Onkyo tx850 receiver no phono sound!

[brakescoop]

Hi...great forum, first post...

I picked up an Onkyo TX850 receiver at a garage sale ("...of course it works great!!") and discovered that the "phono" function isn't working.

The unit powers up fine, performs perfectly in all other tested input modes, but when a known good turntable is connected to the phone input jacks and the "phono" button is selected, the control panel lights up "phono", but no signal makes its way to the speakers.

I removed the cover to check for obvious problems (unplugged connectors, loose wires, rats, doughnuts, etc and came up empty.

I can't see spending $$ on bench time to diagnose and repair an item I paid $25 for (and could replace with a pretested unit via craigslist for about the same). I hate to just toss it...any ideas?

Regards,
Marc

[HayZee518]

could be the turntable needs a pre-amp for an output to the amplifier. a crystal phono generates a high enough signal to be amplified but a dynamic like a stereo requires a preamp.

[brakescoop]

A TX-850 is a fairly high-end receiver from the late 1980's, and well past the days of crystal cartridges, both in time and technology.

Agreed, there was a transition period when hi-fi/stereo was evolving in the early '60's that cartridge pre-amps were needed when upgrading to the (then)new lower-output magnetic cartridges, but I don't think that applies in this case.

Thanks for the thought, though...

Marc

[Larry at Approved]

Originally Posted by brakescoop

Hi...great forum, first post...

I picked up an Onkyo TX850 receiver at a garage sale ("...of course it works great!!") and discovered that the "phono" function isn't working.

The unit powers up fine, performs perfectly in all other tested input modes, but when a known good turntable is connected to the phone input jacks and the "phono" button is selected, the control panel lights up "phono", but no signal makes its way to the speakers.

I removed the cover to check for obvious problems (unplugged connectors, loose wires, rats, doughnuts, etc and came up empty.

I can't see spending $$ on bench time to diagnose and repair an item I paid $25 for (and could replace with a pretested unit via craigslist for about the same). I hate to just toss it...any ideas?

Regards,
Marc

The TX-850 has a very simple phono stage, only a single op-amp mounted on it's one little circuit board. The connections to the board may be broken (cracked solder connections, something like that). The only other thing it could be is a defective input selector IC, but highly unlikely that it would fail in both channels on the same input. Almost has to be something with the phono IC.

Larry