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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
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2nd May 2020, 10:30 pm | #1 |
Hexode
Join Date: Feb 2008
Location: Wrexham, North Wales, UK.
Posts: 466
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Portadyne U56
This is a really nice set. There's no printed service data for it, though a helpful amateur did draw a circuit diagram, albeit without the tuned circuits. There are no manufacturer's markings on the chassis and it looks and feels very like a Plessey job - solid steel chassis, nicely laid out for servicing etc. with good access to IFTs and coils to alignment.
It was in a poor state; the whole of the power supply with the exception of the dropper had to be replaced. The valve line-up is 6A8, 8K7, 6Q7, 25L6 and 25Z6 - 300mA series heaters, so the dropper is dissipating nearly 50 watts of heat! There's a metal shield over the top of the dropper, presumably to stop it setting fire to the case! The card back showed signs of burning just under the shield, so I replaced that bit with perforated aluminium for safety. It has a wire soldered to the shield and terminating with a 3mm plug which connects to the aerial socket - it's labelled "capacity aerial" and is better than no aerial! When I started on this set the first problem was a vicious 50 cycle hum. It turned out that the reservoir cap and both sides of the smoothing cap were completely open circuit. The reservoir cap was rather a nice looking TCC jobbie, so I drilled out the works and inserted a modern electrolytic into it. The cap from V3 anode to V4 grid looked dodgy, so I replaced it, along with a couple more waxies. Now comes the confession. I never, of course, try to clean glass dials with a damp cloth, but just dust them with a fine brush. Fortunately I had photographed it before removing it, as even the lightest touch of the brush removed all the white paint (the other colours remained intact). In the end I made up a dial and printed it on photo paper, glueing it lightly to the back of the dial compartment. Sooner or later someone will come up with a method of stencilling white paint onto glass, and I will then replace the original! The case was rather knocked about, so I stripped and French polished it. It's rather nice, with maple and I think walnut inlay. The speaker cone was quite fragile with a lot of tears and cracks - this got my usual treatment of rubber solution and tissue paper. But the performance of this set is remarkable. With just 16ft of aerial over what I optimistically term the "back garden" it pulls in all sorts of exciting stuff, especially on SW where both sensitivity and selectivity are exceptionally good. |
3rd May 2020, 3:36 pm | #2 |
Hexode
Join Date: Jun 2009
Location: Cheshire, UK.
Posts: 363
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Re: Portadyne U56
Good work, kestrelmusic . Glad you were able to recover the dial (potential) disaster!
That set looks like a substantial lump. Could you post anymore photos that show it's size (and the inside, of course)! It looks as if you're keeping yourself well occupied during the virus restrictions. |
3rd May 2020, 10:07 pm | #3 | |
Hexode
Join Date: Feb 2008
Location: Wrexham, North Wales, UK.
Posts: 466
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Re: Portadyne U56
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