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Old 10th May 2010, 2:53 pm   #1
audiomagpie
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Default Another Fergy: a 988T

Saw this at the NVCF and it had my name on it! A slightly younger brother to my 978T.
Had a quick look when I got it home. Chassis can only be described as filthy, covered with black dust and white spots (spider plop?), the cabinet having some worm, possibly still active as there is pale fresh wood dust on top of the dirt, so it's been treated and is sealed in a big bag in the garden!

A quick visual reveals that the vol pot/switch has been replaced, the dropper is giving piggy back to a couple of smaller cousins but otherwise looks pretty original. I'll snip out the mains filter cap and check HT to ground resistances, heater chain continuity, check the more critical caps etc. If all's OK I'm inclined to do a 'Steve P', although I'm a big chicken and will wind up slowly with the variac.

I'll let you know how it goes!

Greg
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Old 10th May 2010, 2:56 pm   #2
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Default Re: Another Fergy: a 988T

If we hear reports of an explosion in the Midlands we'll know what's happened I like the approach of getting the heater chain up first, without HT. As a devout coward this seems sensible. It's also possible with many sets to get the heaters up to full power and then use a variac on HT only.
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Old 11th May 2010, 1:14 am   #3
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Default Re: Another Fergy: a 988T

Mains dropper totally shot (see pic), all but one section o/c. It needed 60 ohms before the branch off to the rectifier PY82 and 290 ohms before feeding the heater chain (the ballast and shunting resistor thereafter being OK). Fortunately, at the NVCF I bought a few droppers, high wattage low value resistors being something I was short of. I found one that gave the combinations required for the 240 volt setting (as per trader sheet), 66 ohms and 289 ohms respectively! The intermediate tapping wires to the voltage selector plug for other voltage settings now u/s so disconnected, meaning the set is now 'fixed' for 240 volts only.
The mains rf filter cap was snipped out. The main smoothing/res can was bulging and looking crusty, so I lashed up in my temporary fashion some replacements under the chassis secured by cable ties. Nothing else as yet replaced.
Using the variac and isolating transformer wound up the juice over a period of minutes.
At only 170volts, a distant line whistle started to rustle up! Valves lit and a weak but none the less spark from the anode of the EY51 with an insulated driver! Wound up to 200v, whistle more pronounced, varied in pitch by horiz. hold pot adjustment but no display. Was just about to check for EHT with a grounded driver (couldn't see if the EY51 heater was lit due to the amount of crud) and line whistle died, accompanied by a swirl of smoke from under the chassis.
That'll do for tonight, I know I'm still a long way from proving the LOPT and tube, but a good start with good results so far. I guess a little waxie, after years of hibernation, has objected to having HT shoved up its jaxie!
Good job I also re stocked on caps at the NVCF, you certainly get thro' em with tellies.
Congratulations to the Ferguson engineers of the time, another well laid out chassis with components all easy to find and accessible.
Anyone thinking of venturing into vintage TV (as I've just done, it's only my second set) could do a lot worse than one of these old fergy's if you find one, the whole chassis complete with tube can be removed from the cabinet within a couple of minutes. And because they're in a square wooden box and not a retro bakelite moulding, they're as cheap as chips!

Greg
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Old 11th May 2010, 9:01 am   #4
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Default Re: Another Fergy: a 988T

Well Greg, it shows some promise. Looking forward to following this one.
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Old 11th May 2010, 9:26 am   #5
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Default Re: Another Fergy: a 988T

That's how the antiques road show like them 'in original condition'. Looks as though its been kept in a hen house. Well worth doing though, not many of those about.

Peter
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Old 11th May 2010, 8:36 pm   #6
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Default Re: Another Fergy: a 988T

A real cracker Greg. Gives a bright clear picture. Very popular model and a simple circuit. B9A valves and a superhet circuit.
The later version known as the 'Super Twelve' has a gold mask and gives a slightly larger picture. Same model number and tube/chassis. LOPT and tube should be ok. Good luck with it. Regards, John.
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Old 11th May 2010, 8:54 pm   #7
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Default Re: Another Fergy: a 988T

Quote:
Originally Posted by Heatercathodeshort View Post
has a gold mask and gives a slightly larger picture. Same model number and tube/chassis.
This one has the gold plastic screen surround, with the pink tinted implosion guard.

Greg
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Old 11th May 2010, 9:21 pm   #8
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Default Re: Another Fergy: a 988T

Just took these two pics. The early version has a dark gold mask and quite a dark mauve filter. The later versions have a larger mask, light gold and a grey filter screen.
J.
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Old 11th May 2010, 11:30 pm   #9
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Default Re: Another Fergy: a 988T

'Tis the one in the first picture!

Wow! To have a collection like yours John (one day, maybe one day!)

Greg
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Old 12th May 2010, 7:23 am   #10
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Default Re: Another Fergy: a 988T

It all started with 'Another one won't hurt'........and then you realize you are talking about outbuildings and not receivers..Nice clean underchassis shot there. Probably worked when put aside. The mains droppers are cement covered and this rots the resistance wire hence all O/C. I have a 989T in exactly the same condition. Mains droppers that have been coated in vitreous enamel never fail. J.
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Old 19th May 2010, 12:53 am   #11
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Default Re: Another Fergy: a 988T

Some success at last! Couldn't get the PL81 combined line oscillator/line output valve to oscillate, so no output to drive the LOPT and thus no EHT! Working only from the Trader sheet (no. 1027, not the luxury of the Ferguson manual this time!) started going thro' the waxies in the L/O stage, then replaced R29 150k (was o/c), other resistances being reasonably close, I was getting 68 of the 73 recommended volts on the screen of PL81, no other measurements given and otherwise unsure what to expect. Studying the schematic, reading Spreadbury's excellent sections on combined L/Osc & L/Op stages and Steve P's Old Tellies site , then even dusting off the old 'scope and seeing if I could pick up the sinc pulses from the previous stage, I was at a bit of a loss and condemned the PL81. Another is on order so decided to leave things 'till it turned up.
However, not being able to leave things alone, I decided to power up the set and have a prod with the voltmeter. Fiddling with the line hold pot, which I had done many times before, I heard the line whistle start up, and was rewarded with frame collapse. The line hold pot only makes contact in one very exact position. The bad connection being between the centre tag and the rotating brush rather than the brush on the track itself!
So I've got EHT and a glow from the tube, which is good news so far!
I'll now turn my attentions to the frame driver circuit.

This only being my second set (so far...) still a good feeling to get anything at all on the screen!

Greg

Note: in photo, chassis propped on its side, so it is frame collapse not a line fault!
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Old 19th May 2010, 8:52 am   #12
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Default Re: Another Fergy: a 988T

Good news Greg. I guess way back in post #3 when you heard the line whistle, the pot must've been hanging on for dear life then.

Keep going!

Good luck
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Old 19th May 2010, 5:56 pm   #13
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Default Re: Another Fergy: a 988T

Nice one! Nice bright tube. I may have a few odd bits if your stuck. J.
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Old 20th May 2010, 12:12 am   #14
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Default Re: Another Fergy: a 988T

Well a waste bucket full of old waxies from the frame stage and in return a nice full screen of raster. Goes very bright too! Contrary to my previous post, the line hold pot (which is wirewound) was found to have a break in it. When the wiper sits to bridge the break, in that one position only I get line scan. I've tried to smear solder across the break, but whatever wire they used doesn't have an appetite for solder, so I'll have to obtain a replacement 10k Welwyn type pot. I'll photo it tomorrow and put in the wanted section.

I connected the Aurora but nothing is getting thro', no audio either, so I'll have to look at the early stages of the receiver. There are a lot of small Hunts caps, not waxies but the light brown ones about 1cm long, 4mm diameter, typically 0.00X uF values. I've noticed that the plastic casing is cracked on many of these, although the few I tried measured ok with a capacitance meter. Advice please- should I replace?

The chassis now looking better for a wipe/vac over. The wonderful Mullard label from the tube (which came adrift) will eventually be stuck back on, but I will scan it first so if anyone wants to print one to decorate an un labelled tube, I can send a copy of the file.

See the manufacturers label on the speaker 'R&A Wolverhampton'. Just curious, not heard of them before- anyone got any info?

Thanks,

Greg
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Old 20th May 2010, 7:07 am   #15
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Default Re: Another Fergy: a 988T

Hi Greg, looking good

For what it's worth from a newb, I would change the little Hunts blighters, all in my V4 were causing problems, each time one was changed an improvement followed, even ones which looked to be in ok condition.

Chris
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Old 20th May 2010, 8:19 am   #16
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Default Re: Another Fergy: a 988T

The speaker is a RICHARD ALLEN. I might have spelt the Allen bit wrong but they made very good speakers for television receivers.
I have checked my stock of wire wound pots and have just about every value but 10K ! I have a 20k Colvern and if all else fails you may be able to press it into service with a resisitor across its winding. I also have the original 988T manual. I can send it to you for scanning together with the pot if of use. Regards, John.
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Old 21st May 2010, 5:17 am   #17
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Default Re: Another Fergy: a 988T

Quote:
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The speaker is a RICHARD ALLEN. I might have spelt the Allen bit wrong but they made very good speakers for television receivers.
I have checked my stock of wire wound pots and have just about every value but 10K ! I have a 20k Colvern and if all else fails you may be able to press it into service with a resisitor across its winding. I also have the original 988T manual. I can send it to you for scanning together with the pot if of use. Regards, John.
I'd heard of Richard Allen (I was 'in to' hi fi in the 70's/80's) but it looks like 'R&A' rather than 'RA'.
Thanks for the kind offer of a pot John, but I did find a 10k with a carbon track which seems to do the job OK. I will have to find a direct replacement, as it should be a plastic bodied pot as it protrudes thro' the back panel, this one being metal bodied/shaft (+ live chassis!), although I'm using the isolating transformer at the mo. A copy of the manual would be very handy, I'll send you a PM.
I replaced all the small light brown Hunts caps, they mostly desintegrated on contact and there were about 20 odd of the little blighters! TV sets certainly deplete the capacitor stocks! But see the pic below, there is now a test card trying very hard to get out! And a feint test tone on audio. The contrast pot has to be fully turned to one end to get anything though, so I think that may be o/c also, that's where I'll start next session.
I also notice that this set has crystal diode detectors, did I recently read on another TV thread that they can give trouble also? It has them both in the video and audio sections.

Greg
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Old 21st May 2010, 9:35 am   #18
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Default Re: Another Fergy: a 988T

Check the forward back resistance of the vision detector. Probably o.k. but I've had a number that have gone O/C during years of storage.
I think the speaker name is the same. It was known as Richard and Allen in the early years and was probably shortened to just RA. Looks good so far. J.
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Old 21st May 2010, 11:41 am   #19
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Default Re: Another Fergy: a 988T

The R & A logo stands for "Reproducers and Amplifiers", of Wolverhampton.
Richard Allen were a Yorkshire outfit... from Cleckheaton.
Pye also used a lot of R&A speakers.

Pete
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Old 21st May 2010, 6:46 pm   #20
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Thanks for clearing that up Pete. You learn something new every day.
Hello again Greg, that looks a classic case of I.F. instability probably caused by the decoupling capacitors connected to pin 8 [screen grid] of the EF80's in the sound and vision I.F. amplifiers. [O/C] Worth a check. J.
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