Onkyo Tx870 problem

[skater770]

Hello, and here is my story.

My grandfather and I were going through his basement a couple years ago and I found his old receiver. He told me about how long it lasted and how it was a top of the line receiver back in the day. (1979 I believe)
He said I could have it because it didn't work and I bet him I could get it to work. (it also doesn't have a remote..)

Whenever I turn it on the main power and system power, it will turn on and off 3 times and then power off compelely.

If I just turn on the main power and let it sit there with the main power on for 2 minutes and then turn the system power on, it will work just fine.



Does anybody have any information about this problem and how I can fix it?

Any help is appreciated!

 

[TLS Guy]

Hello, and here is my story.

My grandfather and I were going through his basement a couple years ago and I found his old receiver. He told me about how long it lasted and how it was a top of the line receiver back in the day. (1979 I believe)
He said I could have it because it didn't work and I bet him I could get it to work. (it also doesn't have a remote..)

Whenever I turn it on the main power and system power, it will turn on and off 3 times and then power off compelely.

If I just turn on the main power and let it sit there with the main power on for 2 minutes and then turn the system power on, it will work just fine.



Does anybody have any information about this problem and how I can fix it?

Any help is appreciated!

As far as I can tell this is the way it is supposed to work. The instruction manual states that the main power has to be turned on first. I think this main power is supposed to be left on, then the unit is in standby mode, which allows the system to to be powered on from system power and the remote.

I think this receiver is probably early 80s and is a first generation microprocessor controlled receiver. The memory is volatile, as settings are only kept, if the main power remains on and the unit kept plugged in. If the unit is unplugged, or the main power switched off, then all settings are lost.

I suspect that you have to leave time for the system to boot, before pressing system power on the front panel or remote. What you describe would be pretty typical for a boot time for processors of that vintage. They were very slow.

Obviously there is a boot time involved, or there would not be a main and a system power. Since the memory is volatile, when everything is shut down, you would expect there to be a time for the unit to boot from the BIOS in the control board.

If this unit ever gives trouble related to the control system, I'm certain you won't fix it, as all the devices of that generation will be NLA. I think that will also go for the output devices, which appear to be integrated, from what I can gather. That was a system popular for a while back then, but caused a servicing nightmare, because of availability of parts. I'm actually surprised the unit is working. Those types of first generation processor controlled devices were not known for longevity. The earlier generations of receivers were much more durable and would still be serviceable.

You can download a user manual here.

 

[skater770]

Wow, ty for the help. I will certainly leave the main power on now. I checked the back of the receiver and it says it was made in 1979. Since there appears to be no problem I will continue to use it and I can start looking for a remote for it now that I know there is no problem. I believe it sat in a basement since the early 90s and was pulled out back in 2006 and I have been using it since. It sounds as good as the modern Onkyo receivers I hear today so I have no complaints.

I did not have the service manual, thanks for the link.

Anyway, I plan on keeping this baby until it breaks. If it breaks, it breaks, no big deal.

How many years do you think it has left in it?

 

[TLS Guy]

Wow, ty for the help. I will certainly leave the main power on now. I checked the back of the receiver and it says it was made in 1979. Since there appears to be no problem I will continue to use it and I can start looking for a remote for it now that I know there is no problem. I believe it sat in a basement since the early 90s and was pulled out back in 2006 and I have been using it since. It sounds as good as the modern Onkyo receivers I hear today so I have no complaints.

I did not have the service manual, thanks for the link.

Anyway, I plan on keeping this baby until it breaks. If it breaks, it breaks, no big deal.

How many years do you think it has left in it?

Impossible to say. Solid state failures are very random.

 

[Stereo Lab service]

We found that replacing C923, 100mfd 35v capacitor would solve this problem. We used a 220mfd capacitor just because the 100 seemed a bit small. The original value replacement would probably also work.