1964 Zenith Console Stereo with Microtouch 2G Changer
 

Hello everyone recently I just picked up a 1964 Zenith Console Stereo with a first generation Microtouch 2G Record Changer that uses single-ended 7695 tubes in the amplifier and I was curious as to what kind of tubes those were and what kind of power they were rated for because I had never heard of those tubes before, and these tubes are in the larger 9-pin tube package, and this unit has all of its original Zenith tubes in it yet, as from what I was told it was mainly used as a decor item in the house it came out of.

It is FM Stereo Multiplex, and actually I was kind of surprised that it was tube powered because I had thought that by that point everyone went solid state on the big consoles.

The cabinet is kind of trashed as the grill cloth on the speakers is torn up and there are cigarette burn marks all over the top of the cabinet (which at first I thought it was bird poop because it was a curbside find that a friend of mine who knew the owners of the house that the stereo came out of told me about, but when I was cleaning it that's when I realized it was cigarette burn marks because they weren't going away with soap and water.)

Anyways I would like to know a little more about what I have here, it actually has the magnavox style slide cover top rather than the flip-top lid that Zenith usually used.

Its model number is ML2420-3 Chassis No. 3L02.

Thanks for your help.

I have one of those stereos with those output tubes. The tubes are good for about two watts at 140 volts B+. It has 6X9 speakers and a small hard cone tweeter.
Good stereo for use in an apartment, as it's not very powerful!

That's what I figured, the turntable though is a nice first gen Microtouch 2G record changer which would be a nice little stand alone changer in a nice wooden plinth.

That home it came out of must be a real pit!
It's a good scrapping piece. The changer is a V-M! Does the tuner have a power transformer or transformer-less. They made them both ways.

:worthless

Well from what I was told, (and from what I could see of the cabinet on the unit) they were heavy smokers, there were tons of cigarette burn marks on the top of the cabinet.

The unit is a hot chassis set unfortunately, and it was too bad that the unit was so badly trashed because the unit still had all of its original tubes in it yet! :sigh:

A little update, I pulled all of the tubes from the chassis, and tested them all, and as I suspected, they tested NOS (100+ on emissions, and no grid leakage) which confirms what the guy that went with me to pick this unit up, told me about this unit, which was that it was used as a piece of furniture and nothing else (or in this case an ashtray.)

I also pulled the Microtouch 2G changer from the cabinet which was still in good shape yet, and had a woodworker friend of mine make me a plinth out of solid oak for the changer so I could use it as a stand alone unit for my computer for record transfer work, I just need to stain the plinth and get a new needle installed and a standalone powercord and a RCA to 1/8" stereo jack and I'll be all set. :thmbsp: :music::banana:

Pictures of the changer below.

It's a shame how some people treated their things.

OK so quick question regarding my Zenith Micro-Touch 2G Turntable that I made into a Standalone unit to use with my computer, I've hooked it up to my computer's Line Input on the back of my computer, but for some reason or another there is a somewhat noticeable ground-loop hum coming through the speakers and is also picked up by my recording software, is it necessary to add a separate ground wire to this turntable when using it as a standalone unit like this or is just that my audio cable I'm using is going bad?

Hard to know from here.
Easiest way to check is grab a clip lead, clip it to the chassis of the changer and the chassis of the PC... Situations like this are why I keep lots of clip leads on hand. Never know when you need to make a quick temporary connection to test or fix something, but it'll be often if you do enough servicing work.

Ok, I'll give that a shot.

The reason why I was asking was because I have an old Motorola record changer from 1974 (it came with a stereo receiver with a built-in 8-Track player that was also a Motorola made unit) that the changer mechanism was a BSR unit that used a Tetrad cartridge and that unit which I have hooked up to my Pioneer SX-737 receiver didn't use a ground wire to make it work.

It also depends on if it's a ceramic or magnetic cartridge.

I'm assuming that the cartridge that Zenith used in their Microtouch 2G changers was a ceramic cartridge but I'm not sure.

Yes, I believe they all are ceramic, Pfanstiehl 898 or similar on E-V 5188 cartridge (Zenith 142-167)

As the original set had a transformerless power supply, the platter ground was probably floating, that is, not connected to the amplifier´s B-. Maybe only thru a 0,05 microfarad condenser in parallel with some high value resistor.

Do you hear the hum always, or only while the turntable´s motor is running?

I hear the hum all the time, but it's worse when the turntable is turned on.

The instructions that came with the old-time radios used to say that you could reverse the line plug (back then they were not polarised) and leave it where the hum was minimal. But today the only acceptable hum level is the inaudible one.

If the hum persists even with the turntable unplugged from the wall (not just turned off), there must be something wrong with the cabling. Either the RCA-to-1/8" cable, or the shielded cable within the platter.

Sometimes a RCA-to-1/8" can have a bad ground contact, even when new. (I assume you put two RCA jacks somewhere in the plinth to plug the RCAs end of your cable). Try unplugging both RCAs from the turntable. I think the input impedance of the computer will not be so high as to pick hum from the cable while it is disconnected, so if the cable is OK, you should have no hum.

I suppose you are using the original flexible cable going from the cartridge, along the tonearm, and down to the RCA jacks. Check if there is some connection between the shield of this cable and the turntable's ground, maybe thru a condenser. Try removing this connection. Many old time cables have the shield exposed along the metallic pick-up arm, so it will be not an easy task to do this.

A quick test would be to disconnect the cables from the cartridge, and connect the computer's line input directly to the cartridge terminals, using a temporary cable. This cable need not go thru the tonearm, just leave it hanging between the cartridge and the computer's line input. You don't need to play a record, because you will be just troubleshooting the hum. Check for hum a) with the turntable disconnected from the mains, b) connected but turned off, and c) while the motor runs.

If you still have the hum, it is coming from the cartridge itself.

If the above three tests are hum-free, the trouble may be in the original shielded cable that goes inside the tonearm: either a high resistance (or open) in the inner conductors, bad contact with the cartridge pins; or an high resistance or open shield.

If the resistances check OK, and the test with the independent (provisional) cable was OK, there must be some connection between the shield and the platter's ground that should be avoided. If you need to substitute the original cable you will need a very flexible one, so it does not interfere with the side movement of the tonearm.