Ferguson 3727 (8000? Chassis) Line Fault - UK Vintage Radio Repair and Restoration Discussion Forum

Mikey405 · 7th Jul 2007, 9:36 pm

Hi everyone.

I had a slightly odd fault on a Ferguson 3727, or at least a fault that wasn't immediately obvious, which I thought I would share with people lest anyone else get the same problem.

The line oscillator had completely stoppped and no amount of prodding around (figuratively speaking) with the actual oscillator part would get it going. The fault was C414, decoupling for the emmiter end of T403, which had gone low in value (It measured only 4μF instead of 10μF on my meter).

Actually, I'm not entirely sure what chassis this set uses as it's not entirely the same as the 8000A, the dropper has 3 sections: 56R, 1K and 47R. The set looks like quite a late set judging by the Ferguson logo and the general look of the TV.

Anyway, after a bit of tweaking here and there the set now has a pretty good picture - Excellent in fact considering it's a 17" 8000 with a low-focus-voltage tube. I have slight Hanover blinds though which will need sorting out. Maybe. Perhaps. One day. If I get round to it.

The colours in the enclosed picture are a bit off because I took the picture in the semi-darkness of my workshop.

Thanks everyone.

Kind regards.

From Mike.

Tazman1966 · 8th Jul 2007, 11:32 am

Hi Mike.

A nice result and good to see that set back in the land of the living as well as me

...ouch, it hurts when I laugh!

All the best,

ALANS ANITAS · 8th Jul 2007, 3:44 pm

Hi Mike

The Ferguson 3727 uses the Thorn 8004 chassis. Details are in the Radio & Television Servicing 1977-78 Book.

From your photo it would seem to have a cabinet made of some kind of real wood and veneer, how much better than all plastic.

Regards

ALAN

Mikey405 · 8th Jul 2007, 4:13 pm

Wow. Thanks Alan. I've never even heard of the 8004 chassis. I have to say though, other than the slight convergence problem at the bottom-left and the slight hanover blinds, this has to be the best picture I've ever seen on one of these little 17" sets. I'll get these problems sorted out soon and it'll be a cracking little TV.

The cabinet is that nasty old chipboard stuff with some kind of Fablon covering. It's still quite nice though.

Thanks Alan.

Kind regards.

From Mike.

FERNSEH · 9th Jul 2007, 1:13 am

Quote:

Originally Posted by Mikey405

Wow. this has to be the best picture I've ever seen on one of these little 17" sets.

The reason why the picture on the 8004 receiver is better than the earlier 8000 series set is likely to be the installation of a redesigned IF/ chroma PCB. I believe the PCB is designated as the PC651. A similar PCB was fitted to the 8800 series. The RF gain control in the mechanical tuner sets was omitted in the varicap tuner versions.

The 9000 series employed another version the PC651, the only difference was the fitment of DC level pots. for grey scale set-up.

DFWB.

Mike Phelan · 9th Jul 2007, 7:22 am

That's interesting, David. I had never heard of the 8004, either! I always thought that the 8800 and 9000 performed much better than the 8000, signal-wise, so Mike's set should look really good in the flesh.

FERNSEH · 9th Jul 2007, 11:05 am

I was never sure of the date of the introduction of the 8000 series. Was it late 1970 or 1971?
I always thought it was a set designed to compete with the products of such firms like Hitachi.
In it's final form, the 8000 series developed into the strange 9800 series. Anyone remember this chassis?

DFWB.

Welsh Anorak · 9th Jul 2007, 2:11 pm

I think the 8000 was introduced in late 71, swiftly followed by the 800A and then the 8500 in June 72.
Whatever you might think of them (!) they were very advanced for their time - a thyristor PSU, single-transistor LOP stage, extensive ICs in the signal stages and all in a small cabinet for £200 ish! Considering this was around the introduction of the hybrid Decca 30, the Pye 693 and the single-chip Bush A823 they did clearly have their sights set on the Far East, even to the extent of buying in one of their least reliable tubes...
The 9800 - that had the awful touch sensors, and looked like the nightmare 9600 - it was always a relief to find it was just a grown-up 8800!

Glyn

Mikey405 · 9th Jul 2007, 6:02 pm

Hi everyone.

I started to have a look at the Hanover-blinds problem and began by following the complete decoder setup instructions. This done, the hanover blinds are fractionally better, but still there. I also noticed that on playing a DVD, the colours on the 8004 weren't exactly the same as the colours on my video-monitor so I thought I would try something. To get reliably stable pictures on some old sets I have to feed the DVD signal through a digital timebase corrector (because of the Macrovision and the like). When I fed the signal through the TBC the picture was just the same, until I adjusted the chroma phase using a control on the TBC, when suddenly the colours became more natural (they weren't that badly out previously though) but interestingly there was a point on the control where all the Hanover blinds would disappear. This struck me as odd as presumably the Hanover blinds are caused by the phase error between the burst and each alternate line which has been phase inverted. So why, when I adjust the overall phase (as opposed to the phase on alternate lines only) does it cure the Hanover blinds?

I have a few ideas as to where to look and a few components which I want to check, but I wonder if anyone else has any thoughts on this?

The decoder is the 5-chip PC651 variety as fitted to the 8500 and 8800 (slightly modified for non-varicap tuner). (As mentioned previously by Fernseh).

Thanks everyone.

From Mike.

Mike Phelan · 10th Jul 2007, 8:34 am

Mike
As the B-Y is of constant phase, and the delay line has already separated the R-Y chroma from it, if the relative phase of the reference osc and B-Y chroma feeding the B-Y chroma demod changes it will just give reduced amplitude of the B-Y, whereas the switched R-Y will cause a phase error on alternate lines - one line will be "greener" and the next one "redder" hence blinds.

I think.

7th Jul 2007, 9:36 pm	#1
Mikey405 Octode Join Date: Jul 2006 Location: Solihull, West Midlands and Beaford, Devon Posts: 1,626	Ferguson 3727 (8000? Chassis) Line Fault Hi everyone. I had a slightly odd fault on a Ferguson 3727, or at least a fault that wasn't immediately obvious, which I thought I would share with people lest anyone else get the same problem. The line oscillator had completely stoppped and no amount of prodding around (figuratively speaking) with the actual oscillator part would get it going. The fault was C414, decoupling for the emmiter end of T403, which had gone low in value (It measured only 4μF instead of 10μF on my meter). Actually, I'm not entirely sure what chassis this set uses as it's not entirely the same as the 8000A, the dropper has 3 sections: 56R, 1K and 47R. The set looks like quite a late set judging by the Ferguson logo and the general look of the TV. Anyway, after a bit of tweaking here and there the set now has a pretty good picture - Excellent in fact considering it's a 17" 8000 with a low-focus-voltage tube. I have slight Hanover blinds though which will need sorting out. Maybe. Perhaps. One day. If I get round to it. The colours in the enclosed picture are a bit off because I took the picture in the semi-darkness of my workshop. Thanks everyone. Kind regards. From Mike. Attached Thumbnails __________________ G7TRF

8th Jul 2007, 11:32 am	#2
Tazman1966 Nonode Join Date: May 2006 Location: St Albans, Herts, UK. Posts: 2,193	Re: Ferguson 3727 (8000? Chassis) Line Fault Hi Mike. A nice result and good to see that set back in the land of the living as well as me...ouch, it hurts when I laugh! All the best, __________________ All the very best, Tas

8th Jul 2007, 3:44 pm	#3
ALANS ANITAS Rest in Peace Join Date: Jun 2006 Location: North West Northamptonshire, UK. Posts: 346	Re: Ferguson 3727 (8000? Chassis) Line Fault Hi Mike The Ferguson 3727 uses the Thorn 8004 chassis. Details are in the Radio & Television Servicing 1977-78 Book. From your photo it would seem to have a cabinet made of some kind of real wood and veneer, how much better than all plastic. Regards ALAN

8th Jul 2007, 4:13 pm	#4
Mikey405 Octode Join Date: Jul 2006 Location: Solihull, West Midlands and Beaford, Devon Posts: 1,626	Re: Ferguson 3727 (8000? Chassis) Line Fault Wow. Thanks Alan. I've never even heard of the 8004 chassis. I have to say though, other than the slight convergence problem at the bottom-left and the slight hanover blinds, this has to be the best picture I've ever seen on one of these little 17" sets. I'll get these problems sorted out soon and it'll be a cracking little TV. The cabinet is that nasty old chipboard stuff with some kind of Fablon covering. It's still quite nice though. Thanks Alan. Kind regards. From Mike. Attached Thumbnails __________________ G7TRF

9th Jul 2007, 7:22 am	#6
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Ferguson 3727 (8000? Chassis) Line Fault That's interesting, David. I had never heard of the 8004, either! I always thought that the 8800 and 9000 performed much better than the 8000, signal-wise, so Mike's set should look really good in the flesh. __________________ Mike.

9th Jul 2007, 11:05 am	#7
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Ferguson 3727 (8000? Chassis) Line Fault I was never sure of the date of the introduction of the 8000 series. Was it late 1970 or 1971? I always thought it was a set designed to compete with the products of such firms like Hitachi. In it's final form, the 8000 series developed into the strange 9800 series. Anyone remember this chassis? DFWB.

9th Jul 2007, 2:11 pm	#8
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,925	Re: Ferguson 3727 (8000? Chassis) Line Fault I think the 8000 was introduced in late 71, swiftly followed by the 800A and then the 8500 in June 72. Whatever you might think of them (!) they were very advanced for their time - a thyristor PSU, single-transistor LOP stage, extensive ICs in the signal stages and all in a small cabinet for £200 ish! Considering this was around the introduction of the hybrid Decca 30, the Pye 693 and the single-chip Bush A823 they did clearly have their sights set on the Far East, even to the extent of buying in one of their least reliable tubes... The 9800 - that had the awful touch sensors, and looked like the nightmare 9600 - it was always a relief to find it was just a grown-up 8800! Glyn

9th Jul 2007, 6:02 pm	#9
Mikey405 Octode Join Date: Jul 2006 Location: Solihull, West Midlands and Beaford, Devon Posts: 1,626	Re: Ferguson 3727 (8000? Chassis) Line Fault Hi everyone. I started to have a look at the Hanover-blinds problem and began by following the complete decoder setup instructions. This done, the hanover blinds are fractionally better, but still there. I also noticed that on playing a DVD, the colours on the 8004 weren't exactly the same as the colours on my video-monitor so I thought I would try something. To get reliably stable pictures on some old sets I have to feed the DVD signal through a digital timebase corrector (because of the Macrovision and the like). When I fed the signal through the TBC the picture was just the same, until I adjusted the chroma phase using a control on the TBC, when suddenly the colours became more natural (they weren't that badly out previously though) but interestingly there was a point on the control where all the Hanover blinds would disappear. This struck me as odd as presumably the Hanover blinds are caused by the phase error between the burst and each alternate line which has been phase inverted. So why, when I adjust the overall phase (as opposed to the phase on alternate lines only) does it cure the Hanover blinds? I have a few ideas as to where to look and a few components which I want to check, but I wonder if anyone else has any thoughts on this? The decoder is the 5-chip PC651 variety as fitted to the 8500 and 8800 (slightly modified for non-varicap tuner). (As mentioned previously by Fernseh). Thanks everyone. From Mike. __________________ G7TRF

10th Jul 2007, 8:34 am	#10
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Ferguson 3727 (8000? Chassis) Line Fault Mike As the B-Y is of constant phase, and the delay line has already separated the R-Y chroma from it, if the relative phase of the reference osc and B-Y chroma feeding the B-Y chroma demod changes it will just give reduced amplitude of the B-Y, whereas the switched R-Y will cause a phase error on alternate lines - one line will be "greener" and the next one "redder" hence blinds. I think. __________________ Mike.