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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 14th Dec 2018, 12:50 pm   #1
John_BS
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Default Tannoy 78 rpm record player

A local friend has aquired an unusual Tannoy record player, which appears to include an amplifier but no speakers. The turntable is clockwork, and the valves are all "*30" types. The instructions taped under the lid suggest it was intended for operation from a 12V battery, but with possibly another unit which may have been some kind of HT invertor?

If anyone can supply any further information it would be gratefully received.



John
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Old 14th Dec 2018, 12:53 pm   #2
Peter.N.
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Default Re: Tannoy 78 rpm record player

It could possibly have been designed for use with a Tannoy PA system of the time.

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Old 14th Dec 2018, 2:04 pm   #3
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Default Re: Tannoy 78 rpm record player

Or rather, it is one of their PA systems, albeit a portable one with inbuilt gram facilities.

Just the thing for celebrations on the village green.

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Old 14th Dec 2018, 2:54 pm   #4
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Default Re: Tannoy 78 rpm record player

The B30 output valves are interesting- listed as class B double triodes so presumably in parallel push pull here. Couldn't find any actual data, just a mention in a prewar Marconi catalogue .
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Old 14th Dec 2018, 10:26 pm   #5
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Default Re: Tannoy 78 rpm record player

The pickup head looks very like the Garrard magnetic units of the 1930's.
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Old 14th Dec 2018, 10:40 pm   #6
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Default Re: Tannoy 78 rpm record player

Just the thing for Spinal Tap: the volume controls go up to 20!
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Old 14th Dec 2018, 10:50 pm   #7
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Default Re: Tannoy 78 rpm record player

I've not had an proper look at it yet, but I couldn't see any evidence of a transformer. The Valves are all 13V 300mA heaters, apart from the rectifier U30 which is centre-tapped 26V / 300mA . Perhaps the external invertor fed ac to the box? It's most unusual to not find any data on a valve: H30 and L30 both triodes with only CV equivalents. Some data on the former here:

http://www.r-type.org/exhib/aag0144.htm

Do you think this amplifier might be a transformerless push-pull output direct to a 100V line?

John

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Old 14th Dec 2018, 11:51 pm   #8
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Default Re: Tannoy 78 rpm record player

One or two thoughts that might be helpful:

I recall the loudspeaker van which used to provide PA at our annual school sports days in the 1950s. It had four 'directional baffle' type short horns on the roof and the amplifier which drove them was operated from a substantial car battery. Those horn speakers would have been pretty efficient so that probably a 10 W amplifier may have sufficed for coverage over a few hundred yards. There was a rotary converter running continuously from the battery which presumably supplied HT to the amplifier. With hindsight, it was surprising that the HT wasn't supplied from an integral vibrator pack. Perhaps John's Tannoy amp also relied on a rotary converter for its HT, probably housed in a separate power pack with its suppression and smoothing. Or perhaps a heavy duty HT battery was used.

In a loudspeaker van, or any similar PA with local speakers, it may not matter much where the output transformer was located. With triode output valves rather than tetrodes, the inherent danger of disconnecting the anode load while the amp is in operation is avoided because the valves have no screen grids to draw the resulting excessive current. So perhaps , as John suggests, the amp provided an 'open anode' high impedance output and Tannoy located the output transformers on the speakers themselves.

The spring-driven gram motor isn't too surprising. Back in those days the motor had real work to do hauling a shellac disc around under the load of that weighty pickup. An electric drive would have been quite an additional drain on the battery which was avoided by getting the operator to do the work of winding. It would though have led to long pauses in the music continuity, lacking the slickness of a twin turntable disco!

Martin

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Old 15th Dec 2018, 12:55 am   #9
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Default Re: Tannoy 78 rpm record player

What a wonderful contraption! I think Martin's on the right track with the visiting Tannoy (geddit!!?) van with the miracle of music between the announcements.
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Old 15th Dec 2018, 9:46 am   #10
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Default Re: Tannoy 78 rpm record player

I'm not sure about the open anode theory. These are "class B" triodes which strongly suggests push-pull operation and I'd be very surprised to find any "Philips style" transformerless output here. In any case, with battery operation, class B or quiescent push-pull would be attractive.

Could be a few too many angels dancing on the head of this pin! A good look at the innards would be handy......
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Old 15th Dec 2018, 10:10 am   #11
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Default Re: Tannoy 78 rpm record player

Quote:
Originally Posted by Hartley118 View Post
The spring-driven gram motor isn't too surprising. Back in those days the motor had real work to do hauling a shellac disc around under the load of that weighty pickup. An electric drive would have been quite an additional drain on the battery which was avoided by getting the operator to do the work of winding. It would though have led to long pauses in the music continuity, lacking the slickness of a twin turntable disco!

Martin
The other reason for a spring driven gram would have been the expense and difficulty of finding a constant speed 12 volt motor whereas the spring motor (Garrard?) would have been off the shelf and cheap.
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Old 15th Dec 2018, 10:54 am   #12
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Default Re: Tannoy 78 rpm record player

I'll take a photo of the instructions under the lid, which give some clues to the use etc. The owner did say there were some horn-like speakers which apparantly went separately to auction.



John
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Old 15th Dec 2018, 12:53 pm   #13
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Default Re: Tannoy 78 rpm record player

Here's the old "instructions" pinned under the lid, plus photos of the various connections. It's now clear there was an external invertor of some kind, and given that there are two sets of valves, two volume controls and two speaker sockets, are there twin amps in there?

There's a mystery "bulb" lurking under the tone arm pivot: looks like an incandescent lamp, but it's quite well buried. Note that the woodworm appear to be on good form, judging by the piles of frass!

Now, what should be done wit this RP: my friend had thoughts of removing the Tannoy badge and junking the rest. It's almost certainly unique, so I feel it should at the very least be properly recorded for posterity?

John
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Old 15th Dec 2018, 4:00 pm   #14
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Default Re: Tannoy 78 rpm record player

Arrrgh- by all means remove the Tannoy badge, but don't junk the rest- it's much too interesting! See if he can be persuaded to offer it on here (with or without the badge) for a sensible sum. A sum based on a several interesting old valves and maybe an output transformer rated for a few watts would get it a reprieve from someone and a return for your friend.
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Old 15th Dec 2018, 4:23 pm   #15
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Default Re: Tannoy 78 rpm record player

That mystery bulb may be a Barrettor thermistor to enable the amplifier to be used on AC/DC mains.

The barrettor will regulate the current through the 300mA heaters.

I have a Tannoy amplifier of similar vintage with the same valve types.
No schematic or handbook unfortunately.

You can find information on the L30, H30 and U30 valves, but I have never found anything for the B30.
It may be a modification of the B36 valve.
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Old 15th Dec 2018, 4:37 pm   #16
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Default Re: Tannoy 78 rpm record player

The L30 valves have an anode current rating of 25mA. The ra is 2860 Ohms. B7 valve base.

They may be the output valves.
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Old 15th Dec 2018, 4:54 pm   #17
barrymagrec
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Default Re: Tannoy 78 rpm record player

I think the B30 would have been much earlier than the B36 which came out in 1948 - even the original 12SN7 came out tin 1940, long after the other "30" types.
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Old 15th Dec 2018, 5:27 pm   #18
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Default Re: Tannoy 78 rpm record player

The L30 / H30 appear to date from 1934. Can anyone find a pin-out for the B30?



John
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Old 15th Dec 2018, 5:40 pm   #19
barrymagrec
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Default Re: Tannoy 78 rpm record player

The B30 doesn`t appear in the 1949 edition of the Wireless World Radio Valve Data book. The L30 and H30 both do, listed as obsolete and replacement respectively.

B30 must have been an unpopular type.

Looks to be a CV2865 - nothing on that either.

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Old 15th Dec 2018, 6:01 pm   #20
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Default Re: Tannoy 78 rpm record player

B30:

From a Marconi valve data book...Class B Double Triode, heater assumed to be 13v@300mA.

Ea=180

Load=7000

Eg=0

Input impedance=6000

Output=5.0 Watts.

Book page 33:

https://frank.pocnet.net/sheets/179/...Valves1938.pdf

Lawrence.
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