Pye445 u

[Yorkie]

Come, come young David, 130R is an E24 value.
See, for example, ebay Item 390831358596.

Alan

True enough, but most suppliers seem only to stock the E12 decades. I must confess I only looked as far as ESR Electronics:

http://www.esr.co.uk/components/products...istors.htm

Hopefully, when Robin has checked out the individual sections of the two droppers, he'll find that some sections will still be intact.

Some people get round the problem of not having the correct value resistor by wiring more than one is series. The best (or rather worst!) example I've known of was when someone had an Ekco AC86 'professionally' restored and under the chassis there was a daisy chain of nine resistors in series! Some nifty handiwork with caps too! Insulation? That's for wimps! For those of a nervous disposition, the pics are best viewed from behind the sofa.

As the saying goes "Don't try this at home"!

[Skywave]

Could you not use a small transformer or capacitor dropper to replace?

Caution needs to be exercised when using a 'capacitor dropper' for this purpose. At switch-on, the cap. will initially look like a short-circuit, thus causing the filaments to be over-run for a short period: that does the filaments no good at all and will shorten their life.

David: your post above. That's not 'electronics', but 'bodgetronics': appalling.

Al.

[pwdrive]

The valve heaters and dial bulbs chain is a 200 ma chain in total, regarding R25 the two 100 ohm resistor sections across the dial bulbs will dissipate approx .36 watts each, the 1k ohm section will dissipate approx 10 watts, the 130 ohm section will dissipate approx 5.2 watts.

Regarding R24, the 450 ohm section will dissipate approx 18 watts and as a guess the 300 ohm section will dissipate approx 5 watts, I'm assuming that the 450 ohm section is part of the valve heaters/dial bulbs chain and that the 300 ohm section is the rectifier limiter.

The above is based on normal operation with 230 v mains input once everything has warmed up.

You might want to factor in what might happen if one of the valve heater goes open circuit...I didn't get that far.

I don't know why I wrote this..

Lawrence.

[Yorkie]

Very helpful info Lawrence.

We don't know yet which - if any - sections of the two wire-wound droppers are open circuit, but if the 450 Ohm one, dissipating 18 Watts is duff, personally, I'd be inclined to replace it with a 25 Watt or even 50 Watt metal-clad resistor as they have the merit of being relatively small and easily obtainable. They're only capable of dissipating their full Wattage if mounted on a heat sink and need to be de-rated by at least 50% if in free air - fitted to two existing tags of the dropper for example to bridge the faulty section. In that case, to have a margin of safety I'd be inclined to use a 50 Watt one, which is only 2" long. EG:

http://www.esr.co.uk/components/products...istors.htm

When Robin has had a good poke around with his Ohmmeter he might find the picture is rosier than it may seem at first sight.

On a set like that, with nine wavebands, I'd be more worried about the switchery in the front end.

But first things first - get the power supply working, then the AF and RF stages and keep my fingers crossed as to the front end behaving itself!

[pwdrive]

"Very helpful info Lawrence."

Yes, if I've got it right...!

Sometimes NOS Radiospares dropper sections come up on Ebay, they can be assembled on a threaded rod, not sure if they went as high as 1 k ohm can't remember, we used those RS sections a lot in the telly trade, "grapes on a dropper"

Lawrence.

[pwdrive]

That bodged AC 86 doesn't look very good for a restoration.

The multiple series resistor trick was very common in the telly trade for field service engineers working for the large rental outlets, it got the customer match of the day on a Saturday afternoon or whatever and the engineer out of a pickle, me included until the proper resistor arrived to replace the assemblage with, by which time the boss had moved you to another service area.

Lawrence.

[Radio Fixer]

Wow! David that 'pro' restoration makes me puke!

I have a large stock of mains droppers but without knowing the chassis I have no clue to how much room is available. Also at the moment finding time to go through them and measure and look for taps etc is a problem.

If the Poster can add some pics of whats there and wait a bit I might have something to do the job.

Gary

[singlepentode69]

Thank you for your replys there is no power coming out of the dropper heater section or any set totally dead .that cap has been changed for an x type.i have also changed thr0,05 for a new1kv type .Gary I will take some pictures tommorow and post them as I usually get the wife to do these as I am not that good at sort of thing .
Regards
Robin

[Yorkie]

Thank you for your replys there is no power coming out of the dropper heater section or any set totally dead. Regards
Robin

Have you checked each individual section of both droppers Robin, as shown in the attached diagram? It's highly unlikely that every section is open circuit. You can do that of course with your Ohmmeter with the set unplugged from the mains - far safer than having it plugged in and looking for voltages at each tag. Apologies if I'm stating the obvious and you've already done these tests and every one of the sections in both droppers are open circuit.

Presumably you've also checked all of the valve heaters for continuity? If they all test good out of the set, plug them into the sockets, then apply one prod of the Ohmmeter to the lead from the dropper to the heater pin of V5 that it connects to (pin 1 or 8) and the other prod to chassis. If the meter shows open circuit, that points to a problem with one or another of the valve-holder connections somewhere in the heater chain. Leave one prod clipped to the V5 heater pin/dropper junction, then as all of the heaters are pins 1 & 8 of the valve-holders, check at those pins of V4, V3, V2 and V1 till you find the break in the heater chain.

Again, apologies if I'm stating the obvious, but have you checked that the two poles of the on/off switch aren't open circuit, which is quite a common problem? If either or both poles are open circuit, you'll get no AC live to the droppers or neutral to the chassis. Once more, you don't need to check for mains voltage - just put the prods of your ohmmeter across each pole of the switch to see if you get continuity when you turn the switch on. If you do, with the set plugged into a lamp limiter, if you put your prods across C47 on the high AC Volts range, you should see mains voltage across that capacitor. Then with the set unplugged from the mains again, and your meter on the Ohms range, you need to check that the voltage selector panel isn't misbehaving when set to position 'C' - 225-250V.

Hope that helps a bit, but sorry if I'm trying to lead you down a path that you've already trodden!

[Yorkie]

Wow! David that 'pro' restoration makes me puke!

Gary

They walk among us, with 'delusions of adequacy'.

My theory is that such people were put on Earth so that the rest of us - however lowly - have someone with whom to compare favourably with!