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Coming soon - Decca TP22 transistor radio

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Katie Bush
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Well, it's been a long day,

And..... I had some time to wait in town. As we all know, the Devil makes work for idle hands, and I took a look around the St Leonard's Hospice shop in Selby - I came away with the above mentioned radio (and an early 'TV table').

Visually, the TP22 isn't the most inspiring of radios, but it was begging me to take it home, so I took of the back cover and could see it was all still there.... "It doesn't work" said the lady behind the counter. "It is battery, but you can't get the batteries anymore and we were told it doesn't work anyway, so it's only for display or decoration etc".

So with that in mind, I bought it, complete with the original brown envelope containing:- one guarantee card, one operating instructions card, an identity tag for shop purposes and the original advert, to point of fact, the complete page from a newspaper dated October 3rd 1960 (makes interesting reading in its self).

I was intrigued by the battery connections - the radio uses two PJ996 'lantern batteries' and I'm certain you can still get those. But those connections? The batteries are linked in series, but the 'interconnect' between the batteries also connects to one side of the speaker - split power supply?... If anyone has any gen on this radio, I'd be interested to know.

At the moment, the radio and its documents are resting peacefully in the car, but I do recall reading that it's a six transistor, two diodes, with push-pull output. It's nicely dusty inside, but the chassis is a bit bent (should straighten easily), one corner of the cabinet has suffered a bit of a bash and the dial glass doesn't sit properly in its window, but otherwise it looks pretty good. There are no pictures for me to post right now, but that will be remedied when I get back from town tomorrow, but it looks about the same condition as the one pictured below.

 

decca tp22
 
Posted : 05/04/2018 9:07 pm
PYE625
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And so to a new home.... well done for saving it Marion  ? 

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 05/04/2018 9:10 pm
Marc
 Marc
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Hi Marion,

Not a bad little prize from the old hospice shop, was it the one in town or the one over the bridge ?

Marc
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RSGB call sign 2E0VTN

 
Posted : 05/04/2018 9:18 pm
crustytv
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Just uploaded the service data for the Decca TP22 to the data library  ? 

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Posted : 05/04/2018 9:18 pm
Katie Bush
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Posted by: PYE625

And so to a new home.... well done for saving it Marion  ? 

Well, that's just the first step, and I couldn't let it get turned into a table lamp or whatever.

It's full of transistor types that I'm not familiar with, which is why mentioned any gen on the set, and I do believe I saw an 'Orrible 'Unts or two in there. It's obviously been a busy little set in its day, with plenty of evidence of the batteries rubbing against the back cover, and the knobs are well and truly grimy. The cabinet is quite grubby, but I'm hopeful for its scrub-up ability!

 
Posted : 05/04/2018 9:19 pm
Katie Bush
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Posted by: Chris

Just uploaded the service data for the Decca TP22 to the data library  ? 

Cheers Chris,

That should help to incentivise me into some sort of action - and it's nice lightweight project, and hopefully not too difficult to work on.....

 
Posted : 05/04/2018 9:21 pm
Katie Bush
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Posted by: Marc

Hi Marion,

Not a bad little prize from the old hospice shop, was it the one in town or the one over the bridge ?

The Ousegate branch, the one just over the bridge.. The telly table was a steal at £1, last chance saloon I reckon before a trip to the tip.

The TP22 cost me a princely £25.. Not sure where it should be on the price scale, but it was right there in front of me, and I had to have it. ? 

And besides, I just had nightmares of some 'steampunk' fiend sticking a 40W bulb inside it, and a load of old clock parts on the outside of it - Euch!

 
Posted : 05/04/2018 9:29 pm
crustytv
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Posted by: Katie Bush
Posted by: Chris

Just uploaded the service data for the Decca TP22 to the data library  ? 

Cheers Chris,

That should help to incentivise me into some sort of action - and it's nice lightweight project, and hopefully not too difficult to work on.....

Excellent idea and way better than tiring yourself out lugging a hefty old TV onto the bench. Look forward to our Yorkshire correspondent "Katie Bush" frontline report of the TP22's return to health, some interesting transistors in there.

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Posted : 05/04/2018 9:36 pm
Katie Bush
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To be honest, Chris, I was thinking in terms of something I could work on, on a coffee table or suchlike.

Just three screws holding the back on, two, I think, holding the chassis in place. The batteries are held down by a simple piece of hardboard which slides out without fuss to allow the chassis to be drawn out from the back - the control knobs and dial all come away with the chassis, so shouldn't take more than a couple of minutes to un-crate. Four 4BA screws secure the speaker, and that's about it!

 
Posted : 05/04/2018 9:45 pm
Cathovisor
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PJ996s are readily available, Marion - otherwise there'd be nothing to power all those roadside lanterns and many a big torch!

Chances are the centre-tap of the batteries passes through the speaker to the junction of the output pair (edit: it does) - it's an uncommon arrangement, but it saves on a coupling cap and gave you a real DC-coupled output stage!

The transistors are Ediswan-Mazda.

 
Posted : 05/04/2018 10:01 pm
Cathovisor
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Posted by: Katie Bush

And besides, I just had nightmares of some 'steampunk' fiend sticking a 40W bulb inside it, and a load of old clock parts on the outside of it - Euch!

You mean, rather like someone did to a lovely Belling 'Cubic' electric fire I have? (Well, the lights bit anyway) That now has heating elements again (a Belling 'Dinkie' gave itself up to a noble cause) but now it needs a bit of cast-iron welding and re-enamelling.

 
Posted : 05/04/2018 10:07 pm
Katie Bush
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Hi Mike,

That's what I thought, regarding the 996 batteries... A lot of years ago, I had a couple of "Til-Dawn" amber warning beacons that I kept in the car - they used PJ996 batteries, though it's a long time since I saw them.

I think I'm going to kill off these DWP forms at the weekend (said Florence, hopefully) and see about looking into this Decca.

Yeah.... What a pity those steam punkers don't realise the harm they're doing - I always thought they were supposed to "upcycle" 1980's junk, or something, but the number of gutted TV carcases I've seen suggests otherwise.

I suppose nothing is sacred to the punka wallahs?

 
Posted : 05/04/2018 10:23 pm
crustytv
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For those wondering who don't have access to data the transistor line-up is as follows :-
 
TR1 XA102 - Self Oscillating Mixer
TR2/TR3 XA101 - I.F.Amp
TR4 XB103 Driver
TR5/TR6 XC101 Output pair (push-pull)
 
Posted by: Cathovisor
 
The transistors are Ediswan-Mazda.
 
Oh yes, thanks  ? a little digging on the web revealed to me and others might find useful (I'm sure you already know) the following : - 
 
Germanium PNP junction transistors released in 1956, all in a characteristic 'top hat' package. The XA101 and XA102 were described respectively as an IF amplifier and a "frequency changer and/or oscillator on the medium and long wave bands". They had a maximum collector-emitter voltage of 16 volts and a maximum power dissipation of 60 milliwatts
 
XA101
 
The  XB103 from 1956 AF amplifier, with a maximum collector-emitter voltage of 35 volts and a maximum power dissipation of 90 milliwatts, and a gain range of 18-47 
 
XB103
 
The XC101 from 1956 was an AF output type, with a maximum collector-emitter voltage of 35 volts and a maximum power dissipation of 100 milliwatts. Uniquely amongst Ediswan's top hat transistor types, it was unpainted. The 'C' in the part number apparently designates 'power output', although the XC101 is relatively restrained in its capability. 
 
XC101
 
 
Lets hope they are all OK as it would be a shame to have to replace them, although I do believe you can get Russian equivs that are in the same package, should the need arise.

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Posted : 05/04/2018 10:28 pm
Cathovisor
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That's a very useful guide to these often-forgotten transistors  - thanks, Chris.

I'm afraid my opinion of Ediswan transistors is somewhat coloured by the trouble I had sorting out record player transistor amps for someone; in several examples the Mazda AC156s had become incredibly noisy to the extent that the amplifier sounded like an FM radio off-tune! I redesigned the amp (read: calculated the bias point for a silicon transistor!) to use a BC549 in its place.

 
Posted : 06/04/2018 8:57 am
Terrykc
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I would expect those Ediswan-Mazda transistors to be broadly equivalent to the Mullard - Philips OC44, OC45, OC71, OC72 range. The OC72 is only rated at 16V max but would be fine here as it has a much higher maximum power dissipation of 165mW.

Back in the 60s we never stocked anything else other than the Mullard range so, if one of these sets had needed repair, that is exactly what we would have fitted! I dare say a lot of service departments would have done the same so, if anybody has any of them left, it wouldn't be out of touch with reality, despite the different physical appearance.

After all, what is better - a working (but not quite original) radio or a decorative 'brick' on a shelf?

When all else fails, read the instructions

 
Posted : 06/04/2018 11:31 am
Cathovisor
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Posted by: Terry

 

After all, what is better - a working (but not quite original) radio or a decorative 'brick' on a shelf?

Depends upon whether you're repairing or restoring.

 
Posted : 06/04/2018 12:38 pm
PYE625
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Generally I seem to find germanium transistors are pretty reliable, perhaps with the exception of some AFxxx series due to internal whisker problems.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 06/04/2018 12:39 pm
Cathovisor
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The other germanium transistor that's utterly unreliable is the AL102 as used in Armstrong 400/500 series amplifiers.

 
Posted : 06/04/2018 12:47 pm
Nuvistor
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The AF output transistors AC128/176 have the same problem as the AF11X Range.

The earlier OCXX range were decent, not that much trouble for me, mind at something like 22/6d old money in around 1962-5 they were expensive, didn’t want too many of those replacing.

 

 

Frank

 
Posted : 06/04/2018 1:53 pm
Cathovisor
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Posted by: Nuvistor

The AF output transistors AC128/176 have the same problem as the AF11X Range.

 

You surprise me, Frank? Never knew it was an issue with them?

 
Posted : 06/04/2018 3:40 pm
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