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-   -   Ferguson 247T: huge console TV set. (https://www.vintage-radio.net/forum/showthread.php?t=119613)

FERNSEH 16th Sep 2015 12:37 pm

Ferguson 247T: huge console TV set.
 
4 Attachment(s)
I'm having a tidyup in the workshop. Last night I dug out this huge Ferguson 21" CRT console TV, model 247T. It's one of the first 21" CRT sets to be marketed in the UK, I'd reckon it was made in 1955. The HMV 1820 was the first 21" UK made set, that was 1952.
One thing that always puzzled me was how the CRT was installed in the set.
Then it dawned on me, the wood panel that the CRT is fitted on is slides into the top of the cabinet, you flip the whole assembly upside down and just push it in. Actually, it's not that easy.
A new safety glass is required, that's not too much of a problem for me, a local firm will cut a piece of 6mm glass anytime.
The truth is I'm not all that keen on the set, do I restore it, chop it up for spares, or alternatively is there anyone interested on taking over the restoration job.?
The only way to watch 405 in on a set like this one.

DFWB.

beery 16th Sep 2015 1:57 pm

Re: Ferguson 247T: huge console TV set.
 
So when you received it, it was atually a sub woofer with doors?
Every subwoofer should have door of course!

Andy

FERNSEH 16th Sep 2015 2:56 pm

Re: Ferguson 247T: huge console TV set.
 
Hi Andy,
It sure was, a great big fifteen inch speaker. It's now stored away in a safe place, upstairs above the shop.

DFWB.

Heatercathodeshort 16th Sep 2015 5:41 pm

Re: Ferguson 247T: huge console TV set.
 
I had the number of the bomb squad here David but I seem to have mislaid it..Might be as well to have them around when you refit that MW53-20 CRT..

247T. An absolute monster but very high gain with flywheel sync. My parents had a 236T in the mid 50's. 17" console without doors. A nice job if anyone is willing to take it on and quite straightforward overhaul wise. I hope it goes to a good home. J.
[PS If you have no takers David I thought it might make a trendy receiver if you suspended the CRT unit from the ceiling via chains and cup hooks and ran the wires down to the receiver chassis. At least it would give a bit more floor space. just a thought.]

FERNSEH 16th Sep 2015 5:57 pm

Re: Ferguson 247T: huge console TV set.
 
Quote:

Originally Posted by Heatercathodeshort (Post 786730)
[PS If you have no takers David I thought it might make a trendy receiver if you suspended the CRT unit from the ceiling via chains and cup hooks and ran the wires down to the receiver chassis. At least it would give a bit more floor space. just a thought.]

Hi John,
what a good idea! Rather like in the manner of that spherical shape JVC TV.
The chassis could be located well away from the suspended tube, a long cable run for 17KV though.

The MW53-20 is 23 inches from the faceplace to the the base.

DFWB.

Heatercathodeshort 16th Sep 2015 6:31 pm

Re: Ferguson 247T: huge console TV set.
 
I'm glad you like the idea David, You could screw four brass batten holders, one in each corner, some frilly shades and maybe a few carbon filament lamps.
It could then claim to be the first 'Dual Standard' receiver..

Seriously it would be a pity to see this scrapped. It is huge but I doubt if there is another one in the UK. Strange that many post war receivers are now rarer than pre war models. I guess the Murphy V114 is one of them. John.

FERNSEH 16th Sep 2015 8:49 pm

Re: Ferguson 247T: huge console TV set.
 
The set has a future. Restoration will start soon.
It's likely this set is the only example in existence. A major recapping job required of course and the complex flywheel system will receive special attention.
The line timebase employs a sinewave oscillator and the frequency and phase is controlled by a reactance valve which in turn controlled by a double-diode phase discriminator. The circuit works beautifully but only when high quality silver mica capacitors are used in the oscillator and reactance stages.
A similar circuit was employed in certain earlier Ferguson models and the later models 305T and 405T.

DFWB.

gec2110 17th Sep 2015 4:36 pm

Re: Ferguson 247T: huge console TV set.
 
Nice collection of sets there.
I noticed in the picture a Rigonda VL100.
Is that a working set?

FERNSEH 17th Sep 2015 6:46 pm

Re: Ferguson 247T: huge console TV set.
 
I can't remember what happened to the Rigonda. It may have been given away to another collector, or, it might be upstairs above the shop.
The Ekco console TV and one of the 14" GECs have already been rehomed. The 17" Ferranti was serviced last year and is working really well.
I'm not going to keep the dark cabinet Pam and the Pye CTL58.
The two sets I made the 440 mile round trip to mid Wales and back are the Philips 600A projection set and the Ekco TV138.
A home has been found for the big Ferguson.

DFWB.

Heatercathodeshort 17th Sep 2015 7:00 pm

Re: Ferguson 247T: huge console TV set.
 
Quote:

Originally Posted by FERNSEH (Post 786783)
The circuit works beautifully but only when high quality silver mica capacitors are used in the oscillator and reactance stages.

Hello David,
I surprising number of Ferguson fringe models used to turn up in London. They are the ones with the model number ending in an odd number.

The Flywheel line sync as you say works very well once you have replaced the .01uf's [I think they are from memory] in the discriminator circuit.

Guys used to twiddle the transformer in an attempt to lock the line. It never worked for more than a few days leading to customer frustration.

If I remember correctly you had to O/C the line sync feed often done by a small switch on the back of the line hold control.

After setting the user control mid way you adjusted the primary untill the line frequency just 'ran through'. The sync was then reinstated and the secondary core was adjusted to centre the picture within the raster. Once set up they performed as designed.

The LOPT is usually ok. The only other stock fault I can remember was breakdown of the scanning coil tag board to the core. It was simple matter to lift the cardboard strip and insulate it. The focus magnets used to become unglued causing weird picture centering faults, again a simple strip down and reglue.
Nice sets these Ferguson. John.

ukcol 17th Sep 2015 7:24 pm

Re: Ferguson 247T: huge console TV set.
 
3 Attachment(s)
In the 60s I used to own an HMV 1867 which was a slightly later set (1957) than the Ferguson 247T. The HMV used an identical chassis to the Ferguson 317T but had a completely different cabinet.

In about 1968 I gutted it and made a single standard 625/UHF set on the original chassis. Well it seemed a good idea at the time. :(

FERNSEH 17th Sep 2015 11:22 pm

Re: Ferguson 247T: huge console TV set.
 
2 Attachment(s)
Pictures of the chassis. There is some surface rust in places but otherwise it is in good condition, just needs a good clean.
That smoothing capacitor is the first component to be replaced.
The circuit design is a development of the 14 and 17" models, the 203T series, called the nine star chassis. For the extra power required for the 21" CRT the PY32 valve HT rectifier is replaced by a finned selenium metal rectifier. The reason for the change was to increase the HT voltage. The frame output valve is a PCL83 instead of the ECL80 used in the smaller sets.
The build date is confirmed as late 1955.

DFWB.

Heatercathodeshort 18th Sep 2015 7:52 am

Re: Ferguson 247T: huge console TV set.
 
Watch the position of the tuner unit valves David. I believe it is of German origin and the valves are reversed to the UK normal. The PCC84 is at the front and the PCF80 at the back..Smoke if you get it wrong. J.

Radio Wrangler 18th Sep 2015 8:13 am

Re: Ferguson 247T: huge console TV set.
 
Quote:

Originally Posted by Heatercathodeshort (Post 786730)
[PS If you have no takers David I thought it might make a trendy receiver if you suspended the CRT unit from the ceiling via chains and cup hooks and ran the wires down to the receiver chassis. At least it would give a bit more floor space. just a thought.]


Calls to mind Gilliam's film "Brazil" but he didn't have huge CRTs, just little tiddlers with fresnel lenses!

David

FERNSEH 18th Sep 2015 9:44 am

Re: Ferguson 247T: huge console TV set.
 
No Fresnel lenses for us. Better still if a 24" CRT removed from a KB Regina could be suspended from the ceiling. That'll look even more scary.

Getting back to the Ferguson. I just couldn't believe that set was not equipped with floor castors. Well in fact it was fitted with such items so I'll fit them with any out delay. It weakens the cabinet if it is dragged about too much without castors.
Hi John,
That's right, the two tuner valves are positioned with the PCF80 frequency changer at rear of the unit. GEC TVs were fitted with a similar tuner. The advantage of this type of tuner is that the outer control shaft rotates the turret drum and the inner shaft is the fine tuner.
It's a great big robust unit.

DFWB.

FERNSEH 18th Sep 2015 3:16 pm

Re: Ferguson 247T: huge console TV set.
 
1 Attachment(s)
Main smoother replaced by a NOS can of similar capacity, same diameter but slightly shorter.
The next task is to supply a limited current through the line output transformer windings in order to drive out any moisture.

DFWB.

FERNSEH 20th Sep 2015 4:57 pm

Re: Ferguson 247T: huge console TV set.
 
2 Attachment(s)
We all acknowledge that passing a small current through the line output transformer windings to drive out any moisture is a good idea. Well, the transformer in this set the EHT overwind has a resistance of 19Kohms therefore supplying 30 volts from a bench power supply will not warm the transformer by any significant amount. 30 volts will result in only 00158mA passing through the winding which will mean that the heating effect will be only 0.047 watt. That's not enough. However, apply 200 volts will result is 1.05mA through the 19000 ohm winding which is going to be just over 2 watts.
Four new wooden blocks have been made for the new cabinet castors.
Once these have been fitted it will be possible to move this heavy set about without any difficulty.

FERNSEH 21st Sep 2015 5:20 pm

Re: Ferguson 247T: huge console TV set.
 
1 Attachment(s)
It goes without saying there will have to be a major capping job done to this chassis, all the TCC waxies and Hunts capacitors are useless. Flashes and sparking going on inside the PCL83 frame and sound output valves, it was never a good valve anyway.
The screen grid supply to the PL81 line output valve has been disconnected and also the same valve's anode top cap. The grand plan is to connect the anode connector of the EY86 to chassis and as mentioned in my last post supply 200 volts or so across the overwind so as to warm up the transformer.

The chassis will be run in this condition for a considerable time and in the meantime I'm sure all sorts of exciting things will happen, bangs and flashes no doubt.

DFWB.

Heatercathodeshort 21st Sep 2015 9:46 pm

Re: Ferguson 247T: huge console TV set.
 
Quote:

Originally Posted by FERNSEH (Post 787477)
Four new wooden blocks have been made for the new cabinet castors.
Once these have been fitted it will be possible to move this heavy set about without any difficulty.

You think so! It might be a better idea to screw a large hook into the centre of the cabinet top and employ the services of my lorry crane!

It might be worth checking the goodness of that MW53-20. It is probably OK if not suffering from the Mullard partial heater short problem, almost as bad as Mazda's infamous heater cathode leak saga.

I have checked my tube stock David but I'm afraid you are on your own with this one. A CRM211 could be fitted but I suspect the chances of finding a good one is slim. Regards, John

FERNSEH 22nd Sep 2015 12:49 pm

Re: Ferguson 247T: huge console TV set.
 
Quote:

Originally Posted by Heatercathodeshort (Post 787760)
You think so! It might be a better idea to screw a large hook into the centre of the cabinet top and employ the services of my lorry crane!

Hi John,
don't need the crane, with the castors fitted the mighty cabinet can be moved around with ease.
I've left the chassis on the bench to "cook" so to speak and although the line output stage is inactive 33 volts negative is present at the grid of the PL81 so we know that the line oscillator is working.
The main HT line has risen to 242 volts.
I've checked the CRT for emission and I reckon it's capable of a reasonably bright picture.

This set will be displaying pictures soon.

DFWB.

FERNSEH 22nd Sep 2015 5:11 pm

Re: Ferguson 247T: huge console TV set.
 
2 Attachment(s)
Both timebase oscillators are now functioning. The frame oscillator delivers between 5 to 30 volts of sawtooth drive to the grid of the PCL83 output valve. First picture
The negative going drive to the line output valve is 150 volts P-P.

DFWB.

FERNSEH 2nd Oct 2015 10:39 pm

Re: Ferguson 247T: huge console TV set.
 
Time to perform more tests on the chassis. The line output transformer has been reconnected into the circuit and also the sawtooth drive to the PL81 control grid.
Even without the scan coils connected there is a healthy spark present at the anode of the EY86 EHT rectifier. The EY86 heater was unlit so in went a replacement.
I reckon it's time to refit the chassis and see what the results will be like on the screen of the CRT.

DFWB.

FERNSEH 3rd Oct 2015 11:39 am

Re: Ferguson 247T: huge console TV set.
 
The chassis has been reinstalled in the cabinet. The CRT socket and the scan coils plugged in, the results? No EHT. Unplug the scan coils and the EHT returns, it would seem like the scan coils are faulty or perhaps a component associated with them.

DFWB.

FERNSEH 3rd Oct 2015 3:57 pm

Re: Ferguson 247T: huge console TV set.
 
The line scan coils have a DC resistance of 2.9 ohms, this may the correct figure, the line scanning coils in the later model 308T have a resistance of 2 ohms.
Reference to post #10. John mentions the possibility of the insulation the tag strip on the scan coils breaking down.
The service notes on page 380 of the R & T servicing book inform us that the scan coil assembly can be removed without the need to withdraw the CRT from the cabinet.

DFWB.

Heatercathodeshort 3rd Oct 2015 5:46 pm

Re: Ferguson 247T: huge console TV set.
 
Another monstrous horror that has found its way up North to David rather like an under fed cat...J.

FERNSEH 3rd Oct 2015 6:19 pm

Re: Ferguson 247T: huge console TV set.
 
I'm certain now that the scan coils are not faulty. I've hooked a another scan assembly, albeit not Ferguson, and when those coils are connected into the line circuit it's the same effect, the EHT dies.

In these line timebase circuits the stored energy in the scan coils is at the time of flyback contributes the first part of the scan. It could be possible that another component is breaking on account of the extra energy from scan cols.

DFWB.

Heatercathodeshort 3rd Oct 2015 6:25 pm

Re: Ferguson 247T: huge console TV set.
 
I hope you changed the boost capacitor..Truth please. John.

FERNSEH 3rd Oct 2015 6:31 pm

Re: Ferguson 247T: huge console TV set.
 
Hi John,
I cannot tell a lie, I have not but rest assured I will.

DFWB.

FERNSEH 3rd Oct 2015 9:34 pm

Re: Ferguson 247T: huge console TV set.
 
It was the boost capacitor all right, open circuit! . Glasnost, mea culpa. Well to be honest it was disconnected.
Anyway, in with a new one.

DFWB.

FERNSEH 3rd Oct 2015 10:20 pm

Re: Ferguson 247T: huge console TV set.
 
That's more like it! EHT is present with or without the scan coils plugged in.
Strange that the boost voltage could be measured at pin 10 of the CRT without the boost capacitor in the circuit.

DFWB.

FERNSEH 3rd Oct 2015 11:42 pm

Re: Ferguson 247T: huge console TV set.
 
1 Attachment(s)
News Flash! Real results at last. A bright raster, seems that the CRT is good, plenty emission. The line hold control has no effect so it's likely the lack of width could be caused by the oscillator running at the wrong frequency.
The original PCF80 in the tuner had to be be replaced in order channels could be tuned in on band 1.
The contrast control doesn't work, it's part of a complex gated AGC system.

So there we have it, real progress today.

DFWB.

FERNSEH 5th Oct 2015 5:02 pm

Re: Ferguson 247T: huge console TV set.
 
2 Attachment(s)
The reason why the line hold control was inoperative was due a leaky 1 mfd Hunts make capacitor C161. Down to 20Kohms! This capacitor is part of the filter network which supplies the control voltage to the reactance valve V15, an EF80. C161 provides the long time delay necessary for the flywheel line sync system to function properly.
V15B, ECC81 is the line oscillator and the A section is a pulse shaper.
In fact all the waxies and Hunts capacitors in the line discriminator had various degrees of leakyness and so the whole lot have been replaced.

A number of capacitors in the vision AGC line had leaks and so those components have been replaced also.

The next stage of the restoration is to reinstall the chassis to find out if all this work has proven worthwhile.

DFWB.

Heatercathodeshort 5th Oct 2015 7:06 pm

Re: Ferguson 247T: huge console TV set.
 
Nice bit of detective work there David. That line oscillator/flywheel sync circuit should be 100%.
The EF80 reactance valve used to go to sleep due to under use but would wake up if swapped with one of the IF valves.

If you don't get any video signal but all seems ok, remember the vision detector crystal inside the final vision IF can. These tend to become O/C after all these years. Changed a few recently.

Looks good so far. That monster started life as a little 203T 14" table model!
John.

FERNSEH 5th Oct 2015 9:53 pm

Re: Ferguson 247T: huge console TV set.
 
Quote:

Originally Posted by Heatercathodeshort (Post 790549)
That monster started life as a little 203T 14" table model!

Hi John,
That's right, in fact the main chassis is quite compact. Additional metalwork is added to accommodate the wider control panel used in the 21" models.
The OA60 vision detector checks OK. However, two additional germanium diodes are employed in the video amplifier, W106 (OA70) and W102 (OA61). A short circuit in the PCF80 video amplifier valve has resulted in the failure of W102 the OA61 vision interference limiter diode. It's gone short circuit. For the time being there is no need to replace this diode.
The other diode W106 functions as an extra white spot limiter and is employed only in the 21" models. An additional feature on schedule B 21" models is a picture quality control which takes the form of a variable resistor R233 (2Kohms) in series with the vision detector load resistor.

DFWB.

FERNSEH 6th Oct 2015 9:06 pm

Re: Ferguson 247T: huge console TV set.
 
After reinstalling the chassis into the cabinet I discovered that the line hold control still doesn't alter the frequency of the oscillator. So it's out with the chassis again and back on the bench.
The slider of the line hold control is connected to the line discriminator via a tag strip on a separate line oscillator module which is located above the main chassis. It was found that the screening plate was shorting line hold control to chassis. I've made a spacer to prevent that happening again.
Upon testing the chassis again I found the line hold control still doesn't work.
Another short circuit, this time metallic particles were found in the special line hold control. The control was removed and cleaned up. At last the line hold control works.
A video waveform can be monitored across the diode load of the video detector, but there was evidence of over loading from the signals from the Aurora and my own make standards converter. All the Hunts and waxie decoupling capacitors in the vision AGC system were as expected found to be leaky so the whole lot were replaced.
The result of this action now the overloading is even worse. Now I'll turn my attention to the gated AGC circuit. This consists of an EF80 pentode which functions as the line sync back porch sampler and amplifier. The amplitude of the negative going pulse present at the EF80 anode depends on vision signal amplitude, this is rectified by an EB91 diode and filtered and supplied to the AGC line.

DFWB.

FERNSEH 7th Oct 2015 12:15 pm

Re: Ferguson 247T: huge console TV set.
 
1 Attachment(s)
The circuit of the gated and amplified vision AGC system. The negative going line sync pulse present at the anode of the sync separator is differentiated by a low value capacitor and the positive going trailing edge which is co-incident with the back porch of the line sync allows the V7 to conduct only in that period. The resultant vision signal amplitude dependant pulse is rectified by the EB91 V8A. Delayed AGC is supplied to the tuner from diode W103.

The vision AGC system is now working correctly but there are still problems with the line flywheel discriminator to sort out.
Refer to the circuit on post 32. The cathodes of the EB91 are not receiving any sine wave drive from the discriminator transformer. The coils rsistances are correct, 66 + 66 ohms. It's possible the 0.01mfd capacitor C172 is OC.

DFWB.

FERNSEH 7th Oct 2015 1:00 pm

Re: Ferguson 247T: huge console TV set.
 
1 Attachment(s)
Well here's a surprise. I've opened up the line oscillator transformer can. I was expecting super quality silver mica tuning capacitors but just look at the nasty things found instead inside the can. Just ordinary Hunts 0.01mfd capacitors.
And both are leaky! Let's see if I can something better.

DFWB.

Heatercathodeshort 7th Oct 2015 5:22 pm

Re: Ferguson 247T: huge console TV set.
 
'I've changed everything Captain Mainwaring and it still does not work.'
You missed these you stupid boy..

I must admit David I thought that you had changed those nasty brown cockroaches as they are clearly marked on the circuit diagram. Number 1 trouble spot even back in 1956!

You should see some real results now.
Now let's get this buttoned up, back on, cleaned up and soak tested. It will be a cracker by the look of it. John.

dazzlevision 7th Oct 2015 5:41 pm

Re: Ferguson 247T: huge console TV set.
 
2 Attachment(s)
As they used to say:

FERNSEH 7th Oct 2015 7:36 pm

Re: Ferguson 247T: huge console TV set.
 
Quote:

Originally Posted by Heatercathodeshort (Post 791031)
Now let's get this buttoned up, back on, cleaned up and soak tested. It will be a cracker by the look of it. John.

Hi John,
changing those capacitors has certainly improved matters, although the picture will need centering by adjusting the phasing coil on the transformer.
Now the bad news. The vision AGC system has packed in again, no control of contrast. So it'll be out with the chassis again.
Just wait one more week and it will really be a fine set again.

DFWB.

Heatercathodeshort 7th Oct 2015 8:01 pm

Re: Ferguson 247T: huge console TV set.
 
Quote:

Originally Posted by FERNSEH (Post 791072)
Just wait one more week and it will really be a fine set again.DFWB.

You have a problem there David. With that chassis spread over your kitchen table you will probably suffer from malnutrition before you finally get it finished..

Don't forget the PCC84 in the tuner. They tend to develop internal shorts.

John.

FERNSEH 9th Oct 2015 3:57 pm

Re: Ferguson 247T: huge console TV set.
 
Found the fault. A replacement capacitor, C134 was found to be leaky. See post #36.

DFWB.

Heatercathodeshort 10th Oct 2015 9:57 am

Re: Ferguson 247T: huge console TV set.
 
I'll dig out the old Coronation day flags from the bottom of the wardrobe..J.

FERNSEH 10th Oct 2015 10:34 am

Re: Ferguson 247T: huge console TV set.
 
Hi John,
even after replacing the short circuit AGC filter capacitor C134 (which was an LCR make) the vision AGC system was still not working as well as it should. The contrast control did not reduce the picture contrast down to an acceptable level. Replacing the PCC84 RF amplifier improved matters considerably, the valve had a grid to cathode leak. Finally, after replacing the M3 AGC delay diode the AGC system is working as the designer intended to should. This very sensitive receiver can handle very strong signals without any intermodulation effects.
Imagine what this set would have been like if it had been equipped with frame grid valves? The ultimate 405 dx receiver.

DFWB.

FERNSEH 10th Oct 2015 3:45 pm

Re: Ferguson 247T: huge console TV set.
 
1 Attachment(s)
All this effort is at last showing encouraging results. The CRT is excellent, as long as the heater remains intact and doesn't go partially short circuit there's plenty life left in it. The scan coil leads will have be reversed.
The picture appears too wide, that's because the width control is stuck in the minimum position so for the time being it has been bypassed.
For the frame output valve I'm using a Mazda 30PL1 in place of the PCL83.
Interlacing is good, Ferguson have taken extra efforts to ensure this by employing an ECL80 as the frame pulse clipper and shaper.
That complex gated AGC system is really good, much better than any mean level system.
So just a few minor jobs to do and this set will be the perfect big screen 405 line receiver.

DFWB.

Heatercathodeshort 10th Oct 2015 9:23 pm

Re: Ferguson 247T: huge console TV set.
 
That is an absolute cracker David. The Mazda 30PL1 is a very good valve and puts the Mullard PCL83 to shame. They gave so much trouble in the Pye television receivers that they used up what stock they had in the 'Black Box' record players. They even produced a special mains transformer for the job. They must have had thousands!

A good soak test should sort out any minor problems but I'm sure you will easily solve them.

That picture takes me back. As I mentioned, we had the 17" version back in the 50's. Very rarely broke down until the tube went partial S/C heater.
This was almost as bad as the Mazda problem with H/C shorts but did not appear to create the upset that Mazda quite rightly suffered.

Regards, John.

FERNSEH 10th Oct 2015 10:46 pm

Re: Ferguson 247T: huge console TV set.
 
2 Attachment(s)
Hi John,
This set is getting better all the time. The line scan coils have been reversed and the width control repaired.
The tuner unit will receive attention next.
That slow heating PY81/17Z3 has to go. Note the ceramic cathode sleeve.
The later PY800 has a much quicker warm up time.

DFWB.

ukcol 11th Oct 2015 3:13 pm

Re: Ferguson 247T: huge console TV set.
 
Really good focus, contrast and linearity, just a small amount of shading at line rate to sort.

FERNSEH 11th Oct 2015 3:59 pm

Re: Ferguson 247T: huge console TV set.
 
Quote:

Originally Posted by ukcol (Post 791993)
Really good focus, contrast and linearity, just a small amount of shading at line rate to sort.

It's possible that the 0.01mfd CRT A1 supply smoothing capacitor has gone OC. It's C137 in the Ferguson 203T service manual. Another possibility is the line flyback blanking capacitors, C138 and C139. The flyback pulse present at the line scan coils is fed back to the CRT grid through C138 to effect suppression during the line blanking period..

DFWB.

Heatercathodeshort 11th Oct 2015 4:12 pm

Re: Ferguson 247T: huge console TV set.
 
I'll go for the blanking caps.. J.


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