Classic Hifi Care

A little background: During COVID times, I picked up the vintage radio bug, after finding a late 40s Motorola AM/SW radio on Craigslist for $20. I re-capped, re-resistored, and re-wired that unit successfully after practicing on a similar vintage Packard Bell that they guy with the Motorola threw in for free when I went to pick it up. Recently, my early 90s Sony stereo receiver decided to blow something inside, rendering my ability to play my beloved LPs, so I decided to look for an AM/FM/Turntable console to restore, like so many units I remember seeing in older relative's homes growing up. So this weekend I found something cheap, after doing zero research, and I just picked it up. Now after having it a few days, I've pulled the amp and preamp and spent some time on the internet trying to see what I've got. The paper label on the cabinet reads 1ST288G. It looks exactly like the unit on the right, in this exerpt from the 1963 Magnavox catalog.
Here's what it looked like when I picked it up: Note that only one side of the top slides. Unlike earlier units, this model was cheapened by eliminating the record storage area.

As I mentioned, I pulled the amp and preamp to see what I'm dealing with, and it turns out to be as follows:
Amp: 8601-20, the well-known single ended micro-power amp with 6BQ5 tubes
Preamp: 7907-00
Record Changer: Micromatic G-600
Speakers: 12-inch woofers (square magnet) and 5" cone tweeters

A couple of interesting things in comparison to the catalog text. The cabinet I have is clearly the "Contemporary" model and it's labeled 1ST288G. There must be something in the G, because the catalog says Model 1-ST288 has an FM/AM Radio and the Model 1-ST289 has Stereo FM and FM/AM. The preamp faceplate on the model I have with the "G" has the following stops on the selector switch: Radio Off/Phono On, Stereo FM, FM, FM AFC, and AM. However, this unit does not have Stereo FM. The preamp chassis has unused RCA jacks for Stereo FM (CH1 and CH2) and TV (mono). Presumably, if you select Stereo FM, you get nothing, unless you plugged in an add-on Stereo multiplex circuit, which is clearly not included on this thing. Also, I have no idea (yet) which selection on the front dial corresponds to the TV audio input.
But this is all good news, because, of course, I'm planning to plug in a bluetooth unit to those Stereo FM input jacks, and get all modern with this thing.

Anyways, give me a while to get set up better on my bench, and I'll take a few photos of the "guts" of this thing, and any other interesting things I find as I go through this. The next steps are getting caps and drifted resistors on order from Mauser, and a few turntable parts from V-M Audio Enthusiasts. It's pretty dusty/grungy inside, but there's no evidence of rodents, the turntable platter spins freely, and I think this will clean up nicely. I could have gotten something more desirable, or with more features, or a higher-powered push-pull amp, but I think this will be fun and turn out okay. I'm really looking forward to firing up the soldering iron again!

Regards,
Eric

Thanks for sharing, Eric, we love photos and sharing stories of how we found our different toys. Speaking of toys, as you read through the forum you will find most of us have different interests, so please share if you fall into that category. If you haven't already, be sure to check out the downloads there is a lot of info there.

Bill

Here are the two chassis in “as-pulled” condition (minus an eighth-inch of dust):
The 8601-20 amp: The 7907-00 preamp: The G-600 changer (minus the platter): And finally a photo of the faceplate. Note the apparently unused “stereo fm” position on the selector switch. Still unclear to me where the mono TV audio input goes, but I haven’t yet spent any time studying the schematics. Also I’m wondering why no L-R balance knob was included? Question: Is there a source for a Magnavox crest sticker to put on that faceplate where some kid likely peeled the original off? If not I have an idea how to re-create something there, but wondering what others may have done.

Cheers,

Eric

By the way, I love this cabinet with the one non-sliding side. It makes for a convenient little work bench, since I have this in my living room, my garage bench is a disaster, and it’s been too hot here in SoCal to spend any time cleaning in the sauna conditions that exist there. I’ll just find a convenient piece of cardboard to protect the wood, bring the soldering station in from the garage, and I’m good!

Eric

Aha! The 7907 does have a balance control! One of these control shafts is not like the other. It’s the bass control, which is a 7 meg pot with a 50k pot on the back for balance control. Down inside that hollow shaft is a little screw head. There’s also a screw on the back of the control inside the chassis. One or both of those adjusts the balance. I’m hoping it’s just a matter of popping the knob off and inserting a skinny flat blade screwdriver down in there will adjust the balance. Seems really dumb to have to pull the chassis to do that. I do wish they had just used some kind of knob that pushed in slightly to adjust the balance instead of making you pop the knob off, but now I’m getting picky.

Cheers,

Eric

I have a thin screwdriver that I bought back when I was twisting wrenches to adjust the K-Jetronic fuel injection on European cars. Works like a charm to adjust the balance on Magnavox stereo amps. There is a procedure for adjusting the balance and I believe that procedure is in Downloads on this forum. Basically, the procedure involves using voltmeters on each channel speaker, using a known clean mono source, then adjust so the voltage is the same on both channels. And old 78 rpm record on a 45 that isn't stereo works pretty well. If you have a signal generator that generates a 1000 cycle audio note, that works well too. On the 88-and 93-series amps, you can't use the FM stereo position to run an audio source. It is designed to work with a Multiplex adapter. I don't know for sure about your amp, but assume the procedure would be similar. You might want to clean the balance, and other controls, before you make a lot of adjustments. They are known to be dirty, some even intermittent after cleaning.

On the 81-series amp in my Imperial, the balance control is in the hollow shaft of the bass control. On the 82-series amps in the Concert Grand, there is no balance control whatsoever. There is a phono balance control on the tuner chassis, but that's about it. As far as I know, Magnavox never put a separate balance control on any of their tube consoles. The 88-series mounted the power switch on the treble control, a horrible idea. The 93-series actually had a separate power switch, we called these tuners "6-knobbers". Your tuner would be a "5-knobber".