[Paul Philco322]

I have had an odd experience, I swapped a Glass 12J5 out of this set with a metal tube, set would not play, tubes lit though. Thought I had a bad metal tube so tried another, same result.

I thought swapping a glass/metal as long as the same type was always OK. They could both have been duds, I do not have a tube tester though. I believe both are good as I got from a good source I use a lot.

The tube layout on the bottom of the set indicates a 12J5 GT. Would it be possible that a glass tube is required? It is a six tube RCA
AC/DC, dial glass says Radiola but that was just marketing schmaltz.
She ain't no Radiola. Any thoughts folks?

Thx.

Paul

[morzh]

Paul

Don't know, the tubes are identical, but 12J5 may need the shield grounded and I think the respective pin for 12J5GT is NC.
Try to ground it, see if it helps.

Also I wonder if you may have had some problem even with glass tube where the radio does not really work correctly and plays because a tube may act asn an antenna. But when you introduce a metal tube the antenna effect stops, and what is supposed to work as the antenna amp does not really get anything from the real antenna.

Things like open coils do that.

[Paul Philco322]

Thanks Morzh:
I swapped because I was getting a little squealing around 680 on the BC band. Thought the harmonic effect may be minimized with the glass tube. Otherwise set performs well good sound and sensitive......

Paul

[Paul Philco322]

From what a friend told me if pin 1 is grounded metal tube is required, if schematic calls for GT give it a GT.


Paul

[codefox1]

Pin 1 must be grounded if a metal tube is used. BUT! if pin 1 is used as a convenient tie point for another component it must isolated or re-routed so pin 1 can be properly grounded. Thereafter, either type metal or glass should be just fine. Metal type is probably better anyway from standpoint of shielding and microphonic tendencies.

[Paul Philco322]

Thanks for the info gents.

Paul