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What do I do with the woodwormed A640 ?

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slidertogrid
(@slidertogrid)
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I managed to buy the Top Rank A640 recently mentioned in suppliers and sources.
I have needed a Tube for one of these sets for over a year, that set is an early model with separate tuners and a valve IF strip and is in good condition apart from a broken tube.
I wasn't going to bid for the Top Rank due to the distance from me, but a friend who was retuning to Peterborough today kindly offered to collect it for me if I won the auction.
I bid and got it for start price, it seems the woodworm put everyone off!
However, since Mike mentioned Top rank was only used for personal export sets I wonder if I should save this set and keep looking for a tube for the original one?
The chassis looks in good condition, The Tuner is free and the set still switches standards when the buttons are pressed.
The tube face is unmarked and the front panel will clean up. so it has the makings of a restoration. however the woodworm attack is fairly major! The set is outside at the moment and will stay there for the time being!
What should I do? Nick the tube or restore the cabinet?
:thumb
Rich.

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Topic starter Posted : 21/06/2015 10:29 pm
freya
(@freya)
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Have you tested the tube yet ?; looks like its going to take a fair amount of work to get it looking anywhere reasonable.

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Posted : 21/06/2015 10:37 pm
crustytv
(@crustytv)
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With that amount of woodworm infestation I would seriously check the integrity of the cabinet. The flight holes are just that, the hidden damage may well be extensive. I had a set that on the whole looked ok, but when pressure was applied to the surfaces the flexed and all but collapsed in various places, it was a write off. This one may well end up the same and live on as an electronic parts donor only.

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Posted : 21/06/2015 10:44 pm
Katie Bush
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One thought comes to mind - Do the minimum to to the electronics to make it safe to power up, then power it up! If it shows first light, consider saving it.. If it stinks, it's a parts donor!

As has already been said, the worm damage may be more extensive than at first appears, so I'd definitely go about squeezing/pressing the cabinet parts to see how resilient they are.. If it crumbles to dust, it's a parts donor.. If it proves solid, consider saving it.

Of course, if your other set is otherwise good, then why not put the CRT in the better cabinet? Or perhaps now is time to consider becoming a cabinet maker!

Marion

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Posted : 21/06/2015 11:46 pm
ntscuser
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Personally can't see anyone wanting a Top Rank version of the set unless they at one time worked for the company or something.

I'm just grateful another another A640 has been saved, and with the comparatively rare push-through tube as well

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Posted : 21/06/2015 11:59 pm
slidertogrid
(@slidertogrid)
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Thanks for the replies, The cabinet really is in a state and is beyond just filling the holes. every part is holed, the right hand side looks as if it has been blasted by a shotgun!
I have given it a bit of thought and as Katie says I might as well power the poor thing up one last time and see what happens. it will hopefully show some sort of picture to enable me to asses the CRT.
I can't test the tube as I don't have a tester myself. Mick has a B&K but I don't trust them on mono tubes, a tube that produced quite a good picture tested very low emission last time I tried.
The LOPT is a bit of a worry as the overwind looks a bit melted, but I will give it some warmth in advance of powering it up and see what happens..
Realistically there is not much point in trying to save this cabinet when I have another nicer set needing a tube. I hate breaking sets up but it will save another.
I will keep the chassis for spares, I have another three sets with similar chassis. Two 19" and a late 20" Coop, so the parts may come in handy someday.
:thumb
Rich.

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Topic starter Posted : 22/06/2015 1:47 am
ntscuser
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The LOPT is a bit of a worry as the overwind looks a bit melted, but I will give it some warmth in advance of powering it up and see what happens.

It may have suffered from arcing at some time in the past? I was once offered a 20" Co-Op version which suffered from that.

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Posted : 22/06/2015 2:24 am
Terry
(@terrykc)
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Is there a very liquid resin that could be injected vià the flight holes to reinforce a cabinet that you might WANT to save?I

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Posted : 22/06/2015 12:36 pm
Cathovisor
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Is there a very liquid resin that could be injected vià the flight holes to reinforce a cabinet that you might WANT to save?I

There are resins intended for just this purpose, practical application of which in the link below:
http://www.czajkowski-furniture.co.uk/f ... vation.htm

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Posted : 22/06/2015 1:39 pm
Terry
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Excellent craft work there. The company name looks as if it might be pronounced the same way as a certain Russian composer ...

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Posted : 22/06/2015 2:26 pm
Cathovisor
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Excellent craft work there. The company name looks as if it might be pronounced the same way as a certain Russian composer ...

I suspect it is - Polish version of same...

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Posted : 22/06/2015 3:02 pm
Niall
(@niall)
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Is there a very liquid resin that could be injected vià the flight holes to reinforce a cabinet that you might WANT to save?I

Something like WEST epoxy resin from the chandlers would run into the holes.

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Posted : 22/06/2015 4:01 pm
slidertogrid
(@slidertogrid)
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I have decided not going to scrap the cabinet when I have robbed the tube. I will douse it with worm killer and wrap it in bin liners and store it. I will keep the chassis complete unless I get desperate to rob anything. Then I always have the option to rebuild the set should a tube become available.
I have re read the drying out a pitch overwind thread and at the moment I have the lopt gently baking away with 45 volts through the overwind.
Once it has had a reasonable time to evaporate any moisture I will put it back in and see if the smoothers will reform.
Then pop in a couple of valves to replace the cracked ones, snip the filter cap and give it some mains... :aah
I just hope the bl@@dy tube is ok! :bba
Rich.

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Topic starter Posted : 22/06/2015 7:28 pm
freya
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Should you decide to use the epoxy method in the future it can be thinned somewhat to aid penetration, an old credit card will squeeze it in.
Having just received the replacement cabinet for the Ekco T164 set, it was time for the badly wormed one to go. It only took very slight pressure on the top to make the joints collapse like a pile of cards and dust. I counted 45 holes in a 10cm ringed area, so mine really were holding hands with each other :cch

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Posted : 23/06/2015 9:58 am
slidertogrid
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Well it's not looking good on the LOPT front... after reforming the smoothers I fitted the lopt switched to 405 so I could hear if the timebase was working and switched on.
After a little while I could hear the line whistle coming up. I had a diminished spark at the top cap of the line output valve and boost diode but nothing on the DY802.
Then smoke started to rise from the back of the chassis, I though at first it was crud burning off the dropper, but no, there was a little puckered hole in the overwind blowing out smoke and pitch like a little volcano. :ccb
Not to be defeated I fitted the lopt from the set with the broken tube, (being one from a set with a valve IF it lacked the purple flylead for the lt supply but I should at least get a raster) that lopt had been in the warm for over a year and has the plastic covered overwind so I was hopeful.
with that lopt I have even less of a spark on the top caps and still nothing on the DY. no signs of overheating though, the overwind stays cold, so maybe this one has a duff primary?
I am going to try this lopt in a known working set before I go much further.
:bbd
Rich

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Topic starter Posted : 23/06/2015 3:53 pm
slidertogrid
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After the setback with the two duff Lopts I dug out my working A640 19". I tried the second lopt with the plastic overwind that had come from the set with the broken tube. This set then had low EHT with no visible heater on the DY. So I fitted the lopt from the working set into the Top Rank.
The set then had something on the screen at last.. frame collapse. After a prod around I found one of the lin controls was o/c unless wound hard over to one end. I now had frame scan but no line lock. The picture would false lock and float across the screen.
I flicked the discriminator diode block with my finger in disgust , saying to it " I should think it's you! " It was! The flick woke it up and the line locked. :bba
(It's nice to know I have remembered all that training I had at "Bodgeitt & Scarper" all those years ago... :cch )
The good news is that the tube is brilliant! Much better than I had dared to hope.
So now I have a good tube for the early set but it's one step forward one back, as now I need a LOPT for it.
Has anyone had a similar Lopt rewound recently? I am curious as to the cost , as the chances of finding a good second hand lopt is probably more difficult than finding the tube... :aab
Rich.

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Topic starter Posted : 24/06/2015 2:55 pm
bassoonbloke
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Hi Rich,

If the original LOPTX's primary is good (just a duff overwind), I suppose you could try the tripler to PL504 top-cap and see if you get anything worth while (disconnect the old overwind first). Other people seem to have some luck with this, though I've never tried it myself.
An old thorn 1400 / 1500 style one would be a good bet.
Worth a try ?

Cheers,
Alan.

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Posted : 24/06/2015 5:21 pm
Focus Diode
(@focus)
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Posts: 729

I tried a 1500 doubler on a 19" model, it worked but the primary failed a few months afterwards. This is not meant to put you off trying this but from personal experience the success is short lived. Anyone out there successfully re-wound Rank LOPTs?

That's a great result. There's something about these push through 19" and 23" CRTs, they weren't in production for long as they were soon replaced by the squared up 20" and 24" types. I've yet to see one of these CRTs suffering the effects of low emission but admittedly I've only seen a handful.

Brian

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Posted : 24/06/2015 8:36 pm
freya
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Probably talking rubbish here but wont the electro magnetic field flux will still be acting on the faulty overwind in its damaged state, dragging the primary down in the process ?

Edit, took my time posting and see Jeffrey said this:

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Posted : 24/06/2015 9:08 pm
Tazman1966
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...If the original LOPTX's primary is good (just a duff overwind), I suppose you could try the tripler to PL504 top-cap and see if you get anything worth while (disconnect the old overwind first). Other people seem to have some luck with this, though I've never tried it myself.
An old thorn 1400 / 1500 style one would be a good bet...

I did this many many moons ago with a 23" Bush TV166 adding a 180pF cap for tuning to get the width/EHT right. It worked very well indeed and speeded up the warm up time too!

Tas

PS you need to remove the overwind completely not just disconnect it or the shorted turns in it will damp the action of the the primary

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Posted : 25/06/2015 12:00 am
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