Motorola SK-29M Restoration

[Brettzky99]

Nice job there are some paper caps in the pre amp section and more 12ax7''s

[stbasil]

Preamp finished up. I didn't see any paper caps, unless those fat brown ones are disguised culprits. The two in the power amp, and the ones in the preamp are apparently working OK. I did test a few, they were OK.

The one electrolytic can (10 uF @ 400) was going to be a real pain to replace, 4 resistors and a wire terminating on its single pin. But it tested about 20uF with reasonable ESR, so I left it alone, and all voltages are good, no ripple. However, after running both amps for a while, that cap is too hot, so I guess I'll have to replace it anyway

[TC Chris]

Nip the cap's single pin off, leaving all wires attached. Re-stuff the can and run the new cap's lead to the old pin and its collection of component leads.

Chris Campbell

[electra225]

Or you could cut the can in half, take out the old guts, then put a new cap in the can. Drill a hole in the bottom of the can, run the wires thru to the original connections. You don't have to cut the single pin off that way...Two different ways to accomplish the same thing. Good luck.

[stbasil]

Yep, I cut that sucker off, put the cap negative lead through a hole, and tacked the positive lead to the stump of the post inside the can. I'll glue the can back on and wrap with clear Gorilla tape to stiffen it up.

When I first powered up the preamp, the right channel was weak. After some checking around with the DVM, I remembered the connection issue with these wafer tube sockets. Even though I had deoxed them, and the 12AX7 tube pins, sure enough, at least one pin was loose. Tightened them all, which fixed the bad channel.

Can't figure out why they put the power switch on the balance pot, necessitating adjusting the balance every time you turn it on! Also, that control has only about a 90 degree travel. And the function selector has three phono equalization options, should be fun to play with. All these little quirks of the wild and wooly days of early stereo and record equalization!

Now to get the changer working along with its new Tetrad cartridge....

[electra225]

Magnavox attaches their power switches to the treble control. It's an equally silly setup as Motorola's method. The upline, Series 200 Magnavox tuners get a dedicated power switch, a vastly superior setup. You wear out a control by using it with the power switch. Aluminum HVAC tape wrapped around the filter cap can makes an almost invisible repair. I have a Motorola ST-82 stereo with the power switch as part of the function switch, an indescribably horrible setup.

[stbasil]

I hate to cover up the cool Motorola logo on the side of the can, so that's why I was considering the clear tape. Of course, no one will ever see it again, at least not for a long time! I used Elmer's glue to put the can back on, but I don't trust it to hold permanently. The Gorilla clear tape is only rated up to 140F, the HVAC tape much higher, of course. What do you think?

[electra225]

Looks fantastic to me! You have to look real close to see it's been worked on....

[TC Chris]

If you're worried about durability, the old favorite J-B Weld is a gray color that would not look bad, especially if applied carefully and then the excess is trimmed before full hardening. Make sure you scrape off the Elmer's.

Chris Campbell

[stbasil]

Yeah, I forgot about JB, don't have any on hand, but even our grocery store has some!