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Forum 141

[Closed] One of the ugly sisters (Defiant TR949/T)

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Brian Cuff
(@briancuff)
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Hi all
I've just bought, on ebay, a set which I have been looking for for a long time. I was always struck by the cabinet design which went against all normal practices - namely the Defiant TR494. The last time I saw one for sale was at the MBL auction at Bonhams (but I had my sights on another set that day!). It really does prove the Defiant by name, defiant by nature. A most strange looking set with the speaker above the CRT.

The cabinet is in a terrible state (but the mask is perfect :=D ) and I have decided to have a go at veneering. I have a glue pot and will make a veneer hammer and try. A company called Capital Crispin in London will supply any sort of veneer - their website is worth a visit - so I will order soon.

On removing the chassis (a Plessey), which is in reasonable condition, I noticed an alloy rod sticking up about 9" from the chassis towards the rear of the CRT. It is fixed with a hex bolt and there are no wires to or from! Does anyone know what it's there for?

I can find no data for the 494 but looking on Jon's TV disc, I found that the Regentone T15 chassis is almost identical so I have enough to go on. If it turns out to be identical, I will rename a copy of the file TR494.

Today, I'm going to do a John W (HKS) and apply mains after removing the filter cap - how exciting!

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Posted : 23/01/2012 1:07 pm
Anonymous
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Surely it's upside down!
Or else for a very tall table.

I hope you are good at cabinet work.

 
Posted : 23/01/2012 2:00 pm
Brian Cuff
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Surely it's upside down!
Or else for a very tall table.

I know they're called "Defiant" but hanging the chassis upside down is going too far even for them. Anyone got a very tall table? :=D

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Posted : 23/01/2012 2:23 pm
crustytv
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I saw that and thought they had photographed it upside down!

what year are we looking at here Brian, late 40's - early 50's?

As for the rod, some sort of dropper heatsink? hollow ceramic dropper slots down over it? perhaps something is missing.

p.s I have manufacturer service data for the Regentone Big 15/5T if that's the same.

Chris

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Posted : 23/01/2012 2:25 pm
sideband
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No idea about the rod but just speculating from it's position near the scancoils, maybe some sort of shift or centering device. Maybe it's to cure some sort of picture distortion.....just guessing.

Rich.

 
Posted : 23/01/2012 7:08 pm
Till Eulenspiegel
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Hi Brian,
Moreover because of it's strange looks it deserves to be restored.

The TV chassis. As suggested it's likely to to similar to that one used in the Regentone T15 so it will employ a self oscillating line timebase with flyback EHT.The line OP valve will be an EL38 or Mazda 6P28. No boost diode.
The frame timebase is I believe a 6SN7GT twin triode. Amazing how some circuit designers can get away with a simple triode frame OP stage and yet others insist on using a large beam tetrode or pentode valves such as the EL33 and Pen45. My Ekco 9" CRT TSC30 actually employs a PEN46 for the frame output. The usual function for a PEN46 is as a line output valve and has a max plate dissipation of 20 watts! Surely that's over specified for a frame timebase for a receiver using a 9inch 57 degree CRT operating at 5KV

The Defiant TR494 will be a superhet using that RF/IF unit which is fitted just below main chassis level.

Generally a very reliable chassis.

Till Eulenspiegel.

 
Posted : 23/01/2012 7:49 pm
Brian Cuff
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Firstly, I got the model number wrong (my friend Al Tzeimer). It should be TR949/T not 494 as the title suggests so please can the mods change the title?

As to date, after looking at Jon's site, http://www.thevalvepage.com , I reckon it's the Plessey Mk1 chassis 1949/1950 as it uses 6F13s in the RF section and there is reference to London and Birmingham stations only. The Plessey Mk2 chassis from '51/52 uses 6F1s and series heater chains, not the transformer used in the 949. So Chris, the Regentone Big 15/5T uses a different chassis but thanks anyway.

As to the "rod", the first thing I thought of was a device to allow the chassis to stand upside down but it's too short. There is nothing missing so it's not a heatsink for a dropper - there's no dropper used in this chassis - so that leaves some sort of scan correction as Rich suggests!!!! When I get it going properly, I'll try removing it and see what happens.

I got first light this evening, doing an HKS. There was line scan activity but no EHT so I replaced the EY51 with a solid state diode and replaced the Visconal capacitor with a suitable C and got a horizontal line with the brightness control only at max - faulty slider. At least the CRM92A has life left in it! So it does seem that there will be a lot of work to do on this set but I know it will be worth it. I agree with you, Till E - its challenge to the normally accepted styling makes it particularly important to save it.

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Posted : 24/01/2012 12:23 am
peterscott
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Hi Brian,

Is the number not TR949?

Peter

Oops! You got there first. :ummm?: I think we have your friend Al in common.

www.nostalgiatech.co.uk

 
Posted : 24/01/2012 1:40 pm
crustytv
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The bench mark to aim for 8)

Chris

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Posted : 24/01/2012 1:51 pm
peterscott
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I wonder if it was related to this...?

Forum 147

www.nostalgiatech.co.uk

 
Posted : 24/01/2012 1:53 pm
Brian Cuff
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Hi Peter, Al asked to be remembered to you :D .
The Philco is almost identical - a bit like the difference between HMV and Marconiphone pre-war TVs, one with molding and the other with bent plywood. Checking in R&TVS Volume 3 Shows that it has a Plessey MK 1 chassis. Thanks for the tip about the Philco as the more info I have, the better.

As to the restoration, ALL the slider-type preset controls are open circuit, including the 100k carbon line linearity control. It will be impossible to replace the whole lot so I have made a replacement panel using 5W wire-wound pots. The sliders were on 16mm centres and two rows of pots, a three and a two, can also be spaced at 16mm which means that the printing on the back line up with the knobs. The panel will stay with the set. More to follow.

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Posted : 24/01/2012 11:38 pm
Lloyd
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Hi,
This looks like an interesting set, I wonder if maybe the rod was put there to help with removing the chassis from the cabinet?! Just a random crazy thought :=D
Regards,

Lloyd

 
Posted : 25/01/2012 12:30 am
malcscott
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The rod is used to bend the beam as Rich says. You will find it is slightly magnetised.

 
Posted : 25/01/2012 12:15 pm
Electrical
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A copy of the service information for the Philco BT1410 and BT1840 television receivers is in the Library, in the Television Section. The information is a PDF copy of the servicing information from the 1946 to 1953 Volume 3 of Radio and Television Servicing.

https://www.radios-tv.co.uk/dmanager/php ... =11&sort=0

Regards Stan.

 
Posted : 25/01/2012 12:53 pm
peterscott
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A copy of the service information for the Philco BT1410 and BT1840 television receivers is in the Library, in the Television Section.
Regards Stan.

Still doesn't seem to mention the flag pole though!

Peter :ummm?:

www.nostalgiatech.co.uk

 
Posted : 25/01/2012 4:29 pm
Brian Cuff
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No, it doesn't, Peter. We'll have to wait until i can see the effect it has on the raster - or not, as the case may be.
I've now replaced the slider controls with normal pots and will get the main chassis up and running tomorrow. However, I removed the recessed RF chassis, replaced all the waxies and a few resistors and powered it up with the bench supply and wow - video & audio immediately. The Philco circuit flags a cap in the oscillator tank which changes in value depending on the area the set was used in. In my case, it was the Midlands so it's channel 4. That's three ch4 TVs and one ch2, the rest being ch1in my collection so far. When I get my display area set up - this summer, hopefully, I will need a three channel system. What fun!!!

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Posted : 26/01/2012 12:47 am
Brian Cuff
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Progress! I reinstalled the RF chassis and applied power - nothing. Found the wire I had not connected (only HT to the RF chassis). Reconnected it and - lo and behold - Testcard C and tone. The tube looks a little tired (it is, after all, a CRM92A) so I'll run it for a few hours and maybe it will improve. The EHT is only 4.5kV - should be 6-7kV - so there is something wrong with the line TB. Plenty of width and linearity not bad so could be a damp LOPT. Time will tell. Here are some pics.

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Posted : 26/01/2012 4:12 pm
crustytv
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Blimey Brian you don't hang about do you! :thumbl:

Superb results, I especially like the new panel, that looks very neat and I'm sure the idea will come in handy for me in the future. Where do you source your pots are they pulls or new?

Hopefully the CRM will wake from its slumbers, lets hope the LOPT has not suffered, I guess going by the state of the cabinet it is a possibility though.

I'm toying with starting an early round tube Vidor, trouble is it has been pulled about by someone, wires loose everywhere. I have been putting it off until my skill levels matched the task ahead, I fear that day is not yet upon me.

Look forward to more updates, good to have you posting your efforts, it is very much appreciated and enjoyed

Regards
Chris

CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
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Posted : 26/01/2012 4:56 pm
Brian Cuff
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It was a fairly simple job Chris. Cleaning took the most time.

The pots came from DigiKey Corp. http://uk.digikey.com/ . I bought a load of them some time ago but checking the price this evening, it has doubled over the last couple of years and they are now over £3 each 8))

They are good pots, 5W dissipation and compact enough to fit on those 16mm centres. I have also modified an LV20 which had a very bad slider assembly and that fitted too!

I'm off to the Isle of Wight tomorrow so won't be in my workshop for a week but I'll be on line now and again.

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Posted : 26/01/2012 8:34 pm
Anonymous
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Yes, I find with the old sets I recently acquired the electronics is quick and easy bit. It's the cleaning, mechanics, dial and cabinet is the tricky hard work.

Nice job Brian,

 
Posted : 26/01/2012 10:46 pm
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