Rebuilding a Hoffman 610
 

I finished up the Motorola 105 was working on so I decided to start on this cute little Hoffman, I think it's a model 610, the chassis is a model 140.

I was able to coax a feeble picture from this set when I first got it several years ago, there was some evidence that it had been serviced up till the 1980's.

It's doesn't work now, even after replacing a lot of the paper caps I get nothing except a little high voltage, probably the filters have died completely by this time, I placed an order for caps with Justradios on Friday right before I left on a trip to N.Y.C. (My birthday present!)

The chassis is stamped with the date of Jun 15 1949.

The early Hoffmans always seem to be a very high quality set, right up there with RCA and Dumont, but then most of the parts seem to be RCA...

That's a nice looking set. Is the stand a matching item for the TV?

John

Thanks John, I don't know if the stand was made for the set, it's not marked Hoffman anywhere (It came with when I bought it) but as you can see it matches perfectly.
Unfortunately the top of the stand is scarred up pretty badly from protruding screw heads and no feet on the TV, it doesn't show though so that's OK.

That's a pretty set. There was one like it for sale about 4 miles from me a couple of years ago... it was on ebay and seems like the lady want 250 bucks for it. I did not feel very generous that day, so I left it there. The CRT checked on the borderline. I often wonder if she ever got rid of it.

Good luck with it!

Cool set... And I agree, that table sure looks made for it.

Yes, that is a pretty set. I like that rounded, glossy cabinet. What do the doors look like ?

Good luck with the restoration!

Bob

Great looking set Eric!

Great thread...Thanks! This has helped me to identify my "mystery Hoffman" that has been left un-restored for too many years in my garage. :yes:

Time has not been so kind to my set, however :tears: ... Picture1

It is missing one knob and the Ch selector knob is broken... Picture2

Big "ouch!" on the cabinet...Picture3

Chassis is missing one tube, but seems more or less complete... Picture4

Anybody know what the missing tube behind the tuner might be? ... there was no layout chart or model number on my set (back was missing). Stamps on chassis say
"B013380, Feb 21 1950, Chassis 155"

Good luck with yours, I will be following along for inspiration to begin work on mine.

jr.

That missing tube is a 6AG5.

Steve

Thanks Much! :)

Another question, my set has a 6K6 plugged in just to the right of the 5U4, when I brought the set up slowly on a Variac, it did not light up although it tested ok... I suspect from the pictures in the first post that it should be a another 6SN7 like the one next to it. Is this correct?

jr

Yes, that is the vertical osc. and output and should be a 6SN7.

Steve

Hi Jr. Welcome to Videokarma.

I have four Hoffmans total, a couple of them are the same model as yours I think, one is pretty nice, one is a parts set.
I'm not sure what the actual model number is since mine are missing the backs also.

The chassis in the parts set was built Jan 13 1950.

I can probably spare the knob, the cabinet doesn't have any holes in it that I can remember but it's coming unglued and the finish is shot, your welcome to it (the cabinet) if you can pick it up, where are you located?

Thanks...I am in Oregon, so I can't exactly swing by and pick it up. Let me get a little more into work on this chassis, if I don't find something really bad (like a blown power transformer or something), I would be really interested in buying some knobs from you. I think I can fix the dented in hole ok, (all the pieces are still there).

Thanks Much!
jr

This set is coming along pretty well, replacing all the paper caps really didn't make it work any better than it did when I got it, the picture was shrunk up and folded over at the top.

I replaced the last electrolytics tonight and that did the trick, I left one filter can alone since it's a replacement Sprague and it seems to be fine.

I'm not sure how good this CRT is, emissions are OK but it just doesn't seem all that sharp, I tried another one and it seemed somewhat better.

One thing that made a big difference was plugging it directly in to the wall instead of the Isolation Transformer, the voltage drop on my little 5 amp transformer is significant, I have to remember to remove it if I'm having a problem getting the picture to fill out on a set.

It's starting to look pretty good. You said you only got a little HV when you started. Is it normal now that you replaced the bad electrolytics?

John

My HV probe seems to be inaccurate but based on how the set works now I'd say it's up to spec.

I had a faint bright drive line on the right side of the screen that wouldn't adjust out so I went through and checked a bunch of resistors in the sweep circuits.

I found an 82 ohm coming off the Horiz Frequency coil that had gone up in value to about 145 ohms, replaced that and the drive line in gone, it's also very stable at this point.

Replaced a couple other drifted resistors and this set has a really good picture now. :thmbsp:

There is one 200Mf @ 6v cap to replace, I'll pick one up tomorrow at the local Electronics store and finish it up.

The controls still need to be cleaned and lubed.

The chassis was covered in a white powdery dust, I'm sure we've all seen this, it's more often yellow but this one was white.

I'm treating it like it's Cadmium Oxide, i.e. being very careful, I vacuumed as much as I could with a Hepa Filter in the Vac, the rest I'm cleaning off with a very diluted solution of Naval Jelly and water, this is about the only thing I've found that gets it off well, cleans it down to bare metal I think or at least down to whatever plating is left.

It's slow going, doing a small area at a time so I don't get Acid in anything important like the i.f coils.

John, I found the answer to this question and it's yes!
It might be a better fit for the 12" set though.
It also says the 610 has a receptacle for a Phonograph but mine doesn't.
From tvhistory.tv:

http://www.tvhistory.tv/1950-Hoffman-Brochure1.JPG

That chassis is looking pretty good! Your experience with the white line will be helpful to the rest of us also.

On my Sylvania I'm supposed to adjust the horizontal linearity until one shows up in the center and then back off. I used to get this before I finished fixing some other problems, but now I can't get the white line back. They say to leave the pot. at max in that event. I feel nervous doing that. I still backed it off some.

I have several HV probes. Though they all seem to be calibrated properly, two of them draw a lot more current than the other. Those two read lower when I use them because they cause a big drop across the resistor that's in series with the HV CRT connector. They do seem to read correctly on sets that have lower impedance HV supplies. Sounds like you're having the same experience.

John

Cool! That's a great find getting the original stand!

Jon

Got it back in the cabinet. (the last cap can be changed from the bottom)
It always makes big difference watching it in the cabinet, especially with a thick piece of Yellow/Green glass in between you and the CRT. :D

I tried to capture the color as best as my camera would allow, the second and third pictures are probably the closest to accurate.


The safety glass is seriously thick on these, about 1/2" total, 3/8" of Yellowish glass laminated to a piece of clear 1/8" glass, perhaps the rumor that Hoffman got a deal on some surplus window glass from a high rise was true? Though why anyone would want that color in their office building I can't fathom.

that's awesome looking, Eric! Aunt Bea never looked so good! :D

IMPRESSIVE! :thmbsp:
Very nice to see it running so well! Gives me some hope for mine.
So all of the orig. paper caps were replaced?
jr

Nice job :thmbsp:

Maybe to block UV or glare ?

I've been using Naval Jelly lately too for cleaning up metal surfaces. Works pretty good I think, but like you said, be careful with that acid!

I have restored some later model(1953-1954) Hoffmans. The green glass is thinner, but still laminated with plastic and true safety glass.

I like what the ad above implies when it says "Easy Vision Television Price of Ordinary". It means-green glass at no extra cost!

Aunt Bea never looked so good!

Thanks guys, this set was a pretty straightforward restore, it worked somewhat when I got it so I knew everything was more or less OK and it just needed caps.

Jr, yes, all the paper and electrolytics have been replaced, except one small lytic that I will replace as soon as I get a new one, also the line filter caps are still original, I have the X type (or maybe it's Y) safety caps to replace them with but just haven't done it yet.