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Michael
Michael, Technician
Category: Consumer Electronics
Satisfied Customers: 9130
Experience:  Over 25 years experience in the field of electronics repair, TV, VCR and computer repair.
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I have an Onkyo TX-SR875 receiver. The receiver just died

Customer Question

I have an Onkyo TX-SR875 receiver. The receiver just died with no standby light or any sign of life. Measuring the voltage on the secondary winding of the standby transformer T9001 it is 9.8v. Readings on the connector JL901A are
1 (+ SUB) 12.8v
2 (GND) 0V
3 (POFF) 7.4v
4 (+9V) 0v
5 (APOWER2)0v
6 (APOWER1)0v
7 (HPOWER)0v
I am guessing that some components on the power supply board are fried. Hope you can point me in the right direction.
Thanks
Dave
Submitted: 1 year ago.
Category: Consumer Electronics
Expert:  Michael replied 1 year ago.

Hi Dave I'm sorry to hear that.

How old is your receiver?

Also were there any power outages or storms just prior to this event?

Thanks

Tech Michael

Customer: replied 1 year ago.
Hi Michael the receiver is 4 years old. It is possible that there was a storm prior to the receiver dying.
Thanks
Dave
Expert:  Michael replied 1 year ago.

Thanks for that Dave.

This could be almost anything have you checked the fuse in the unit on the power supply? That would be the first step.

Thanks

Tech Michael

Customer: replied 1 year ago.
Fuses are all ok. Voltages on connector JL901A on the power supply board are not ok. eg The +9v reads 0v.
Thanks Dave
Expert:  Michael replied 1 year ago.

Thanks Dave,

On this one they don't sell just the transformer inside on the board, But that is the part most likely to have failed anyway as they will over time. One of the biggest killers of theseisi unplugging them after they have been powered for a long time. Te reason is that this part is live all the time when plugged in even when its off.

So the part heats up and thats fine, but then it cools if unplugged and usually cracks the tiny wire windings inside.

The best way to fix this is to replace the supply board.

You can get that from Sears parts direct or this site I prefer if they have one, I also have other sources if we end up needing to go there.

Please check : https://www.partstore.com/OpenSearch/Model/Onkyo+Corporation/Onkyo.aspx

Or call them as I would recommend as theydo not list all parts and products on site;-)

1-***-***-****.

In any case, I will stick with you until this is complete.

Please rate kindly thus far, it won't cost you anything to rate my service to you kindly,

Then you can reach me by simply replying to this message anytime.

Thank you and have a great day Dave!

Tech Michael

Expert:  Michael replied 1 year ago.

H Dave please don't forget to rate so we can stay together until your receiver is working as it should. Thanks

No cost for rating;-)

Thanks

Tech Mike

Customer: replied 1 year ago.
Hi Michael thanks for that. Partstore only has remotes controls for the TX-SR875 and Sears has spares for many Onkyo receivers but not the TX-SR875. A replacement power supply board is not easy to find, which is why I am here. Either I need help finding a replacement board from places I don't know about, or if there are no spares anymore I need help working out which components have most likely failed on the board so it can be repaired.
My initial thoughts were also the standby transformer (NPT-1520GQ), however the standby transformer output voltage measures 9.8v. Primary winding resistance is 11.2 ohms and the secondary winding 4.38 kohms measured with the transformer still in the pcb.
It is a 240v receiver purchased in Australia so the power supply board is slightly different to the US model also.
Hope you can help.
Thanks
Dave
Expert:  Michael replied 1 year ago.

Hi good morning Dave, with this one it could be the transformer as even though they will show near normal voltages they cant "sink" the current.

Meaning they have the proper voltage but there is no power behind the voltage amps.

So you will see this by the supply isn't delivering the needed power. This could also be another part on the power supply board as well that con only be determined by testing each component. I will check to see if a schematic is available for that board. This may take a day or so, I will let you know when I have it.

It looks like you may the experience needed to do this so I will help you either way with a new board that I will search out for you or repair on the old one.

But please rate at this time so we don't lose your question as sometimes happens if time passes with no rating. Once you do that, I will see this and reply to you so you can keep going with me. ALso there is no cost to rate.

Thanks for your understanding Dave.

Tech Michael

We can go step by step on the testing procedures;-)

Expert:  Michael replied 1 year ago.

One way to find out where tto get the part is by calling Onkyo: 1-***-***-****.

Thanks Dave.

Tech Michael

Customer: replied 1 year ago.
Hi Michael haven't heard back from you & not sure if you found the service manual, so here it is. http://oli189.free.fr/Service.Manual_TX-SR875.pdf
Thanks
Dave
Expert:  Michael replied 1 year ago.

Hi Dave lol, I'm sorry the site I use was down because of bad weather damage to their internet access. But thank you for that.

I have a question for you I know you sent me the outputs from the secondary, but I'm not sure on one of them. you have POFF) 7.4v 4 (+9V)?

Can you send just the voltages you observe on each pin

Thanks Dave.

Tech Mike

Customer: replied 1 year ago.
Hi Michael sorry for the confusion, what is written in the brackets is what is printed on the standby power board PCB next to connector JL901A. I am including this as that is what is printed on the board and it is not quite the same as in the service manual, most likely because the manual is a US one an the Australian power supply board is slightly different being 240v. The main difference is pin 4 is +12v in the manual and +9v printed on the board in my amp.
So the readings on connector JL901A when the board is connected are Pin 1 0v (MPOWER) , Pin 2 0v (APOWER1) , Pin 3 0v (APOWER2) , Pin 4 0v (+9V) , Pin 5 7.4v (POFF) , Pin 6 0V (GND) , Pin 7 12.8v (+ SUB).When I disconnect JL901A the readings on two of the pins change, pin 5 reads 10.4v and pin 7 reads 13.4 v. The rest are still zero.
Thanks
Dave
Expert:  Michael replied 1 year ago.

Hi Dave, thanks so much for clearing all that up. For one, you need a new supply transformer. I'm not sure if that is available separate you likely need the entire board.

Do you have a source for that?

I may be able to help there.

Tech Michael

Expert:  Michael replied 1 year ago.

missing some outputs.

Customer: replied 1 year ago.
Hi Michael is it the standby transformer that you think is the problem or the main transformer? I have had no luck finding the a replacement for the standby transformer.
I have tested many of the components on the standyby power supply board and all the capacitors, resistors and diodes seem ok. The only component that looks suspect is the zenner diode D9007 which reads open circuit measured both ways on the multimeter set to resistance. When measured in diode mode it measures 0.679v and 0v the other way
Also there is another tech Louie who mentions this diode as well as false triggers on the Poff
http://my.justanswer.com/question/guest/9d56aced60cc43c7b8650d4857a76ebf
Not sure if this is useful
Also when I disconnect JL901A the voltage on Pin 5 (POFF) changes from 7.4v to 10.4v and Pin 7 (+SUB) changes from 12.8v to 13.4v. I noticed that the these readings are similar to those taken on this amp which Louie was working on which has a different fault, which could possibly indicate the transformer not being the problem.
Thanks
Dave
Customer: replied 1 year ago.
Hi Michael is it the standby transformer that you think is the problem or the main transformer? I have had no luck finding the a replacement for the standby transformer.
I have tested many of the components on the standyby power supply board and all the capacitors, resistors and diodes seem ok. The only component that looks suspect is the zenner diode D9007 which reads open circuit measured both ways on the multimeter set to resistance. When measured in diode mode it measures 0.679v and 0v the other way
Also there is another tech Louie who mentions this diode as well as false triggers on the Poff
http://my.justanswer.com/question/guest/9d56aced60cc43c7b8650d4857a76ebf
Not sure if this is useful
Also when I disconnect JL901A the voltage on Pin 5 (POFF) changes from 7.4v to 10.4v and Pin 7 (+SUB) changes from 12.8v to 13.4v. I noticed that the these readings are similar to those taken on this amp which Louie was working on which has a different fault, which could possibly indicate the transformer not being the problem.
Thanks
Dave
Expert:  Michael replied 1 year ago.

Hi Dave, Louie is an excellent tech as well ;-)

In this case you are correct I cant seem to locate one either, so, that means if you want to fix this or get it operational you will need to do a little trick. Basically you need a couple of supply transformers to make up the various voltages you need. Modify basically.

I have done that many times when a supply transformer isn't available.

Its really the only realistic way of doing this.

I will help you locate the supplies you can use if you want o do it that way. Just let me know on that?

In any case, I will stick with you until this is complete.

Please rate kindly thus far, it won't cost you anything to rate my service to you kindly,

Then you can reach me by simply replying to this message anytime.

Thank you and have a nice day Dave.

Tech Michael