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Old 25th Sep 2018, 12:06 am   #1
1100 man
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Default Murphy V410 TV

I seem to be on something of a mission to re-acquire TV's that passed through my hands when I was a kid.
I still have a folder full of photocopies of circuits, so I can pretty accurately identify the model numbers of sets that I had.
I also still have a list of TV's (without model numbers) that I repaired back then. I was a strange child!!

The first ever set that was given to me was a Murphy V510. According to my list, that was in March 1979 and I would have been 12 years old. I didn't know much about TV's and poked about inside measuring voltages with dad's AVO 7. However, I managed to conclude that the boost cap was short:- replacing it restored the set to working order.
I recall there was a lot of arcing going on around the top of the line O/P transformer can which I cured with liberal amounts of car body filler! As we had an Austin 1100, body filler was in good supply!

Dad was obviously aware I was messing around with live chassis sets (mum would have had a fit if she had known the potential dangers!) but must have concluded I was OK doing so. No RCD's in our house back then.

Anyway, this V410 was very kindly given to me by Davidh1041 and I collected it yesterday at Harpenden. Looking at the circuits, there are a few differences between the V410 & V510 but basically it's the same thing.

Back at base, I was itching to have a look at it. During the next hour, I realised that Murphy, like Philips, did things in their own slightly weird way!

The first noticeable thing was that it weighed a ton for a 17" set. I removed the two large screws holding the back on and found the back was glued to the wooden case! After levering at it with a screwdriver, I found the case plus back parted company from the works!
This revealed an incredibly substantial chassis with everything mounted to it in a non removable manner. At least the components are facing outwards and are accessible. The speaker connections are via the two large screws that hold the back on- I'm sure that led to some intermittent problems!
The on-off switch is actuated by a mechanism connected to the top flap which covers the controls and speaker grille.

The LOPT is contained within what looks like an oversized electrolytic capacitor can. It is oil filled. Consequently, there is an oily residue on the back of the tube and the chassis. Luckily, I was aware that these things needed to be transported the correct way up and not on their side!
Usually, the tube base is easily accessible but not on this set. There is a whole mass of stuff built round it including the mains droppers and voltage selectors, frame linearity controls and focus plus the selenium rectifier. So a quick check of emission with the tube tester was not an option!
The tuner is also a weird looking thing, operated by a long rod from the top of the set.

I'm not planning to do much with it at this stage as there are things on the go which I need to finish, but it's very nice to have in the pipeline!

What I would be interesting in seeing, however, is sales brochures from the time. This must have been more expensive than many other sets of the time due to it's engineering, so it would be nice to see how they marketed it to the general public.

I like things that are quirky in design and so this will be an interesting restoration when I get round to it.

I'll try and take some pictures of it tomorrow.

All the best
Nick
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Old 25th Sep 2018, 8:07 am   #2
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Default Re: Murphy V410 TV

Photo of the V310 which I think looks similar and prices for the V410 on this page.
http://www.thevalvepage.com/tvmanu/murphy/murphy.htm

I only fixed a few of these sets, one thing to be aware of is the small decoupling capacitors in the IF strip, they fail like most capacitors of this period, they look like small resistors.

I am not sure if this is the same but some of these sets had no fine tuner control.
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Old 25th Sep 2018, 9:49 am   #3
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Default Re: Murphy V410 TV

Very good quality TV. Very popular and it is a lot easier to service than it appears at first sight.

Ha! Ha1, I'm surprised you fell for the back puzzle. The V510 has the same arrangement! The Murphy 'Service News' shows pictures of 'hatches' that had been cut in cabinets to gain access to the valves!

Chassis is bolted with large thumb screws to CRT assembly and yes, watch those caps as Frank has mentioned. Complete lack of sound, vision, or both were common when they went O/C. Tube is Mazda CME1702 and on the whole had a good life. The LOPTs were always an expensive pain. John.
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Old 27th Sep 2018, 9:25 pm   #4
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Default Re: Murphy V410 TV

Here's my Murphy V410 being prepared for restoration.

DFWB.
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Old 28th Sep 2018, 12:29 pm   #5
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Default Re: Murphy V410 TV

For the time being the Murphy V410 will be connected to the variac and the mains supply will be progressively increased over the course of the day.
There is quite a few TCC waxie capacitors in this set so no doubt these will be leaky.
Note the position of the line oscillator valve, between the boost diode and 30P4 line output valve. It's the same in the model V330 and the metalwork in the V310 is prepared for the fitment of a valveholder for a 6/30L2 or ECC82 line oscillator valve.

DFWB.
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Old 28th Sep 2018, 4:41 pm   #6
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Default Re: Murphy V410 TV

With 150 volts supplied to the receiver a 5mm spark is present at the top cap of the U26 EHT rectifier valve.
The attachment shows the circuit diagram of the line timebase. The V410 series has a flywheel sync circuit which uses two diodes supplied from a phase splitter valve.

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Old 28th Sep 2018, 7:02 pm   #7
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Default Re: Murphy V410 TV

Really was the best looking TV of its age and time. Also very reliable and easy to work on due to being a Murphy. Tuner was rock solid. I think it was C69 used to be the cause of a howl on start-up. It needed a special type of replacement. Brings back great memories.
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Old 28th Sep 2018, 8:26 pm   #8
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Default Re: Murphy V410 TV

akuram1 wrote: "Really was the best looking TV of its age and time."

I have to agree with that. I'd been on the lookout for a V410 for many years and was delighted when a Forum member donated a spare set to me.

The attachment shows the sound circuits.

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Old 28th Sep 2018, 8:40 pm   #9
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Default Re: Murphy V410 TV

I landed a V410 a couple of years back, and whipped the cover off. A sharp intake of breath at its construction and the back went on again. Looking forward to your step by step resto..both of you!
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Old 28th Sep 2018, 9:17 pm   #10
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Default Re: Murphy V410 TV

C62. Murphy recommended a Hunts W99 type .001uf. J.
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Old 28th Sep 2018, 10:03 pm   #11
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Default Re: Murphy V410 TV

Mains voltage from the variac adjusted to 225 volts, now things are beginning to happen.
Looks like there's a load of waxies to replace. Tuner has coils for Channels B1 and B9.

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Old 29th Sep 2018, 11:35 am   #12
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Default Re: Murphy V410 TV

Ease of service. First disconnect the CRT base socket and EHT connection, then remove four 4BA screws and the chassis complete with scanning coils can be parted from the CRT and front moulding assembly.

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Old 29th Sep 2018, 10:03 pm   #13
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Default Re: Murphy V410 TV

So how comes your chassis looks like it's just come out of it's delivery box? It looks brand new!!
Thanks for the dismantling tip: I wouldn't have thought of doing that, but it certainly makes the initial clean up easier. Mine seems to have an oily residue over much of the upper part of the chassis and back of the tube- from the LOPT I assume.
Talking of which, are LOPT's particularly problematic being oil filled? Do they suffer from the same moisture ingress problems as 'dry' ones?
The worst problem with my set, and the main reason it was given to me, is the tube mask. It has drooped & sagged at the bottom and there is a large gap between it and the tube.
However, I'm sure my bodywork colleague will be able to do something with it:- he's a dab hand with fibreglass, body filler and paint.

To answer Frank's point in post no2, this set does not have a fine tuner. They must have been very confident of their local oscillator stability to consider not fitting a fine tuner!

All the best
Nick
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Old 30th Sep 2018, 8:30 pm   #14
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Default Re: Murphy V410 TV

Once set they stayed solid.
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Old 30th Sep 2018, 11:18 pm   #15
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Default Re: Murphy V410 TV

The set is in exceptionally good condition, almost like new. Makes a pleasant change to restore a set that doesn't have the appearance of something that was fished out of a canal or a shed with a leaking roof.
I'm busy restuffing the TCC waxie capacitors. There's a fair number of Hunts capacitors in the set so it's likely these will need replacement as well.

DFWB.
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Old 1st Oct 2018, 8:06 am   #16
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Default Re: Murphy V410 TV

It was only used as a prop David. I don't think it ever had mains applied to it. John.
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Old 1st Oct 2018, 10:29 pm   #17
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Default Re: Murphy V410 TV

The manufactures service manual with modification supplements will have to procured. I've found quite a few differences in the circuits in this receiver compared with those in the 1959/60 Radio and Television servicing book.

All the decoupling capacitors in the vision AGC circuits were found to be leaky, the worst examples were the Hunts 0.25mfd 150volt components. Really bad leaks indicated on the Simpson 260 multimeter, >100Kohms.

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Old 6th Oct 2018, 10:44 pm   #18
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Default Re: Murphy V410 TV

Just about all the waxie and Hunts capacitors needed replacement.

The attached picture shows the results achieved so far. There's that frame linearity fault to sort out and also a curious disturbance on the picture which takes the form of random horizontal lines. The latter is the result of line timebase pulses entering the IF amplifier and causing bursts of oscillation. The effect is most apparent when the contrast control is turned down to minimum.

The V410 has a "gated" vision AGC system. I'm certain that this not a back porch sampling system and is more likely to be a sync cancelling circuit.

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Old 6th Oct 2018, 11:21 pm   #19
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Default Re: Murphy V410 TV

Hi David,
That's starting to look pretty good! Obviously more capacitors in the frame stage to replace. Personally, I like to do the whole lot in one go before I apply power especially in sets where access is not good.

In the case of my set, I will remove the chassis from the tube and overhaul the chassis first- just my preference!

I wonder why my tube mask has turned to cheese? Presumably, the one on your set is still hard plastic? My one is like hard rubber- you can distort it by pressing your finger into it!

I think it's a very stylish set- its looking forward to the '60's rather than back at the '50's!!

Cheers
Nick
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Old 7th Oct 2018, 12:19 am   #20
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Default Re: Murphy V410 TV

Hi Nick,
all the usual suspect capacitors in the frame timebase have been replaced. Somehow, I'm thinking that the linearity fault is of my own making.

I might add that after an hours use the EHT voltage reduces to 11KV.
The EHT transformer can doesn't run unduly hot. The 0.22 microfarad boost capacitor has been replaced as well as the 0.01uF coupling capacitor between the oscillator and the grid of the 30P4. The negative going drive waveform is correct @ 100 volts P - P.

Tomorrow I'll check the value of the two series screen feed resistors of the 30P4.
The CRT mask is in good condition. The CRT has to come out for cleaning so then I can determine the material was used to make the mask.

DFWB.
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