Major Magnavox and Motorola score today

[Charlie]

Originally posted by H2s04
I havent powered any of the sets up yet (although Im biting my nails like crazy wanting to) because I dont have a variac *yet*. Its arriving on friday (purchased it online sunday night). I know that theres some sort of order you need to follow when you power up a set for the first time in about 20 years, and I'm wondering what that is.

As far as bringing it up slow, we probably all have our different procedures. But, the most important thing to remember that applies in any set is to remove your horz output tube before starting.

Myself, I start out on 20 volts, wait 10 or 15 minutes, then go up to 30, wait another 10 or 15 minutes, up to 40... so on and so forth. I feel the electrolytic cans as I continue up to make sure they aren't getting hot. They should be relatively cool, but if one seems to be getting hot, there is likely a short and it needs replacing before coninuing further. A little bit of warmth may be okay, but monitor it well. Also keep an eye out for any other signs of trouble.

Some guys take more time during this process... usually to give the lytics a better chance to re-form. In most cases, I plan on replacing them all anyway.

This Sams shows plenty of paper/wax and black-beauty caps under your chassis. It may be in your best interest to go ahead and change them out while you're waiting on your variac. The same goes for the main lytics. Being 50 years old, it would probably be better than trying to bring up the old ones slowly. Besides, it'll give ya something to do while you wait on the variac to arrive.

If you need the Sams for it, send me your address in a PM and i'll get it out to you. I have two copies for this chassis, so you're welcomed to one of them. See if you can get some numbers for the Maggies and I'll look to see if I can find those as well.

[H2s04]

Wow! thanks for all that info chuck, i had a feeling some tubes were missing up on top

One quick question: why is removing the horizontal out tube a good idea? isnt there some sort of HV going/coming out of the cap that goes on top of it; wouldnt that lead to arching if left unplugged? is there ever a time when i can put it back in and try to get a picture while im powering it up? And whats the deal with black beauties? theres some buzz about them, and I dont know what its about. Yeah, im a tv n00b sorry.

[Charlie]

Jeff,

You want to pull the HO tube out because it would end up running too hot. Since you are only giving the set partial power, the horz osc tube won't be reach the correct frequency to drive the output tube. The plate of the output tube will get hot enough to glow... not good.

You only want the HO tube in there once you can give the chassis the full line voltage.

Black beauty and paper/wax caps are always prone to failure. It's best to simply get them out of there. I've been changing alot of BB caps in my Zenith, and in doing so, I've corrected a lot of problems. Many of the BB's i've changed actually checked good out of the set... but in the set and under a load, they simply couldn't hack it.

In any case, they're 50 years old and need to go.

My motorola 12VT13 from 1949 also has the flyback and the HV rect. tube under the chassis.

[H2s04]

Thanks for the info Chuck,

What do I replace the BB's with? paper caps instead? I'm also wondering how one reads the BB's color bars; what values they make.

I just finished cleaning the Moto chassis tonight, and have included some pics

Right after removing the unit from the cabinet:

[H2s04]

Seconds after cleaning the whole chasis; shines nicely doesn't it?

[peverett]

I am working on a Hoffman with the high voltage rectifier and flyback under the chassis. This Hoffman has a removable bottom to allow you to change this and the tuner tubes. It also has several black beauties which I am changing. I have removed a couple with nice cracks down the sides.


Another interesting feature of the Hoffman is that it has a transformer for the filiments but uses a selenium rectifier voltage doubler for the DC power supply. This supply is not isolated so the entire metal chassis could be 120 volts. All except one of the controls, front and back have insulators between them and the chassis and the chassis mounts on plastic insulators. I am guessing that the one control is not original.

Of course I am using an isolated variac to work on this set.

You would replace the black beauty caps with mylar caps of the correct value and voltage.The link below has a table for calculating bb's values.It is a very good idea to use at least an isolation transformer when working on a non isolated chassis set.

http://antiqueradio.org/recap.htm

[Charlie]

Man that chassis looks awesome! Looks good enough to display out of the set! Although that wouldn't be very safe being a series string chassis. Still looks good, though. Very impressive!

Would you like to have the Photofact folder for the set? As i said, I have multiples of this particular one and would be happy to send it to you.

[Tubejunke]

I've never seen a chassis that nice looking! Looks like a production line shot. Great job my man & great find!

H20 did you spray engine detailer on that chassis. Hey! That may be a good idea fellows. I'm talkin about the stuff car dealers spray under the hood after degreasing. Makes everything look shiny and well kept. You can buy the stuff at your local Auto (Twilight)Zone or Advance (retard)auto.

The reason for the parts/toy store comments is a whole other long topic.

[Charlie]

Being that this set has heaters in a series, jerking the HO tube would knock out most of the other tubes. If it used a 6BQ6, ya could just put a jumper across the filament line at the socket for bringing the set up slowly with no major issues. But, I just noticed that Sam says this set uses a 25BQ5 for the HO tube. Would it be unsafe to jump the filament line where a 25 volt tube should be?

What do ya'll think?

[Big Dave]

Would it be unsafe to jump the filament line where a 25 volt tube should be?


Don't do it. If you have to, take another 25 volt tube and jump those heaters in or use a suitable resistor. Jumping a 25 volt tube without suitable resistance will cook the rest of the heater string. On my RCA metal portable, I substituted a 6 volt tube for the CRT for the soft start. It didn't light up, but the rest of the string lit up normally and I was able to finish the soft start. Also, I disconnected the top cap for the hor out, but left the tube in. No problems.

[H2s04]

WOW! This is the largest forum post I've ever had!!

You know, there must be somthing about this town; somthing magical in the air . Like, every set I've ever brought home has had a fantastic chassis, regardless of the condition of the cabinet. I cleaned off a similar looking Admiral 19G1 (for sale, mind you) that came out the exact same way. I'll fill you guys in on how the other two sets come out (yet ot be cleaned) but they look pretty good even now!

I swear, all I used was some generic distilled water and some paper towels, nothing else. I considdered using some noxon 7, but was worried about how the ammonia would affect the lytic cans.

I'm still pretty confused about the HO tube discussion, remember, I've onl been doing this for about 2 years, and I've never actually powered up a 50's set. I've only done actual work on 60's b&w sets that didnt need much work.

So how does the whole HO thing play out again, im sorry

Here are some more pics of the moto, and i'll take a smaller format pic of the admiral soon

[H2s04]

another

[H2s04]

and yet another