Restoration Strategy - Ferranti U1032

[Martin G7MRV]

Chaps,

I am now in possession of a Ferranti U1032 AM/FM table receiver, and beginning to restore it. On inspection (visual) it seems to have little wrong other than needing a darn good clean, it's full of dust, and grimy outside. Little looks amiss internally other than the big multi-electrolytic is bulging, and a number of waxy caps have dripped. Only one component looks to have any heat related damage.

What I'd appreciate is ideas on a restoration stratagem. My plan so far is as follows -

1. Seperate chassis from cabinet.
2. Throughly clean cabinet inside and out.
3. Seperately, clean the dial glass very gently!
4. Hoover the dust out the chassis.
5. Replace the mains lead (original perished).
6. Replace the bulging electrolytic (possibly restuffing the original can).
7. Replace the 'waxy' caps *
8. Test and replace any resistors that look 'off'.
9. Power up slowly via a variac (I dont yet have a variac, so this could take some time!).
10. Align and soak test.

What are the experienced restorers thoughts on this proposal?

There are a couple of things i'd like advice/clarification on before I start -

1. There are two runners inside the cabinet for the chassis, which seem to be made from some fibrous white material, can anyone advise what this is?

2. *I hear the term 'waxies' a lot, but haven't seen a real definition as to what this really refers to! This set seems to have a number of wax coated capacitors that look like silver mica types to me, and also a few cyclindrical wax filled types. These cylindrical ones are all Hunts, and ive heard that name enough times in negative comments to appreciate that I ought to change them anyway! But what about the 'square' ones?

3. What is a safe way to clean the valves without removing the printed markings?

So far, I have removed the chassis from the cabinet, and removed the loudspeaker and dial glass from the cabinet. I have also removed the valves from the chassis to clean seperately.

[Herald1360]

The critical "waxies" (think of it as a generic term for paper dielectric capacitors) are any whose leakiness may cause serious problems like output valve/transformer failure or burning out another component.

In most sets, these are just the coupler from audio driver anode to output grid, any tone corrector from output anode to 0V, any old mains RF filter capacitor plus anything else used for decoupling where HT applied to any series resistor would cook it. Leaky decouplers may affect performance, but it's usually safe enough to diagnose them with a voltmeter once the set is running.

Wax covered silver micas are usually OK.

Valves- apart from a light dusting, why bother? They won't work any better for it. (Pins excepted, of course).

If you replace the main electrolytics, there's little point in a variac- a simple lamp limiter will stop any major fryups.

Otherwise, sounds like a perfectly good plan of action.

[Mike Phelan]

I'd add any AGC decouplers to the wax cap list as it's a very high impedance circuit.

Don't spend any money on a variac, not needed.

[Martin G7MRV]

OK, so, looks like we have a plan. I understand this set was working not so long ago, so much of the work is precautionary. It looks like cleaning it up and doing some hardware work will be the main jobs (the original back panel is present but has a few issues to repair).

I understand then that the idea of bringing it up to full working voltage on a variac if in order to try and reform the original electrolytics? But if I'm changing them anyway I can see how that wouldn't be needed.

As for cleaning the valves, they are very dirty, so the idea is to give them a once over to remove most of the muck, but hopefully without removing the print. I've lots of baby wipes (due to having a baby...) so might give those a go. I'll try very gently at the edge of the print to see what happens.

[Herald1360]

For electrolytic reforming, a variac may work if the set has a solid state rectifier, but not very well even then. Best is to apply the working voltage to the capacitor via a high value resistor. Size the resistor so that it can pass only a few mA even if the capacitor is shorted and won't cook at that dissipation level. Monitor the voltage drop on the resistor- if the capacitor is reforming it should fall off with the increasing insulation resistance. Once it falls to (say) half its original value, you could try adding more resistors of the same type in parallel to speed things on their way....

Their are some circuits for dedicated reformers around in the forum if you search, but working voltage can of course come from the set itself- disconnect the HT feed to the set from the smoothing circuits and put your resistor between the rectifier +output and the reservoir capacitor. It's worth noting that the unloaded HT supply voltage may well exceed the capacitor voltage rating especially on a "budget" set, so keep an eye on the actual voltage on the capacitors as well as resistor drops.

Be careful especially if it's a non isolated set!

[Steve_P]

Why change the smoothing electrolytics if they are OK? If they are faulty, and you'll find out by way of a loud buzz if they are, then OK, change them.

If they are not faulty, why change them?

Don't fall into the trap of CCCD - Compulsive Component Changing Disorder. The only benefit from that is capacitor manufacturers, and you won't learn anything.

The manual is here: http://www.service-data.com/product.php/2168/2904 and it is money well spent. Just change the O/P stage grid capacitor (C51) and the AGC capacitor (C23) and go for it.

The only other likely problem is VHF, and the valve, UCC85, is probably the problem here. It's also a good idea to have the dial lamps working to warn you that the set is still live.... and check that the chassis is connected to neutral.

Cheers,

Steve P.

[richrussell]

The 'fibrous white material' that the runners go against is just felt, nothing to worry about. It's there to stop vibrations by ensuring a snug fit for the chassis.

I tend to replace all wax coated paper capacitors on sight (the cylindrical ones) if they look like they've swollen or melted, and I check the resistance of any burnt looking resistors are within 10% of what they should be. If the electrolytics look unwell, I'll replace them too - either by stuffing new ones inside the original can, or under the chassis depending on what's neater. But if they look clean and in good condition, they'll generally sort themselves out in the first few minutes of the set being on.

I take out all the valves and clean the pins gently with glasspaper and contact cleaner, and give them a wipe if they've got thick greasy dirt on them. But if it's just dust, just blow off the worst. I clean the valve sockets with a fine round file to just take a bit of any coated dirt off, whilst checking they're still springy.

Then bring it up on a lamp limiter gently (volume set to zero) to see if it draws excessive current. If the bulb brightens then dims I'll turn the volume up a little and see if it'll tune anything in. If it gets something, I'll clean the case, and then shut it down and reassemble it all.

[westcliff]

Don't let a baby wipe get anywhere near the printing on a valve! It's not called "wipe" for nothing. I found out the hard way with an EL33.

Gus.

[ukcol]

Hi Martin

If you haven't done a lot of radio restoration before its a good idea to take lots of photographs. Even cheap cameras commonly have a a macro function allowing you to take close ups.

This gives you a before, during and after record to look back on and has the added advantage that if you make a wiring mistake, or a wire comes adrift during the work, you have your photographic record to help you.

Colin M

[Sideband]

Originally Posted by Steve_P

Why change the smoothing electrolytics if they are OK? If they are faulty, and you'll find out by way of a loud buzz if they are, then OK, change them.

That's quite true but the OP pointed out that the electrolytics were bulging which is not a good sign. They may be OK at the moment but probably won't last. If I see bulging electrolytics, I replace them.


Rich.

[Nickthedentist]

Going back to one of your original Qs, the "Hunts" and similar capacitors that I would change are all the tubular ones with a value (roughly) between 1nF (0.001uF) and 500nF (0.5uF).

More info here. The top two types are the ones you're most likely to encounter: http://www.vintage-radio.com/repair-...apacitors.html

Apologies if this has been said above.

Nick.

[Martin G7MRV]

Originally Posted by ukcol

Hi Martin

If you haven't done a lot of radio restoration before its a good idea to take lots of photographs. Even cheap cameras commonly have a a macro function allowing you to take close ups.

This gives you a before, during and after record to look back on and has the added advantage that if you make a wiring mistake, or a wire comes adrift during the work, you have your photographic record to help you.

Colin M

This will be the first restoration, but ive been a comms engineer for 20 years. I learnt a long, long time ago to take photos of every stage! I already have this set photographed inside out before even thinking of touching anything.

I'll be changing the miniumum I can get away with, which will probably be the big electrolytic (bulging) and the Hunts cylindrical waxies (most of the wax is in the base of the cabinet!)

Thanks for the info on the runners. I'm happier with them now.

[richrussell]

You're welcome to borrow my lamp limiter if you haven't made one yourself, or have something else to limit the supply current when you first power it up. It's a handy thing to have as you can immediately tell if something's wrong and prevent damage. I'm just a mile or so out of Selby, on the Camblesforth Road.

[G0HFCFrank]

I can only add one thing to the advice above, don't just check the ugly resistors; the beautiful clean shiny ones often go high too.

[Martin G7MRV]

Originally Posted by G0HFCFrank

I can only add one thing to the advice above, don't just check the ugly resistors; the beautiful clean shiny ones often go high too.

Sound advice!

My first electronic task is going to be the 40+40+30uF electrolytic. I have it out of the circuit, and its innards gone, removed using specialist tools (hammer and chisel), I plan to replace the innards with modern equivalents, so that part at least from above looks authentic.

My only question is, how close in value do i need to be? All three are part of the smoothing post-rectifier. I would have thought going up to the next nearest modern prefered value for each would be fine, is 47+47+33uF? In fact, the service sheet shows the 30uF as 32uF anyways.

Apart from taking this cap out, and giving the chassis a damn good dust with a soft brush, ive worked on the cabinet, which has had a good going over with warm soapy water and a toothbrush in the grooves and on the knobs. The dial glas (which i removed earlier) cleaned up beutifully with very gentle and careful application of a baby wipe. The rest of the cabinet is now in the airing cupboard. It was thick with dust and melted Hunts wax! and took some cleaning.

[Martin G7MRV]

Originally Posted by richrussell

You're welcome to borrow my lamp limiter if you haven't made one yourself, or have something else to limit the supply current when you first power it up. It's a handy thing to have as you can immediately tell if something's wrong and prevent damage. I'm just a mile or so out of Selby, on the Camblesforth Road.

Thanks for the offer. I'll see what i have about to make one up first, but might give you a shout if im stuck. Incidentally im the other way out of Selby, over in Hambleton

[Herald1360]

47+47+33uF will be fine. The only one to worry about is the reservoir, but a UY85 can cope with up to 100uF. Just make sure the ripple current rating is adequate.

[Martin G7MRV]

Good stuff. Theres a few other electrolytics that i might do at the same time as this one and the waxies, but i can get away with a lower voltage rating on those.

Time to start shopping. Blimey these high voltage caps are priced steep!

Having seen the price being asked for the 33uF caps, im wondering if i can get away with 47+47+47uF?

The 30uF is the third cap across the HT rail, after a 820r resistor, the HT to the audio transformer comes off before it, the two 40uF and a 330r are between this and the UY85, so im thinking its not too critical and a 47uF would serve ok in that spot? It means the contents of the can are no longer as marked but thats hardly a major issue

[Herald1360]

47uF will be fine for the 32uF spot. Apart from the reservoir the others have hardly any ripple current and within reason, the more uFs the merrier.

Not sure what expensive means- Farnell do this:

http://uk.farnell.com/panasonic/eeue...0mm/dp/1673482

for about £1-40 inc VAT which should do fine given the quoted 243V for UY85 cathode when the radio is running.

though you could spend three times as much if you wished.

33uF is probably expensive 'cos it's not in the basic 10 - 22 - 47 range of values.

[Martin G7MRV]

I think i was just a touch surprised at the greater cost compared with 35v and 63v rated caps! Knew they'd be dearer but wasnt expecting such a jump. Ive seen the 47uF for a quid a throw, but the 33's were at least three times that.

My only problem with using Farnell/CPC or RS is the shipping costs on low orders, or reaching the minimum for free shipping. This isnt likely to be a big order, and its rare these days that i can tag onto a works order anymore.