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Old 1st Jul 2018, 5:33 pm   #21
Vakito227
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Default Re: GEC Dual standard TV identification

Hi Nick, according to the service sheets for this set, it uses a PCL84 valve
Peter
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Old 1st Jul 2018, 8:16 pm   #22
Focus Diode
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Default Re: GEC Dual standard TV identification

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Originally Posted by steve1010uk View Post
I think that might be the sobell 195, the one that often seemed to have low brightness due to leaky capacitors
Yes, my mistake. The McMichael I had must've had the rear cover of a ST195.

A long time ago when I had the set.

Brian
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Old 1st Jul 2018, 8:40 pm   #23
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Default Re: GEC Dual standard TV identification

Sorry David I beg to differ on the fact that the 2000 series was never sold as a convertible set as I have 2 of these sets one of them has never had the uhf tuner fitted & the uhf aerial socket cutout on the back cover is intact
The set in question on this thread is definitely a BT455 if you look closely at the pictures you can see the timebase panel on the right has a EF80 valve fitted which was omitted on the 2000 series
Good luck with the restoration I’ll be following this closely with great interest

Chris
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Old 1st Jul 2018, 9:37 pm   #24
Vakito227
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Default Re: GEC Dual standard TV identification

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Originally Posted by 1100 man View Post
Hi Peter,
From what I can see in your picture it is the same chassis as my GEC 2000 DST. My thread, with some chassis pictures is here. Have a look and see if yours is the same as mine!

https://www.vintage-radio.net/forum/...d.php?t=137452
Hi Nick, your set looks extremely similar to mine. I'm just wondering how exactly you removed the chassis from the cabinet. I tried giving it a go earlier today, removed 2 fasteners from the top and 2 from the bottom and pulled out the knob from the VHF tuner on the side. I managed to pull out the chassis including the CRT a few inches but not any further due to the UHF tuner and the controls on the side still being fastened in place. I have no idea how to get in and remove them with the chassis in the way. Service sheets are very vague and not much help it seems very hard to work on by early 60s standards.
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Old 2nd Jul 2018, 12:31 am   #25
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Default Re: GEC Dual standard TV identification

Quote:
Originally Posted by The teleman View Post
Sorry David I beg to differ on the fact that the 2000 series was never sold as a convertible set as I have 2 of these sets one of them has never had the uhf tuner fitted & the uhf aerial socket cutout on the back cover is intact
The set in question on this thread is definitely a BT455 if you look closely at the pictures you can see the timebase panel on the right has a EF80 valve fitted which was omitted on the 2000 series
Good luck with the restoration I’ll be following this closely with great interest

Chris
Hi Chris,
I'm sorry I might have created some confusion about TV standards capabilities of these receivers.
This is as I remember these sets, but please remember we are discussing sets that were made over fifty years ago.
GEC BT455 and Sobell ST196. Convertible models with dual standard timebases for 405 or 625 operation. It's possible that these 405 line only sets were announced to the trade in late 1962.
GEC BT455DS and Sobell ST196DS. These receivers require an UHF tuner for full dual standard operation. Late 1963.
GEC BT455DS-T and Sobell ST196DS-T. UHF tuner factory fitted. Ready to receive BBC2. On sale 1963/64.
The video amplifier is a PCL84 and the line timebase oscillator is an EF80 in a blocking oscillator circuit. EF80 sync separator.

GEC 2000 series and Sobell 1000 series: Late 1964
Model 2000DS and 1000DS dual standard ready, require the UHF tuner to receive BBC2.
2000DS-T and 1000DS-T UHF tuner factory fitted and ready to receive the new 625 UHF station.
PFL200 video amplifier and sync separator. A PCF802 as the line oscillator in a new circuit employing the triode section as a reactance valve.

DFWB.

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Old 2nd Jul 2018, 7:54 am   #26
Focus Diode
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Default Re: GEC Dual standard TV identification

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Originally Posted by The teleman View Post
Sorry David I beg to differ on the fact that the 2000 series was never sold as a convertible set as I have 2 of these sets one of them has never had the uhf tuner fitted & the uhf aerial socket cutout on the back cover is intact
I have a GEC 2015 13" portable version that falls into that category. Never had a UHF tuner fitted yet is otherwise fully dual standard. I've got my set to operate on 625 as well as 405 on VHF. Moving one of the tags to another allows for this (details in the manual). The 2015 has a separate 405/625 change over switch incidentally.

Personally to me the term, "Convertible" apllies to a single standard set that can be converted to dual standard by replacing the IF panel with a dual standard one in addition to fitting a UHF tuner. The timebase are usually dual standard ready as David pointed out. These sets were generally sold from 1962.

Later sets were fully dual standard, or, "Dual standard ready" rather than convertible, but may lack only the UHF tuner, as with my 2015.

They were usually sold for a few £ less than versions that already have a UHF tuner fitted. Made sense for areas that wouldn't be served by a UHF transmitter for the expected user life of the set, or if BBC 2 was of no interest!

Brian

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Old 2nd Jul 2018, 9:35 am   #27
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Default Re: GEC Dual standard TV identification

My understanding of “ Convertable” and “Dual Standard” is the same as David’s and Brian’s. There was the very early models that had a 405/625 control but it was connected to nothing, that would have meant Line timebase changes as well, was the Bush 105 like that? I think the 115 had the LT sorted out but required IF and Tuner, the 125 was available as 125 or 125U, the U had a UHF tuner fitted.

Has David says it’s a long time ago so corrections to my post appreciated

I know some in the trade had “Convertable” sets fitted with an IF panel and tuner to make them dual standard but the customers I had would not pay, quite expensive plus the cost of another aerial.
Not many decided to have a UHF tuner fitted, they saw the BBC2 listings in Radio Times and decided it was not for them.

By the middle of 1965 we only sold sets with the UHF tuner fitted to Dual Standard sets, most wanted a new aerial so we generally fitted a combined Band 3 and Group C UHF. All on one boom, not a great deal more expensive than a Band 3 only aerial. All received from Winter Hill, ITV Ch 9, BBC1 Ch 12 and BBC2 Ch 62.

Happy days, the sun always shined in the daytime, only rained at night and beer was cheap. I think I better put my rose tinted spectacles away.
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Old 2nd Jul 2018, 11:25 pm   #28
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Default Re: GEC Dual standard TV identification

Hi Peter,
I think we can safely conclude that this is a BT455 or 456 which is the predecessor to the GEC 2000 and uses a slightly different valve line up. It looks almost identical and it would be nice to see some close up pictures of the PCB's so I can compare it to my 2000.

Whilst the chassis & tube assembly may look neat and tidy, access to the PCB's for component testing & replacement is not great. The line scan PCB under the LOPT housing is particularly bad!
For that reason I completely removed both the lower PCB's completely from the chassis and overhauled them on the bench in comfort.
I did not want to blanket change all the capacitors but I do like to get all the obviously faulty components out of the way in one hit. After all a good many will need replacing anyway.

My method is to work on a section at a time, correlating the PCB layout to the actual circuit diagram. This is very instructive as you become familiar with the circuit and also where the components are.
Capacitors above 1000pf have a leg lifted and are tested with an insulation tester set to 250V or 500V where applicable. Particularly leaky ones are replaced.
In my set, all the bright red Hunts ones were very leaky (unsurprisingly!) but almost all the 'mustards' were perfect. The 400V rated yellow poly caps are fine for everything except the boost cap which needs to be higher. There are a couple of strange values which couple the line scan coils on each standard which need to be made up out of two caps in parallel. Most of the caps you remove will have the voltage rating marked anyway.

I test the resistors similarly but most can be done without lifting a leg. All mine were a good 20% high but with valve stuff that doesn't usually matter too much. Even if, say a 470K measures 570 or 600K, it will be good enough to at least get the thing working.

With the PCB's on the bench, I gave the system switch a good clean to remove the tarnish and checked each set of contacts for correct operation.

By removing a few wires, the line scan panel below the LOPT can be lowered enough to check & change the components in a similar way.

This is a very different animal to your Ekco TCG316 and it's interesting to see just how far the technology had advanced in only 5 or 6 years.

I hope you enjoy the restoration: the end results are well worth it!

All the best
Nick
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Old 6th Jul 2018, 1:54 pm   #29
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Default Re: GEC Dual standard TV identification

LOPT pictures for Nick
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