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New Telly Arrival month: Fergy 3710, Fergy 3712, Bush CTV 1120 & Beovision 3200-SJ

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Cathovisor
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Downloaded and being read.

Fantastic 🙂

 
Posted : 02/08/2018 3:11 pm
crustytv
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Interesting the 4 clamp EAA91's are not counted in the valve line-up description. Reading up on the EAA91 its electrically the same as a EB91 only physically smaller by 10mm. Well If I need any of those I bought a box of 100 NOS about 8 years ago and not used one since.

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Posted : 02/08/2018 3:32 pm
Cathovisor
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It's probably like how they traditionally didn't count the rectifier or a 'magic eye' in a radio, because it's viewed as a 'passenger' as valves go. Also, you've solved something that bothered me back in the days when I had my 3200, viz. the difference between an EAA91 and an EB91! Mmm, bi-phase clamps.

Must stop thinking about this set and the 3200, I'm starting to want one of my own.

 
Posted : 02/08/2018 3:51 pm
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Posted by: Cathovisor

Must stop thinking about this set and the 3200, I'm starting to want one of my own.

I know the feeling. The more I peruse over the manual, the more fascinating it becomes with striking evidence of a very well thought out and implemented design. The timebase, convergence and EHT generation stages being immediately notable.

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

 
Posted : 02/08/2018 5:08 pm
crustytv
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Taken from Beolink Magazine: 'The First 50 Years of Television' © Bang & Olufsen a/s 2002

" Its 625-line only circuitry initially made it of limited use, as BBC1 and ITV were not widely receivable on this standard, leaving BBC2 as the only viewable programme. Beovision 3000 made up for this though by offering the best quality colour picture yet seen, so good in fact that in certain areas it remained unsurpassed for years after it was withdrawn. When B&O released its first solid state colour sets in 1974, these had to be modified in the field, as their contrast levels seemed 'washed out' compared to the then 6 year old 3000s!

Quality was achieved at the cost of considerable complexity. It is well known that cost was not a factor in the design of the 3000, and so any extra parts or stages that could possibly up the performance were added without question. The result was a set with 18 valves, 53 transistors and 48 diodes arranged on two massive chassis. Technical highlights included decoder circuitry working at high voltage to improve colour linearity, DC controlled static convergence, apparently less susceptible to mains voltage variations, separate line scan output stage and EHT generator employing two transformers and two sets of large valves, which improved geometry and dimensional stability, an electronic EHT stabiliser which helped to ensure uniform focusing, and of course, a comprehensive audio amplifier employing three transistors, one valve and heavy negative feedback, all driving a high quality loudspeaker.

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Posted : 02/08/2018 5:22 pm
Nuvistor
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Looking at the 3000 info in the library the first item I saw was the Luminence delay line, 830ns, G.H. Hutson in his Colour Television text book states the delay line depending on circuitry will usually be between 500ns and 1000ns, ( 0.5us and 1us).

From memory most U.K. designs were around 600ns or just over, presume the Beovision had more Chroma circuitry, the Luminance channel wider or both compared to many UK sets at the time.

 

Frank

 
Posted : 02/08/2018 7:33 pm
Jayceebee
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That's a very "busy" circuit diagram and nice to see the EHT regulation achieved without the wasteful PD500 shunt stabiliser. I notice that two of the triode sections of the ECL84s are connected in parallel and used in the blanking circuit, I can't see the third one utilised for anything or is it hiding somewhere?

John.

 
Posted : 02/08/2018 8:51 pm
PYE625
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What surprised me is why other set makers of the time didn't use a similar regulation circuit for the EHT, instead of the rather crude direct shunt type. Surely it would have been more reliable, and not too expensive to design.

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

 
Posted : 02/08/2018 9:24 pm
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Posted by: Jayceebee

That's a very "busy" circuit diagram and nice to see the EHT regulation achieved without the wasteful PD500 shunt stabiliser. 

I haven't studied the circuit in any great detail and to be honest I knew very little about the set other than it was the one using the two line-output valves. I made an enquiry to Tim Jarman of Beocentral a couple of days ago and he responded this evening. He also kindly offered a word of caution which is worth repeating here. As I say, I was unaware of much about this set and quite possibly others here or guests looking in, might be in that same position too.

Tim Jarman of Beocentral

All the information you'll need is in volume 1 of Gordon King's 'Colour TV Servicing Manual' (the red one). It is also covered in the R+TV S red books and was detailed at length in 'Television' magazine (3 part series, late 70s). All you'll need to know is there. I set mine up to the reduced operating conditions outlined in 'Television' (final article in the series), it didn't change the performance that much but things seemed a lot less stressed. As ever, the EHT transformer is the thing to worry about.

These sets are very dangerous as the stabilised EHT supply can produce 12.5mA under full regulation, which is far more than any other colour set of this era. Please be careful when working inside the line scan cage.

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Posted : 02/08/2018 9:26 pm
crustytv
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Anyway the Beo 3000 has dominated this thread (which is understandable) but what I'm really excited about  are two other sets, as its only two days to go and the Fergy 3712 (8000 series) and Bush CTV1120 (A823AV) arrive in crustys colour collection.

What's more I get to test the 9600 modules (Scanning, PSU, SYclops and Line&Field Osc) from my recalcitrant Ferguson 3734 in Mikey66's working 9600. I'm hoping with Gary and Mikes help we collectively get to the bottom or at least isolate it to a particular module, what's causing that voodoo shrunken raster on mine.

Then Monday its pick up or perhaps even roll the 25" Keracolour  ? into the Lexus along with the Beo 3K. Nice to have a car that can carry large loads after spending almost all my years driving two seater or 2+2's with zero load capability.

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Posted : 02/08/2018 9:38 pm
Cathovisor
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Having looked at the Aphelion, then looked at a Keracolor, my thoughts are that a lot of space is wasted in the Keracolor and to be honest, I think the Aphelion is the more 'sensible' design. The Keracolor must be *huge*...

I also note that a warning has been posted about the EHT stage on the B&O - this is worth noting because they do not take prisoners and was actually a factor in my originally wanting to get my 3200 running - because I knew there would be a rock-steady picture even allowing for the worst excesses of Top Of The Pops and its flashing lights back in the 80s!

 
Posted : 02/08/2018 10:53 pm
crustytv
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Great day out today, a leisurely drive down to Manchester with Gary, over to Mikey66's place to collect the Ferguson 3712 and some *TV playing. Also took delivery of the Bush CTV1120 from Gary.

Place holder collection repair blogs started, threads should follow in due course.

Next stop Monday when the Keracolour and Be0 3000SJ arrive.

P.S.

* We also spent time with my Thorn 9600 panels in Mikes 9600 set in an attempt to isolate the cause of my Voodoo Raster. More on that will follow over in the Fergy 3734 thread a little later.

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Posted : 04/08/2018 5:25 pm
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PYE625
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Yes....the 3712 looks a tad overdue for some TLC Chris.   ? 

The A823 will be a walk in the park.

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

 
Posted : 04/08/2018 5:46 pm
Jayceebee
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Oh dear, looks a lot of work required with the 3712. I don't see any PSU in your pictures, it's normally mounted alongside the LOPT, not the most accessible position . Have you determined if it's an 8000 or 8000A? Look at the dropper, the 8000 only had two or three sections whereas the A version had five or six, the A version was supplied as a replacement for the 8000 but the extra sections were not used.

John.

 
Posted : 04/08/2018 8:38 pm
crustytv
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Hi Jon,

I'm afraid its in a very sad state and yes the PSU/sound output is missing as well. I have the timebase but not the PSU/SND and the CRT PCB being so badly cracked another is really needed. This set will be put to one side in a hope parts will turn up in the future.

Lets hope the Keracolour and Beo 3K are found to be in better shape when I collect them on Monday. Apparently the Beo 3K has suffered over-heating.

Still on the plus side the Bush CTV1120 is gorgeous (just need to find the bow tie chrome stand) and the Fergy 3710 is good

 

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Posted : 04/08/2018 8:45 pm
crustytv
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Posted by: Jayceebee

Have you determined if it's an 8000 or 8000A? Look at the dropper, the 8000 only had two or three sections whereas the A version had five or six, the A version was supplied as a replacement for the 8000 but the extra sections were not used.

The dropper fitted is an A version, two sections not used the dropper is very rusty, I think the chassis has sat in water as the signals panels and that bottom corner of the chassis has a tide mark and very bad corrosion as a result.

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Posted : 04/08/2018 8:54 pm
crustytv
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Started the repair of the 3712 CRT PCB, glued the 3 parts together, just need to stitch the various tracks and replace a couple of broken resistors. Its not going to win any beauty awards but it will have to do.

see here 

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Posted : 05/08/2018 4:51 pm
crustytv
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Track stitch done and continuity tested see here I think this is going to be OK

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Posted : 05/08/2018 6:32 pm
PYE625
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A good repair  ? 

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

 
Posted : 05/08/2018 7:06 pm
crustytv
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@jayceebee

Hi John, I need your advice, put your Thorn head on  ? 

I was hunting through my PCB stores and to my absolute delight I came across a PSU/sound output module which is an 8500 type (see photos below). Now I might be wrong which is why I need to call upon your encyclopedic Thorn knowledge.

psu 2
psu 1
psusnd1

I believe an 8500-PSU/SND module can be used in an 8000, conversely however, an 8000-PSU/SND module cannot be used in an 8000A/8500 as damage will occur.

If my thoughts on this are correct, this 8500 PSU/SND module "should" be perfectly fine for my 8000 chassis and I can proceed to the testing stage of this saga. However I'm not at all certain and need guidance. Does that all makes sense? Am I right or am I completely wrong? I eagerly await your thoughts. 

 

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Posted : 05/08/2018 11:25 pm
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