Mullard GZ34 5AR4 identification

[MNmarantz]

Thinking this is an f31? Not real familiar with rectifier tubes. Wondering if anyone can confirm this for me. Decent Mullard rectifier or just average? Thanks in advance!

 

[heyraz]

I see a "B" etched in the glass to the right of " MADE IN GREAT BRITAIN".
Anything else etched?

I'm not 100% sure, but I think the plates of the f31 version aren't notched.

 

[Dave_in_Va.]

That's a very good tube. Period.

 

[Dswankey]

Thinking this is an f31? ...Wondering if anyone can confirm this for me. Decent Mullard rectifier or just average?

f32 maybe?

I see a "B" etched in the glass to the right of " MADE IN GREAT BRITAIN".
Anything else etched?

Tube Classics - Philips Audio Tubes

 

[MNmarantz]

f32 maybe?

Etching says f31. Wow I need cheaters.
So the 136 and 1022 must be date/plant codes?

 

[Dswankey]

From what I know the f31 were the early version circa 1958-62, the f32 later

What comes after the B as seen in the pic?

So the 136 and 1022 must be date/plant codes?

I'm not sure, from what I can ascertain using this as an example



The "B" stands for the Blackburn plant
The "7" stands for 1967
The "F" stands for June?
The "4" stands for 4th week of that month

 

[heyraz]

Google "Mullard Plant Codes"

MULLARD VALVE ETCHED CODES - HOW TO INTERPRET THEM

There is much conflicting fokelore on the internet about the Mullard etched valve codes so I thought I would add our two penny-worth. The etched codes have value to us today as they contain two discrete nuggets of information; firstly, should a valve loose it's printing you can identify the...

mullard.org

 

[MNmarantz]

From what I know the f31 were the early version circa 1958-62, the f32 later

What comes after the B as seen in the pic?


I'm not sure, from what I can ascertain using this as an example

View attachment 3074721

The "B" stands for the Blackburn plant
The "7" stands for 1967
The "F" stands for June?
The "4" stands for 4th week of that month

Thanks Dswankey. I can’t quite make out what comes after B. Prob doesn’t matter tho

 

[Tom Bavis]

1022 is the code for the US distributor, IEC Electronics. 136 is a (US style) date code, 1961, week 36

 

[MNmarantz]

Thanks Tom. Cool to have that info!

 

[Dswankey]

Thanks Dswankey. I can’t quite make out what comes after B. Prob doesn’t matter tho

I hear you, either way it should be a nice tube provided it tests well, have you tested it yet?

 

[MNmarantz]

I don’t have a tester yet. But it came from a working knight amp with a quad of 7189 Mullards.

 

[kvflyer]

I don’t have a tester yet. But it came from a working knight amp with a quad of 7189 Mullards.

Which means that it wasn't worked very hard and probably is as good as new... literally. I have worked on many HH Scott tube amplifiers and have never found one that does not test new or almost new. Scott used them with 7591 amplifiers which as you know, required even more current. Don't discard it!!! For that matter, your Allied Radio Knight amplifier can be an excellent performer and probably has Mullard ECC83/12AX7 tubes as well?

 

[Dswankey]

I don’t have a tester yet. But it came from a working knight amp with a quad of 7189 Mullards.

KA-40?

 

[Dr. Beaker]

I thought genuine vintage Mullard GZ34 tubes all had glass that was the same diameter as the base. The pictured tube has a smaller diameter glass envelope. Am I mistaken?

 

[MNmarantz]

Which means that it wasn't worked very hard and probably is as good as new... literally. I have worked on many HH Scott tube amplifiers and have never found one that does not test new or almost new. Scott used them with 7591 amplifiers which as you know, required even more current. Don't discard it!!! For that matter, your Allied Radio Knight amplifier can be an excellent performer and probably has Mullard ECC83/12AX7 tubes as well?

Yes it has a full Mullard compliment. I was kind of suprised someone would outfit a knight amp with those tubes.

 

[MNmarantz]

KA-40?

Yes. KA 40

 

[MNmarantz]

I thought genuine vintage Mullard GZ34 tubes all had glass that was the same diameter as the base. The pictured tube has a smaller diameter glass envelope. Am I mistaken?

Must have changed after the f31? I’ve noticed this in researching this tube.

 

[MNmarantz]

Which means that it wasn't worked very hard and probably is as good as new... literally. I have worked on many HH Scott tube amplifiers and have never found one that does not test new or almost new. Scott used them with 7591 amplifiers which as you know, required even more current. Don't discard it!!! For that matter, your Allied Radio Knight amplifier can be an excellent performer and probably has Mullard ECC83/12AX7 tubes as well?

Gotta love old stock. Don’t make ‘em like that anymore.

 

[MNmarantz]

My original plan for these tubes was to install them in a pilot 500 console amp I just picked up. I have a pilot 505 I bought from Wharfcreek that now has all teles. Thought it would be cool to have basically the same amp with English and German brands. I may have to give the knight an honest chance to prove herself.