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Old 20th Oct 2020, 8:30 pm   #1
clockman
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Default HMV 2634 12 inch mains portable Thorn 980

My discovery. I found this set in my loft from 1966 we used this TV in the kitchen for a few years to watch when having our meals but with the arrival of 625 it was put in the loft and has been there ever since till this weekend. I wonder the reason these old sets are sold and bought as to me they seem highly unrepairable and there are no channels available i am wondering what i should do with this set as it is a nice looking 55 year old family hairloom ? TAB
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Old 20th Oct 2020, 9:35 pm   #2
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Default Re: HMV 2634 12 inch mains portable Thorn 980

It'll definitely be repairable unless there's a major fault with it. Whether it's worth it or not is a different matter as the CRT could be low emission, failed LOPT or both. But as this is a Thorn chassis I doubt the LOPT has failed. Though that might not be 100% true for all Thorn LOPTs

If it's worth the repair and it does get repaired, you can use an 'Aurora' or 'Hedghog' standards converter which converts an input into 405 lines.

It's definitely worth saving, in my opinion

'77
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Old 20th Oct 2020, 10:06 pm   #3
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Default Re: HMV 2634 12 inch mains portable Thorn 980

We Have a slighly tatty one at the wireless and television museum at Dulwich and I have the Ferguson equilivent here in my collection , once restored , they will give a very good picture ( assuming the tube is ok ) but you will need a standards converter to be able to use it , I am sure sombody on here would be delighted to have a look at it for you .
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Old 20th Oct 2020, 10:50 pm   #4
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Default Re: HMV 2634 12 inch mains portable Thorn 980

These are brilliant little sets. A bit hot running to be fair.
One thing that you mustn't do is to plug it in and switch on.
At least it needs to be awakened slowly with a lamp limiter or gradually with an variac, observing the HT and capacitors for getting warm.
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Old 21st Oct 2020, 11:03 am   #5
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Default Re: HMV 2634 12 inch mains portable Thorn 980

These were the last 405 line only Thorn sets IIRC.

I remember someone mentioning there were a lot on the market in the mid 1980s, as a lot had been kept as second sets right up to the 405 line shutdown.

As the styling was fairly modern a few people bought then thinking they had picked up a bargain, only to find they were no longer useable! At least until the first standards convertors came along.
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Old 21st Oct 2020, 2:00 pm   #6
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Default Re: HMV 2634 12 inch mains portable Thorn 980

No i have had a peep inside the PL81a is missing i must have pinched it for an other set. the TV looks well used but the outside condition is perfect including the aerial it has the original service manual and does look nice for its age so i will not be plugin it in . TAB
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Old 21st Oct 2020, 2:07 pm   #7
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Default Re: HMV 2634 12 inch mains portable Thorn 980

I would examine the circuit board around the grey wirewound resistors as resoldering
may be needed.
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Old 21st Oct 2020, 3:20 pm   #8
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Default Re: HMV 2634 12 inch mains portable Thorn 980

Quote:
Originally Posted by Richard_FM View Post
These were the last 405 line only Thorn sets IIRC.
At least some of them were assembled at the Baird TV factory in Bradford when I worked there. The track was brought up from Gosport, I think, to the annoyance of another department who wanted to use it for training purposes (hearsay of course). I believe they were a freebie to encourage the very slow initial take up of colour TV, as they were effectively obsolete by then.
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Old 21st Oct 2020, 10:34 pm   #9
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Default Re: HMV 2634 12 inch mains portable Thorn 980

That''s very interesting, the price for them that was nearly half the 16" dual standard sets using the same basic chassis.
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Old 21st Oct 2020, 11:13 pm   #10
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Default Re: HMV 2634 12 inch mains portable Thorn 980

I'm not sure where it was assembled, there was also the 981 chassis (16" version)
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Old 22nd Oct 2020, 9:17 am   #11
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Default Re: HMV 2634 12 inch mains portable Thorn 980

Some years ago I had a visit from a guy in Gosport. He worked for BRC and designed the majority of their tuners. He worked at the Ultra factory purchased by Thorn in the early 60's.
He informed me that the 980 was manufactured at Gosport as were many of the later Thorn colour portables. John.
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Old 22nd Oct 2020, 10:24 am   #12
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Default Re: HMV 2634 12 inch mains portable Thorn 980

Quote:
Originally Posted by Richard_FM View Post
That''s very interesting, the price for them that was nearly half the 16" dual standard sets using the same basic chassis.
Not quite. The HMV depicted in the photo employed the 1400 chassis which is completely different from the 980. PL504 line output valve for one thing. Unlike the earlier dual standard 900-950 chassis they didn't always perform well on BBC 2. Certainly not worth nearly double the price!

The 980 is a single standard 405-line chassis.
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Old 22nd Oct 2020, 12:14 pm   #13
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Default Re: HMV 2634 12 inch mains portable Thorn 980

Yes my memory was the same when the 908 was put away i purchased a brand new Thorn 20" inch B/W 405/625 Ultra TV on HP to have BBC 2 it was a very good set it never had problems and it was replaced with a R.B.M 22" inch solid state Colour set a good TV set to work on as a engineer Thorn BRC did have a factory at Gosport and Enfield
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Old 22nd Oct 2020, 10:57 pm   #14
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Default Re: HMV 2634 12 inch mains portable Thorn 980

Quote:
Originally Posted by Focus Diode View Post
Not quite. The HMV depicted in the photo employed the 1400 chassis which is completely different from the 980. PL504 line output valve for one thing. Unlike the earlier dual standard 900-950 chassis they didn't always perform well on BBC 2. Certainly not worth nearly double the price!

The 980 is a single standard 405-line chassis.
OK I see, thanks for putting me right.
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Old 23rd Oct 2020, 11:24 am   #15
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Default Re: HMV 2634 12 inch mains portable Thorn 980

Hi.
The 16 inch version uses the 981 chassis, very similar to the 980 chassis with just a few component differences.
The bigger set has less issues with heat dissipation and discoloured PCB's. I have a 981 which works very well but the mask is in a sorry state and it could do with a better cabinet, I think its has a few knocks in its time, the CRT is very good though. Both the 980 & 981 have an important part in our TV heritage as the last production 405 line only TV in the world.
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Old 23rd Oct 2020, 7:56 pm   #16
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Default Re: HMV 2634 12 inch mains portable Thorn 980

I have ordered a New old stock PL81 valve so i can check the heater chain resistance. While in loft again i have found a Evershed & Vignoles crank handle Megga 70143 amazing like brand new but case tatty will keep searching for more finds TAB
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Old 23rd Oct 2020, 8:24 pm   #17
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Default Re: HMV 2634 12 inch mains portable Thorn 980

The correct line output valve for the 980/1 should be a PL81A but a normal PL81 doesn’t seem to cause any problems. I have the Ultra 6645 “Cub” version and they are capable of producing good results. Even more remarkable is the audio given that the output stage is a puny little PCF80.

John.
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Old 24th Oct 2020, 2:14 am   #18
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Default Re: HMV 2634 12 inch mains portable Thorn 980

Hi all,
My first 405 line set was the 16" version which my physics teacher gave me. He complained that it had stopped receiving a signal. Of course the reason was because the 405 line signal had been switched off!
The set worked a bit straight off, but had poor frame linearity. However I had no signal to test it with. The answer came when I watched 'The secret life of the television' and discovered Gerald Wells and his museum. I brought the set up to him and it produced a picture straight away. A new PL81 restored full width and new frame caps restored the linearity. The verticals were ragged which Gerry correctly suggested was due to the sync discrimination diodes. These were in a 3 legged housing that looked like a TO92 transistor, which is odd because I didn't think that TO92 cases existed back then. A couple of 1N4148 diodes fixed that. I still have the set and it pretty much gives the best picture of any set in my collection.

BTW, I remember asking Gerald Wells about the PL81A and he said that it was a graded Mazda valve that had been selected for very good emission. He suggested that any new Mullard PL81 would be just as good.

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Old 1st Nov 2020, 7:48 pm   #19
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Default Re: HMV 2634 12 inch mains portable Thorn 980

Update on my Thorn 980 6641 12 inch portable
I have fitted the new PL81 and checked the heater chain continuity now 1.5 k including the W10 heater rectifier i have had a good look round it has had some repair work done on the PCB so i must have bought it second hand or part/ex but it was working when i put it in the loft . i have given it a bit of a spring clean there nothing missing or damaged . i will not be plugging it in as my days as a TV repair man are now in the distant past .and i do not think spares are available so i will put it back on the shelf for now . PS i have just done a perfect restore job on a Philips B23G25U a great little set TAB
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Old 5th Nov 2020, 10:47 am   #20
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Default Re: HMV 2634 12 inch mains portable Thorn 980

I ran my Ultra 980 up last weekend. It gives an amazingly bright sharp picture and with good sound considering its size.
If you were an ex TV engineer the 980 will make a great project for you. If you can get a manual for it, which are still available, the straightforward all valved design with the clearly drawn out circuit diagram which is typical of Thorn will soon bring those old skills of yours back into play.
You will also need a 625-405 convertor which will probably be a good investment for you.
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