Onkyo DTR-80.1

[freethink]

Hi guys, I'm working on an Integra DTR-80.1 receiver, with complaint of smoke, and some channels not working. Upon inspection, I immediately noticed some exploded/bulged caps on what looks to be the preamp stage(?) 5 out of the 9 channels have the same bad cap (C6026, C6021, C6022, C6023, C6025), also, those bad channels, also each had a resistor way out of spec (R6286, R6281, R6282, R6283, R6285). Fuses F6603 and F6604 are blown. Is there anything else I should check before I throw fuses at it, and function check? Also, do these channels pop out with just one screw at the bottom? It would be so much easier to replace and inspect components with the board out. Any help would be much appreciated. Thanks!

[tibimakai]

Re: Onkyo DTR-80.1

I'm 100% sure that you have a bunch of other components that are bad. I would go over at each channel, and test all the components.
I would test those final transistors on the big heat sink as well.
I have never heard something like this, where so many channels are blown at once.

[eccerr0r]

Re: Onkyo DTR-80.1

This design, if the idle bias is set wrong, that would easily destroy the cap and resistor and probably more downstream...this schematic fragment doesn't include the actual driver transistors does it?

[freethink]

Re: Onkyo DTR-80.1

I'm 100% sure that you have a bunch of other components that are bad. I would go over at each channel, and test all the components.
I would test those final transistors on the big heat sink as well.
I have never heard something like this, where so many channels are blown at once.

Okay, so you are correct. 6 out of the 9 output transistors are toast. Do you think this thing is worth fixing at this point?

[freethink]

Re: Onkyo DTR-80.1

This design, if the idle bias is set wrong, that would easily destroy the cap and resistor and probably more downstream...this schematic fragment doesn't include the actual driver transistors does it?

Can the idle bias be checked on a dead circuit? I also found 6 out of the 9 output transistors to be toast. Do you think this thing is worth fixing? I think it was a $3000 amp back in the day. If you care to look at the manual, the output stages are on page 10 and 11.
https://manualmachine.com/integra/dt...ervice-manual/

[eccerr0r]

Re: Onkyo DTR-80.1

up to you if you want to fix it. schematic there that's available without registering is crap, and I'm sure not going to register/pay for a copy.
you can try to adjust it if instructions are in there, but probably need to have those burned parts replaced and somehow set the idle current to minimum and increase until it hits the recommended current. Make sure the 82 ohm resistor (R6071 and whatever it is on the other duplicate boards) are also intact.

[tibimakai]

Re: Onkyo DTR-80.1

I'm pretty sure there are still a lot of burned/bad parts in there.
If you have the patience to go through each component, on each of those channels, then yes you could fix it. You will have to take it apart completely, to be able to measure all the components at those bad channels, even the main bottom board as well.
Usually, I measure all the components when I start, I make a list what is needed, I buy them, replace them and measure again all the components all over again, just to be sure.

[eccerr0r]

Re: Onkyo DTR-80.1

also ... 9 output transistors? weird, usually they're in pairs - two transistors per channel at least, or do you mean all the npn drivers are fine?

[freethink]

Re: Onkyo DTR-80.1

also ... 9 output transistors? weird, usually they're in pairs - two transistors per channel at least, or do you mean all the npn drivers are fine?

I only checked the PNP's on top. The mates are way down in there. I'm still trying to figure out how to get the preamp boards out, so I can access the lower ones. It looks like I might have to take the whole thing apart. If the idle bias is out of spec on one channel, can that cause other channels to fail? I'm kind of a noob. Thanks for you patients and understanding.

[eccerr0r]

Re: Onkyo DTR-80.1

Usually one channel does not cause others to fail; been trying to poll what causes these failures, as far as I can tell it's abuse like accidental output shorts and/or turning volume up way too high. Did you ask how it failed, what happened just before? These don't usually spontaneously fail as far as I can tell, but shorting outputs can be quite detrimental.

[petehall347]

Re: Onkyo DTR-80.1

its been abused or there is a power supply issue .

[freethink]

Re: Onkyo DTR-80.1

It was free on Craigslist. I didn't want to grill the guy to hard on how it broke.

[tibimakai]

Re: Onkyo DTR-80.1

I have noticed that on Onkyos, the final transistor mounting screws are pretty loose.

You will have to take the whole thing apart. You will have to test the bottom main board as well.