Metropoulos Forum

Newbi here. I have a stash of old tubes, here a couple that I would like someone to ID for me if possible.

The first pic is of Mullard EL37's. Are they a direct replacement for 6L6's?
The next two pics are of 12AX7/Ecc83's. The one on the left is a 2.1 Hammond, made in Holland. It has numbers 79 09
The one on the right is a HEATH by Mullard, 1022-007 (I think)Also some worn off numbers/letters. I can only read part of them, B8K. This tube looks similar to other Mullards that I have but the plates are longer.

I also have a Raytheon 7025 JAPAN FO4 that I know nothing about.

Any help would be greatly appreciated

The one on the right does indeed appear to be a 50's Mullard longplate, but it looks like it's had a very hard life judging by the flashing and the condition of the plates. B8K is a Blackburn date code - Blackburn plant, 19?8 (most likely 58 since longplates weren't in production by 1968), and K for November.
The one to the left of it could well be a Heerlen production tube (Philips plant) by the looks of it, and SHOULD have a delta (triangle) symbol on it somewhere if it is.

I know little about EL37's though. I know Neikeel tried installing a set in his JTM45/100 instead of KT66's, but was having redplating problems, so it's possible they don't handle the higher voltages too well.

Thanks Demon!!