3rd Dec 2018, 9:36 pm | #181 | ||
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
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Re: Help needed restoring a Murphy V310
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Regards David
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4th Dec 2018, 10:44 am | #182 |
Dekatron
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Location: Warnham, West Sussex. 10 miles south of DORKING.
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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. |
5th Dec 2018, 5:28 pm | #183 |
Nonode
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Location: Norwich, Norfolk, UK.
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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.
Regards David
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5th Dec 2018, 9:29 pm | #184 |
Octode
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Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
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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 |
5th Dec 2018, 10:04 pm | #185 |
Nonode
Join Date: Jun 2004
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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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5th Dec 2018, 11:17 pm | #186 |
Dekatron
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Location: Warnham, West Sussex. 10 miles south of DORKING.
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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. |
6th Dec 2018, 12:14 am | #187 | ||||
Nonode
Join Date: Jun 2004
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Re: Help needed restoring a Murphy V310
Quote:
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Regards David
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6th Dec 2018, 12:20 am | #188 | |
Octode
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
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Re: Help needed restoring a Murphy V310
Quote:
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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6th Dec 2018, 12:27 am | #189 |
Octode
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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 |
6th Dec 2018, 12:40 am | #190 |
Nonode
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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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6th Dec 2018, 8:49 am | #191 |
Octode
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
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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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6th Dec 2018, 11:48 am | #192 | |
Nonode
Join Date: Jun 2004
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Re: Help needed restoring a Murphy V310
Quote:
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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6th Dec 2018, 4:29 pm | #193 |
Octode
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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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6th Dec 2018, 8:42 pm | #194 |
Nonode
Join Date: Jun 2004
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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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6th Dec 2018, 8:55 pm | #195 |
Octode
Join Date: Jan 2009
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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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19th Jan 2019, 7:27 pm | #196 |
Nonode
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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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19th Jan 2019, 7:40 pm | #197 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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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. Last edited by ms660; 19th Jan 2019 at 7:45 pm. |
19th Jan 2019, 10:47 pm | #198 |
Octode
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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 |
19th Jan 2019, 11:06 pm | #199 |
Retired Dormant Member
Join Date: Oct 2015
Location: Fenwick, Glasgow, UK.
Posts: 127
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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. |
19th Jan 2019, 11:19 pm | #200 |
Nonode
Join Date: Jun 2004
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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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