Dumont RA-103 With Additional Tube Under Chassis?
 

Saw this on E-bay. Factory version of the chassis? or did somebody add a tube for some reason. Set looks unmolested.
My RA-103 does not have a tube under the chassis.


http://img.photobucket.com/albums/v2...%203zchasv.jpg

Looks like a 6AL5. Is it connected to a relay? If so, it's for B+ delay.

Are you sure? Mine does, and that is consistent with all the service documentation I've seen. It's the audio demodulator. Crosley clones have not only the 6AL5 down there, but the first video IF tube as well. ETA: the relay delay tube is also a 6AL5, but that one is located topside.

Upon closer scrutiny, it does look like it's connected to an IF can rather than a relay.

No tube in my set. Looking at the Sams, it looks like it is the discriminator. Wonder why my set has no tube...I took a quick look to see if there are any SS diodes underneath, but could find none...I will have to see what happened to the discriminator when I get this chassis on the bench.

I was wondering, in my original post, if there were 2 versions of this set where a tube was on the bottom, and another one where tube was on top- or eliminated.

http://img.photobucket.com/albums/v2...d/IMG_3249.jpg

I never looked at it that carefully, but I thought it was the video detector.
I have the Dumont that has the upright sub-assembly that has the 2 6X4's.

That sure looks to be the case.

http://i452.photobucket.com/albums/q...psjvjtzkom.jpg

http://img.photobucket.com/albums/v2...%203zchasv.jpg

Oh, good eye Kevin!!
I did not have a chance to look where the tube went to. I am just glad now that someone did not cut it out as part of a modification.

I've worked on a Doghouse and a Crosley with that chassis and they both had that tube.

They also had open windings on the B+ relay so if yours doesn't work suspect that.

by the way, the 6X4s are not for relay control, they are bias rectifiers.

I did look at the schematic and I do agree. :thmbsp:

I wonder if a batch of steel chassis were made without the hole punched for the tube, and this was the most practical solution.

The set is serial number 100346.

Could this be a very early one, like the 346th one made? And for some reason they moved the tube underneath in later sets?

Tube is topside on my Dumont doghouse and Stromberg Carlson TV-10, no 6X4s on either set. That 6AL5 is smack dab below the CRT so it is possible it was in the way of some CRTs (or not removable with the CRT installed) and Dumont's solution was to move it under chassis.

I can't imagine that tube being much easier to replace topside with the chassis in the cabinet.

Wasn't there some application in which 6AL5 was run at reduced heater voltage? I can't remember if it was as a detector or a relay driver for B+ delay.