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Old 2nd Sep 2018, 5:00 pm   #41
Nanozeugma
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Default Re: Help needed restoring a Murphy V310

"Ballooning" describes a condition whereby as one advances the brightness or contrast, and thus increases the beam current, the picture on the screen appears to move toward you, increasing in size with the edges disappearing off screen and becoming defocussed.
This is frequently caused by a knackered EHT rectifier.
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Old 2nd Sep 2018, 8:49 pm   #42
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Default Re: Help needed restoring a Murphy V310

For some reason the BBC coil biscuits for channel 5 have been placed in the ITA position.
This may have been carried out to allow the V310 to work on a wired system but this is only a thought. As far as I know, channel 5 and 9 is an odd combination.

It really does not matter but you can unclip the channel 5 coils and place them in the 'BBC' position. This will correct the sensitivity pot reversal . The coils are fragile so I would suggest leaving them as they are fitted to prevent damage. John.
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Old 2nd Sep 2018, 9:18 pm   #43
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Default Re: Help needed restoring a Murphy V310

Sorry John I've confused matters when I said earlier I had Channel 5 coils, I don't, I have actually have Channel 2 and 9 .

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David
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Old 2nd Sep 2018, 9:22 pm   #44
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Default Re: Help needed restoring a Murphy V310

Channels 2 and 9 were used from transmitters at Holme Moss and Winter Hill, probably others as well.
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Old 2nd Sep 2018, 11:43 pm   #45
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Default Re: Help needed restoring a Murphy V310

Channel 9 was also used by Croydon.
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Old 7th Sep 2018, 10:10 pm   #46
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Default Re: Help needed restoring a Murphy V310

I finally got round to adjusting the ion trap magnet today. It's now a good further 3/16" further back than it was and is on the bakelite base. I hope this isn't indicative of a fault?

Is the ion trap magnet now "set up" and nothing else I do will require me to readjust it again? I would of liked to leave it longer to warm up but I was worried about the araldite softening.

The picture isn't that much brighter and it's now off center and out of focus but I guess that's to be expected.

Regards
David
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Old 7th Sep 2018, 11:03 pm   #47
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Default Re: Help needed restoring a Murphy V310

Hi,
I had a similar thing with a Ferguson set, I thought maybe the ion trap magnet had lost a bit of magnetism, so I took it off the tube and stuck a rather powerful magnet to it, removed the powerful magnet then refitted the ion trap, I was then able to set it in place much further up the neck an it also fixed a corner shading issue I was also having.

I’d like to hear what more experienced members think of this idea before you go trying it! They might think it’s a daft idea, but then I am full of such ideas!!

Regards
Lloyd
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Old 7th Sep 2018, 11:34 pm   #48
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Default Re: Help needed restoring a Murphy V310

The ion trap should never be on the tube base. Yes they do lose magnetism and they were also made in different strengths back in the day. Either try and find another ion trap or try re-magnetising your existing one. If you've had the ion trap off completely, it does matter which way round it goes so try reversing it.
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Old 8th Sep 2018, 9:02 am   #49
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Default Re: Help needed restoring a Murphy V310

The Mazda ion trap should be OK. Adjustment of focus and picture position will effect the setting of the trap.
You need to center the picture with the device above the focus dome. Unlock it by turning half a turn then juggle it like a joystick, up and down and side to side to center the raster. You will then need to tighten it up again then re adjust the ion trap for maximum brightness. Warming the Araldite will make it harden faster not soften it.
John.
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Old 8th Sep 2018, 9:34 am   #50
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Default Re: Help needed restoring a Murphy V310

Thanks for the replies. I'll have a go at centering the picture when I get time. The manual mentions a focus knob but I can't see one anywhere

David
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Old 8th Sep 2018, 11:54 am   #51
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Default Re: Help needed restoring a Murphy V310

To focus the picture you rotate the plastic dome. Have a look at the mechanism. Simply rotate it either way but if stuck take care. it is easy to break off the plastic tabs that hold the three small screws that secure it to the gantry. J.
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Old 20th Sep 2018, 11:19 am   #52
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Default Re: Help needed restoring a Murphy V310

Here's the latest update.

I've changed several 1000pf decoupling caps, set the ion trap to get highest brightness and centered the picture as best I can (the adjuster seems notchy and vague).

Unfortunately there's not enough adjustment on the focus adjuster to bring it into focus. Tomorrow I'll have another go at the ion trap, hopefully I'll be able to move it forward and improve the focus, without loosing brightness.

Compared with the photo in post #15 there seems to be minimal improvement, maybe the contrast is slightly better but I'm now beginning to worry the tube is tired?

Regards
David
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Old 21st Sep 2018, 6:15 pm   #53
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Default Re: Help needed restoring a Murphy V310

I've checked that the focus assembly is in the correct position, as described in the service manual but I still don't have enough adjustment to bring it into focus.

I've rechecked the ion trap magnet for maximum brightness and it's still more on the the tube base than the neck.

The focus was alright before I moved the ion trap magnet so do I need to remagnetise it? If so please tell me how.

Regards
David
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Old 21st Sep 2018, 6:27 pm   #54
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Default Re: Help needed restoring a Murphy V310

I have never known it necessary to remagentise an ion trap. Does the focus dome turn? That is the focus adjustment. The service manual does not tell you this. J.
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Old 21st Sep 2018, 7:42 pm   #55
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Default Re: Help needed restoring a Murphy V310

Hi John,

Yes the focus dome turns and works. Unfortunately it stops turning before it's fully focused.

As I mentioned at the start this is my first television repair, so please assume I know next to nothing. Is there any other reason for the ion trap magnet being so far down the neck of the tube?

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David
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Old 21st Sep 2018, 7:46 pm   #56
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Default Re: Help needed restoring a Murphy V310

Could it be the wrong way round?
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Old 21st Sep 2018, 7:51 pm   #57
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Default Re: Help needed restoring a Murphy V310

It certainly is an odd one. Mazda traps are usually about a half inch from the base.
Have you adjusted the whole focus assembly? It can be moved closer or further away from the screen. It should focus with the dome [fine focus] mid way.

It is possible that you have low EHT. It does look a bit dull. A low emission CRM172 should focus with correct EHT voltage. It really needs to be measured to get a definite answer.

Just a thought, is the tube the original Mazda? It may be fitted with a poor grade regun and this might explain the odd ion trap position. J
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Old 21st Sep 2018, 8:33 pm   #58
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Default Re: Help needed restoring a Murphy V310

Thanks for the replies


The magnet is facing the right way, red paint dot facing the rear of the set.


I don't know how to tell if the tube's been regunned. It is a Mazda but I'm fairly sure it's been removed in the past and so could have been replaced with another one. The tube wasn't clamped in and fell out when I turned it on it's face to remove the cabinet. It's been refitted as described in the manual but could something have been damaged?


Regards
David
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Old 22nd Sep 2018, 8:41 am   #59
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Default Re: Help needed restoring a Murphy V310

I doubt if anything has been damaged. I suspect that the EHT is low, probably around 9-10KV. This will put the focus magnets out of range preventing correct focusing.

Unfortunately an EHT meter or probe is required to confirm this. The raster should be oversize if the EHT is low. I am not familiar with your test card being weaned on Test Card C so cannot judge this.

If the EHT is low it may well be the oil filled LOPT.

Another possibility is that decades ago the LOPT may have failed and the customer decided to purchase a new model. The repair shop may have salvaged the good CRM172 substituting a low emission one into the chassis without tightening anything. This was quite a common occurrence. We can only guess.

It should still focus OK even if low. John.
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Old 22nd Sep 2018, 9:04 am   #60
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Default Re: Help needed restoring a Murphy V310

My thought is that the tube is very low emission and or it's gone soft, the sensitivity and contrast are turned up to give the raster but it has excessive beam current hence the focus issue.
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