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1969 Baird 8724 - Single Standard CTV (A Rebuild)

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Anonymous
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Jeffrey,
That sounds like marketing hype to make the set design sound better or at the least to explain a design quirk.
I can't believe that mounting the CRT upside down would make any difference whatsoever!
John

 
Posted : 19/12/2013 8:03 pm
Alastair
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Might be worth giving Neil a shout--He had a BRC 3000 off me a few months ago, not sure what he's done with it....
Its case was in pretty poor condition, but internally complete and fairly reasonable as I recall.....

 
Posted : 20/12/2013 7:11 pm
crustytv
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Hi Alastair,

If anything turns up in your shop please think of me, I have zero spares for these chassis and seeking 3 boards, to get this set going. I will cover any costs and shipping.

Regards
Chris

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Posted : 21/12/2013 10:04 am
crustytv
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As ever Malc's Speedy Spares came up trumps with a nice chroma board, just minus a 4.43 crystal, which I have.

However as always, one step forward often means one step back!

The donor chassis video board has a crack running the entire width.

I found this when the board was removed for inspection, I spotted a coil had one loose wire, I decided to solder it back. Looking under the mag lamp to do the fine soldering, I noticed a hairline crack. I flipped the PCB over and was horrified to see that the crack runs from one side to the other, crossing multiple tracks. I think the slightest pressure and the whole think will snap in half. :aai

So I will have to now find a video board along with I.F. and convergence

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Posted : 21/12/2013 4:58 pm
Terrykc
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Chris, I'd try buffing off the resist either side of the crack with a Dremel of similar to expose the bare copper, then solder links across the crack.

There will be a lot of links so they will probably add sufficient strength without any other measures.

When all else fails, read the instructions

 
Posted : 21/12/2013 5:51 pm
sideband
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Yes I'd give that a go as well. Fiddly and time consuming but you don't have a customer (or a manager) breathing down your neck to get it working for Christmas! I have repaired worse than that (for my own use) before. We weren't allowed to repair damage like that at Philips but as Terry said, if you clean the solder resist off and use tinned copper wire, it will probably take an hour or two to do the job.

Rich

 
Posted : 21/12/2013 9:07 pm
Katie Bush
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Hi Chris

Solid core internal telephone extension wire is ideal for that! :aad

Marion

 
Posted : 21/12/2013 9:12 pm
Anonymous
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For broader or higher current carrying tracks used solder wick is also good. The breadth of the wick will also give greater mechanical strength.

If you can find a piece of fibreglass PCB material cut it into strips and glue it to the topside for greater mechanical strength.

Al

 
Posted : 21/12/2013 10:26 pm
Refugee
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What I have seen used for cracks in boards is slow setting epoxy.
I have noticed that the Wilco branded slow setting one is quite runny and if it is dabbed onto the crack on the component side with a cocktail stick where ever the crack can been between the components it should soak in a reasonable distance along the crack from each spot.
The quick set version is a bit too fast for this sort of job.

 
Posted : 21/12/2013 10:36 pm
crustytv
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I've done the best I can do with little jumpers. I've always saved all my component lead clippings as I find them useful and even more so for this Franken-Board-Stitch up, It took fifteen stitches to complete.

I've just gone over the entire board performing a continuity check, where there were O/C sections before, they have now all been eliminated. Hopefully it will suffice until a better video board turns up.

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Posted : 21/12/2013 11:23 pm
Katie Bush
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Hi Chris

That looks to be a bit of a pain.

I'm just wondering, what sorts of voltages are present near the break? The thought occurs that in low voltage areas, you could run some superglue into the crack, for additional strength.

To be honest, I once reassembled a smashed Sony portable set, and used superglue to secure the bits of PCB, and that was around the LOPT.. I doubt there would be any problematic voltages on you panel, but I wouldn't want recommend it, then cause an additional fault.

Marion

 
Posted : 21/12/2013 11:42 pm
stuie319
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Hi,

I've always found a fibre pen extremely useful for removing the etch resist on damaged panels such as this.

Maplin sell this one
http://www.maplin.co.uk/p/abrasive-fibreglass-pencil-kr61r

I'd expect that particular board will be fine.
Very interesting restoration, by the way!

Regards
Stu

 
Posted : 22/12/2013 12:13 am
crustytv
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I'm just wondering, what sorts of voltages are present near the break? The thought occurs that in low voltage areas, you could run some superglue into the crack, for additional strength.

Marion

I mapped the voltages along the crack, all but two places are sub 27V.

The two high tracks are 140V and 206V

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Posted : 22/12/2013 11:40 am
itmog57
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Chris

Looking at the first Pic. Is there a crack at the top of the board near "C205" going down? or is it a bit of hair?

Ivor

 
Posted : 22/12/2013 11:57 am
Duke Nukem
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I'd be wary of super-glueing along the crack. A few microamps leakage in the wrong place even in a low volt circuit could be an issue. Even if it weren't, should a tricky fault need finding on the board, suspicion would always fall n the glue.

If the board is going to flex then most likely the edges will see most of it. Is there mechanically enough clearance to glue some stuff to the top/bottom edges to add strength ?

TTFN,
Jon

 
Posted : 22/12/2013 12:19 pm
crustytv
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Chris

Looking at the first Pic. Is there a crack at the top of the board near "C205" going down? or is it a bit of hair?

Ivor

HI Ivor,

Thankfully not another crack but just a light scratch. I've spent ages going over the entire board under a large mag lamp. The board and I are quite intimate now. :qq1

The only crack is the one I have shown, the 15 stitches have returned the video board circuit to full continuity. Obviously this has not yet been tested in circuit under load when anomalies may then emerge.

I'd be wary of super-glueing along the crack.

TTFN,
Jon

Hi Jon,

I've no intention of gluing, thankfully the crack has not emerged on the opposite side (component) of the board, the straps as Terry suggested have added a level of rigidity, but extreme care is obviously needed, no unnecessary flexing of the PCB. This will be especially true when reconnecting or disconnecting the interconnect plugs, a firm supporting hand to provide opposite force to cancel out the flex.

I'm happy enough that this will suffice for now, hopefully this will be a stop gap board until a more suitable replacement is found.

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Posted : 22/12/2013 12:48 pm
colourmaster
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Hi Chris
sorry about the cracked panel . I did'nt realise it was damaged .

i have the original 3500 convergence panel from that chassis . You are welcome to have it . Just let me know .
regards .gary .

 
Posted : 22/12/2013 2:29 pm
crustytv
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Hi Gary,

Yes please :thumb

Regards
Chris

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Posted : 22/12/2013 2:33 pm
colourmaster
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Hi Chris
that's fine . I'll get. It over to you sometime .

regards . Gary.

 
Posted : 22/12/2013 3:15 pm
crustytv
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This afternoon I wired up the On/off, volume, brightness, colour and cut-out to the chassis loom. Fitted a new 4.43MHz crystal to the chroma board, replaced a cracked 270R ( green colour diff circuit) on the video board, then refitted both boards to the chassis.

Starting to look like a TV again.

That's about it for now, until the new year anyway, when hopefully I can fit a convergence board, track down an I.F. panel. At that point it can be fed some mains to see what first light is produced.

Edit:
Latest news Rich ( Slidertogrid) has found the remaining boards I require and a replacement video board. So in the new year this project should get off the ground and I can get fault finding the many issues that no doubt will come my way. Very excited by this prospect of seeing first light however awful it might be.

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Posted : 23/12/2013 8:07 pm
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