Please Identify this tube/valve

aja

I have this power amp and I cannot figure out what this tube is because of my general lack of knowledge and the markings have come off.

The amp uses two Mullard EL34 and two Mullard EF86 and this one tube I cannot identify.

Here are an EL34, unknown and EF86 for scale

And here is the unknown tube:

Bottom view (the plastic tube in the middle and the "notch" has been broken off by who knows who...

The letters look like:

"SH MADE" or maybe "RH MADE" or "RN MADE"

Maybe it is BRITTISH MADE? The EF86 tubes have that marking and the EL34's say made in Holland...

And Under that it seems to say:

"B 8 C" or "B 8 O"

And here is the rest of the amp if that helps at all. It weighs a ton - those transformers are freaking huge. The unknown tube is removed in these photos - it sits in the middle between the transformers

CD for scale

makepeace

is it a rectifier?

Gearhead

imho it is a recto tube, judging from the wiring. Hard to say which one, maybe the pinout would narrow it down a bit.

TomCat

Gearhead wrote imho it is a recto tube, judging from the wiring. Hard to say which one, maybe the pinout would narrow it down a bit.

I'd also go with the Recto Tube.......The wiring underneath will be able to identify is as one with direct heaters or with separate heaters.

EDIT: Looking at the chassis wiring it seems to be directly heated. i.e. no separate heated cct to the tube.

aja

Thanks for the replies guys. Would any other photos help?

Karel-Mars

aja wrote
The amp uses two Mullard EL34 and two Mullard EF86 and this one tube I cannot identify.

Well, my gues is you have a Quad Amplifier here; only the Quad uses two EF86's for driver/phase splitting

The mystery tube is a rectifier. The Quads used to use KT66's for output duty, but they became scarce and people substituted 6L6GC's, which ran a bit hotter than the KT66's. I have not seen EL34's in such an amp, because pins 1 & 8 needs to be connected for an EL34 to work. For beam tetrodes only pin 8 need to connected to the cathode, and pin 1 is usually used as a wiring tie point. Look at you Fender amp and see pin 1 used as a tie point for the grid blocking resistor.

You need to check the detail around the power tube sockets, before you switch on. Also take note that those electrolytic and paper oil caps are probably leaky. Only switch on with a 60watt lamp in series ? if you do not want to blow a fuse/power transformer/whatever.

This is probably a stunning amp, though I do not personally like Quads in general. I prefer the Williamson amp ?

Gearhead

Eh.. Karel, how many different incarnations of said Quad are there? This does look a series made product, so it should be identifyable from looks alone?

I-M-Biased

Hi Aja

I will also go with the opinion that it is a rectifier tube, probably a GZ34 or GZ32 (as in a Quad), which is commonly used with EL34 based amps.
Agree with Karel Mars that 2 EF86 pre-amp tubes point towards a Quad derived circuit. I have however never seen a Quad amp like this.

Can't quite see on the picture from below how many wires come out from underneath the output transformer, but it looks like only 6, which would not indicate a Quad output transformer. Aja please count the number of wires coming out of the hole just below all those yellow capacitors (the hole just below the green resistor)

aja

I M Biased wrote Hi Aja

I will also go with the opinion that it is a rectifier tube, probably a GZ34 or GZ32 (as in a Quad), which is commonly used with EL34 based amps.
Agree with Karel Mars that 2 EF86 pre-amp tubes point towards a Quad derived circuit. I have however never seen a Quad amp like this.

Can't quite see on the picture from below how many wires come out from underneath the output transformer, but it looks like only 6, which would not indicate a Quad output transformer. Aja please count the number of wires coming out of the hole just below all those yellow capacitors (the hole just below the green resistor)

Indeed there are 6 wires coming out the output transformer it seems ???

Would closeup pictures help?