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1971 Beovision 3200
1971 Bush CTV1120
Granada Television Brochure, 1970s
Long Gone UK TV Shops
Memories of a Derwent Field Service Engineer
PYE Australia Circa 1971
Radios-TV VRAT
Fabulous Fablon
Thorn TX10 Chassis
Crusty-TV Museum, Analogue TV Network
Philips N1500 Warning!
Rumbelows
Thorn EMI Advertising
Thorn’s Guide to Servicing a VCR
Ferguson 3V24 De-Robed
Want to tell us a story?
Video Circuits V15 – Tripler Tester
Thorn Chassis Guide
Remove Teletext Lines & VCR Problems
Ceefax (Teletext)
Suggestions
Website Refresh
Colour TV Brochures
1970s Lounge Recreation
CrustyTV Vintage Television Museum
Linda Lovelace Experience
Humbars on a Sony KV2702
1972 Ultra 6713
D|E|R Service “The Best”
The one that got away
Technical information
The Line Output Stage
The map
Tales of a newly qualified young engineer.
Tales of a Radio Rentals Van Boy
Sanyo SMD
Disastrous Company Rebranding
1969 Philips G22K511
Memories Of The TV Trade
Crazy house
Dirty TV screens
Dual Standard and Single Standard CTV’s
Radios-TV on YouTube
The Winter of 62/63
A domestic audio installation
1979 Ferguson Videostar Deluxe 3V16
Music centre modifications
Unusual record player modification
B&K 467 Adapters
Mishaps In The Trade
1971 Beovision 3200
1971 Bush CTV1120
I have re-stuffed the two capacitors under the brightness/contrast controls, and as before, simply have to moan about how awkward it was. This is mainly because I'm paranoid about tipping up the chassis due to the can of oil, so worked on it in the upright position..... sort of. ?
Before....
After....(Drat, I have one the wrong way around....instant dismissal from Murphy for that.)
Overview of chassis before I re-fit the CRT....
To understand the black art of electronics is to understand witchcraft. Andrew.
Can’t get over how clean and bright it is after 60 years, even the red label on the rectifier has not fallen off.
Wait with anticipation for first light. ?
Frank
That could be a little while off yet Frank.
I have fitted the CRT and all seemed well with sound but no vision. There is no EHT despite line whistle and a good spark at the U26 top cap. The heater of the U26 is lit, so what could be the reason? Furthermore, a faint blue glow can be seen in the U26 plus another new one I tried.
Well, the EHT is being dragged down as there is 11 meg's. dc resistance between the U26 heater winding and ground. This can only mean an insulation breakdown inside the LOPT can. Using another EHT lead with a stick rectifier diode produces a raster, so it is more or less confirmed.
Question is, do I use the LOPT from the other set or open up this can and investigate? Or simply use a stick rectifier in place of the U26?
To understand the black art of electronics is to understand witchcraft. Andrew.
I have decided to neatly install a suitable solid state rectifier within sleeving in series with the EHT cable from the U26 top cap lead out of the LOPT can.
I do not like the idea of ruining the LOPT can without the means to return it to the condition it is in now. It works well with the above arrangement and so to me, pointless to open it up.
To understand the black art of electronics is to understand witchcraft. Andrew.
Here is the result, I have also continued the sleeving of the EHT lead through the chassis. Not as pretty as the U26, but much less ugly than a cut-open LOPT can. I'll leave the U26 holder in place for when a nice NOS Murphy V310 LOPT becomes available..... but I better not hold my breath ! ?
To understand the black art of electronics is to understand witchcraft. Andrew.
And we had high hopes for that LOPTX, just shows there is always something to catch us out.
Just watching the snow on the CCTV , doesn’t look like it is sticking on the ground at the moment.
Frank
That's a pity, but at least it remains functional. Better to do as little destructive work as possible, and the net result is the same, than to make a big ugly scar all the way around the can.
So, does all this feverish work mean that we'll be seeing pictures by Sunday tea-time?
Not quite I'm afraid. Although a faint raster is visible, the CRT is totally flat. Game over once again unfortunately.
To understand the black art of electronics is to understand witchcraft. Andrew.
You have a B&K give it a bop, you may be pleasantly surprised. Nothing to lose.
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Oh no, not another CRT ☹️
I thought you might have tried your B&K on it.
EDIT....Oops crossed posts with Chris.
Marc
BVWS member
RSGB call sign 2E0VTN
Ah Blitzen....
Or, you could let it run a while, and see what happens, but do you know what? I'd have had that B&K on there before I started!
Hi Chris, I have no suitable base to fit this tube and it's not listed (CRM172).
To understand the black art of electronics is to understand witchcraft. Andrew.
Posted by: Katie BushI'd have had that B&K on there before I started!
Agreed, that's always my approach too before investing too much time, effort and components on a set.
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Posted by: PYE625Hi Chris, I have no suitable base to fit this tube and it's not listed (CRM172).
Once you find the pin-outs of the CRM172 just use croc clips, I've done that before adapters are a luxury but not essential.
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Thanks Chris, I'll give it a go one evening, but something tells me that as this tube is a triode, it won't be suitable for the B&K ?
In fact what I have done just now was to connect up my capacitor reformer to the grid of the tube and attempted to measure any cathode current. There was not a sausage, even with the heater voltage slightly raised.
Perhaps this thread should be renamed " The Murphy Curse"..... Part II.
To understand the black art of electronics is to understand witchcraft. Andrew.
My Mullard data book doesn't offer a Mullard equivalent, and the only other equivalent I can find is 7404A.
If the B&K setup data includes that, then you're in business, if not, it looks a bit like you're on your own for the moment.
Posted by: PYE625
Perhaps this thread should be renamed " The Murphy Curse"..... Part II.
"Murphy's Law"?
I can offer the loan of my Leader if you wish to attempt to bop the tube a bit ...
A little bit of an update from lastnight...............
To recap, the Mullard equivalents list (1964-65) shows the 7404A (who made those?) as an equivalent to CRM172.
A little further digging reveals this....
Looks like a tetrode to me..... It's the CRT in my GEC BT2155, and was tested by Marc on his B&K about three years ago. It was tested on the same settings as a Mullard MW43-80. The Mullard is 90* scan, versus the 70* scan on the 7404A, so that doesn't affect the test. Oh, and it tested very good indeed!!
So there you go, before bopping etc, try testing it as a Mullard MW43-80 and see where it stands before doing anything else. Just be mindful of the heater volts. I'm pretty certain it's 6.3V, but I may be fuddling it up with another 70* CRT that I have which is 12.6V.
>>>EDIT<<<
You can also see the pin outs on the picture above, so even without the correct base, you can use Chris' 'fly lead' approach if you wish.
Posted by: Katie Bush[...] shows the 7404A (who made those?)
Brimar
Posted by: Katie Bush
Looks like a tetrode to me.....
It is
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