A quick job on an R33

[AlanBeckett]

I bought this set as a replacement for my greenhouse radio. That's an export Pye - 49Y13 - with no Long Wave. It's feeling its age a bit and I can't listen to TMS while I'm in there so I needed something small that looked as though it would survive the trip.
The R33 is a late three valve plus solid state rectifier set with a PCB. The valve line up is UCH81, UBF89 and UCL83, so really it's 4 valve plus rectifier. Despite the U series valves it has an autotransformer for HT and Heater supplies. It's about 11 3/" wide, 5 1/2" deep and 7 1/4" high, including its feet, so it's quite small.
It all looked pretty good, so .....
Changed the plug fuse from a generous 10A to 3A.
Removed the knobs - wax and grub screws - and remove the chassis.
Checked the mains lead connections - black really does go to chassis.
Both poles of the ON/OFF switch were stuck on but a good dose of Servisol and some vigorous switching cleared it.
Switch on and heaters all OK, HT near enough to what the Service Sheet says.
MW OK but no LW. However, much crackling when tuning and when moving the frequency changer in its socket. A dose of Servisol and pin cleaning restored LW.
Removed the speaker and gave the case and back a scrub in the kitchen sink. They both appear to be moulded - expensive unless the volumes are high.
Gave the knobs a scrub. The big tuning knob is missing its Bright.
Changed the two Waxed Paper TCCs and a black moulded cap - can't read it but I guess it's the usual. All the rest are Ceramic, Polystyrene or Mullard Mustards. Perhaps I should suck them out, clean them up and put them on eBay
Checked a few resistors - they seem reasonable.
Put it back together and recheck - OK.
Make a new Bright for the tuning knob - it's just a bit of brass shim. Glue it in and polish it in the lathe. Found that my aerosol tin of laquer had set so it will have to tarnish.
And that's about it. It works quite well, as it should as it effectively has modern valves, and the UCL83 probably gives more gain than the old combination of Double Diode Triode and Output Pentode. It's a bit shrill compared with say my P75A, but in such a small case with that small eliptical speaker it's not surprising. Bearing in mind its destination I haven't made any great efforts to tart up the case, but as it's self coloured the scratches don't really show.
I'll soak it for a few days and then if all goes well install it in the greenhouse.
I'm quite pleased with it really.
Alan

                           

[ucl82]

That's a pretty little set. Well done Alan

Can't see any reason why it won't survive a greenhouse, so long as the cabinet (acrylic?) doesn't start to deform.
Moisture would be more of a problem with a woody set, and if your P75A survived well then I'm sure this will be more than up to the task.

[Joe]

Looks like a nice set.

I see you share my taste in capacitors as well.

- Joe

[AlanBeckett]

Joe,
It was more Horses for Courses.
The big white one underneath is an X 'cause it's effectively across the Mains, albeit after the autotransformer and protected by a 16R Resistor.
The one across the Output Transformer was originally an axial, but I only had a radial of suitable voltage.
The ones on the PCB just fitted nicely
Alan

[Yorkie]

An intersting post Alan - you'll be pleased with this radio. Once more, your post shows how handy it can be to have a lathe for such things as knob brights and other little radio related tasks.

The little Pye R33 table radio is one of my favourites. I came across two last year which I restored - very easy set to work on. It was produced in 1964, towards the end of the valve era and has some interesting features, with an eye to production costs. It used a PCB to reduce point-to-point wiring, making voltage and resistance checks much easier as the PCB-mounted valveholder connections and other components can be accessed from the top of the chassis.

Unlike many small radios, it doesn’t use AC/DC techniques (which obviates the need for a mains transformer but have undesirable heat-producing mains droppers a la DAC90A). As Alan says, instead, it uses an auto transformer, (no secondary – just a primary tapped at 66 Volts for the series heater chain). Thus, the HT is direct from the mains, so the usual precautions about live chassis apply.

Because the twin core brown flex - which appears to be original - isn’t colour coded, I checked the polarity and found that the line went to the chassis, so I reversed that. Although there are no exposed metal parts, the grub screws on the three knobs would have been live.

The set uses only three valves – UCH81 Frequency changer; UBF89 IF amp, detector and AGC, and UCL83 AF Amp and output. For rectification, it uses a small contact-cooled half wave metal rectifier, which curiously, is referred to as ‘V4’. The UCH81 and UBF89 have 19V heaters – the UCL83 is 38 Volts (all at 100mA) making a total of 66 Volts.

The second of the two sets I restored needed minimal work.

The smoothing and reservoir caps and one other are in one small can – two at 32uF, one at 8uF. Before being tempted to switch on, I reformed all three till the leakage was negligible, did a few checks, such as the continuity of the heater chain, and switched on. The first set worked, but at low volume, and with distorted audio. The input to ‘V4’ – the rectifier was 230V AC, but the output – which should have been 225V DC - was only 125V. Initially I thought the rectifier might be faulty, so I substituted it for a 1N4007, which brought the voltage up a bit, but not significantly, so I reverted back to the metal rectifier.

Then I did what I ought to have done in the first place – checked the smoothing and reservoir caps on my ESR meter. No wonder the leakage was low when I ‘reformed’ the caps. Two were fine, but the ESR on one of the 32 uF sections was so high it might as well have been open circuit. I therefore mounted a new replacement 33 uF under the chassis, and left the other two sections in use.

This brought the HT up to spec.

When new, the stated tolerances of most of the 16 resistors was 20%, with just two at 10%. I checked them all and found that four were out of tolerance by a good margin – 53%, 40% and 35%. One of the 10% resistors was 18% so I change that too, as it was across the reservoir and smoothing caps and may have had a slight bearing on the HT voltage.

I checked the ESR of the 25uF 25 V cathode bypass cap on the output valve (one of those red/black plastic encapsulated jobbies). Unsurprisingly, it was duff, so I replaced that.

There were two Hunts waxies, which I changed as a matter of routine (one had deposited all of its wax on the floor of the set, so had been getting hot). In this set, ‘that cap’ was in fact a 1000V disc, so I left it in situ as they seem not to suffer breakdown in the same way as waxies do.

I switched on and the set gave a very good account of itself, especially on MW. The audio quality and volume from the 6 x 4 speaker was excellent. All of the voltage checks showed that the set was now bang on spec – anode voltages up from 106V as found, to the correct level of 192V.

The last task was to fill the grub screws of the knobs with wax.

It’s clear that some of the design features, such as the use of an auto-transformer, metal rectifier and PCB had an eye to costs – perhaps in the face of rising competition from 'the land of the rising sun', and cheaper to produce transistor radios, but this also helped keep the set compact, and overcame the heat problems that would have arisen with a mains dropper and a valve rectifier, given that the cabinet is injection moulded plastic.

By 1964, the transistor era was well established (the Bush TR82 series was launched in 1959 and the Roberts R200 in 1960) so this little Pye was perhaps one of the last valve models to go into production.

The replaced components above and below chassis can be seen on the pics, as can the metal rectifier on the rear apron of the chassis.

Beauty is in the eye of the beholder, but I think it’s a very attractive little set which deserves its place on my now cramped display shelves. I rather like little sets such as this, the Murphy 198 and the KB Toaster.

I keep a look out for Pye 33s and if I see another, I'll snatch it - you can't have too much of a good thing!

David

[Retired]

Hi,

Well done Alan and thanks for adding the thread. Where would we be without our lathes to play with; the new bright looks the part. Is there any truth in the story that plants grow better with good music played to them?

I'm currently working on assembling the ESR instrument as David very kindly sent me one of his populated circuit boards quite a while ago together with detailed instructions on both the meter and also how to make a router jig for cutting comb joints. The router jig is just brilliant and I made the instrument box easily but I had a disastrous weekend and managed to zap components on the circuit board. The good news is David that I've now got 5V on pin 14 of the chip socket after replacing the regulator and once the new chip and transistors arrive I hope to have the instrument in full working order. I bought the components through eBay at rock bottom prices. So far its ten out of ten for making the box and none out of ten for zapping the components; I must try harder!!

Kind regards, Col.

[Joe]

I think this is another for my 'Wanted' list, not for its looks but for technical interest.

As an aside, when were the last 'mass-market' valve sets made?

- Joe

[AlanBeckett]

David,

Yes, it is an interesting set, and easy to work on, but I thought it had anomolies which I thought didn't quite go with 'Cheap and Cheerful'.
It does indeed have a PCB, but it also has quite an elaborate chassis, not just a bit of bent tin.
The Autotransformer may well be there because the moulded case wouldn't stand the heat of a dropper, but surely it would with a suitable heat deflector. Mind you, I much prefer the transformer.
The moulded case itself must have cost a fair bit in tooling, so why not go the whole hog and get rid of (most of) the chassis?
The back is moulded as well. Could that really be cheaper than the usual cardboard or Elephanthide back? Perhaps so once you'd paid for the main tooling.
The knobs are moulded but have quite a hefty brass(?) insert for the grub screw - see attached. Why not just the usual clip?
On the cost reduction front there's no dial illumination, external aerial socket or means of rotating the Ferrite Rod. I suppose none of those things mattered on a 'Kitchen Radio'.

As far as mine is concerned the mains cable is Red and Black. It looks authentic but who knows. Anyway, the black goes to the chassis which keeps me happy.
My knob bright isn't very authentic really as it should stick out, and I did think of using a thicker piece of brass. However, I didn't in the end and I think it looks acceptable - it'll do for the Pit.

There was a previous discussion somewhere on when the last valve radios were produced. If I remember rightly it depends on where you are in the world. East Europe and China carried on long after us.

Finally, did they come in other colours or just this Red/Maroon?

Alan

[AlanBeckett]

David,
I've just noticed on your picture that you've left C22, a Hunts(?) Moulded installed. Was it OK?
I changed it along with the two waxies.
I thik I'm going to take the chassis out again as the hum is more than I would expect. Not obtrusive when on a station but it's there in between. I've got a 32 + 32 I think, and the 8 can be a tubular.
Alan

[attachment=2497]

[AlanBeckett]

I decided that I'd bite the bullet and put it in the greenhouse. I've half convinced myself that the hum is improving. Anyway, I can always replace the elctrolytics at a later date.
Alan