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Old 31st Jan 2014, 1:41 pm   #1
gridrunner
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Default First restoration: Ferguson 3652

Hi everyone,

I have a working Ferguson 3652 I'd like to restore and I wanted to ask those in the know for any tips when working with this telly. I've done some fault repair on video game monitors in the past, but not a TV and certainly not a valve set. The TV works but on 625 lines has some tearing and a blank band at the top of the screen. My initial thoughts would be to go through and replace the electrolytic capacitors and test and replace any bad resistors.
Can anyone volunteer basic fault finding advice:
Is the chassis live and do I need to use an isolation transformer to work on it?
Are there any known issues or trouble spots to be aware of with this chassis?
Is there anywhere I can obtain schematics to help with repair?

many thanks!

stu
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Old 31st Jan 2014, 1:53 pm   #2
mark pirate
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Default Re: First restoration: Ferguson 3652

The chassis will be live, so an isolation TX is needed.
It sounds as if a recapping should sort out the issues you have, also check the resistors.

Always replace one component at a time, then switch on and note the improvements, I usually start with the power supply, then line and frame stages.

Mark
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Old 31st Jan 2014, 2:33 pm   #3
gridrunner
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Default Re: First restoration: Ferguson 3652

Thanks for the reply Mark, do you happen to know of anyone/where who sells service manuals?
Concerning the isolation transformer - I have one I scavenged from a video game some years back. Can I attach this to the mains supply of the TV?
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Old 31st Jan 2014, 2:57 pm   #4
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Default Re: First restoration: Ferguson 3652

BRC 1400 chassis portable.

Easy to get that going. There are lots of black 'Callins' capacitors on the chassis - change them all Then see what is what.

The Line Output Transformers on these rarely fail. Check the diode that feeds the valves - if it goes short circuit then the picture lock will go due to a safety feature in the set.

Cheers,

Steve P.
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Old 31st Jan 2014, 5:04 pm   #5
mark pirate
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Default Re: First restoration: Ferguson 3652

Quote:
Originally Posted by gridrunner View Post
I have one I scavenged from a video game some years back. Can I attach this to the mains supply of the TV?
If it was running a CRT monitor, it should be fine, I cannot help with service info, but maybe a request in the relevant section may turn up a copy.

Mark
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Old 31st Jan 2014, 5:21 pm   #6
Mike Phelan
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Default Re: First restoration: Ferguson 3652

To add to what Steve says, the 1400 is an easy set to work on in terms of accessibility.

The diode in the heater supply often fails - don't run it for too long as the valves and CRT won't be very happy.

The jelly pot LOPTx will be OK, but the EHT sticks often do fail showing a ballooning raster.

Most of the electrolytics will be past their best. Replace caps one at a time!
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Old 31st Jan 2014, 5:40 pm   #7
gridrunner
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Default Re: First restoration: Ferguson 3652

Thanks for the pointers everyone. I'll take some pictures and make a start tomorrow.
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Old 31st Jan 2014, 8:59 pm   #8
dazzlevision
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Default Re: First restoration: Ferguson 3652

Hello,

I would advise:-

Replace any paper or mixed dielectric (usually tubular in shape) capacitors branded Hunts/Erie/Plessey/TCC/Dubilier (Dubilier types also sold by RS/Radiospares and may be all grey in colour – these would have been fitted after the set was made – during a repair). In the 1400 chassis, most will be mounted “stood up” (i.e. one end abutting the printed circuit board).

Replace any Callins/SPS/TCC branded black (or coloured plastic) cased electrolytic capacitors (radial types, where both lead out wires are at the same end).

To aid identification, there is a photo galley of capacitors (“black museum”) in this thread: https://www.vintage-radio.net/forum/...d.php?p=627374

You will also find that several carbon resistors have gone high in value and they will probably have a noticeable effect on the set’s performance. Some of these are the high value resistors in the set width circuit, the boost HT feed to the frame timebase (PCL85 valve) and the boost HT feed to the CRTs first anode and focus electrodes. Then there are the resistors in the sync separator (30FL1 valve) anode and screen feeds and the anode and screen resistors of the 6F28 video amplifier valve.

The type of "Erie" manufactured carbon composition and PCB mounting type resistor fitted in the 1400 is shown in this thread: https://www.vintage-radio.net/forum/...t=91511&page=2

I would also check the value of the “width” preset potentiometer, as it is likely to have significantly changed in value. There is a mod, change the width pot from 1MOhm to a 2.2MOhm and change the series resistor that feeds the “hot” end of the width pot from 330kOhm to 680kOhm (0.5Watt).

For these high value resistors, I would advise fitting replacement types that can withstand a relatively high dc voltage (e.g. 500Vdc), such as metal glaze type (but not carbon film).

There are several other official Thorn modifications that will usefully improve the performance of the 1400 chassis and I would recommend these be incorporated, if not already done in factory production. There is usually a “Schedule” letter paper label or ink stamp on the copper side of the PCB, to indicate the mod state of your particular version of the 1400 chassis. I think Schedule E was the final version of the 1400. I can look these up for you (but do the above first).

Regards,

Dazzlevision

Last edited by dazzlevision; 31st Jan 2014 at 9:02 pm. Reason: Added text
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Old 31st Jan 2014, 10:59 pm   #9
gridrunner
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Default Re: First restoration: Ferguson 3652

HI Dazzlevision,

thanks very much for the detailed reply, it's very helpful. I had the back off tonight and over a cup of tea decided to remove just one capacitor to start with. I had it beside me now, but I don't recall which number on the PCB it is.

I just wanted to ask about tolerances. I have an assortment of caps I use mainly for modern CRT and PSU repair. I'm used to replacing caps by subsituting with a slight higher capacitance rating if there isn't a direct substitute to hand. The Callins cap I have here is rated 12UF at 300V. In my toolbox I have a 15UF 450V cap. How forgiving are these valve circuits? I'd never go beyond 25%, but is a precise value signficant? I always try to get an exact match if possible, but notice that 12UF is a bit of an odd bird these days.

My other question, and I'm sorry if this is terribly newbie, is about isolation transformers and how to measure powered up in circuit. All the equipment I've worked on is quite modern, and the concept of isolation is eluding me.
Presumably if the chassis is at mains potential, touching it would be very bad. I also notice the set isn't earthed. By adding the isolation transformer how would this affect testing and measurement - of voltages for instance? I have an isolation transformer from an old video game monitor and cabinet. If I rustle up an enclosure and connect the TV to it, where is ground from the point of view of voltage testing?

thanks
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Old 1st Feb 2014, 8:58 am   #10
dazzlevision
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Default Re: First restoration: Ferguson 3652

Hello Gridrunner,

“The Callins cap I have here is rated 12UF at 300V. In my toolbox I have a 15UF 450V cap.”

A 15uF 400V electrolytic will be fine to replace the 12uF 300V one. Electrolytics used in domestic TVs and radios have a very broad tolerance, typically +50% & -20%

“Presumably if the chassis is at mains potential, touching it would be very bad. I also notice the set isn't earthed.”

Most TVs of this era employed “live chassis” design (to save money and weight, by not using a double wound mains transformer in the power supply). This means that, if the mains plug is wired correctly, the “chassis” (i.e. 0V/common line) of the TV will be directly connected to mains Neutral. Neutral is usually a few volts (ac) above true earth potential. However, if the plug is wired the wrong way round (or there are certain faults in the TV, such as an open circuit Neutral pole in the on-off switch), then the chassis will be at full mains (live/line) 230Vac potential (with respect to earth) and thus rather dangerous to work on (from an electric shock point of view).

You must not connect earthed test equipment (e.g. an oscilloscope) to a live chassis set, as the “ground” lead of the scope’s probe will connect the chassis of the TV to mains earth and current will flow (even if the chassis is at mains neutral). If the chassis is at full mains (live/line) potential, then a large current will flow and probably do some damage to the TV and scope, before a fuse or your house’s RCD blows/trips. However, it is OK to use a multimeter for measuring voltages, as it is (usually) a battery powered device that is not earthed.

“By adding the isolation transformer how would this affect testing and measurement - of voltages for instance? I have an isolation transformer from an old video game monitor and cabinet.”

Using a proper double wound mains isolation transformer (specifically designed for this application) has two benefits:-

1. It makes the circuitry of the TV “floating” with respect to earth and thus safe to connect earthed test equipment to.

2. It makes it much less likely you will get a dangerous electric shock if you touch any part of the circuitry, as that part will immediately assume earth potential (via your body). Even so, you should still proceed with care and avoid touching the circuitry, especially the EHT and line output area, where very high dc (up to 20kV EHT) and high pulse voltages are present (for example, on the top cap connections of the two line output vales (PL504 and U193).

A purpose made double wound mains isolation transformer has no direct electrical connection between the two windings (i.e. it provides galvanic isolation of the load from the supply).

Are you sure the transformer you intend to use is such a double wound mains isolation transformer? It may just be a step down autotransformer to allow USA made 110Vac equipment to operate on the UK 230Vac supply. An autotransformer does not provide galvanic isolation and is definitely not suitable for this application.

The use of an isolation transformer will not affect voltage measurements and will allow the coonection of a mains powered oscilloscope (for example). I strongly recommend the use of one; it will be much safer!

Regards,

Dazzlevision

.

Last edited by dazzlevision; 1st Feb 2014 at 9:03 am. Reason: Extra text.
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Old 1st Feb 2014, 9:18 am   #11
dazzlevision
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Default Re: First restoration: Ferguson 3652

Hello again,

Electrolytic capacitors to check/replace:

C54 4uF (12uF in later production, if my memory is correct)
C81 12uF
C85 50uF
C115 1uF.

I'd also check to see if the large multi-section "aluminium can" electrolytic is leaking electrolyte down the PCB (at its lowest point).

Paper/metallised paper capacitors (if of the type/brands mentioned earlier in this thread) to check/replace:

C39 0.47uF
C40, C82, C93, C101, C104, C107 0.1uF
C117 0.047uF
C105 0.22uF
C108 0.3uF (this is the "S-correction" component and its value is important, so use a 0.27uF if you can get one, otherwise a 0.1uF in parallel with a 0.22uF)

For both electrolytics and paper capacitors above, observe their individual voltage ratings - don't use lower voltage rated components.

Carbon composition resistors to check/replace:

R36 3k, R38, 39k, R40 3.3k, R41 2.7k, R45 47k, R47 22k, R48 33k, R49 22k, R139 3.9M, R130 1M, R143 330k (note mod to 680k mentioned earlier, with change to width pot), R140 2.2M, R141 1.8M, R133 220k. Observe their power ratings.

Regards,

Dazzlevision

Last edited by AC/HL; 1st Feb 2014 at 3:54 pm. Reason: Corrections merged
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Old 1st Feb 2014, 10:28 pm   #12
Philips210
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Default Re: First restoration: Ferguson 3652

Hi.

One thing to be aware of on a working BRC 1400 is when the chassis is swung out in the service position. There's a danger of making contact with the top caps of the line output and efficiency diode valves.
The later single standard BRC 1500 chassis addressed this issue by repositioning the line output transformer on to the other side of the chassis.

Regards
Symon.
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Old 1st Feb 2014, 11:09 pm   #13
60 oldjohn
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Default Re: First restoration: Ferguson 3652

ISTR a post on this forum where someone tried cleaning the long 405 / 625 switch, I presume there was switch cleaner about when power was applied and the set caught fire.

John.
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Old 3rd Feb 2014, 3:08 pm   #14
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Default Re: First restoration: Ferguson 3652

Hi
Yes John - it was a colleague of mine who didn't wait for the switch cleaner to evaporate properly! Not a great deal of the set left, but his workshop survived, luckily.
Glyn
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