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Old 16th Jun 2018, 3:49 pm   #1
FERNSEH
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Default Ferguson 705T Phase II

Ref to an earlier topic: https://www.vintage-radio.net/forum/...ad.php?t=95399
I'm now the owner of one of these unusually styled sets. The Ferguson 705T shown in the attachment is the phase II version and is convertible to 405/625 operation. The line timebase can switched to 625 lines by means of the switch on the left side of the cabinet.
The Mullard AW47-90 CRT is excellent, every bit as bright as the tube in the Decca DR101.
It is my intention to have a metal stand made for this set and I even got ideas about converting the set to 625 lines.

DFWB.
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Old 16th Jun 2018, 6:25 pm   #2
TonyDuell
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Default Re: Ferguson 705T Phase II

Do you have the extra IF amplifier chassis shown in the second photo? I had something like it years ago (bought surplus on the Edgware Road) and there is a slim chance I would still be able to find it. I may even still have the circuit diagram/fitting instructions for it...

I know I never had the UHF tuner that connects to a B7G socket on the extra IF amplifier unit.
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Old 16th Jun 2018, 8:19 pm   #3
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Default Re: Ferguson 705T Phase II

Hi Tony,
The converter unit shown in the second attachment has been in my possession for a number of years. It came with many other 625 converter kits which included the Sobell-GEC dual standard IF amplifier that was used in the Sobell ST282 and GEC BT452. Also a Philips "Twin-Line" converter.
Back in the sixties I fitted a good number of those BRC 700/800 series converters. The full conversion also required a new cabinet back and the UHF tuner. Performance on 625UHF was absolutely hopeless and to improve matters the BRC service department supplied a transistor IF preamplifier. This little unit was plugged in the UHF tuner socket SKT304 and the tuner was connected to a B7G socket on the pre-amp unit. The pre-amp really did improve the gain of the IF amplifier which in turn introduced another problem, the PCF80 video amplifier valve couldn't handle the strong negative going video.
This called for another modification. A 0.1microfarad capacitor was introduced between the video detector and the grid of the video amplifier.
That solved the sync crushing fault. The converted sets were displaying good BBC2 pictures at last.
I don't have the conversion instructions, all that stuff was got rid of when the sets were scrapped in the seventies. the truth is I was glad to see the last of these converted horrors.
More than forty years later I'm thinking wouldn't it be fun to convert a 700 series set again.

DFWB.
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Old 17th Jun 2018, 9:00 am   #4
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Default Re: Ferguson 705T Phase II

Quote:
Originally Posted by FERNSEH View Post
I don't have the conversion instructions, all that stuff was got rid of when the sets were scrapped in the seventies. the truth is I was glad to see the last of these converted horrors.DFWB.
We all did this David. I had almost every television service manual from 1936. When colour arrived it was time to clear the shelves for the big thick colour manuals. I remember it took several weeks at a dustbin full at a time to clear the older manuals that had not been opened for years.

After all we were running a business not a museum and collecting vintage receivers was unthinkable.

I did retain a Pye B18T and I still have it. This was followed by a Bush TV12 and a..and a... and vintage was born.
I think a few of us started to do this around 1971.

The 700 series I have been looking for is the Philco 1100 'Selectorflash' with light beam operated remote control. It was released in 1961 same as the 705T.
Regards, John.
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Old 17th Jun 2018, 1:10 pm   #5
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Default Re: Ferguson 705T Phase II

Amazingly I have found a bit of paper entitled 'UHF 625 Line Conversion Service Information' and 'Convertor IF Amplifier Schedule A & B production'. It is not clear what it applies to, but there is a diagram entitled 'Typical 850 Series Chassis after Conversion'

The IF amplfiier looks very like the unit in the second photo in post #1.

Said service sheet has a layout, circuit diagram, components list and alignment instructions. I have scanned it (it was lucky it turned up so quickly here, I would probably not be able to find it again...) and if you (or anyone else) wants a copy, send me your e-mail address by PM and I will get it to you.
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Old 17th Jun 2018, 1:56 pm   #6
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Default Re: Ferguson 705T Phase II

Here's a scan of part of the Ferguson range brochure that includes the 705T.

"72 guineas, including Purchase Tax and surcharge".
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Old 17th Jun 2018, 2:49 pm   #7
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Default Re: Ferguson 705T Phase II

"Amazingly I have found a bit of paper entitled 'UHF 625 Line Conversion Service Information' and 'Convertor IF Amplifier Schedule A & B production'. It is not clear what it applies to, but there is a diagram entitled 'Typical 850 Series Chassis after Conversion"

Hi Tony, That's great news,I've sent you a PM.


Hi Dazzlevision,
So now we know the 705T was a model the "Rome61" range, hence the Italian flag colours in the sales leaflet.

I believe that certain DER TVs employed the same remote control system.

DFWB.
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Old 17th Jun 2018, 2:58 pm   #8
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Default Re: Ferguson 705T Phase II

“I believe that certain DER TVs employed the same remote control system”

Yes, they did. Last year, I bought a wired remote control unit in grey plastic, branded “DER” (a Thorn TV rental company at the time of the 705T, but before Thorn bought Radio Rentals). In all other respects, it’s identical to the one used on the 705T.
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Old 17th Jun 2018, 5:29 pm   #9
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Default Re: Ferguson 705T Phase II

I have sent a copy of the service sheet that I have to the 3 addresses I received by PM.
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Old 17th Jun 2018, 7:40 pm   #10
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Default Re: Ferguson 705T Phase II

Quote:
Originally Posted by dazzlevision View Post
“I believe that certain DER TVs employed the same remote control system”
They certainly did, in the early 60's long before I worked for them I recall seeing an easy chair on display in the showroom with a remote screwed to one of the arms.

John.
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Old 17th Jun 2018, 9:59 pm   #11
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Default Re: Ferguson 705T Phase II

"I have sent a copy of the service sheet that I have to the 3 addresses I received by PM."

Hi Tony, many thanks again for sending me the conversion information.

A brief description of the converter. A valve UHF tuner is connected to a two stage IF amplifier using EF183 and EF184 frame grid pentodes. An OA79 crystal diode detector feeds negative going video to the pentode section of a PCF80, the triode section functions as a cathode follower. A line flywheel discriminator is present on the converter unit and is used on both line standards. The two stage 6Mc/s FM sound amplifier uses an EF80 and the pentode section of a PCF80 V351B. The FM demodulator is an EB91 double-diode. The triode section of the PCF80 V351A is used a the DC amplifier in the line flywheel discriminator.
The converter valve heaters are connected into the existing heater chain. A 177ohm resistor is connected in parallel with the 31ohm heaters section of the mains dropper section R156 and the 172 ohm section R159 is shorted out.

DFWB.

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Old 18th Jun 2018, 5:14 am   #12
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Default Re: Ferguson 705T Phase II

No problems, I am glad the information is of use.

One thing you might be able to clear up. I think there were some 'loose' capacitors (not fitted on the IF amplifier chassis) that you had to connect to tagstrips B and C in the main chassis. What were they for? They are shown on the circuit diagram for the amplifier chassis with no comment.
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Old 18th Jun 2018, 9:18 am   #13
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Default Re: Ferguson 705T Phase II

Quote:
Originally Posted by TonyDuell View Post
One thing you might be able to clear up. I think there were some 'loose' capacitors (not fitted on the IF amplifier chassis) that you had to connect to tagstrips B and C in the main chassis. What were they for? They are shown on the circuit diagram for the amplifier chassis with no comment.
They are for changing the line scan “S correction” and LOPT tuning on 625 lines working.
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Old 18th Jun 2018, 10:29 am   #14
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Default Re: Ferguson 705T Phase II

The circuit of the 625 converter.

DFWB.
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Old 18th Jun 2018, 10:35 am   #15
dazzlevision
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Default Re: Ferguson 705T Phase II

Here's a scan of the front cover and remote control circuit of the Philco Selectaflash 1100 and 1110 Phase II service manual. It's essential a Ferguson 705T chassis, but with visible light remote control operation of the motorised VHF turret tuner and sound muting. A very wide cabinet, by the looks of it.
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Old 18th Jun 2018, 10:59 am   #16
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Default Re: Ferguson 705T Phase II

Quote:
Originally Posted by dazzlevision View Post
Quote:
Originally Posted by TonyDuell View Post
One thing you might be able to clear up. I think there were some 'loose' capacitors (not fitted on the IF amplifier chassis) that you had to connect to tagstrips B and C in the main chassis. What were they for? They are shown on the circuit diagram for the amplifier chassis with no comment.
They are for changing the line scan “S correction” and LOPT tuning on 625 lines working.
Here's a circuit extract. The two new capacitors replicate the functions of C91 and C92, but on 625 lines working.
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Old 18th Jun 2018, 5:29 pm   #17
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Default Re: Ferguson 705T Phase II

Thanks.
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Old 25th Jun 2018, 10:48 am   #18
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Default Re: Ferguson 705T Phase II

All is not well with the Ferguson 705T. The frame sync has gone bad, a total loss of interlace resulting in a crude 188 line picture. The condition has gradually got worse since I acquired the set ten days ago. Initially, to achieve perfect interlace the frame hold control position was critical but with use things have got worse.
The Ferguson 705T along with many other BRC sets doesn't use the usual frame sync R-C integrator, instead a series differentiator is employed between the sync separator and the frame oscillator, a 250pF capacitor.
It's not a particularly nice arrangement but in practise good interlace is possible irrespective of frame hold control setting.
The 'scope traces show the video present at the anode of the video amplifier and the sync pulses at the anode of the sync separator valve, the broad pulses are of reduced amplitude.
The second oscilloscope trace was taken under no signal conditions, note the strange sine wave signal, this not 50Hz ripple but in fact feedback from the oscillator.

DFWB.
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Old 25th Jun 2018, 4:22 pm   #19
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Default Re: Ferguson 705T Phase II

Hello David,

My 705T came with its original “stand”, actually two pairs of legs, so if you need photos and dimensions of it to help with making a copy, as mentioned in your first post just let me know.

I had to do some major woodwork on the base of mine resulting from it being dragged along with the “stand” fitted at some stage, which had partially ripped out the stand mounting bushes.
As the bushes were originally fitted fron the inside of the case, I had to carefully cut away the splintered laminations of the plywood from the underside, until I reached undamaged layers. Then, after delaminating some old ply to get imperial thickness laminations, shape the new layer to suit the missing layer and glue that in place, repeating with the next layer once the glue had set.

It took a few days, on and off, to sort out, but you can’t tell what has gone on.

Also note that the top of the case is very narrow and only properly fixed at the sides, not above the speaker and controls. The top had started to come away on both sides on mine, so I ended up removing it carefully and regluing it and also its mounting blocks.

Some years ago I removed the top on my Ferguson “Goldenglide” 606T to refinish it, that too came off easily. Probably lots of heat at the top of the cabinet over many years helps to reduce the bond of the cabinet glue used.

Regards,

Phil.
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Old 25th Jun 2018, 8:19 pm   #20
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Default Re: Ferguson 705T Phase II

Hi Phil,
Many thanks for your kind offer of photos and dimensions of the metal stand. A friend who is skilled at welding has offered to make the stand for me, it's just a matter of finding the right metal tubing. Square and round section will be required.
I'll continue investigating the sync circuits to find out why the set performs in the matter it does. Considering Ferguson must have made hundreds of thousands of sets using the frame sync differentiator all working without any problems the fault is almost certainly unique to my set. BRC chassis types employing this type of frame synchronising were the 500, 600, 700 and the 800/850 series. 900/950 series have something similar.

I'm sure there is mention of this type of frame sync in one of the Spreadbury books.


DFWB.
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