Motorola SK-29M Restoration

[stbasil]

My first random fix on this guy is the torn off speaker enclosure door, simple enough, actually, since it's due to the glue failing on the hinge side of the enclosure. While I was at it, I found that the inverted magnet oval midrange was completely white with what may be the dreaded cadmium dust. It came off easily with a wet paper towel, as did the same, very thick coating on the inside magnet cover. Both speakers ohmed good, fortunately.

The grille cloth is in decent shape except that it has shrunk upward on the bottom edge of the doors. They didn't wrap it around the speaker board on the top and bottom, so the only thing keeping it in place is glue, and there is not enough surface area below the midrange cutout to keep it secure when it started shrinking.

I can grip the cloth and with a lot of force manage pull it down, but it of course won't stay that way. I tried carefully heating with a hair dryer while pulling, but it won't keep it from shrinking back. Any suggestions on how to fix that, apart from replacing the grille cloth? I may just end up covering the exposed lower edge with some gold tape, but that doesn't fix the waviness.

[electra225]

Check AES to see what kind of grille cloth they have. I used a cloth very similar to that on that old GE stereo I redid, had a touch more red in it, but yours has shrunken and faded. Does that cabinet show signs of being wet? PB Blaster works well on the cad dust. Spritz some on a paper towel, wipe, and the cad dust seems to stay away.

That 6X9 speaker has a 232 EIA code on it. Magnavox!

[stbasil]

Uploaded Sam's SK-29M service manual, and also a single page schematic from 1960 Beitman's, to the Uploads Amps and Tuners section. Neither of those have a tuner schematic.

[electra225]

Thank you!!

[William]

It is weird not seeing the magnet in the normal spot, and this is the first time ever seeing a speaker like that, thank you for sharing that photo.

Bill

[electra225]

Antique Electronic Supply is now called Amplified Parts. They have quite the selection of grille cloth. Hopefully, you can find something close that will work.

https://www.amplifiedparts.com/products ... lex-piping

[stbasil]

I've got some ideas of how to retain the original grill cloth--it's got a more interesting weave than the guitar amp stuff, and my wife thinks the "waves" are really cool! I'll be posting about that later...

But for now, here's a problem I've encountered. The control escutcheon was dirty, of course. I began to clean it, first washing with dish detergent, not much help, theb testing a small area with isopropyl alcohol since it looked discolored from cigarette tar. Lots of brown stuff came off, and it seemed to not affect the black text. But I soon discovered that the stuff that I thought was discoloration was probably some intentional tinting to make the aluminum appear gold to match the brass knobs. And, the text also started to smear, so this is going to be a complete strip and redo for the escutcheon

But, I had an interesting experience with AI, after reading on ARF about a guy who had ChatGPT clean up an old radio label. So I uploaded this photo of the aborted result of my cleaning:

Then, I told it to clean up the text and symbols:

Then I had it remove all color except black and replace with white

I could have done all that in Photoshop, but it was interesting to see what the AI can do and it took a lot less time!

Now, I have to figure out how to transfer the text to the escutcheon. From my research, I think there are a few ways to do this:
1. Print a reverse image onto glossy paper using my laser printer, placing the printed paper onto the aluminum and ironing the toner onto the metal, then soaking in water to soften and remove the paper which will leave the toner stuck onto the metal. Have to seal it with some clear coat, of course.
2. Print the text onto some gold foil paper and stick it onto the escutcheon, add some clear coat.
3. Use some type of dry-transfer film, similar to #1 method, but it would just peel off and leave the toner without having to soak.

I've never tried any of these approaches, so I am hoping to get some advice regarding the best DIY approach to this! Any thoughts?

[TC Chris]

Looking forward to your results. I had the same chore in the pre-computer age, on a Zenith H-725 with a rusted dial ring and kitchen grease that had attacked the numbers. My solution way back then was to paint with spray metallic gold paint, apply press-in numerals, and spray over with clear enamel. Looked good enough for office use. Your method will likely produce a more authentic look.

Chris Campbell