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Murphy V789 "The Oily Beast" Repair

 
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Murphy V789 "The Oily Beast" Repair

Post by marc » Sun Nov 08, 2015 3:53 pm

Hi all,

Thanks to the kind generosity of Steve (Colourstar) this Murphy V789 now resides as part of my collection here in Wakefield. Steve's original Murphy thread is here... viewtopic.php?f=5&t=8709&p=91269&hilit=murphy+v789#p91108

Today I decided to have a look at how this old beast can be brought back to life. First thing to receive attention was the power switch, I shot it with a good dose of WD40 which brought half of the switch back into life on the positive side but the negative contacts just wouldn't give in to the spray so the switch was disassembled from the volume pot and opened up for a proper clean out and now all seems good.

As for the rest of the chassis well it's absolutely filthy, it looks like the whole chassis has been coated in hardened oil deposits from the LOPT so it's out with the cleaning rag and cotton buds to try clean the oily grot away from connections and valves etc.
I have noticed a number of caps that are either deformed or trying to relinquish their innards as you can see on the photo below, trouble is some ID's can't be read so that could cause some fun and games. :aaq

Anyway that's it for now.
Marc.
Murphy V789 Steves shot.jpeg
Oh how the good looks hide the grime.

DSCF3526 forum.jpg
Nice grotty and oily !

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by nuvistor » Sun Nov 08, 2015 4:15 pm

Wear gloves when cleaning that oil up, some transformer oil is nasty stuff.

Only saw a few of this model and unfortunately remember very little about them, always liked the style of them.

Frank

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by marc » Sun Nov 08, 2015 4:39 pm

nuvistor wrote:Wear gloves when cleaning that oil up, some transformer oil is nasty stuff.
Frank

Hi Frank,

Very sound advice indeed !
As it happens I'm already wearing gloves as this stuff aint nice at all.

Marc.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Rebel Rafter » Sun Nov 08, 2015 5:31 pm

Hi, all, RR here. That oil might be very nasty indeed if it's made with PCB's. See my post about it in the wanted section under visconals. Some of the Murphy sets had a LOPT fitted in a can of oil and that definitely should be treated with serious caution, don't let kiddies near it. RR.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by marc » Mon Nov 09, 2015 5:19 pm

Hi all,

Today I replaced the melted/broken caps on the PCB shown above and decided to give the set some power.
Using the variac I slowly wound up the volts, I could feel a small amount of heat from part of the dropper but noticed the valves were not lighting.
After probing around with the meter it became apparent that the heater chain was O/C between V10 & V4 which also happens to be part of the circuit that via the system switch would have fed heater voltage to an "add on" 625 converter plinth. luckily it was just a case that the switch was in the 625 position and pushing it back to 405 restored the heater chain.

Powering up again via the variac showed the valves were now lit and by 190v audio was present. Continuing to wind up the voltage I noticed I couldn't hear any line whistle but I have been told that these sets with oil LOPT's are very quiet but that said I couldn't see any glow from the U26 either, so fault finding continues.

Marc.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Katie Bush » Mon Nov 09, 2015 8:33 pm

Hi Marc,

That's true... In an oily Murphy, silence is golden - one of the beauties of a Murphy, however, a medium wave radio waved around the line stage/LOPT area will sing loudly if there is any life in there.

Just a thought.... Does this set have a line oscillator valve? Or is it one of the "Inherently self oscillating LOP stage" models? The latter can be a bit picky about the LOP valve (30P4 Vs 30P4M - "M" for Murphy, as in special valve for Murphy), and can be a bit choosy about HT voltage and component values.

Marion

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by marc » Mon Nov 09, 2015 9:35 pm

Hi Marion,
In an oily Murphy, silence is golden - one of the beauties of a Murphy, however, a medium wave radio waved around the line stage/LOPT area will sing loudly if there is any life in there.

So my memory of being told of "the silent set" is right and not just me with cloth lugs :qq1
The radio tip is handy to know too.
Does this set have a line oscillator valve?

Yes it does, 6/30L2 I believe so I guess that means I don't have to worry about special LOP valve.

Marc.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Katie Bush » Mon Nov 09, 2015 10:02 pm

Hi Marc,

If truth is to be told, it's not 100% silent, but you'd need the hearing ability of a Cocker Spaniel to hear it..... :bba

As an aside, "dry" Murphys produce an audible line whistle.

Absolutely spot on about the LOP valve - it's only the self oscillating models that need the special valve.. Similarly, the component values won't need to be as critical, but obviously, sensibly within tolerance.

Marion

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by steve1010 » Tue Nov 10, 2015 7:12 pm

I remember putting one of these on my bench face down when i worked at British Relay in the 70's it was just before 5pm and off i went home, following morning i turned it right way up and the CRT mask between screen and glass was full of oil!
in the skip it went !

Steve

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Jayceebee » Tue Nov 10, 2015 9:30 pm

Hi Marc,

I served my apprenticeship with a Murphy dealer and what we did with that transformer oil now sends shivers down my spine. We used it as a substitute for teak oil when refurbishing cabinets, my hands would have been in direct contact with it most days. :ccf

Anyway I'm 60 this month and as yet I don't seemed to have suffered any ill effects but with what we know now it makes sense to be very cautious.

I can only remember one stock fault with this chassis and that was the screen grid resistor on the line output valve, it used to go low value causing lack of width. You'll have to refresh my memory, is the valve a 30P4 or 30P19 (the 30P19 was a drop in replacement for the 30P4 anyway). That small PCB came in two versions, one was direct and the other flywheel sync. The direct sync version was preferred by the workshop engineers at the time, not a problem with 405. I can only remember ever seeing one set fitted with the 625 conversion kit that fitted onto the underside of the cabinet, performance wasn't great.

Marion, the special version of the 30P4 for self oscillating timebases was I beleive the 30P4MR, MR standing for Murphy Radio. Bit odd as it was a TV valve :aak .

John.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by marc » Wed Nov 11, 2015 12:28 am

Hi all,

I remember putting one of these on my bench face down when i worked at British Relay in the 70's it was just before 5pm and off i went home, following morning i turned it right way up and the CRT mask between screen and glass was full of oil!

Steve, I bet you didn't do that twice ! :qq1

what we did with that transformer oil now sends shivers down my spine. We used it as a substitute for teak oil when refurbishing cabinets

Hi John, Isn't it frightening the things we did in the past but at least (touch wood) we seem to have got away with it thankfully.
As for the LOP valve on this set I don't know which is fitted as the markings have rubbed off though 30P19 should be fitted.

I'm afraid not much has been done today due to lack of time though I did grab 10 mins this morning, I replaced C43 0.25uf which was reading short on the Solar cap analyser and tried the set again and this time line whistle could be heard as the set warmed up but then disappeared.
I'm hoping to have a little spare time to spend on the set tomorrow.

Marc.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Till Eulenspiegel » Wed Nov 11, 2015 12:23 pm

The remote control Murphy I acquired in September 2013 still works but after an hour or so the picture width comes in and there is always that smell of oil when the set is switched on. The common belief is that it is the oil that is causing the problem, not the transformer windings.
I do have spare transformer in which the plan is to fill the can with Dow Corning potting jelly so in a sense the transformer will become rather like a Thorn Jellypot.

Till Eulenspiegel.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Spot-Wobble » Wed Nov 11, 2015 2:25 pm

I had both the 19" and 23" versions (at different times though)
The 19" needed a new tube and I fitted a rebuilt one.
Also converted it to 625 with the adapter unit which fitted under the set.
I think I got the unit from Manor supplies?
Anyway as usual it got sold!
The 23" model came along a couple of years later, had a slightly soft tube but gave a reasonable picture.
As usual someone wanted to buy it so off it went after a check over and clean.

Andy

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Colourstar » Wed Nov 11, 2015 8:13 pm

Hi Mark

Very well done on the progress so far. :thumb It was quite a grim prospect to begin with; loads of grime and some very sickly capacitors. I hope the old girl repays your efforts with at least something on screen as a thank-you. I'll be following progress closely!

Interesting to read that there was a 23" version of this set. The 19" model is incredibly heavy for it's size, so the bigger version must have been one heck of a weight. Handsome sets though.

Presumably the last Murphy chassis with the oil filled LOPT?

Steve

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by marc » Sat Nov 14, 2015 4:04 pm

Hi all,

Had to have a bit of an enforced break for the last few days but back on "Old Oily" today.
I have gone through and tested all the waxies and those wonderful Hunts caps in the F&TB section with the result of all of them being very leaky indeed but despite replacing them (which is not easy in the tight confines of this chassis) I seem to be no further forward.
So to sum up, power up the set and as it warms up audio comes on and sounds good followed by a good strong line whistle but just as you would expect a picture to show on the screen the line whistle abruptly stops and of course no picture/raster appears.

I'm going to test the associated valves next and report back.

Marc.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by marc » Mon Nov 16, 2015 4:02 pm

Hi all,

LOP valve 30P19 has heater cathode short and of course I don't have a spare in stock not even one I can pinch from another set. :cch
But at least it seems to make sense as when the line whistle stops it coincides with the LOP valve warming up.
So that's it for now, just sit back and wait for delivery of a couple of spare valves to arrive.

Marc.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Colourstar » Mon Nov 16, 2015 8:43 pm

Sounds like you're getting there Marc. I see the equivalent of the 30P19 is that old familiar favourite we all know and love so well, the, er PL302.... Nope, me neither!

How very Murphy.

Steve

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Katie Bush » Mon Nov 16, 2015 8:50 pm

Colourstar wrote:Sounds like you're getting there Marc. I see the equivalent of the 30P19 is that old familiar favourite we all know and love so well, the, er PL302.... Nope, me neither!

How very Murphy.

Steve


Aye, and what beggar... I gave Marc two brand new PL36 at the beginning of this year, and no darned good on this one... :ccb

PL302? - I don't think I've ever come across one of those before! :aaq

Marion

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by marc » Mon Nov 16, 2015 9:14 pm

Colourstar wrote: I see the equivalent of the 30P19 is that old familiar favourite we all know and love so well, the, er PL302.... Nope, me neither!

How very Murphy.

Steve

And lest we forget that popular old friend "N389" too ! :bbd

Marc.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Till Eulenspiegel » Mon Nov 16, 2015 9:17 pm

PL302 is the pro-electron code for the 30P19. The PL302 was usually marketed as a Brimar and also with both codes by Mullard. There was a Mullard 30P19 but it was a rebranded Mazda. A PL36 can be used as a replacement for the 30P19 and the older 30P4 for that matter, but you have to make sure that certain tags on the valveholder are free of components. For example in certain Ekco TVs if a PL36 was used as the replacement for the 30P4 there was no vision AGC because certain AGC components were anchored on the valveholder.
Isn't it sad having all this useless information in ones head?

Till Eulenspiegel.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Katie Bush » Mon Nov 16, 2015 9:28 pm

Alternatively, there are a couple here......
http://www.ebay.co.uk/sch/i.html?_odkw= ... e&_sacat=0

Grab 'em while they're hot!

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Doz » Mon Nov 16, 2015 10:01 pm

There's a PL36 here if it's any use...

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by marc » Mon Nov 16, 2015 10:07 pm

Doz wrote:There's a PL36 here if it's any use...

Thanks for the offer Doz but thanks to our very own "Till" a 30P19 has been sourced and should be here shortly.

Cheers,
Marc.

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by marc » Wed Nov 18, 2015 3:33 pm

Hi all,

More progress to report, with a replacement 30P19 LOP valve in place (with grateful thanks to Till) first light has now been achieved although with partial frame collapse, there is something getting hot too judging by smoke appearing from somewhere as yet unidentified.

Marc.
DSCF3531 forum.jpg

 
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Re: Murphy V789 "The Oily Beast" Repair

Post by Till Eulenspiegel » Wed Nov 18, 2015 3:57 pm

Hi Marc,
It's got to be bad capacitors. Assuming the frame timebase in the V789 is similar to the V689 then the culprits will be C301 to C304. Just change the lot, they'll almost certainly be TCC waxies. The Mazda 30PL13 is pin compatible with the PCL82. The 30PL13 was developed at the behest of the TV manufactures. It made it possible to use the existing 90 degree timebase PCBs in the latest 110 degree CRT sets. For example the 90 degree Regentone 10-4 timebase PCB could be employed with hardly any modification at all in the 110 degree CRT model TEN-17. More useless information from Till Eulenspiegel.

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