So when I got to this place, I realized I'd already been there once before probably late last year. Turns out the guy is still trying to liquidate, and I almost left right away. But I figured what the heck, might as well look around again and I'm glad I did!

Hauled away a Maggotbox with Tambour doors, spare 25AP22 CRT with the yoke and convergence stuff still on it, Setchell Carlson unitized chassis, 2 boxes of tubes including sweeps and a CTC-28 flyback, and a pair of Maggie horns from an Astro Sonic SS console. Sadly I didn't have enough room in the van to take the S-C cabinet, but most of the stuff left there is pretty roached anyway. Only thing worth taking anymore is the RA-109, and even that had a brightner hanging off the CRT. Paid the awesome price of free 99 for this stuff, he just wants it gone.

Sorry if the pictures are goofed, I can't figure out how to keep them right side up when they come from the IPhone. They are right side up in the computer, then magically turn on their side after upload. No idea why.

http://miniman82.4t.com/images/Maggotbox/maggot1.JPG
http://miniman82.4t.com/images/Maggotbox/maggotchassis.JPG
http://miniman82.4t.com/images/Maggotbox/astrohorn.JPG
http://miniman82.4t.com/images/Setchell%20Carlson/chassis1.JPG
http://miniman82.4t.com/images/Random/tubes.JPG

Tried the Maggie set, but the B+ breaker was open like they always are. Jumpered it and had B+ briefly, but then something started smoking. It was a dropping resistor that went to a filter cap, which was apparently shorted and getting pretty hot. I'll replace that real fast and see if I can get a raster on it. The Setchell looks really nice as usual, aside from 2 aired tubes, but I don't really have a use for it just yet. Gonna hang on to it and maybe play with the modules, probably make good test units for other sets providing sweep and other signals to non-working chassis as they get repaired. If nothing else I can use it with the spare CRT I picked up, or possibly run a roundie with it.

I think that Setchell chassis was from a roundy, because I don't see the pincusion circuitry hanging off the left (back facing) side of the horizontal module.

I think that Setchell chassis was from a roundy, because I don't see the pincusion circuitry hanging off the left (back facing) side of the horizontal module.
I didn't think the CRT connector looked big enough to be from a roundie, so I was thinking it was a B&W chassis.

.

It's from a square color set, the pincushion stuff is there.

Sidenote: this maggie chassis seems shot, anyone got a Sams for it? I can't find any model info on any tags, they must have fallen off. I can't only get about 19kv out of it, and I don't hear that typical horizontal whine. I had to replace a few lytics just to keep it from blowing fuses, now the voltages all seem fine but I don't get much out of it.

Sidenote: this maggie chassis seems shot, anyone got a Sams for it? I can't find any model info on any tags, they must have fallen off. I can't only get about 19kv out of it, and I don't hear that typical horizontal whine. I had to replace a few lytics just to keep it from blowing fuses, now the voltages all seem fine but I don't get much out of it.

See if the chassis number is U920, T919 or something...Pm me, I have the Tab Book and maybe the sams if its a '924.

I think it's U92007 or something like that.

Magnavox U920-07 is SAMS 887-2. All the best,Tom

Found a download for that folder, it really helped!

Found out vertical wasn't running at all and horizontal was at the wrong frequency, which explains why this thing was so quiet. Vertical loss was caused by a broken wire feeding B+ to the output transformer, not sure if it was my fault or it just broke in the course of moving the chassis around. Repaired that and gave the horizontal slug a touch to bring it back on frequency, and now I have this:

http://miniman82.4t.com/images/Maggotbox/maggotraster.JPG


Nice bright raster and some dull colors, but something is goofy with the contrast pot. A picture will only show up at one position, any time I move contrast away from that spot the picture disappears. Pot reads clean end to end on my DMM, and the voltage on the video output tube cathode seems good so not sure what's up with that. At first I thought the CRT was being cut off since it's a DC coupled circuit, but the voltages at the CRT socket seem to fall in line like they should. I'll have to do some luma path troubleshooting when I get home, this was all done with composite injection since I can't get anything through the tuner just yet.

I take it you have the schematic (I have the 904 and 933 but not the 920) but there is a few pages of factory notes on Magnavox's late 60s sets.
Something is up with that 1st video stage. Its not like an RCA's and it causes all kinds of funny stuff to happen. .

Yeah, more stages and it's wired a little differently. But there's a composite injection test point that seems to work on the 1st video tube (schematic says cathode follower), so I've been using that. I think there's some more dead caps in the video chain or something, I'll poke around after work if I have the energy.

That pot may have tin whiskers.

I don't think so, or the cathode voltage would be all over the place. But anything is possible, I guess.


EDIT: I see what you mean now, the cap could be shunting the AC (video) component while leaving the DC cathode potential unaffected if there were a short in the pot in the right spot. I'll clean it out when I get home.

Cleaned out the pot, and some of the resistive element flaked away in the process. It looks old and wore out to me, so I'll sub a different one in there and try again.

Confirmed, contrast pot has no DC path for most of its travel. That means the video tube isn't biased properly leading to CRT cut off most of the time, new one is on order.

New contrast pot installed, now I have a stable picture.


http://miniman82.4t.com/images/Maggotbox/maggotraster2.JPG


All the colors are there, though tough to see with the digital camera and hazy CRT. It's got a really bad cataract, so I don't get much brightness despite having great emission. Next step will be making notes of the convergence circuits, in preparation for the next step...