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Ferguson 3821

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PYE625
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This evening I dismantled the mechanical push button assembly for the tuner as it was sticking. Not only that, a couple of the plastic spring holding washers had rotted and fallen away (see 1st pic). I had a look in my washer draw and found some clips that were exactly the right size to support the springs and easily fit over the thread of the tuning plungers. To make up the correct spacing as the original plastic washer, I used a rubber o-ring. You can see the o-ring and then the clip in the second picture. I replaced all the plastic pieces as the remaining ones were cracked and ready to break.

The result is now a perfectly operating tuner, having lightly greased the sliding plungers. Luckily, the square shaped tuning plungers are threaded on the inside and do not rely solely on the plastic bits for grip to the thread.

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To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 29/04/2019 6:11 pm
PYE625
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I think that about concludes any immediate work on this set, it is working well with all original components. I'll run it for a while with the back on and see how it goes.

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To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 29/04/2019 8:47 pm
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PYE625
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The only thing that is painfully apparent is the lack of any DC restoration to the CRT. It is quite dramatic how the background can vary in brightness according to any peak white picture content that occurs in moving scenes. From soot and whitewash to a low contrast dingy grey.

I feel a black-level modification coming on.....

Cummins3

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 30/04/2019 4:18 pm
Nuvistor
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Surprisingly the lack of a stable black level didn’t bother many, if any at that time. RBM’s introduction of the BL clamp in the late 60’s caused quite a stir and for many not a good one.

The advent of colour tv and its requirement of a stable black level was accepted quite happily, probably because of the colour pictures being more interesting.

Frank

 
Posted : 30/04/2019 5:26 pm
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PYE625
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I did try the modification and yes, it certainly is very effective at clamping the black level.

However, am I really sure that I want to detract from the originality of the set with extra components hanging off the pcb ? Well they can be made fairly neat and tidy, but I am not keen on the idea. If the chassis was hand wired, it would be easier to accomodate.

If I was going to watch the set as a daily viewer, then of course the mod is worth doing. As a collectors item, then no..... I will leave it alone.

Cummins4

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 30/04/2019 5:30 pm
Jayceebee
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I've seen it done to a 1500 some years ago but although the improvement was noticeable there was a drop in definition which spoiled it, I have an idea that it was done without the the 1SJ150 or OA202 diode specified. What type of diode did you use and was there any definition loss?

Like Frank I too certainly had customers complain of their pictures going black especially during adverts on RBM sets, not aware of any complaints at the time of 1500's lack of clamping. Certainly wouldn't be acceptable now.

John.

 
Posted : 30/04/2019 8:51 pm
PYE625
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Hi John, I used a 1N4148 which is unsuitable because the voltage is too high for the diode, but it was just ok for testing.

Not only was there a slight loss of definition, I also found there was a compression effect of peak whites with the contrast set high. Very similar to a poor emission CRT. Furthermore, the brightness level was too high as the control was advanced.

In short, the modification provided good DC restoration, but at the expense of the above. I think some further tweaks of the circuit is needed before I could say it was really worthwhile. As said previously, I will not be going down this route with my set.

I have read somewhere that a version of the 1500 was produced for schools with a black level clamp, it would be interesting to see the circuit employed by Thorn.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 30/04/2019 9:05 pm
Jayceebee
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Hi Andrew, the schools receiver was the 1540 series which employed a proper IF strip instead of the broad tuned PCB coils and I'm pretty sure it did have DC restoration , it also had a sinewave line oscillator using a PCF802. I was amazed to see a domestic version was produced for export, the TX250. I would love to see this set working https://www.radios-tv.co.uk/community/black-white-tvs/ferguson-model-3547/

John.

 
Posted : 30/04/2019 9:40 pm
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glenz75
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Thanks for that info Chris and Till 🙂

My You Tube Channel for those suffering from insomina - Youtube Glenz1975

 
Posted : 01/05/2019 12:41 am
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PYE625
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Today, I thought it was high time to give this set a run. So blow off the cobwebs, set up on the bench and switch on. Proof of the reliability of the 1500 once again is shown as it just simply works perfectly.

Slightly boring I know, so let's have a hair-raising experience from flinging back the curtains to see a hairy werewolf staring back at us.....

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To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 08/02/2020 10:20 am
sideband
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...if it looked a little more horrific rather than a cuddly teddy bear......!

 
Posted : 08/02/2020 1:59 pm
PYE625
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Haha....true, but watching the film it only appears for a moment and it's the surprise/shock factor as she throws back the curtain.

It looks like Bungle had a broader career than just Rainbow then. ? 

0 Rainbow

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 08/02/2020 8:03 pm
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