Have I missed anything to get this set working?

[AmateurRepairer]

Hi all this is just a basic question about my Murphy U198H I am restoring.

I’ve removed and replaced the wax capacitors, I’ve cleaned up the tuning capacitor, all major contacts have been cleaned and I’ve lubricated all the mechanical mechanisms. I’ve also cleaned the wavelength selector switch so there is no dead spiders inside (was full of them)

My audio output transformer fell apart but luckily a forum member close to me has a suitable replacement that may work, hooray!

I don’t think the set needs realigning as the guy who had it before me had it working until about 5 years ago. It only looks to have failed because one of the wax caps had melted everywhere, what a ****** job to remove all that it was.

Thanks all.

[AmateurRepairer]

I’ve also replaced just one of the hunts caps, as it was the only bad one. Only on the tone control so I probably didn’t matter anyway to be honest.

[Graham G3ZVT]

So how does the set perform? Or aren't you ready to try it yet.

I'm not one for bulk replacing capacitors, I even leave wax-paper ones alone if they are not giving trouble or in critical positions, but all Hunts brown mouldseal caps get changed on sight!

[Beardyman]

I've restored one of these & all the Hunts capacitors were split/crumbling or way over value (electrically leaky), I think there was one that was totally open circuit too which caused the set to "motorboat", it was hidden behind another component so I'd missed it. Hunts moulded capacitors do not have a good reputation, usually they are a "change on sight" whether they look good or not. These sets do give a very good account of themselves, ample volume & quite a big sound.

[Techman]

Originally Posted by AmateurRepairer

It only looks to have failed because one of the wax caps had melted everywhere, what a ****** job to remove all that it was.

Melted wax has no relevance to the state of the capacitor (many of them look like that), although being of that type it will probably exhibit some leakage at its working voltage.

Replacing all the capacitors in one go before powering up the set to assess its working condition is the wrong way to go about things. you should first look at the circuit and see which capacitors are 'critical', either across the mains and likely to go bang, or have high DC voltage on one side, as in a coupling capacitor to an output valve grid, also any in such a position that bad leakage will drag HT down through the output transformer primary to chassis and damage the transformer. These should be dealt with along with any other dangers such as shorting wiring etc. Then the set should be carefully powered up, perhaps with a series lamp limiter for a brief period to assess the state of play of any burning or warming of smoothing can capacitors. After this, normal fault finding should take place to replace only genuinely faulty components that are likely to compromise the working and safety of the radio.

[AmateurRepairer]

The ones I have replaced were mains voltage techman. One was 1000v.

It did power up before apparently in the last 6 months but the bloke said after the cap melted it didn’t power on. Guessing I’ve solved the problem by replacing it. And the fuse in the plug as that had blown.

Rambo - I am ready for first switch on when I can go and fetch a new sound output transformer from a fellow restorer local to me.

Beardyman - a new multimeter is on its way so I will test the hunts individually soon, I have already tested them but my old me was dicky anyway

[kalee20]

Originally Posted by rambo1152

I'm not one for bulk replacing capacitors, I even leave wax-paper ones alone if they are not giving trouble or in critical positions, but all Hunts brown mouldseal caps get changed on sight!

I actually DO change wax-paper ones. And yes, agree about the Moldseal, these are a no-no!

I'd defend AmateurRepairer's work, TBH. Granted, starting from scratch, it's probably better to have a look-see at the circuit, and just replace those which are likely to cause trouble, (as Techman says), get it going, and then do the rest - on the basis that extra faults may have inadvertently beef caused during replacement.

But, it's done now anyway. And with new capacitors, these are hopefully above suspicion whereas leaving old ones in, may well have had the radio working, but it wouldn't have given of its best.

[AmateurRepairer]

I have cut out all hunts and modern replacements with larger tolerances ordered so less chance of a failure fingers crossed. Also got a new sound output transformer I’m picking up tomorrow morning (Thanks to vindads, if he reads this) as well as some othe rbtis he is kindly giving me.

[AmateurRepairer]

I’m assuming a set won’t power up if a capacitor(s) are missing? Just wondering if I can try out this new fancy speaker output I’ve wired up today.

[Burnt wire]

I replace every damn wax capacitor I can see, if you leave a few, they usally pop after a while and then you have to take the thing apart again. so I do it in one go regardless. I don't change all the resistors, just the way out ones, the good ones usually stay ok.

[David G4EBT]

Originally Posted by AmateurRepairer

I’m assuming a set won’t power up if a capacitor(s) are missing?

Why would any be missing?

That implies you haven't checked the chassis and compared it with the circuit.

With any radio which is to be restored - especially one of unknown provenance which has passed through several hands, it's always wise to print off the circuit and parts list, check resistors to see if any are more than say 20% out of tolerance, and to check the wiring of the chassis, and as you go, to mark the circuit with a highlighting pen so that you know you've checked that everything is wired correctly and nothing is missing. (I remain perplexed as to how the output transformer 'fell apart' and 'became unwound', but great news that Mick, 'Vinrads' was able to help you out with one which fits perfectly in the confined space).

It goes without saying that when you're satisfied that everything appears to be as it should, you should first power it up through a lamp limiter so if there's anything untoward, it will become immediately obvious.

Well done on your efforts and good luck with the 'MOT' ('Moment of Truth') when you power it up!

[Graham G3ZVT]

Originally Posted by David G4EBT

Why would any be missing?

Post #8 seems to say that A-R has removed all the Hunts caps pending delivery of replacements. Quite a brave move!

[Restoration73]

Not sure if the wax caps are Hunts, but the small brown ones are. Even the 0.04 on the
agc should be replaced. I tend to use 1kV ceramics for 1n, 4n7 and 10n. The Hunts with
the colour bands are troublesome. On the U198H I'm doing, the dial cord has been
strung incorrectly. This is an early set without the tone switch.
The four rubber posts to space the dial and glass are now goo, but easily replaced.
Works well for an economy receiver.

[Station X]

Originally Posted by rambo1152

Post #8 seems to say that A-R has removed all the Hunts caps pending delivery of replacements. Quite a brave move!

Apparently to be replaced with capacitors having larger tolerances.

[David G4EBT]

Originally Posted by rambo1152

Post #8 seems to say that A-R has removed all the Hunts caps pending delivery of replacements. Quite a brave move!

Oh crikey. I guess it depends on what is meant by ‘power up’ and what on earth would be the point of switching on a radio which is missing several key components? What would be the point of doing that? To make an analogy, I guess that if I removed the spark plugs from my car, whilst waiting for replacements, I could switch on the the ignition and ‘power up’ the engine. It would turn over, the lights, washers and horn would work, but the engine wouldn’t start and unburnt fuel mixture would find its way into the catalytic converter.

I’m probably misunderstanding the purpose behind the question.

As to removing several components pending receiving replacements, even if I have new components to hand, painful experience over many years had taught me to first take pictures, then replace items one at a time and take more pics.

[ms660]

Originally Posted by David G4EBT

Oh crikey. I guess it depends on what is meant by ‘power up’ and what on earth would be the point of switching on a radio which is missing several key components? What would be the point of doing that? To make an analogy, I guess that if I removed the spark plugs from my car, whilst waiting for replacements, I could switch on the the ignition and ‘power up’ the engine. It would turn over, the lights, washers and horn would work

You could check the compression while you're waiting.

Sometimes removing components in receivers before powering up can be a very wise move.

Lawrence.

[AmateurRepairer]

Apologies for any confusion, I’ll clear up hear.

By fitting overated components I was told that it was a wise move as the hunts never had much in the way of budging and if a circuit went high voltage for some reason the hunts failed, hence the nickname c—nts caps.

It’s only a question to see if I could get some life, any at all, out of the set prior to the replacements being fitted. Thanks for your time.

[Station X]

I see. Higher voltage rather than larger tolerances which is something quite different.

[AmateurRepairer]

Apologies station x I’m still getting to grips with all the terminology.