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Ferguson 3645 16" portable.

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Focus Diode
(@focus)
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Posts: 729

Just a few loose ends before considering the set fully restored.

The intermittent "ticking" suggests an impending breakdown of the doubler so the three stick rectifiers, which appear to be the originals, will be replaced by HV diodes. Fortunately these are so small they should fit inside the original stick rectifier tubes.

I'll replace the 2M2 height control as well, thanks again Malc.

I've written off the original system change as it's likely the switch point itself is at fault. I had the same problem with a 23" model which responded to having the full system switch replaced. The chances of getting a replacement now would be near impossible.

I should get away with a mechanical slider protruding from the lower centre right of the set on looking at the front, IE: push for 405 and pull for 625.

Then, sort out the VHF telescopic aerial which has come away from the rear back fixing.

Then, full adjustment and cleaning.

It's already looking like a great little set. They're certainly great survivors these 1400 sets.

IMG 20181017 212111
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Topic starter Posted : 18/10/2018 4:11 pm
Focus Diode
(@focus)
Honorable V-Ratter Registered
Posts: 729

The diodes were fitted within the EHT tray and the height control replaced.

The latter didn't help the maximum control setting enabling the height to just fill the screen.

Guess what? The VDR kindly supplied by Malc finally solved the problem when fitted to the X2 position. I don't know if it's old age or storage conditions that led to two of the thermistors to act up. They both looked to be perfect condition.

Unfortunately it's not the end to the problems. The width is still not what it should be even with the control at maximum. It shows up worse on 625-lines. It's thus not possible to adjust the test card for a correct centre circle. Having changed just about everything that could cause the fault in the line output stage it's time to focus on the line oscillator.

One thing I wasn't happy about doing was cutting a slot in the back cover to enable mechanical system switch changes without having to remove the back cover. 

The set's now otherwise working really well. 

They're great survivors these 1400s. I though they were doing well working into the '80s!

First pic 625 UHF, second 405 VHF.

IMG 20181101 145915
IMG 20181101 145943
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Topic starter Posted : 01/11/2018 4:20 pm
crustytv liked
Focus Diode
(@focus)
Honorable V-Ratter Registered
Posts: 729

This is the best adjustment available at the moment. I can't get the boost voltage to exceed 640V on a locked picture. It rises considerably on a blank channel however. I'd expect some variation but does seem excessive. 

I'll look into the line osc. and flywheel DC amplifier stages to see if there's something amiss here.

IMG 20181102 210321

 

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Topic starter Posted : 03/11/2018 12:18 am
crustytv liked
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