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Ultra 6703 - Thorn 3000 chassis

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Tazman1966
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Good evening all.

I have owned the Ferguson 3703 version of the Thorn 3000 series of colour sets for absolutely ages but have been after an HMV or Ultra one to replace it as I fancy the styling of the HMV or Ultra over the styling of the Ferguson and Marconiphone versions. Finally, my wait was over and this Ultra 6703 turned up. It had been stored in a hay loft for at least 15 years but at last was to see the light of day.

The top of the cabinet was badly water marked and the set in general was very dirty. My suspicions that it had been "retired" and "robbed"were aroused by the fact that the plug under the line timebase slab was unplugged and hanging down, the connections to the focus control from the tripler were disconnected as was the tripler connection to the LOPT and to add to it, the aerial socket was missing! On the plus side, I spotted that a "Solus" branded regun tube had been fitted. I slung the tester on it and joy of joys, the readings were right up in the green section for all three guns so one thing less to worry about.

I put the set to one side while I was sorting out the decoder trouble in the Hitachi (see Dave's thread) and waited until I had some time to play. That time finally came this week as having been on a week of early shifts at work my afternoons were free!

Unusually, I thought I'd tackle the awful cabinet top first and after much sanding down, the water damage was eliminated. It's a good job the veneer is thick! I'm not quite sure what I'm going to do to finish the woodwork. I've used teak oil in the past on cabinets and also spray varnish. For the moment. it's in its raw state. The rest of the cabinet and front escutcheon and tube surround were all treated to a damn good clean and a new isolated aerial socket was fitted.

Another day passed and it was time to give the set some juice! I remade the connections to the focus unit, plugged the Line timebase plug back in and made a few cold checks. I disconnected the 30V supply in order to check the "hot" side of the chopper transistor and the high voltage supplies to the video board etc. So with fingers crossed, power was applied and the input to the chopper was fine, CRT heaters on. I left it in this state for a while and nothing untoward happened, phew!

The 30 V supply plug was then reconnected to get the line oscillator going and therefore the chopper power rail. At this stage, I left the tripler input disconnected as it was an unknown quantity at this point and was already suspiciously disconnected. This time the PSU came to life and the HT rail was spot on at 60V. The line timebase was now functioning and we had sound too. Next to see if the tripler was okay. I advanced the tripler input lead to the nipple of the LOPT and got a spark and a quick rustle of EHT. I switched off and connected it properly and switched back on and, hurrah! A snowy raster came up. Adjusting the tuner brought forth a picture - lacking in height, bottom foldover, green tint but a picture nonetheless, and in colour too!

The next instalment will have to wait while I work out how to reduce the file size of my photos. On my old PC, I used to use a program called Picassa but I haven't got this on my new PC and my antivirus won't let me download it!

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Topic starter Posted : 14/10/2018 10:02 pm
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Tazman1966
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So this was the first result.

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More to follow!

 

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Topic starter Posted : 14/10/2018 10:29 pm
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Jayceebee
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Amazing after 15 years in a hay loft, I thought at least one or more beam switches would have been leaky. Must have been quite cozy where it was, well done rescuing it.

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Posted : 14/10/2018 10:45 pm
crustytv
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Posted by: Tazman1966

The next instalment will have to wait while I work out how to reduce the file size of my photos. On my old PC, I used to use a program called Picassa but I haven't got this on my new PC and my antivirus won't let me download it!

You don't need to download or install anything these days, just use an online free service such as Lunapic.  You can do just about anything to any image including resizing. Click on the link, click "edit", select "scale image", upload your image, drag the slider to set it to about 1280 x 720, click "apply changes" and then finally click "save", job done.

That will give you a good size dimension photo and within the 1MB file size limit of the forum ? 

p.s.

 You lucky 'So-N-So', looks like all the really troublesome crap condition 3000's gravitate my way. Good having Tas back at the bench  ?

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Posted : 14/10/2018 11:11 pm
PYE625
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Posted by: Tazman1966

I'm not quite sure what I'm going to do to finish the woodwork. I've used teak oil in the past on cabinets and also spray varnish. For the moment. it's in its raw state.

 

STOP ! This could be a case for...…. Mr Liberon !!

I have used it many times to good effect on cabinets before. ? 

41eAyaNk78L. SX466
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Posted : 15/10/2018 8:21 pm
colourmaster
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Hi Tas

Well done on obtaining your ultra, I have the same model they must be the rarest of the 19" range. I totally agree with Andrew on using the liberion teak oil. I've had excellent results using it. I look forward to your progress.

Regards. 

Gary. 

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Posted : 15/10/2018 9:55 pm
MurphyV310
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Hi Taz.

Good to see you are busy again. I think the CRT will be OK on the set and most likely drive or setting up problems. It's a long long time since I've worked on a 3000 or 3500, at one time it was a good few every day, how things change, mind you its over 12 years since I shut up shop. 

Oh just to let you know the Murphy V320 is still going strong ? 

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Posted : 15/10/2018 9:58 pm
Tazman1966
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Good evening folks!

Thanks for the comments. It is a cosy hay loft by all accounts! Those pesky A1 switches are as you say very prone to being leaky. On the old 3703 I have (at the moment!) I had to remove all three and link the print. 

Thanks for the suggestion Chris. I had a little look around and found a program called Irfanview which does the job nicely. It was in the "app store" on my pc.

I'll try Liberon teak oil although I do have some already but I can't remember the brand.

It is nice to be back in the saddle again too!

Anyway, to continue the story so far, first the frame fault. Any attempt to increase the height and the bottom of the raster folded over and cramped up even more. This turned out to be a couple of dried up frame charging electrolytics. They were the black Callins brand.

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There was a problem with a bit of "blue droop" on the convergence. I attempted to adjust this out but the two appropriate controls most certainly didn't do what they were meant to. One in fact did nothing at all. Dicky Callins caps again. One short circuit across the pot that didn't do anything and the other open circuit across the other pot! While I was at it, I replaced the other one on the convergence board too and went through the setting up procedure and obtained a very nice result.

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I'm left with a problem with a intermittent green level increasing and decreasing. I swapped the drive leads over and proved that the problem is on the video board. My money will be on the thick film unit although it has at sometime in the set's past, been replaced. I also have a very intermittent power supply problem. The cut out, cuts out accompanied by a small wisp of smoke from the PSU slab but I have, as yet, been unable to find out from where! That's where I have got to as it stands but I'm pleased with it so far  ? 

 

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Topic starter Posted : 16/10/2018 11:12 pm
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Lloyd
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Nice telly 🙂 

My 3500 has a habit of randomly popping the cutout, not noticed any smoke with it though. The width twitches in a bit just before it does it.

Regards,

Lloyd

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Posted : 16/10/2018 11:29 pm
colourmaster
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Hi Tas

Well done what a cracking set, I prefer the styling of this model to the Ferguson version. I obtained mine as a worker in fact once I took it to the convention and it performed perfectly.

I wonder how many of this version have survived?.

Regards 

Gary

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Posted : 17/10/2018 9:58 am
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Tazman1966
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Thanks for the comments chaps. Unfortunately, I've been on spreadovers (split shifts where you cover the morning peak and the afternoon/evening peak - good money but long days!) so haven't had the opportunity to progress any further but will update you when I do.

All the very best!

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Topic starter Posted : 27/10/2018 8:30 am
Marcus 3700
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Hello Tas,

What a cracking set and as always a superb account of fault finding and fixing top score old mate.  With regard to Gary's question "how many survive" I have a ruff version of this set plus I know of 4 in private collections, so to my guess is 7, but many more are possibly out there in sheds, garages and attics. I would say the most hard to find version is the HMV model 2703 with date codes starting January 1970. I know of a few HMV 2703 sets dated late 1971 into mid 1972. The later versions have a orange sticker stating MK2 3000 chassis next to the serial number.

This may sound silly but my Ultra 6703 is currently sat in an old dry barn at my Dads small farm in Moulton on Seas End, for at-least the last 4 years.

I still have the Decca CS1830 doubler for you, it's rather rusty at the EHT cap, but should be a worker fingers crossed.

Kind regards,

Marcus.

 

   

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Posted : 28/10/2018 4:11 am
Tazman1966
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Hi Marcus mate.

Long time no hear. Hope all's going well with you. Life is getting very much in the way of my telly fixing these days, however, I did manage to grab some time this afternoon to continue with this Ultra.

I thought I'd turn my attention to the varying green level. I also noticed that the green level altered with varying picture content. Well, my money was on the thick film unit so I set about recreating it using discrete components. There is space on the board to do this and in fact the board has the component references printed on it. Sadly, this effected no change to the symptoms whatsoever!

I started to do some cold checks in the green channel and changed a few high value resistors that had gone very high but without much conviction that this would be the answer, and rightly so. 

Voltage checks proved nothing and I wondered if there was anything wrong with the output transistor. A new BF179 made no difference however, but replacement of the green pre amplifier transistor, VT210 provided a complete cure. The original transistor was a BC184LC but I plonked a common or garden BC108 which worked a treat.

Another fault developed while all this toing and froing on the video board and that was very weak R-Y. This turned out to be nothing more complex than yet another ailing Callins electrolytic on the decoder board, C330 in the R-Y demodulator section.

Time got the better of me again and that's where we are at the moment. The top of the cabinet is still naked and the very occasional cut-out cutting out is still happening but that'll be for the next time, whenever that may be!

TTFN

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Topic starter Posted : 08/11/2018 10:32 pm
PYE625
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It is good to make progress and solve a problem or two....well done  ? 

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Posted : 08/11/2018 10:47 pm
Nuvistor
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The sets is nearly 50 years old, doing well.

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Posted : 08/11/2018 11:05 pm
Tazman1966
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I had some more time to play with this set yesterday and decided to tackle the intermittent cutting out.

I powered the old girl up and set about getting the adjustments tip top. The linearity both line and frame was adjusted and some final tweaks to the convergence got the set performing beautifully.

After about an hour of trouble free viewing, the cut-out operated and put an end to all that! As luck would have it, I spotted where wisp of smoke came from. It was R609 on the top of the power supply slab. This is in series with the input to the chopper transistor and indicated a short from this line to deck. This is how the crowbar trip works in the event of an over volts situation by placing a dead short across this line in order to operate the cut out so could it be the crowbar operating or a faulty chopper transistor maybe. Taking the easy way out I thought I'd consult my trusty stash of television mags, remembering that there was a very comprehensive article in 1978 with a list of stock faults. A common one in the event of intermittent cutting out was C618 which is present to prevent spikes at the output of the chopper triggering the crowbar spuriously. With some confidence and this old electrolytic replaced, I gave the set another run. 

If you remember, I'd already rubbed the top of the cabinet down removing all the dings and dents, not to mention the water marks and decided to finish it off with teak oil which brought up the grain beautifully with a bit of a sheen but not too much. While I was admiring my work, BONK! The cut-out cut out! So C618 was not at fault and a re-set brought the set to life again. More investigation needed!

All the best for now   ? 

Tas

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Topic starter Posted : 19/11/2018 8:13 pm
crustytv
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You might find this handy too

https://www.radios-tv.co.uk/brc-30003500-diagnostics/

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Posted : 19/11/2018 8:18 pm
Tazman1966
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Thanks Chris  ? 

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Topic starter Posted : 19/11/2018 9:40 pm
Tazman1966
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I'd love to be able to tell you what the fault was that was causing the crowbar trip to trigger occasionally but I can't because it has stopped doing it! I gave the set a good 6 hour run in the workshop and not a single trip!

It has therefore become the latest sideboard set in our dining room and has performed faultlessly so far. As is usual, one picture is of the only time that I ever watch a reality show! I really must get my camera out to take photos as these from my phone are poor to be honest. One very minor fault has shown up and was not noticed on a test card and that is feint striations on the left hand side of the screen. My best guess is that the damping resistor across the line linearity coil has gone high and I will check and replace it when I next get the time.

 

Tas

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Topic starter Posted : 30/11/2018 11:23 am
Mikey405
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 Well done Tas. A brilliant job as always. Who'd leave a set like that in a hay-loft? Shame on them! 🙂

 Kind regards. 

 From Mike.

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Posted : 06/12/2018 7:48 pm
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