Old (working) Voice of Music tape recorder amp

[Rand524]

I just purchased a tube amplifier pulled from a Voice-of-Music tape recorder, circa 1957. It has 3 12AX7s, a 6V6 and a 5Y3 rectifier. Plugged in a vintage Electovoice 12L speaker...and it worked. Would like to fashion it into a combo amp. Found a schematic and that will be coming in a few days. First thing is to replace the 2-wire cord with a three-wire. Then, should I think about replacing any of the components - like the large capacitor cans? It has a volume control and a double tone/brilliance pot with on-off, two inputs labeled (with a sharpie) "Phone" and Mic" (guitar sounds much cleaner using the "phono" input) and two outputs - speaker and pre-amp. I was hoping to use this as a project to learn and maybe improve the sound a bit in the process. Any recommendations?

[stokes]

You will definately want to change the filter caps,those are the "large capacitor cans" you describe.And any other electrolytics as well.At that age,and the fact that the unit probably hasnt been used in some time,it is likely they are dried out and could fail.You will want to check the coupling caps to be sure they arent leaky or conductive.These units are built for sound reproduction,so you will also want to tweak it for a little more gain,unless someone has already modded it for guitar,I just realized you said you have only the amp and not the recorder,so it is possible that someone pulled it and already did some mods.

[Rand524]

Thanks. I checked the specs on the Cans - the big one reads (from top to bottom) 40 mfd (with a half-circle shape at the left), then 30 (square), then 10 (triangle), then 10 again (two dashes), all at 450 VDC. Been reading, but not sure yet what to replace with or how. The other one is easier - single value 40 mfd at 450 VDC. Can you provide any help or point me to a place where I can learn? Sorry to ask a (another?) dumb question but what are the coupling caps and how do I identify them? I don't think any modifications have been done, but I am willing to learn and improve it where I can.

[stokes]

Okay,let me know when you get the schem and I'll try to walk you thru some stuff.Which model is it?I have a couple of VoM schems,I did a refurb for someone a while back,if I have the same one it'll give me a reference source.Instead of the can,I would get some single 450v caps to match the values.You can email me if you like,I think its in my profile,but if not here it is stokes1971@aol.com let me know when you get the schem.

[Rand524]

Just got the Schematic

Thanks, Really appreciate the help. Just received the schematic and have been trying to walk through it. This site: (http://www.dogstar.dantimax.dk/tubestuf/4x4howit.htm) has been helpful in understanding the general flow, although some of the theory is a bit beyond me. The amp has an oscillator section which I assume was used for the tape recorder function. It also has a 6E5 for record level and it also uses a 5Y3 rectifier, both of which I'm guessing are not used in the audio stages. I'm getting the impression that there may be so much "extra" here, that it might make more sense to break it down into parts and rebuild from scratch using the chassis. Recommendations?

There are also two clipped wires from the Head Plug (M1) - pin 4/5 and 6/7/8, originally for erase and record/play and labeled them "Input"

I've scanned the Schematic and parts list but they are too large to get uploaded here. Stokes, I will take you up on your generous offer and will send them to your email address. I would be happy to do the same for anybody else interested.

[Rand524]

Sorry - the model is Tape-O-Matic 710A

[stokes]

I sent you an email with some suggestions.Does this unit have the sound on sound feature?If so when you mod it as I suggested,try to keep everything associated with the record/playback circuit intact,as these things can be modded to use as a tape echo,kind of complicated and probably a little too involved for a beginner,but someday you may want to tackle it.Have fun.