'Figaro Special'

[Yorkie]

I collected a little Polish Unitra 'Figaro Special'  woodie  from a VRF member at Redditch for a fiver last May, when I was down that way for the NVCF.  It was minus its back and one knob was missing. From pictures I've come across on internet I've been able to draw a replica of the back, and have now got round to making one. I used the pattern for cutting the panel to shape and drilling the holes, then I printed the diagram minus the marking for the holes, onto a piece of light brown Windsor and Newton art card, which I then sprayed with a couple of coats of lacquer either side. I stuck the card on with Titebond, using a wallpaper roller to firm it down, then when dry, cut the holes in the card with a small craft knife. I just need to make a little thin clear plastic  widow for the 'Voltage setting aperture'.

The cabinet is sprayed with cellulose lacquer which will need stripping and re-lacquering, but that's a summer job.

Haven't checked the electronics to see if it's working - it uses an auto transformer. A weakness on these sets is the wave-change switch but this one is fine.

I've got some 'alginate' casting powder to cast a new knob using the existing one as a pattern.

I rather like these little sets - I've got the plastic version which is restored and works very well. They use a little DM70 'exclamation mark' magic eye.

This restoration is a 'slow burner' - it's taken seven months to get round to making a back! When/if I've got something worthwhile to add to this thread I'll update it.

[Radio Fixer]

Great back David. Brown paper gives realistic finish.

Gary

[Yorkie]

Thanks Gary.

At first I tried using normal brown wrapping paper onto which to print the design, but it all seems to be slightly 'striped', which is quite noticeable close up.

Couldn't find any brown A4 sized paper, so I got a large sheet of 'art paper', - don't know what size it is, but it doesn't correspond to A2/3/4 sizes.

I managed to get five A4 pieces out of a sheet with just a bit of waste.

Cheap enough from 'The Range'.

I need to make a bottom for the radio now.

Howard Craven restored a Figaro Special back in 2012 and you can just see the style of the bottom, which is vented with holes, and slides into 'runners' on the underside of the cabinet:

http://www.vintage-radio.net/forum/showt...hp?t=88284

The bottom panel is just visible in this picture and I can see that there are staggered rows of holes:

http://www.vintage-radio.net/forum/attac...ntid=70734&d=1347920083

I've drawn a sketch of what I think the panel looks like, and have e-mailed the attached sketch to Howard to ask is he'd mind checking it to confirm that I'm on the right lines.

Ordinarily - like most people I guess - I tend to leave the cabinet till last, but I thought I'd sort that out first on this set. I can't see anything untoward about the chassis and no visible signs of tampering, so I'm hoping that 'lady luck' will be on my side! I think they're noted for the selenium rectifier failing, but if so, that easily sorted.  Although it's compact, the chassis isn't too crowded, and the use of an auto-transformer rather than a dropper ensures that there's no excess heat  in the cabinet.

[Yorkie]

I've made some progress with this little set. The two section 32uF smoothing cap wouldn't reform, so I stuffed that, using miniature high ripple rating caps from Farnell.(On reflection, I could have drilled through the centre of the two positive terminal rivets to put the + leads of the new caps through, rather than drilled through the plastic base, but it's neither here nor there). It's a screw fitting cap, 25mm diam x 35mm tall, and I didn't think I'd easily find a replacement, though I later discovered that 'askjanfirst' in Germany stocks them at a reasonable price, albeit plus P&P.  Useful to bear in mind for the future.

I noted the absence of an HT load resistor which should have been across the two sections of the cap - 1k2, and had a suitable 4 Watt wirewound one to hand so fitted that. The auto-transformer and output transformer windings were all intact, and the valves all lit up, though not the DM70 magic eye, which had an open circuit filament. There are no stated Voltages on the circuit, but on checking the AC output of the auto transformer is was 160V AC, and the rectified DC output of the contact cooled rectifier was 165V DC, so the rectifier seems in good shape.  Since the pic of the chassis below was taken, I've replaced all the paper caps as a matter of course, though haven't, as yet, checked the old ones to see if they were leaky. Most of the resistors were well within spec, though one - a 2M2 - had gone high and was 4m8 so I changed that.

Though the HT around the valves looked OK, there wasn't a peep out of the set and a signal injected to the audio stage produced no sound. Well it wouldn't do if the speech coil of the speaker was open circuit! Never though to check that when carry out initial tests. It's an elliptical speaker and as the set is so small a replacement would need to be the same size. I did an internet search, more in hope than expectation, and found a firm at Bognor Regis selling just the right thing at £5.89 post free. It's a general purpose speaker with several alternative mounting holes.  All I had to do was to carefully trim away the surplus metal around the rim and file the edges to shape, using the old speaker as a template. I took the precaution of taping up all the holes in the speaker frame to obviate particles of steel being drawn into the speaker through the magnetic field.

I've managed to find a N.O.S DM70 magic eye for £5.99 plus £2.90 P&P (Buy it Now) on ebay, which couldn't have been better packed had it contained the crown jewels. The circuit of the set contains an error in the it shows the filament being fed from 'point B' yet there is no such point shown.  The actual feed point for the 1V4 heater is tag 6 on the auto-transformer, which the circuit shows as going to ground.

As well as the cabinet being minus its back, it didn't have a base either, so from pictures I found on internet, I've made a replacement base for it. It was also missing a Bakelite headed M3 screw which attached the chassis to the cabinet (one of four), so I used one as a pattern to make an alginate mould, and cast a head onto an M3 stainless steel screw, using 'Super Steel' epoxy, which sets black. The cabinet itself had a few chips  and scratches in the gloss lacquer. I toyed with stripping it back to the bare wood, but didn't think it warranted that, so I gave it several coats of polyurethane spray, cutting it back with a U-Pol pad after each coat.

Still some work to do, including casting a new knob, but as time permits, this little relic of the Cold War era is coming together nicely.

Some pics attached.

Hope that's of interest.

[Yorkie]

A few more pics.

I mentioned that I cast a new chassis fixing screw using an original Bakelite headed one to cast a replica. A few comments on that might be of interest. I used 'Alginart' colour change standard set moulding alginate. It's 'skin-safe' and is used for such things as casting moulds of new-born babies feet and hands, which apparently is a thing that some parents like to do!  It came in a 450G pack, and you mix one part powder to three parts water. You add the powder to water and mix it while the colour is bright pink, then as it turns place pink you put the object into the mixture and leave it in place till the alginate turns white, which takes two or three minutes. For something such as screw-head I wished to cast, or a radio knob say, the screw (or for a knob the securing boss), must be accurately concentric. Hence, I made a simple little jig to hold the original pattern screw central, then did likewise with the M3 screw onto which I wanted to cast the new head. I made a couple to be sure.

Roll on the day when we may be able to get parts made on 3-D printers at a sensible price. Not quite there yet.

There's also a pic of the ventilated base that I've made. (I offset the holes, but I think the original holes might have all been in line).

I have one knob - the other is missing, so I intend to use the knob to make a mould, and whereas the original knobs are push on types (not a good idea on what is basically, an live chassis radio), I'll turn some brass shaft inserts drilled 6mm, and cast them into the new knobs, then fix them with a 4 BA grub screw, which can be sealed with wax. I'll make a pair and will most like use two part Ronseal wood-filler as the casting medium. It's quite fluid when mixed, sets rock hard and is 'natural' in colour, so hopefully, will spray up nicely in the desired colour of beige. Time will tell!

Sorry the pics of the screw heads are indistinct - that's due to the limitations of my cheapo digital camera. )I have no interest in photography beyond taking 'snapshots').

The first pic is of an original screw used as a pattern, the second pic shows it suspended in the alginate, the third pic is the vacated mould, the fourth is of the newly cast screw ready to remove from the mould, and the fifth pic shows the original screw alongside two that I cast. The final pic is of the baseboard that I made.

Lots of fun for little cost - if I keep doing this stuff, maybe one day it might stop my kids putting me in a home!

[Terry]

The circuit of the set contains an error in the it shows the filament being fed from 'point B' yet there is no such point shown.  The actual feed point for the 1V4 heater is tag 6 on the auto-transformer, which the circuit shows as going to ground.

David, there is still an error in your redrawn circuit - the other end of the filament winding is floating!

If the filament of the DM70 is on tag 6 then tag 7 must be ground. This means that the tags 6 & 7 on the schematic are reversed and  tag 6 is Point 'b'.

The revised schematic should look like this:

   

[Yorkie]

Thanks for reading the thread and for spotting that Terry.

Given that it's an auto transformer, and hence, doesn't have a secondary, (or does it - just for the 1V4 windidng?) -  I find the way they've depicted the tappings on the circuit a bit confusing. The drawing of the transformer is a bit odd to say the least, to my simple mind!

It shows points 1 & 7  on the same tag, but point 1 on the circuit is the 240V AC input, with point 2 the 220V tapping, point 3 the HT into the rectifier,  point 4 the 6V3 heater tapping, and point 5 the ground.  Hence, if point 7 is commoned with point 1 (240V input), then  point 5 must be the other end of a 1V4 winding, which seems a bit odd. I've attached a diagram of the transformer tags, but haven't had chance to run my meter over the windings to see how they check out, but I know that there's 1V4 between tag 6 and the chassis. 

Many thanks for your input Terry.

[Radio Fixer]

All coming along nicely David: must make an article me thinks !!

Gary

[Terry]

There must have been a transformer change in production which doesn't match your schematic.

From what you've said, it would appear that the tag numbering on both windings have been reversed so that tag 1(and 7) on the transformer equals tag 5 (and 6)* on the schematic and so.

I will be interested to see what result you get from your investigation.

* Before I reversed 6 & 7 on my version of the schematic, of course!

[Old Sparky]

Yorkie, can you post a link to that firm in Bognor Regis who supply speakers? They sound a useful firm to know