Help with Valve identification - Suttons (Projector?) Amp

[laverda]

Hi folks,
A young student of mine has been give an old valve amp. We think it is an old reel to reel projector amp. Two of the valves are easily identified as 6V4 and 6CA7 (EL34) but the third has its label rubbed off. I'm hoping someone here may be able to help identify the mystery valve.

Here are the pics...

Unknown valve

Its a neat little amp with a 2ohm speaker which sounds pretty good and clean until it beaks down after a minute or so with what is either a dud transformer or shoddy valves. Its pretty microphonic so if we can identify the mystery valve we'll replace them and see where to next. Its point to point wiring internally and pretty clean at that ( I didn't get a pic sadly).

Hopefully the amp gurus here can point us in the right direction
Cheers,
Mick

 

[fronobulax]

Paging default...

 

[beinhard]

To me it looks like a dual-triode preamp tube, my guess would be a 12AX7 or 12AT7.
PS could be the last two letters of "PHILIPS".

The links below have pictures of some variations of these tubes:
https://www.tubeworld.com/12ax7.htm
https://www.tubeworld.com/12at7.htm

There's not much info about Suttons amps on the net, but Google found this: http://www.guitargear.net.au/discussion/index.php?topic=35337.0

Besides tubes, capacitors are often a source of problems in old amps.

beinhard

 

[coastie99]

Mick, try breathing on the glass. You might get lucky and be able to read a faint inscription.

 

[laverda]

To me it looks like a dual-triode preamp tube, my guess would be a 12AX7 or 12AT7.
PS could be the last two letters of "PHILIPS".

The links below have pictures of some variations of these tubes:
https://www.tubeworld.com/12ax7.htm
https://www.tubeworld.com/12at7.htm

There's not much info about Suttons amps on the net, but Google found this: http://www.guitargear.net.au/discussion/index.php?topic=35337.0

Besides tubes, capacitors are often a source of problems in old amps.

beinhard

Mick, try breathing on the glass. You might get lucky and be able to read a faint inscription.

Thanks guys,
I had found the page linked by Beinhard and my guess was 12AX7 as well. I'll give the breath trick a go and see what is revealed
Cheers,
Mick

 

[southernGuild]

Nothing to ad here, but when I saw this one pop up last night I thought "Cool, a good mystery". Great to see this already working towards an answer.
Default should arrive soon. :wink:

 

[Default]

Try putting the valve in the freezer. Let it get nice and cold and sometimes the number will be readable. Failing that, take the chassis out of the amp and take a pic of the tube socket. We can most likely tell by the heater connections. I'm leaning toward a 12ax7, but it could be a 6eu7.

 

[southernGuild]

Here we go!

 

[laverda]

I love this forum! I'll try the suggested ideas and see if the label can be identified.
Thanks default,
Mick

 

[taabru45]

12ax7 was hugely popular in the old 5 tube radios of that period, I built one for an electronics class.........yes, that was in this lifetime. :lol:

 

[Default]

I'm thinking a better speaker and that would be a pretty rocking practice amp!

 

[laverda]

I'm thinking a better speaker and that would be a pretty rocking practice amp!

You read my mind What sort of speaker would you be thinking given the current 2 ohm load?

Hopefully getting hold of the unit again this evening to check out that valve.

 

[Default]

I'm thinking a better speaker and that would be a pretty rocking practice amp!

You read my mind What sort of speaker would you be thinking given the current 2 ohm load?

Hopefully getting hold of the unit again this evening to check out that valve.

It's got a 2 ohm speaker???? It says that on the speaker? :shock:

I haven't heard of a 2 ohm speaker before, Mick. Normally, you'd need multiple speakers, like a Fender Super Reverb, to have that kind of load.

 

[laverda]

I'm thinking a better speaker and that would be a pretty rocking practice amp!

You read my mind What sort of speaker would you be thinking given the current 2 ohm load?

Hopefully getting hold of the unit again this evening to check out that valve.

It's got a 2 ohm speaker???? It says that on the speaker? :shock:

I haven't heard of a 2 ohm speaker before, Mick. Normally, you'd need multiple speakers, like a Fender Super Reverb, to have that kind of load.

Yep, its labelled 2ohm and measures a little over 2 when isolated and checked! So a little pair of 4ohm tens in parallel may be in order

 

[Default]

If it measures a little over two ohms with a meter, it's most likely a three ohm speaker. Resistance through an speaker is roughly 2/3 of the speaker impedance. Weber makes killer speakers and some of them come with a 3.2 ohm impedance, which would be perfect for that amp. Is that a six or eight inch speaker in there?

<edit>
You could probably use a load of 4 ohms without any problem, so I would rewire a Marshall 4x12 cabinet to four ohms.