Belmont 21A21 question

[TV-collector]

Hi,
What are the main differences between the 7GP4 and the 7JP4?
In case that I ever have to interchange them are there changes in
the wiring needed?

Thanks in advance,

TV-Collector

[rld-tv01]

Bottom of this thread discusses 7jp4 vs 7ep4 vs 7gp4
http://videokarma.org/showthread.php?p=3027180

lifted from link:
"come across a Transvision that had a 7JP4 installed in it, worked fair.

7JP4 2nd anode is 5 to 6KV, 7EP4 2nd anode is 2KV.
A 7GP4 is a closer match only requires 3KV, but harder to find than 7JP4. Usually found in Philco 48-700 sets.

Better temp tube is a 5BP4, easier to find than either of the others and is electrically identical to the 7EP4"
================================================== ===

Also 7GP4 was used in Philco 48-700 in early versions and Philco substituted 7JP4 in later versions.

[Eric H]

If I,m not mistaken the 5BP4 is an electromagnetically deflected tube used in Pre-War sets, the 7JP4 and 7GP4 are Electrostats and completely incompatible.

[Eric H]

Never mind, my mistake, I just read that the 5BP4 IS an electrostatic tube!

[TV-collector]

Hi,

Many thanks for the input!

TV-Collector