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Old 27th Sep 2017, 4:29 pm   #1
Ancient Geek
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Join Date: Aug 2017
Location: Bristol, UK.
Posts: 136
Default First restoration: Regentone A155

So, my first restoration is complete, at least for now. I picked this set up from a local auction house. I chose it because it was redolent of my early years: an early VHF woody with a magic eye tuner, although it's not the one I remember us having as a small boy, which I believe was a KB NR30.

This set was filthy with tobacco tar and dust, some scratches and dents to the cabinet, but otherwise complete. The first step was removing the chassis, followed by a lot of cleaning. I discovered that WD40 is very good for cleaning tobacco tar from cellulose lacquered woodwork, but you need to be a little careful, as it does temporarily soften the lacquer a bit.

Step two was extensive reading of this forum to learn as much as I could before starting, followed by the construction of a lamp limiter. I identified 5 or 6 TCC waxies that definitely needed replacing, plus a few other caps that probably did.

I replaced the waxies, then reformed the smoothing caps as best I could with my max. 48V bench supply and then applied power via the limiter. The set came to life on LW, with no bangs or smoke. Emboldened, I switched to full power. Again no bangs. Pots very scratchy, lots of rustling, and very sibilant FM. Measurements showed all the secondary voltages to be about 10% high, despite the correct primary tap being selected. I elected to fit a 100R 10W wirewound in series with the primary, which sorted that out, and the panel lamp was replaced.

All contacts and wipers were cleaned with Deoxit, which made a big difference. Extensive reading of the forum suggested that the ratio detector DC load capacitor would likely be duff ( a Plessey red yellow and black one), so it was replaced. This did not improve the FM, and subsequent checking showed the original to be OK.

All capacitor replacements were carried out using the 'small coil of wire splice' method, which worked well. The EM80 was physically broken, probably when the AM dial cord was interfered with (more on that later), so I ordered a couple of 6E1P replacements from an Ebay seller in Moscow. When they arrived, I found that they worked well, but would not physically fit in the cutout in the rear dial plate, being too tall. I made an enquiry to Langrex, who assured me that theirs would fit, so I ordered one. Guess what? It was almost identical to the Russian ones. Having already thrown quite a bit of money at the set, I decided to bite the bullet and enlarge the cutout.

Having read that FM sibilance may be cused by alignment issues, I decided to have a go at FM IF and discriminator alignment, following the steps outlined on the trader sheet. I have an old HP 8116A function generator and a Rigol 'scope. I used an XR2207-based triangle wave generator as the modulation source for the 8116, via a homebrew opamp circuit to tweak the levels and to ensure it was centred on 10.7 MHz (the 8116 is out of cal).

I got nowhere with this, and ended up getting further and further out of alignment. I found a Youtube video ( https://www.youtube.com/watch?v=4Z2JCMavhr0&t=649s) showing a simpler method, which I found easy and, seemingly, accurate. The FM is now reasonable and less sibilant, although not impressive by today's standards.

I did encounter a problem with intermittent rustling, with was independent of the volume setting. Replacing the EL84 cathode bypass capacitor seems to have cured this.

The AM tuning was slipping, and I discovered that it was incorrectly strung, with the spring in the tuning capacitor pulley and the cord too short for correct stringing. I acquired some new cord and restrung it according to the diagram on the trader sheet with no problem.

Regarding the cabinet, I repainted the metal speaker grille and the gold rings on the knobs. Restoration was rounded off by replacing the twin core mains cable with a three core one and earthing the chassis. I decided not to attempt any further cabinet restoration, but live with the fact tht it's have a few knowck and scratches. I'm pleased with the end result -- AM reception in particular is very good.

As my other main hobby is photography, I thought I'd try and round this post off with a shot of the set with a period atmosphere, hope you like it. Thanks to all of you who offered helpful advice to a beginner to the world of glass bottles. Not a difficult restoration by the standards of this forum, but a satisfying one for me as a beginner.
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