B&W TV Murphy V410

Well I seriously doubt I will ever find a 410 cabinet so I will set about myself or will commission someone to build a see through perspex case. The chassis on the Murphy is fantastic and is worthy of being on view anyway.

Hopefully a set of knobs might be obtainable, if you have a picture of your version 3 & 5 it might help, maybe 60 oldjohn may have some, you never know.

Any tips on dealing with the lopt can and oil how to fix. How and why it leaked, can it be replenished or does it need replacing with a pea can etc

Cheers
Chris

Cabinet making is a great hobby too..

The question, to re-create the original or design something unique and beautiful for the Chassis?

How about this for the Murphy? http://www.murphy-radio.co.uk/murphybil ... inside.jpg

Thanks for that Jamie a nice read.

I have a 17" mask spare from a scrapped French 819 line set that I needed the AW43-80 from and the implosion screen. This set is supposed to have the Mazda CME1702, I've not checked as there isn't a label. I offered the mask up to the screen and it is a snug fit so this mask & implosion screen should do nicely if & when I set about building a cabinet.

Chris

R&TS / ERT Service data loaded into the Technical Library for those interested.

Chris

The main reason why Murphy LOPTs leak oil is that they have previously been opened to replace the U25 EHT rectifier! This won't apply in your case because the later U26 is external to the transformer.

I can only assume that Murphy intended their dealers to replace the entire LOPT assembly because of a low emission U25. Did they really have such a distrust of the quality of their their transformers?

The spun aluminium can is very well sealed, with quite a deep overlap and is a right pain in the proverbial to open. Remember that, once you start, the can must be kept upright, which makes the job harder as it is not easy to grip the round can - particularly if some of the oil has already leaked out! - whilst keeping fingers and other fleshy parts out of harm's way.

If only they had provided a screwed lid or even a clip of some sort ...

Why Murphy adopted this approach, I don't know. No other manufacturer had problems using air for isolation!

The golden rule of transporting a Murphy is, of course, that it must always be kept upright!

As for topping up, I've never done it or heard of anyone else doing it. It wouldn't be easy to judge how much oil is missing anyway, as the can will only be half full when the transformer assembly has been removed!

In the case of the V410, the can will still be sealed and any leakage is unlikely to amount to much - probably far less than an older one that has been opened - and I would leave well alone. Incidentally, I can't see any noticeable trace of oil in the picture.

What happens if they are run without oil? will that kill the LOPT? is there a window of grace before disaster?

Not sure how much oil has been lost yet, some of it is over the surrounding chassis and adjacent CRT DAG.

Trevor is doctor Murphy in these here parts, having done many, he even makes new cans using pea tins and tops up with oil (vegetable or mineral I cannot remember)

Chris

EDIT:
One of his pea tin marvels
http://www.vintage-radio.net/forum/show ... stcount=14

Another good read
http://www.vintage-radio.net/forum/show ... urphy+LOPT

As ever excellent advice Trev, I will dipstick the can as you suggest just to get an idea of where we stand with regards to oil.

Currently enjoying reading all the Murphy threads of which you contribute to many over on UKVRR.

As you and David point out and myself have noticed the chassis' on the Murphy are exquisite, beautiful design and way over engineered. It makes a real difference from the usual pressed steel affairs. I guess as I don't have a case the I might see if someone can make as similar case out of clear plastic rather than hide it all.

Chris

I have a little stock of rectifier sticks (TV11,13,14 & 20)and some of those excellent EHT Diodes (BY8410) from Stan

The 410 seems to have more controls up top that the 530

I think the on/off is this push in sprung affair, the channel selector is obvious the other three must be vol brightness and contrast.

Voltage setting?? weird!! do you set the dial to the line on the right? if so its set for 250V AC ,however the brass point under the glass is pointing at 230DC but this pointer seems to be fixed. When you unscrew the centre nut you can rotate the dial but the pointer is fixed to the dial

Looks like the CRT has to come out to get at the components too

Installed a new 2A F1, Snipped C113 (.05 uF) and gave it full mains, all valves lit up, line whistle could be heard but not strong one. Nothing on screen and no flashes when channel operated hmm sounds familiar (RGD) will investigate later on.

Trev can you confirm the Dropper tapping, as I'm confused how it works. I can see a brass pointer behind the glass dial which seems to be on 230 DC. If i unscrew the centre nut the unit can be rotated, I can see the brass pointer can be positioned on lugs behind but as the pointer is fixed I don't see where or how you line it up or what with. The bottom half of the dial reads AC the top half DC talk about complex, no doubt you will kick me in the goolies for dissing Murphy but why not keep it simple like all the other manufacturers (runs for cover)

I do enjoy reading these 'resurrection' threads, but I'm afraid I can't contribute a great deal as I don't have the knowledge or experience

Earlier on you mentioned rectifier sticks, Chris. I presume they must be some kind of diode for high voltages or a miniature version of the prewar selenium rectifiers. How do they work and what are they made from? Just curious.

Keith

here is a picture of a 21kv stick that can be used to replace a valve eht rec
rob t

Thanks for the manual extract Rob, however its the same info I have in R&TS and still it makes no sense on mains adjustment. I'm probably being thick so still need someone to explain how the bloomin thing works.

Keith,

Yes as Rob showed the rectifier sticks can be used in place of say the EY51 (wired) or U26 (B9A) and even smaller, the BY8410 10kV can be strung together or in singular format. I've also shown a few TV11,12,13,14 & 20 numbers relate to kV the old valves as a size comparison

Chris

Thanks Rob and Chris, I've not come across those before. I guess that they must be a relatively recent introduction, otherwise they would have been used instead of, say, an EY51 in the first place?

Keith

chris from your photo i would say yhe voltage is set at 250 volt ac
rob t

That's what I thought but are you basing that on the line to the right? I know I did, but I think that line just shows the way to the Line Lin. I'm unsure though at least the chassis is not round

Thanks Rob and Chris, I've not come across those before. I guess that they must be a relatively recent introduction, otherwise they would have been used instead of, say, an EY51 in the first place?

Keith

Well, I remember Selenium stick rectifiers in Triplers in 1970s and I think small silicon EHT rectifiers after I stopped repairing TVs. Likely late 1970s or early 1980s, so if "recent" is 30 years ... My memory on this is about +/- 5 years at worst I think.

Metal Rectifiers (Copper Oxide and later Selenium) used for mains from 1930s to mid 1960. Power Germanium Rectifiers (low voltage) from late 1940s but not I think in domestic equipment. I suspect Selenium saw 5 or 6 years only wide spread use for mains instead of valves before Silicon took over. When was BY100? BY127 by 1971 I think.
Silicon for EHT replaced the Selenium sticks later. I don't think Selenium Sticks came in till after the Silicon rectifier for mains on TV sets.

German Radio sets seem to have adopted Selenium 4 diode mains bridge while UK sets still using dual diode rectifier valve and centre tap transformer. Oddly Irish made Philips using EZ41 while a German Philips of same year would use a Selenium Diode. Valve Mains rectifiers used up to 1960s at least.

Germanium seems to have only been commonly used for detector diodes, firstly in VHF-FM discriminators. Seems rare even for LT power on Domestic sets.

On an AC/DC set, especially a US model Radio the dual diode rectifier valve drops HT on heater chain by another 25V. So really no advantage to Metal Rectifier (Copper Oxide) or Selenium (really a Metal Rectifier too) except on AC only Radios I suppose.

The long tubes/sticks are full of Selenium rectifier discs each about 1.5mm thick so achieve the high PIV. I don't know how the silicon ones are made.

Thanks for the chronology and explanation Mike. The selenium sticks sound like a modern and high voltage version of the Westector (introduced I think in 1933). The picture is a Westector from my HMV 800.

Keith