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! :sigh: 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.

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.

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.

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.

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.

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.

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

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.

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!

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?

pictures, of the set in its current state.

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 (http://audiokarma.org/forums/showthread.php?t=59832&highlight=refinishing+project)

The finished cabinet:
http://audiokarma.org/forums/attachment.php?attachmentid=7302

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

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

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

Adam, do you need the knobs for that set?

I may have some laying around and failing that I have a set I'm probably going to junk that has some.

And I (gulity, gulity!!!) still have them too...

Charles

Wow! The cabinet on that Hoffman looks fabulous. My 1949 Motorola 9VT1 is in a very similar cabinet and needs refinishing. Now that I see what it can look like, I will definitely have to do mine. It's about the same size screen too, only with electrostatic deflection.

Adam -

The set looks great!

My first thought on the exploded red goop is that it was a very liberal application, by a previous owner or serviceman, of Corona Dope. I didn't really see it in your open-chassis pictures -- did you remove it?

The photos also show a great deal of the outer conductive coating missing from the picture tube. Did you re-coat it? If so, what product did you use (I have a 10BP4 that needs it)? not, what's the penalty for leaving it off?

All-in-all an excellent thread with good before-and-after shots and lots of good chatter. Great work, all!

Adam -
My first thought on the exploded red goop is that it was a very liberal application, by a previous owner or serviceman, of Corona Dope. I didn't really see it in your open-chassis pictures -- did you remove it?

The photos also show a great deal of the outer conductive coating missing from the picture tube. Did you re-coat it? If so, what product did you use (I have a 10BP4 that needs it)? not, what's the penalty for leaving it off?


I left the flyback as it is in the earlier picture. I was so relieved to find it was good, that I didn't want to mess with it anymore than I had to.

On the 10BP4 all I did was remove the loose bits of coating. It doesn't seem to have any problems the way it is. Is anybody aware of any products out there for recoating it?

Adam, do you need the knobs for that set?

I may have some laying around and failing that I have a set I'm probably going to junk that has some.

And I (gulity, gulity!!!) still have them too...

Charles

Charles already went through the trouble of digging those knobs and a few others out for me awhile ago, but if you do decide to junk that other set, I do need the top of the HV cage, and the back. Thanks.



And thanks for all the compliments on the refinish, this is the first one I did, and I was worried when I started that it was going to turn out bad, but it is actually easier to do than I thought it would be.

I searched this forum and found two applicable posts:
http://audiokarma.org/forums/showthread.php?postid=147119#poststop
and
http://audiokarma.org/forums/showthread.php?postid=142285#poststop

which discuss the re-application of the outer tube coating.

I recently picked up an old Farnsworth, its 10BP4 has a similar loss of outer coating. The seller had a box of junk too which included a motorola chassis that had been sitting in a puddle in a wet basement for a hundred years and was hopelessly lost to corrosion. The 10BP4 was so filthy I had to cut it out and then spray it hard with a garden hose to remove the accumulated gook. It has good phosphor, good filament and good vacuum. Probably still works, but it's not yet tested. I sprayed ALL the aquadag coating off of it though. I sure would like to recoat both tubes.

The two other posts refer to a product, one even gives a part number, but I haven't been able to find a supplier yet. Does anybody have any, or know the best place to get it?