Hoffman troubles

[Adam]

I got my Hoffman 610 put back together enough to try today. It was as if someone had started repairing it a few decades ago and never finished, all the tubes were in a bag, some capacitors and resistors were missing, disconnected, etc. In this condition I just decided to recap the whole thing, check all the tubes and such before doing anything. I finally got it put together just now, and I turned it on and, nothing happened! No picture, no sound, nothing. All the tubes lit up, including the crt, which tested good, I heard the yoke ringing when I adjusted the horiz and vert. And there was a bit of static out of the speaker whenever I changed the channel. When I turned it off, I went to discharge the HV, and there was nothing there, or atleast not enough to see.
Now the flyback looked like it had barfed up this red stuff all over the inside of the HV cage a long time ago, not just leaked underneath it, but on all sides. I would bet it is bad, now I have seen them that leaked a lot and still worked, but since I found this stuff a good ways from the flyback it looked like it exploded this stuff at some point.
Does any more service information for this set (Hoffman 610, chassis 140) exist than what is in sams 97A, which I have. It is a schematic only and does not give any voltage readings, or parts information, so I can't check things out further.

[Eric H]

Hi Adam,

Have you checked to see if you can draw an arc from the cap of the 1B3?
Just to see if your getting any HV at all.

I seem to recall I have the same Sams 97A for my set but nothing more.

The fly in these looks an awful lot like an RCA of the same era.
If worse come to worse I have a really beat up Hoffman I might part out for you.

[John Folsom]

Riders Vol. 3 has complete service data for your Hoffman 610, ch. 140. It is the large format volume, so I cannot scan you a copy. Sorry. Check your flyback winding for continuity. If they still ohm good, chances are the flyback is still good. The flyback is a Thrdarsen FLY1. If you need one, I can send you a used on, if this would help.

[Adam]

Thanks, I might need one of those flybacks. But, I checked the flyback for continuity, and it was fine, despite all the red goop that came out of it. There was also some HV ontop of the 1B3.
I located the major HV problem. With all the monkeying around with this set that was done by a previous owner, I should have thought to check more closely in the HV compartment. That 3.3 ohm resistor going to the 1B3 filament was just removed and bypassed. The 1meg resistor from the other side of the filament carrying the high voltage to the crt was nearly burned out (it read 15meg).
While that shouldn't be too hard to fix, unfortunately there is more: the horiz width coil was damaged, it was just left unconnected on one side, and that .05 mfd capacitor across it is missing. The coil at least is not internally broken, but it appears as if it may have lost a few turns. I think I'm just going to try it as it is. Does anybody know the voltage for that .05 mfd capacitor I'm missing, the schematic I have doesn't tell me.

[John Folsom]

My Riders shows a 0.02uF cap across the width coil. No voltage is specified, but I suspect 600V will do. A similar RCA circuit topology uses a 0.02 @ 400V.

[Adam]

That's odd, I double checked my sams and it does have .05, maybe its from a silghtly later or earlier version of the same model, I hope its not full of mistakes, I had to reconstruct several other missing bits based on it.

[John Folsom]

Adam, I would try it with both values (.02, .05). I suspect it is not terribly critical.

[Adam]

It works! I thought that flyback would be bad for sure by the looks of it, but its not at bad all. I started with the .05, put it all together and got a blank raster only. After cleaning the tuner, it pulled in a few channels. The horiz. linearity was way off, I was about to change to the .02, but I tried adjusting that big resistor first, and that did it. So I left the .05 in there. Adjusting width coil has no effect on the picture at all, I don't know if that has to do with the .05, or that it lost a few turns, but the width is about right where it is anyway.
The tuner even after cleaning it a bit, still only pulls in ch 2, 4, and 5. It will get ch 7 if I hold it inbetween channel 7 and ch 8, it will also get ch 9 if I hold it between 9 and 10. It won't get ch 11, 13 or 3. There is no ch 6, 8, 10, or 12 here. I really only watch tapes, dvds, and uhf anyway, so even if I can't fix this, as long as I keep getting ch 4 it doesn't really bother me too much.
I think I'll try cleaning the tuner once more, then move on to another broken set.

[John Folsom]

Adam, congratulations! Those old fly1 type HOTs are amazingly reliable. If your width coil adjustment has no effect, changing capacitor values won't change things. Are your sure your width coil is good? Try unhooking one eend of the width coil. If this does not change things, check for continuity of the width coil, or possibly a shorted turn on the coil (you can only find this by measuring inductance). A few missing turns will have no effect. Of course, if it works good enough, I guess you don't have to fix it!

[Adam]

I had checked the continuity of the coil before I connected it and it was good. I never tried the TV with it unhooked, maybe it is shorted, but then the width is ok anyway. I fixed the tuner on some more channels, it turned out that some of those contacts on the strips were really worn down, and I built them up with solder.

I decided to refinish this cabinet, the combination of it being really scratched up and it not being a console made it a good one to experiment on. I've sanded most of it and I really like the way the wood looks without that dark stain on it better. I think I'm just going to put a clear finish on it. Anyone have any particular product they've had a good experience with?

[Adam]

pictures, of the set in its current state.

[jpdylon]

The Minwax Helmsman spar urethane finish I put on my sansui 3000 cabinet turned out nicely. Incredibly durable. I don't know how many times I accidentally bumped the receiver but there are still no scratches or dings. You can get it in a can and use a brush to apply it, or spray can. Personally I would use a nice soft fine bristle brush and apply 2 or thre coats, sanding between each. You can get it at about any hardware place.

My thread is here

The finished cabinet:

[Adam]

I finally got around to refinishing this set. The cloth in front is not original it is off a '59 Magnavox.

[Sandy G]

Awww, man, Adam, I'se in LOVE...That's Bee-Yoo-Tee-Full !!

[jpdylon]

holy chite Adam! That hoffman looks beautiful! Most excelent. I'd say that's a keeper, but If you decide otherwise.....