Zenith Console MK2635

[balez5809]

I have a 1962 Zenith MK2635 Console that has a 12K26 Tuner/Preamp and a 3K32 amplifier. I was thinking of introducing a preamp output and an amp input. Has anyone done this before? I have a copy of the schematic and it appears there is a separate shielded cable (with left channel/right channel/ground) as part of a harness that connects the 12K26 and 3K32. Would it be as simple as introducing in/out jacks on the shielded cable. I have attached a couple of schematics as reference.

Any help would be appreciated.

Thanks
Bill

 

[gadget73]

Can you post the amp schematic too? I suspect the feedback loop might come back up to the preamp. I see connections to the cathodes of the audio output tubes on the preamp that come from that plug. If so, it will be a little more difficult than just breaking that connection.

 

[century tek]

If you are wanting to run a separate amplifier from the existing preamp/tuner, you can do so as you were right about left and right shielded cable. You can just tap in from there. But, you need the amp chassis to power the tuner/preamp so there needs to be some kind of a load on the amp at all times whether it's a speaker or resistor.

If you are wanting to run the amp stand alone all by itself, it would probably need its own 12AX7 tube to do the AF amp / phase inverter duty as the amp chassis does not have one.

 

[balez5809]

Thanks for your information. Very helpful and gives me some additional insight. Good to get expert opinions.
I do plan to leave the 3K32 amp in place. My thoughts was to introduce either an equalizer or maybe a reverb unit into the signal path - I believe adding a little reverb my help the speaker configuration sound a little fuller (just to experiment). I have attached schematics of the amp (3K32) and partial of preamp (12K26). As a note I am just getting back into tubes (did a few solid state units in the past - hobby) and work the dust out of my brain attic. Any help/advice is very much appreciated.

 

[gadget73]

yup, no driver on the power amp. In a practical sense you can't seperate the preamp from the power amp by breaking the connection at the umbilical. The feedback won't be complete and it won't have a voltage amp stage.

Honestly the easiest place to do this is using the reverb socket. Pull the jumper plug out and insert your EQ or reverb unit there. That will be upstream of the volume control, but it shouldn't affect how anything operates.

 

[balez5809]

Thanks! Always pays to have another set of eyes look at the details. Glad you saw the jumper plug. Completely overlooked that section of the schematic! I think that is my best option. Really appreciate your review and insight. Thanks Again

 

[balez5809]

Added note to share information with you since you helped me.
I did so research and found the reverberation unit that was an option for this console. It was a mechanical spring reverb unit with its own amp. I attached a picture from a SAMS. Ordered the SAMS to look at schematic and see how this integrated into the system.