Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: luthierwnc on August 31, 2021, 02:32:30 pm

Title: tube ID question
Post by: luthierwnc on August 31, 2021, 02:32:30 pm: Hi All, I just got a late 1960's Traynor Voice Master PA head with the intention of making something Hiwatt-ish. It is is exceptional shape without a nick in the tolex. It doesn't look like it was used very much either. In any event, the tubes (which look original) are Rogers -- 6CA7s for the output and 7025a in the four preamp holes. In my cursory research it seems these were private-label, made by Mullard in the Blackburn plant. That's not a lock since the dates I found were before 1969. Not visible in the pictures; the 6CA7s have D9E and 'Made in Great Britain' along with the codes XF2 and 8981. The 12AX7s all have F9E on the glass.

At any rate, if anyone recognized these units, I'd love to hear what you know. More and better pictures are available for the asking. Cheers, Skip
Title: Re: tube ID question
Post by: PRR on August 31, 2021, 09:39:49 pm: Quote from: luthierwnc on August 31, 2021, 02:32:30 pm
... late 1960's Traynor Voice Master PA head ...., the tubes (which look original) are Rogers .... cursory research it seems these were private-label, made by Mullard in the Blackburn plant.

Traynor was/is Canadian. Rogers certainly was and is Canadian. All through the 1970s.
https://en.wikipedia.org/wiki/Rogers_Vacuum_Tube_Company
https://en.wikipedia.org/wiki/Rogers_Communications
Rogers' best tube-making *may* have been in the past when Pete called for parts, and sure Blackburn plant is likely source for own-brand bottles (like Ken-Rad plant was for US tubes).
Title: Re: tube ID question
Post by: luthierwnc on September 01, 2021, 06:04:21 am: Thanks PRR, This was sort of a nice find since I usually expect to have to replace all the glass. They could be dead as disco but this is promising. Cheers, sh
Title: Re: tube ID question
Post by: HotBluePlates on September 02, 2021, 02:28:40 pm: Quote from: luthierwnc on August 31, 2021, 02:32:30 pm
... the 6CA7s have ... codes XF2 and 8981. ...

Clear closeups of the codes would have been very helpful. I strongly suspect your EL34 has "B" as the first character on the second line (below Xf2). As this Philips Factory Code List (https://frank.pocnet.net/other/Philips/PhilipsCodeListAB.pdf) shows, "B" was Mullard Blackburn while "8" was Philips Eindhoven. Philips would have no problem printing "Made in Holland" if they were made at Eindhoven.

"B981" could be Mullard Blackburn, 1st week of August 1969.

Quote from: luthierwnc on August 31, 2021, 02:32:30 pm
... The 12AX7s all have F9E on the glass. ...

Don't know where you're seeing "F9E" (which isn't an important code), but I believe I see a "B" as the 1st character of the 2nd line of codes in the photo below.

The upper line will indicate the tube type & revision. Uppercase/lowercase matters in this: "Xf" is an EL34 but "XF" is a 12DJ8.

(https://i.imgur.com/YpCrlJp.jpg)
(https://i.imgur.com/8xsfwd8.jpg)
Title: Re: tube ID question
Post by: pdf64 on September 02, 2021, 04:18:45 pm: Great, thanks for that @HotBluePlates
I’ve been going through my stash of vintage pulls to populate my new Marshall-ish build, and have been puzzling over those codes :w2:
Title: Re: tube ID question
Post by: luthierwnc on September 02, 2021, 04:35:01 pm: Good eyes! They still look like 8's but the code is B981 or B9B1 with Xf2 stenciled directly over that. Another shot shows the 'Made in GR Britain'.
Title: Re: tube ID question
Post by: HotBluePlates on September 03, 2021, 07:10:40 pm: Quote from: luthierwnc on September 02, 2021, 04:35:01 pm
... They still look like 8's but the code is B981 ...

After you see a bunch of Mullard tubes, you will recognize the specific font of that leading "B."
Title: Re: tube ID question
Post by: luthierwnc on September 03, 2021, 08:24:38 pm: Thanks HotBluePlates, Lucked into this one. I'm not sure they'll more playing time in the next 50 years but it's nice to know. Cheers, Skip