Admiral 30A12 restoration

[brianweber4]

Originally Posted by bandersen

I've spent far more time on this set than I ever expected trying to track down the excessive width issue.
Finally, as I was about to abandon all hope, I noticed the huge power resistor in the HV cage was cold! An ohmmter confirmed that it was open.


Now where to find a replacement ? Luckily, I have an entire space 30A1 parts chassis but it too was bad.


So, I pulled one from another of my Admiral sets,. Ugh! All three are bad I'm guessing this was either a common point of failure back in the bad or they go bad just sitting idle over the years.

I have a coupe more sets to scavenge from otherwise I'll cobble something together.
Regardless, I'm going to have to find a source of replacement 5,300-6,300 ohm 50W resistors if I want to get all my sets working properly.
Note the taps are 500 ohms apart and used to correct horizontal linearity if needed. All my sets use the center tap so that would be 5,800 ohms.

That's a hard working part! in my Dumont Doghouse the 6K 35 watt dampening resistor was open and the ceramic was cracking and falling off of it. I got an exact replacement from Surplus Sales.

[kvflyer]

On the RF digital adapters, I too have found them to have weak audio. Don't know if that is a mandated design or not. Also, most DVD players that I have encountered are very weak audio.

[bandersen]

Nuts I tried reducing the size of the 1st filter cap after the 5U4 from 47uf to 33uf to 22uf then took it out entirely. No luck. I still get flash over inside the 5U4 on power up

So, I'm just going to put this on the back burner while I finish restoring an identical 30A1 chassis. This one came from a "triple thrill" combo I parted out down in a filthy basement near Wrigley field a couple summers ago.

Underneath the filth rust free and the identical revision to the one I just recapped.

So my plan is to shotgun the paper caps and electrolytics get it running and compare the performance to the other chassis.

Hopefully, between the two I can iron out the remaining issues.

Here's the next patient up on the workbench.

[Findm-Keepm]

Bob,

Ohmite makes a D50K7K5 7.5K 50W adjustable that works in these sets - my late dad had one and used the adjustable 7.5K resistor to get things going.

Mouser had them in stock at the time.

Cheers,

[bandersen]

I thought about it but they are $16.69 each and I need five. Also, the power rating drops in drops in proportion with the slider. So if you drop it to around 5,300 it's only a 35W resistor. Probably still OK in this application, but I'm not positive.

http://www.mouser.com/ProductDetail/...%2f4LcrvZrs%3d

[bandersen]

I got the second 30A1 chassis up and running by just replacing all the paper caps and a few resistors. I made sure not to touch the tuner or IF coils.

It has exactly the same issues as the first chassis - low audio and the 5U4 flashes over on power up.

So I''m going to add a CL-90 on the primary side of the power transformers to give it a soft power up and just live with the low sound volume for now.