FINALLY! DuMont RA-108 Mansfield lives

[bigaudioal]

Originally Posted by kvflyer

Make sure you don't have "tin whiskers" on any of the pots. I had similar issues with an Admiral set and aggressive cleaning of the exterior of the controls fixed the linearly issue. That's the easy thing to do. Still may be an issue with the yoke or flyback. Let's see if it is an easy fix.

Will try cleaning pots again. Original fly was shot. On the advice of Nick Williams I pulled the flyback out of a spare 630 clone set I had and threw it in. Putting out plenty of HV for the set and I can adjust it with Horiz drive control from 9kV to upwards of 14kV. I have it set on about 10.5kV, the mid range. Stays cool and raster is stable overall. Now the yoke might be a different story. Have not tested or messed with it at all.

[earlyfilm]

Big Al,

That picture is starting to look like a Du Mont !!!

On your Barkhausen, check the antenna dress between the tuner and the plug on the back of the set. I cannot remember which RA's had this very unusual cause for Barkhausen, so check your service bulletins on the ETF website. It had to do with how the lead was grounded and where they were clipped.

On insufficient width, resolve the vertical linearity problem first.
The reason:
Vertical linearity being off can cause the vertical output tube to conduct too much and that drops the B Boost and drops your width.

On any pre-about 1952 set that uses 6AL5 tubes:
If the set uses a center terminal post for those sockets, test each 6AL5 by removing any shield and with your finger on the tip of the tube, attempt to gently "bend" the tube moving your finger in a 1/2 inch circle for this test to see if the tube is seated properly in the socket.
The reason:
Early 6AL5 tubes had a recessed area in the center between the pins. Most manufactures switched to the standard flat pin base for their 6AL5's about 1952. If this problem is found, try removing the center pin tip extending from the top of the tube socket with wire cutters or a small grinder.

James

[bigaudioal]

Originally Posted by earlyfilm

Big Al,

That picture is starting to look like a Du Mont !!!

On your Barkhausen, check the antenna dress between the tuner and the plug on the back of the set. I cannot remember which RA's had this very unusual cause for Barkhausen, so check your service bulletins on the ETF website. It had to do with how the lead was grounded and where they were clipped.

On insufficient width, resolve the vertical linearity problem first.
The reason:
Vertical linearity being off can cause the vertical output tube to conduct too much and that drops the B Boost and drops your width.

On any pre-about 1952 set that uses 6AL5 tubes:
If the set uses a center terminal post for those sockets, test each 6AL5 by removing any shield and with your finger on the tip of the tube, attempt to gently "bend" the tube moving your finger in a 1/2 inch circle for this test to see if the tube is seated properly in the socket.
The reason:
Early 6AL5 tubes had a recessed area in the center between the pins. Most manufactures switched to the standard flat pin base for their 6AL5's about 1952. If this problem is found, try removing the center pin tip extending from the top of the tube socket with wire cutters or a small grinder.

James

Thanks so much for the tips!!! Will try some of these over the next few days. Really appreciate it!!!