Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: zapped on June 08, 2017, 12:41:46 pm

Title: Zenith OT wiring ??
Post by: zapped on June 08, 2017, 12:41:46 pm

I have an old Zenith stereo amp from a console. 2 x 6bq5's 1 per channel ? and 1 12ax7. I assumed it to be single ended however the OT's seem to be push/pull. I assume this because both OT's have the common red, blue and brown input wires and 2 output to the speakers. The blue and brown for each channel seem to go to a 6bq5 power tube. I thought single ended would have only 2 input wires. This is my first encounter with this tube and a SE amp ???? What do I have here?  Thanks for listening.   Ed

Title: Re: Zenith OT wiring ??
Post by: sluckey on June 08, 2017, 01:03:53 pm

It is a single ended amp. Which tube pins do the blue and brown wires connect?

Title: Re: Zenith OT wiring ??
Post by: zapped on June 08, 2017, 03:03:40 pm

I will report back with the pin connections.  Thanks

Title: Re: Zenith OT wiring ??
Post by: PRR on June 08, 2017, 10:24:09 pm

Zenith chassis numbers are well documented, and many schematics are available.

The "extra" wire may go to G2. This is Ultra Linear. (Yes, you can do it SE as well.)

Don't cut it up. The entire output stage can be used as-is with minor mods for guitar.

Title: Re: Zenith OT wiring ??
Post by: zapped on June 08, 2017, 11:21:03 pm

Thanks to Sluckey and PRR. Yes the brown wires were went through a 1.6K resistor to pin 9 (G2) and blue to plate pin 7. Can I assume the OT's are being used as SE but in Ultralinear and can't be used as push/pull? I have not been able the find a schem. for this unit using the marking on the chassis (amp or tuner)  I don't have the model of the console unit, but I will keep looking. All tubes were removed from tuner and sockets are not marked. Thanks for the help.  Ed

Title: Re: Zenith OT wiring ??
Post by: shooter on June 09, 2017, 08:27:45 am

Quote

Can I assume

Yes you can :laugh: