebody with a better display screen will be able to lead you through tracing to locate the failure point.
 
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Thread Starter

spike1947

Joined Feb 4, 2016
496
OK, YES, it is those coils. From the circuit attached to post #12 we see that those coils are connected to the amplifier module pin 12, which is the output, AND the notation is that the voltage should be zero, or very close to zero. So this is why the relay is not operating, because that would damage the speakers.
Since the same voltage is present on both outputs that implies that the negative supply voltage is not present, indicating some sort of failure in the negative part of the power supply.

It appears that we do not have that circuit, which may be on sheet 20. I will investigate the manual attachment that I see toward the first posts of this thread.
What I see is that there are two power transformers shown and that there is a dual voltage regulator circuit, and it is not easy to follow the +45 and -45 volt supplies on my screen.
But based on the +22 volts on the output of the amplifier modules, the failure is in the negative 45 volt supply, and the protection IC is doing what it should do. There should be a -45 ormaybe -47.5, volts on pin 16 of the amplifier modules. THAT is what is missing. So the problem seems to be in the power supply section. That is on page 19, sheet 20, in the service manual attached to post #1. Somebody with a better display screen will be able to lead you through tracing to locate the failure point.
Hi
Thanks for your reply, am attaching all the readings for Power Amplifier (IC 01) and readings from (IC901) , there was some errors before becaus I did not have all the srews in fixing the PCB back into the chassis, and there was a ground screw missing so have done all the readings again as per attachment in a .pdf , have it in Word as well !

Spike
 

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Thread Starter

spike1947

Joined Feb 4, 2016
496
The speaker switch is between the output of IC601 (Pin 6) and the other side of the relay. There are also two resistors in series with the relay coil. These are to drop the voltage on the relay coil down from 49 volts to 24 volts. (The relay coil voltage rating.) The relay does not pull in just because there is 49 volts on one end of the coil. There has to be current through the coil for it to pull. So the speaker switch has to be closed AND pin 6 of IC601has to be pulled down close to zero volts for the relay to close. IC601 only pulls pin 6 low when there are no fault conditions in it's inputs AND C603 has been charged up to 2.2 volts. This is done by current by current from the + 49 volt rail through R606 and R605 in series. I am waiting for the results of you removing C603 to see if that has become electrically leaky and shunting that current to ground. You have re fitted that capacitor before testing the voltage on pin 7 properly with the capacitor removed.
I initially assumed you had more experience than you have at repairing electronics. As a result of this wrong assumption I only said to test the voltage on IC301 pin 12 without saying to find a safe point to connect your meter probe if it was difficult to connect directly to pin 12.
Les.
Hi
Thanks for your reply, attached all the readings for both the IC301 and the IC9601 !.
cheers
Spike
 

Thread Starter

spike1947

Joined Feb 4, 2016
496
The speaker switch is between the output of IC601 (Pin 6) and the other side of the relay. There are also two resistors in series with the relay coil. These are to drop the voltage on the relay coil down from 49 volts to 24 volts. (The relay coil voltage rating.) The relay does not pull in just because there is 49 volts on one end of the coil. There has to be current through the coil for it to pull. So the speaker switch has to be closed AND pin 6 of IC601has to be pulled down close to zero volts for the relay to close. IC601 only pulls pin 6 low when there are no fault conditions in it's inputs AND C603 has been charged up to 2.2 volts. This is done by current by current from the + 49 volt rail through R606 and R605 in series. I am waiting for the results of you removing C603 to see if that has become electrically leaky and shunting that current to ground. You have re fitted that capacitor before testing the voltage on pin 7 properly with the capacitor removed.
I initially assumed you had more experience than you have at repairing electronics. As a result of this wrong assumption I only said to test the voltage on IC301 pin 12 without saying to find a safe point to connect your meter probe if it was difficult to connect directly to pin 12.
Les.
Hi
Thanks for your reply, attached all the readings for both the IC301 and the IC601 !.
cheers
Spike
 

Attachments

MisterBill2

Joined Jan 23, 2018
18,167
Am I seeing only positive voltage readings??Or is that short line after the voltage reading to indicate negative voltage? It is not the system I am familiar with, is the reason I am asking.
 

Thread Starter

spike1947

Joined Feb 4, 2016
496
Am I seeing only positive voltage readings??Or is that short line after the voltage reading to indicate negative voltage? It is not the system I am familiar with, is the reason I am asking.
Yes - after reading is negative and others are possitive .
Cheers
Spike
 

MisterBill2

Joined Jan 23, 2018
18,167
OK, then. If the correct supply voltages are present then it would not be a power supply issue. It does appear that the anticipated voltages are shown on the drawing. But if the output pin is at half of the positive supply voltage then certainly there is a problem that is not the protection relay system.
 

LesJones

Joined Jan 8, 2017
4,174
Can you measure the voltage on both sides of C351 and C301. Also for IC301 pin 4 you show that you tested it a C353 L. As C353 is shown drawn vertically on the schematic I don't understand which side of C353 you mean. (Top or bottom.)

Les.
 

Thread Starter

spike1947

Joined Feb 4, 2016
496
Can you measure the voltage on both sides of C351 and C301. Also for IC301 pin 4 you show that you tested it a C353 L. As C353 is shown drawn vertically on the schematic I don't understand which side of C353 you mean. (Top or bottom.)

Les.
Hi
Thanks again for your reply.

C351 L..100mV ( running down to 0)
C351 R-0

C301 R. -0
C301 L. -26v

As for C353 it lies horizontal on the boardas per pic attached , !, has does for most of the Caps.
C353 L: 26v -
C353 R: 26v-

Ps: C603 back in place !.
Regards
Spike
 

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MisterBill2

Joined Jan 23, 2018
18,167
I just realized that both of the output sections are i a single module! I had been thinking that they were separate modules. My mistake there, folks.
I am also guessing that this might be a DC coupled amplifier, which means that a failed transistor in a much earlier stage will produce a large problem much farther towards the output stage, such as what we are seeing here. So probably a detailed reading of the circuit description is in order. In the last Directly Coupled amplifier it appeared to be the power amplifier module, but it was a small transistor three stages before that which had failed.And certainly the failure is not in the protection system.
 

Thread Starter

spike1947

Joined Feb 4, 2016
496
I just realized that both of the output sections are i a single module! I had been thinking that they were separate modules. My mistake there, folks.
I am also guessing that this might be a DC coupled amplifier, which means that a failed transistor in a much earlier stage will produce a large problem much farther towards the output stage, such as what we are seeing here. So probably a detailed reading of the circuit description is in order. In the last Directly Coupled amplifier it appeared to be the power amplifier module, but it was a small transistor three stages before that which had failed.And certainly the failure is not in the protection system.
Hi
Thanks for your reply, at the min we are trying to find out why the speaker relay is not pulling in, that was the initial problem, the Amp was working fine, appart from the relay kept dropping out after a few seconds, but now is not energising at all !.
Cheers
Spike
 

LesJones

Joined Jan 8, 2017
4,174
Things seem to keep changing. I seem to remember at one point you had close to zero volts on pin 12 of IC301 which is why I asked for the voltages on IC601 (The protection IC) to see what kind of fault was preventing the relay from closing. The only thing that seemed wrong at that point was the power on delay input. now that you have a large offset on both outputs of IC301 we will try to sort out what are the causes. In post #54 you had about +44 volts on IC301 pin 12 In post #63 that had changed to -40 volts. I am still trying to work out what may be causing this. For misterbill's benefit here is a link to the datasheet on IC301
https://www.alldatasheet.com/datasheet-pdf/pdf/41600/SANYO/STK4192II.html

Les.
 

MisterBill2

Joined Jan 23, 2018
18,167
The reason that the speaker protection relay is not operating is because it is protecting te speakers from the large voltage present on the amplifier outputs. If it operated with that voltage present the speakers would be quickly damaged by the 45 or so volts across the voice coils. And that voltage appearing is probably why the relay was dropping out after a short time. so presently the protection circuit is working as it should.
The problem is the very large DC offset voltage on the amplifier outputs.
MY GUESS, based on experience, is that there is a DC offset voltage at the amplifier input, which is caused by a failed component much earlier in the amplifier.
MY GUESS, also, is that this is one of those DC coupled amplifiers that were so very highly touted years back.

So it will be needed that additional investigation will be required to even see just where the DC offset is being introduced. With the several multipin connectors in the circuit that will require a fair amount of time and patience to just understand the signal flow.
 

Thread Starter

spike1947

Joined Feb 4, 2016
496
The reason that the speaker protection relay is not operating is because it is protecting te speakers from the large voltage present on the amplifier outputs. If it operated with that voltage present the speakers would be quickly damaged by the 45 or so volts across the voice coils. And that voltage appearing is probably why the relay was dropping out after a short time. so presently the protection circuit is working as it should.
The problem is the very large DC offset voltage on the amplifier outputs.
MY GUESS, based on experience, is that there is a DC offset voltage at the amplifier input, which is caused by a failed component much earlier in the amplifier.
MY GUESS, also, is that this is one of those DC coupled amplifiers that were so very highly touted years back.

So it will be needed that additional investigation will be required to even see just where the DC offset is being introduced. With the several multipin connectors in the circuit that will require a fair amount of time and patience to just understand the signal flow.
Thanks for that info, will plod on and see if I can try my best to save it from the tip, quite attached to it, and the Sony Turntable (both made in Japan !) I purchased with it at the time.
cheers
Spike
 

LesJones

Joined Jan 8, 2017
4,174
Hi MisterBill, I have just come across something odd. From the datasheets on the three possible amplifier ICs that can be fitted to this amplifier unit two of them (STK4221 and STK4201 match the pinout on the schematic but the STK4192 has a different pinout with the inputs on 1 and 2 , 17 and 18 and the outputs on 10 and 13. The input to the power amplifier section is AC coupled at C351 and C301.

Spike, Can you confirm that you have fitted exactly the same part number amplifier module that you removed ?

Les.
 

MisterBill2

Joined Jan 23, 2018
18,167
Oh WOW!!! A wrong pinout would surely cause serious problems. No question about that!
And as for the capacitors in series with the inputs,I was not able to identify the series elements on my screen here.
And I must have missed the post about replacing the amplifier module. That would indeed explain the problem.
 

Thread Starter

spike1947

Joined Feb 4, 2016
496
Hi MisterBill, I have just come across something odd. From the datasheets on the three possible amplifier ICs that can be fitted to this amplifier unit two of them (STK4221 and STK4201 match the pinout on the schematic but the STK4192 has a different pinout with the inputs on 1 and 2 , 17 and 18 and the outputs on 10 and 13. The input to the power amplifier section is AC coupled at C351 and C301.

Spike, Can you confirm that you have fitted exactly the same part number amplifier module that you removed ?

Les.
Hi
Yes they are both " STK4192 II ", was having this prob before I changed the Amp !.
cheers
spike
 
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