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Old 3rd Dec 2018, 9:36 pm   #181
Radio_Dave
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Default Re: Help needed restoring a Murphy V310

Quote:
Originally Posted by Heatercathodeshort View Post
One down, one to go.
I would investigate the frame flyback suppression circuit. It comprises a low value capacitor connected from a sub winding on the frame output transformer to the first anode on the CRT. It's value is .002uf C90 Murphy circuit. Your picture is a bit confusing.
Check the capacitor is connected to the correct tag on the FOPT. John.
The original cap was a crumbly Hunts Mouldseal and I have already changed it for a 2200pf. Sorry about the picture, I've attached another one with the brightness very high to show the flyback lines. The lines in the lower half of the picture are not continuous and where they stop and start is where the bright dots are. I've put the implosion screen back on and the photo is taken from a mirror so there's lots of reflections in afraid.

Quote:
Originally Posted by Freya View Post
Check the source that's feeding the Aurora too, I had vertical line that was caused by a Humax freeview box.
I'm thinking (hoping) the same thing. That line isn't there when the aurora is showing it's testcard. Unfortunately I don't have any other sources to try at the moment, but I'm working on it

Regards
David
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Old 4th Dec 2018, 10:44 am   #182
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Default Re: Help needed restoring a Murphy V310

The frame flyback should be fully suppressed on the V310. It's worth a very careful check to see that the connections from the special frame output transformer, supplying the blanking pulse to the CRT A1 are in order.

The FOPT has a separate winding for this purpose and I suspect that something is amiss here.

1. Check that the winding is not O/C. [207 ohms approx]
2. Check that C98 is connected correctly across the winding and has not
been connected to earth. I seem to remember you had a problem with
components on the FOPT tag strip.
3. Check that the blanking pulse to the A1 of the CRT has not been
accidentally connected to the boost side of R151 thus removing the pulse.
4. If you have a basic scope you can check if the waveform is present.

Ignore the vertical line. As suggested it is probably the signal
source and only adds to the symptoms.

Looks good so far and that CRM172 appears to be serviceable. John.
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Old 5th Dec 2018, 5:28 pm   #183
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Default Re: Help needed restoring a Murphy V310

I don't have an oscilloscope but I've checked everything else, including C111, and I can't find any faults. I've tried a freeview box and the vertical white bar still shows as well.



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David
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Old 5th Dec 2018, 9:29 pm   #184
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Default Re: Help needed restoring a Murphy V310

Hi Dave,

Is the vertical line still there with no signal connected to the set? If so, either the cathode or perhaps the grid is being modulated at line rate. In many sets, the cathode wire is dressed clear of other wiring to prevent such problems.

The other possibility is velocity modulation where the scanning speed slows down momentarily, causing a brighter part of the scan. It would be interesting to display a picture which would allow you to see if the linearity changes at the bright line.

It might be that part of the scan, about a third in, where the efficiency diode runs out of steam and the line output valve takes over. I'm a bit hazy on line timebase theory, so that may not be totally correct.

If the line is not there with no signal, that would indicate other issues!

Cheers
Nick
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Old 5th Dec 2018, 10:04 pm   #185
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Default Re: Help needed restoring a Murphy V310

The tube shows nothing without a signal (hope that's normal!) but there's no vertical line, or flyback lines, when the aurora is showing it's internal testcard.

Regards
David
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Old 5th Dec 2018, 11:17 pm   #186
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Default Re: Help needed restoring a Murphy V310

I'm a bit confused. Is the screen still blank with the brightness turned up?
The default test card stored in the Aurora is Test card 'C'.

It's very difficult to narrow this down with an unfamiliar test card and reversed image.

You say you have checked 'everything'. Could you list the components you have actually checked in the blanking circuit including the resistance of the feedback winding.

Another remote possibility is that you may have fitted an 82k resistor in place of an 820K, R151. A very easy mistake to make.

Is C111 on the correct side of R151 i.e the boost 'transformer' side? It will short the blanking pulse to chassis if incorrectly connected.

I cannot understand why you have flyback lines on the raster if the blanking circuit is operating correctly.

I can only suggest that you check this wiring loop very carefully from the transformer winding to the CRT A1 via C99.

Other than this I have come to a blank with this odd symptom. Regards, John.
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Old 6th Dec 2018, 12:14 am   #187
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Default Re: Help needed restoring a Murphy V310

Quote:
Originally Posted by Heatercathodeshort View Post
I'm a bit confused. Is the screen still blank with the brightness turned up?
No, sorry, I've just tried and the screen does light up if I turn up the brightness. There are flyback lines but they're rolling now and look different to the ones when showing a picture. The white vertical bar has gone though. I've attached a photo

Quote:
Originally Posted by Heatercathodeshort View Post
The default test card stored in the Aurora is Test card 'C'.
I brought this second hand so I guess the previous owner flashed this weird test card on it. I'll have to try and revert it to the test card C.
Quote:
Originally Posted by Heatercathodeshort View Post
You say you have checked 'everything'. Could you list the components you have actually checked in the blanking circuit including the resistance of the feedback winding.
I've checked C98, C99, R151, C111, R131, C97, R129, R149 & C109. The winding for the blanking pulse measures 204R, should be 207R and everything is hooked up correctly to the Tx. A1 voltage was a bit low at 415V, it should be 433V. HT was a bit low at 200V, it should be 205V. CRT heater voltage was again a bit low at 11.5V, should be 12.5V.

Quote:
Originally Posted by Heatercathodeshort View Post
Is C111 on the correct side of R151 i.e the boost 'transformer' side? It will short the blanking pulse to chassis if incorrectly connected.
Yep this is all fine.


Regards
David
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Old 6th Dec 2018, 12:20 am   #188
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Default Re: Help needed restoring a Murphy V310

Quote:
Originally Posted by Radio_Dave View Post
The tube shows nothing without a signal (hope that's normal!) but there's no vertical line, or flyback lines, when the aurora is showing it's internal testcard.
Having read the above and looked back to post 160 (yes, this really has been a long thread!) Your pictures then showed no flyback lines or vertical white line.
I would say therefore, that the TV is blameless and that it has something to do with the external signals.

With no signal applied to the TV, if you turn the brightness control up you will get an evenly illuminated screen.

IF it's all fine with the Aurora's internal testcard, but the line is present with signals fed into the Aurora, then the issue must be there rather than the TV.

What source are you using to feed signals into the Aurora? Can you try a different source and also try powering the Aurora from a different power supply? Even a 9V battery will do temporarily.

Cheers
Nick
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Old 6th Dec 2018, 12:27 am   #189
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Default Re: Help needed restoring a Murphy V310

Your picture looks just as I would expect. There is no evidence of the vertical white line. The flyback lines will be random and dance about as there are no sync pulses with no signal. I would expect them to be visible at high brightness settings.
That confirms my belief that the source of the problem is external to the TV!

Cheers
Nick
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Old 6th Dec 2018, 12:40 am   #190
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Default Re: Help needed restoring a Murphy V310

I have a dual standard Sony 9-9UB somewhere which will hopefully work if I plug it in. It definitely worked a couple of years ago on 625 lines. Tomorrow I'll connect my aurora to it and see if I get the same problems.


Regards
David
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Old 6th Dec 2018, 8:49 am   #191
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Default Re: Help needed restoring a Murphy V310

Coming back to post 181, the raster is showing to me that the crt is still on the low side emission and that you are having to advance the brightness up to compensate, this is what is bringing the fly back lines on the raster.
You wouldn't see the vertical line on testcard c as it is only apparent on a back raster, if you have a small magnet, try holding it near the line output valve whilst observing the line to see if it moves.
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Old 6th Dec 2018, 11:48 am   #192
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Default Re: Help needed restoring a Murphy V310

Quote:
Originally Posted by Freya View Post
Coming back to post 181, the raster is showing to me that the crt is still on the low side emission and that you are having to advance the brightness up to compensate, this is what is bringing the fly back lines on the raster.
I can get a watchable picture if I turn the brightness down enough to get rid of those bright dots in the flyback lines. The vertical white line doesn't go what ever I do. The photo in post #181 is taken with the brightness set way above normal viewing levels only to emphasis the lines in the picture.

I've just hooked up my aurora to a Sony 9-90UB (annoying it works perfectly!) and there's no sign of flyback lines or white bars so I think we can rule out the aurora as a cause. I've also just tried a third input source and a different connection lead on the Murphy and the same problems are still there.

I've ran out of ideas now and I'm sure I'm trying everyone's patience with my ignorance, is it time to call it a day and just use it as it is?

Regards
David
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Old 6th Dec 2018, 4:29 pm   #193
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Default Re: Help needed restoring a Murphy V310

Few last things come to mind, is the choke and resistor in good order that is connected to the top cap of the line output valve ? Also it may be beneficial to fit a 30P4MR version of the output valve.
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Old 6th Dec 2018, 8:42 pm   #194
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Default Re: Help needed restoring a Murphy V310

A new 30P4MR is already fitted.

I've just checked the choke and resistor you refer to (L29 and R253). The choke is wound over the resistor but it's loosely wound and has lost it's insulation (that's if it ever had any?). The resistor reads high at 135R, should be 100R. I don't know how important that choke is or whether it will be OK to wind the old, uninsulated, wire over a new resistor, or should I buy some new enameled copper?

Regards
David
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Old 6th Dec 2018, 8:55 pm   #195
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Default Re: Help needed restoring a Murphy V310

So long as the choke and resistor are there that's fine, seen them missing in the past.
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Old 19th Jan 2019, 7:27 pm   #196
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Default Re: Help needed restoring a Murphy V310

Ok, One last ditch attempt at sorting out his telly.

I've finally flashed a test card C onto my Aurora and got rid of that weird thing that a previous owner must have put on there. The results are interesting in that the vertical lines seem to be notched now whereas the previous test card never showed this?

I'm hoping somebody can see something in the test card which can help solve the problem with that annoying vertical white bar, shown in the second picture. All I can say is it shows up in when the picture is dark and it moves side to side when I turn the Line Hold control.

Thanks
David
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Old 19th Jan 2019, 7:40 pm   #197
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Default Re: Help needed restoring a Murphy V310

The first pic might be video in sync.....overloading?

The second pic looks like Mr Barkhausen might be doing his stuff or some feint arcing.

Lawrence.

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Old 19th Jan 2019, 10:47 pm   #198
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Default Re: Help needed restoring a Murphy V310

Hi Dave,
That looks so much better with TCC than whatever that weird thing was you had before!

That notched effect on the verticals is what I can get if the TV is slightly off tune. Most normal TV's have a fine tune control, but I assume like my V410, it doesn't have one? I find the fine tune control is a pretty critical control on normal TV's. The Murphy is far from 'normal'!

That white band is also something I have come across before. Where, or how I got rid of it is another matter entirely!

Looks like you are so close to having a really good picture too!

Maybe you should ask Mr Heatercathodeshort very nicely if you could pay him a visit with the TV and get him to cast his eye over it. He has worked wonders with other member's sets. If anyone can- John can!!

All the best
Nick
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Old 19th Jan 2019, 11:06 pm   #199
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Default Re: Help needed restoring a Murphy V310

Hello.
The set is simply off tune very slightly. You'll never see the vertical line on a black raster, on a normal transmission a slightly off tune set will always show this phenomenon. You'll need the Murphy tuning stick or a fine long plastic knitting needle entered via the hole next to the channel selector to gain access to the oscillator coil. Trust me this is 100% the issue, very common on any 405 line set and surprised no one else has mentioned this.
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Old 19th Jan 2019, 11:19 pm   #200
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Default Re: Help needed restoring a Murphy V310

Thanks for all the replies. I'll be as pleased as punch if it only needs fine tuning! Just wish I had a plastic knitting needle.


David
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