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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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22nd Jul 2006, 12:43 am | #1 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,129
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Regentone A133
As discussed elsewhere on these forums, this set is the result of using parts from a set acquired through eBay (referred to as set “b”) to replace missing parts from a set donated by a forum member (set “a”).
Although set “b” was electrically complete, and was probably in something approaching working order (it looked OK below decks), it had suffered badly from damp causing rusting of the exposed side of the chassis. I therefore chose not to try powering it up. Set “a” was generally sound, but was missing its mains transformer. Apparently a substitute transformer had been fitted, which was more use to the donor of the set than to me, so was removed prior to my acquisition. It was also missing two of its five valves and had a damaged rear panel. On removing the chassis of set “a” from its cabinet the first sight that greeted me was a set of replacement electrolytic capacitors (two pairs of 8µF to make 16+16µF) wired up floating beneath the chassis to replace the existing 32+32µF can, which had been taken out of circuit. I removed these, along with a piece of extra circuitry (whose purpose I did not ascertain) consisting of capacitors, wirewound resistors and a solid-state rectifier, which was clearly foreign. Having decided that I preferred the look of the electrolytic from set “b”, I installed this in set “a” and reconnected the components as per specification. Next, I transferred the mains transformer from set “b”, along with the valves needed to fill the empty sockets. I also fitted a new mains lead. All the waxed paper capacitors looked distinctly unwell, so these were all changed (apart from one in the tone control, which I couldn’t be bothered with as I didn’t have a suitable replacement, and didn’t consider urgent). At this point I decided to power up the set (using a variac to bring it up gradually over a number of hours). By the time I reached somewhere between 150 and 200 volts, I was clearly getting crackles that could be varied by the volume control, so I knew the AF stages were working. I now encountered the phenomenon known as “microphony”. I had heard of this, but never actually encountered it quite so unmistakably before. If I tapped anywhere on the set, the sound of doing so was emitted loud and clear through the speaker. Tapping each valve in turn identified the EBC41 as the culprit – it made other nasty noises when I did so. Fortunately, substituting the valve from set “b” cured this. I now had a set which could pick up Radio Scotland but nothing else, as described here. Having obtained a replacement ECH42 (oscillator/mixer) to no effect, this was finally traced to a leaky 65pF capacitor dragging the voltage on the oscillator anode down to about 30V from the intended 94V. When I replaced this (using three 22pF ceramic capacitors in parallel), I found the set sprang into life, with stations on all three bands (SW/MW/LW). Finally, I ought to say a word or two about the cabinet. Again, I decided to go with the cabinet from set “a”. Neither was brilliant, but this looked the more easily redeemable, but with the tuning dial, speaker grille and plastic trim from set “b”. I resprayed the speaker grille using Plasti-Kote “antique gold” – slightly darker but quite an acceptable hue. The cabinet had what I can only describe as “brown stuff” in patches over the walnut veneer, which did not respond to scrubbing – merely resulting in scratches to the varnish. In the end I decided to try surgical spirit, which certainly worked, but gave me a bit of a fright when I discovered that it had partly dissolved the varnish, making it sticky. I discovered, however, that once it had dried I was able to polish it up quite successfully. I’m not sure that I would want to risk this again, but I got away with it this time. Having reassembled the set (including the back from set “b” and just about a full set of screws and washers between the two sets), it just remains to reiterate my thanks to those members of the forum who have helped me to resurrect this set. I have taken a photograph of the finished set, but it may be some time before I can post a copy here, as my camera is of the old-fashioned type which needs a finished film to be sent off for processing, and I haven’t finished the film yet. When I do, a number of pictures might find their way to various parts of these forums. |
22nd Jul 2006, 8:56 pm | #2 | ||
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,853
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Re: Regentone A133
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Look forward to a picture. Do get yourself a digital camera... they're SO useful, even if you're a film fan and plan to stick with film for most things. Even the tiny £40 ones (often branded Vivitar) that Woolworths and Argos sell give excellent results in daylight (so long as you don't need decent flash or macro facilities). Nick. |
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3rd Oct 2006, 5:42 pm | #3 | |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,129
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Re: Regentone A133
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