Finally...something like success

[ggregg]

I have a DuMont RA-109 that I have been working on for the last couple of months. I've replaced every electrolytic and paper cap and while I had a working (although very weak) 19AP-4, I just could not get it to lock up. Last week, a fellow collector contacted me regarding an RA-112 he has that he had no use for anymore. He said the 19AP-4 was good (very good as it turns out). To make a long story short, I finally decided to go back and check my work on the filters. One 10mfd cap was shorting to a resistor lead. I pulled the leads apart and put the chassis back in the set. When I turned it on, the picture was immediately stable, albeit way out of adjustment. I adjusted the yoke as best I know and everything looks good except the bottom of the picture is somewhat stretched out while the top is compressed. Time to go back to the books and find out what needs to be adjusted now or if I still have some issues someplace. Comments are appreciated.

[ggregg]

After playing with the yoke some more and adjusting the vertical linearity, I got this. Getting pretty close.

[bandersen]

Look like you've just about got it squared away. Nice job!

[Kevin Kuehn]

Looks pretty good from here too.

Kevin

[ggregg]

Thanks alot guys. Haven't done a TV since 1998. Now I have a 16" porthole and a little Admiral in line. Don't know if this DuMont was the one to start with. Holy cow, these have a lot of caps. But I'm pleased with the result and now remember how important it is to recheck your work. Here is a picture of the case again, which was the main reason why I bought this.

[Kevin Kuehn]

Originally Posted by ggregg

Here is a picture of the case again, which was the main reason why I bought this.

That's a real beauty.

Kevin

[jeyurkon]

Looking really good!

[Eric H]

Nice job!
Those DuMonts really have a great picture.

[ggregg]

AHHH...lost the raster. I had it almost completely buttoned up and I decided to watch it again. Had raster, no picture, had audio. Looked on the back and found the green wire disconnected from the neck connector and the bridge on the horizontal outputs had disconnected on one side (must have bumped it). I connected the wire and the bridge thing back up and had no raster. Disconnected the green wire and raster came back. Changed the connector with the one off the other DuMont, same pins and color code. Now no raster whether the wire is connected or not. I tested every tube associated with the horizontal section and they all tested good. HV seems fine from the spark I get when I discharge it. Picture tube heater is working. ??????????????????

[ggregg]

OK after a ton of checking, changing one cap, moving another (the original was apparently wrong according to schematic ??), a new horizontal output wire and finding a broken wire off a filter cap, I have it back. Maybe I can start my porthole pretty soon??

[DaveWM]

glad you found it, it does not take much to mess up a hand wired chassis.

I was checking a B+ for ripple, the set was on its side, the scope lead very lightly was hanging from the B+ and just bumped a disc cap that happened to have very thin leads. Well that pushed the cap lead against something it did not like. No smoke No damage and No pic, just the raster (it was an IF cap).

I was totally baffled how hookin up a scope lead to the B+ would cause a loss of signal. I just started looking very carefully to what I had just done and and tapped around that area, very very lightly. well the signal would pop back and then be lost, looking more I saw the cap right under the scope lead, eureka, I see it.

Moral of the story is when some works and then stops working , triple check all around where you were just before the loss. I have run into this several times, very old wires that break, parts move etc...

[ggregg]

You are correct sir. I watched it for over an hour, tweaking the picture again the whole time. It's just about there now.

Interesting thing is when I changed the filter cap, I taped the connection to avoid a short. The break was under the tape, which is why it took me so long to find it.

[Dan Starnes]

Looking good.