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Old 3rd Nov 2019, 3:09 pm   #21
Niechcial,Steve
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Default Re: Murphy V659/759 restoration

Thanks Dave. The 'no delay' mod would certainly be helpful. Stephen
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Old 3rd Nov 2019, 4:56 pm   #22
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Default Re: Murphy V659/759 restoration

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Thanks Dave. The 'no delay' mod would certainly be helpful. Stephen
It was in Murphy Service News issue 68, November 1964. I have emailed the scans to you.
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Old 3rd Nov 2019, 5:01 pm   #23
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Default Re: Murphy V659/759 restoration

I was intrigued to see in the second photo in post 12, a white label stating "KTM5"(if I have made out the characters correctly) - the photo of your UHF converter (with its bottom cover removed). I’d expect it to be “K659X”.

I wonder if it might be a special version for use with Astra sets made by Murphy for British Relay, as Murphy had a stake in this company. The sets would be for use with lower frequency "wired" (cable) TV signal distribution systems over twisted pair cables, similar to the Rediffusion ones.
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Old 5th Nov 2019, 8:18 pm   #24
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Default Re: Murphy V659/759 restoration

Thanks for the mod details Dave.
A bit more progress on the set. The frame linearity problem and the non-operational contrast control have magically cleared themselves!
The HT feed resistor to the line hold control had gone high, and replacing that has brought the line lock into the centre of the control, but line hold is both sensitive and drifts steadily. I will try a new line osc. and then do some scoping of waveforms.
The bad news is I have low width. Replacing the S capacitor and the osc/output coupling made no difference. I have tried new PY and PL and tried artificially bumping up the HT to the correct value of 215V. No change and so I think I am heading towards a diagnosis of faulty LOPT. I will try removing it from the can and heating the re-assembling with new oil. However before I go there, I will try and work out what has been done with the standards switching and see If I can get the set back to D/S operation.
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Old 5th Nov 2019, 8:20 pm   #25
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Default Re: Murphy V659/759 restoration

By the way, the converter did have a '659X' label as well so I guess it is a standard receiver and not a cable one.
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Old 9th Nov 2019, 11:39 am   #26
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Default Re: Murphy V659/759 restoration

I was not surprised that while I was running the set I got a 'phut', and the LOPT now appears to have shuffled of this mortal coil. So it will go off to Mike Barker for a rewind. That's likely to take at least 3 months, so in the meantime I will continue to work to restore the standards switch etc. to dual standard operation. I will also put an ad out for the loan of a LOPT just in case someone has one.
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Old 17th Dec 2019, 2:21 pm   #27
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Default Re: Murphy V659/759 restoration

I've now had time to go back to this set. The LOPT is away with Mike Barker for rewind, but there is plenty I can do in the meantime. I've put new aquadag on the tube and set it aside for the present. Having the tube out makes the whole chassis much more accessible.
I've started to investigate the issues around this set seemingly being hard wired for 625 only. When it left the factory as a convertible set it was fitted with a partial systems switch which switched the timebase functions only. The converter kit then came with another few switch wafers which attached to those already fitted to make a full switch which switched over video, sound and signal valve heaters. That extra bit of switch is not there on my set and the signal and heater connections are hardwired to 625. I can only conclude that this set was had the 625 kit added after all stations were available on 625 and so the switch was dispensed with. Unless somebody has got that switch on a scrap chassis, I am very unlikely to be able to get one or improvise one so my plan is to use relays to do the necessary switching. While I am at it, I will do the Murphy modification which keeps all valve heaters running and thereby avoids the warn up delay switching between 405 and 625.
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Old 17th Dec 2019, 2:35 pm   #28
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Default Re: Murphy V659/759 restoration

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Originally Posted by Niechcial,Steve View Post
Unless somebody has got that switch on a scrap chassis, I am very unlikely to be able to get one or improvise one.
Hello Steve,

I have almost certainly got what you need, as I have dismantled a few Astra Mark 1 chassis over the years. I'll have a look and get back to you, but it may take several days.

Dave
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Old 18th Dec 2019, 12:04 pm   #29
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Default Re: Murphy V659/759 restoration

Thanks Dave. That's really kind. You've helped me an awful lot on this one! All the best for Christmas.
Steve
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Old 1st Jan 2020, 1:20 pm   #30
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Default Re: Murphy V659/759 restoration

I have done a bit more work on this. Having now disconnected the UHF convertor and effectively put it back temporarily to being a 405 set, I hoped I might get some sound up on VHF and some video on the scope (no tube or LOPT present at the moment). Unfortunately no results- just a faint hiss on channel 5 when the signal is plugged in. Meanwhile, Dave has kindly sorted out the missing part of the system switch conversion for me, so I can give that a go.
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Old 10th Apr 2020, 6:14 pm   #31
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Default Re: Murphy V659/759 restoration

Still waiting for the LOPT on this, but as I now have all the standards switching bits thanks to Dave, I might as well go a head and try and sort that.
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Old 24th May 2021, 10:04 am   #32
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Default Murphy Astra V659 (resumed)

I last posted on this set a year ago here:
https://www.vintage-radio.net/forum/...d.php?t=160941
I left off work at the time because the LOPT died. It went off to Mike Barker for rewind, but because of Covid it maybe sometime before I see it again so I thought I would do some more work and experiment with using a LOPT from a KB VC2 which Peter Sanders kindly gave me. In the meantime a mate has also done an amazing job of reassembling the cabinet which had basically fallen apart.
Where I left off last year was the set hard wired to UHF/625 and displaying a good quality 625 picture with no sound. There were no results on 405, because as I say the set had been hard wired to 625/UHF and also the extra bit of system switch needed to make it 405/625 convertible was not fitted. The UHF part of the set comes in the form of a plinth which screws on underneath the set and is a whole additional receiver up to and including video output valve and sound detector.
Fortunately last year Dave (Dazzlevision) kindly provided me with that piece of system switch NOS, so I set about fitting it. In the original conversion the heaters between the VHF/405 and UHF/625 signal valves are switched, resulting in a delay on switching systems while the relevant heaters warm up. Murphy later published a mod which kept all heaters in circuit so I incorporated that while I was at it.
Having completed the conversion mod, I disconnected the screen feed to the to LOP valve and hooked up a 60W bulb across the HT line to take up the load of the missing LOP, attached a speaker and a scope an switched on. My previous good results on a UHF picture were there on the scope, but nothing on 405, and no sound on UHF. The lack of UHF sound was due to not one, but both sound discriminator diodes being o/c. Lack of VHF picture was due to the PCB track to the on board 405 video output having been cut as part of the previous hard wiring process. restoring that brought up a lovely 405 trace at the connection to tube cathode. I have to turn up the contrast control though to video overload levels to get any 405 line sound. I am not sure what that is about- I will leave it until I can get a picture up.
So I have now turned my attention to the KB LOPT which looked in a pretty sorry state -by the looks of it having been out in the cold and damp for may years. Lashing it to the scan coils via an S correction cap and using the set's valves and boost cap in-situ gave me initially 650 volts boost and 16KV EHT via a silicon rectifier on 625. Almost inevitably both voltages began to drop as damp transformer syndrome showed up. I have since given the LOPT Many hours of the DC heating process and that has improved the situation a lot but it is still not completely stable. Holding a screwdriver anywhere near the windings produces fizzings and arcs so I guess it could die at any moment, I will try putting some solid setting silicon on it and press on. One of the challenges is that the set needs a 150-0-150 v pulse from the LOPT for the flywheel sync. I will have to experiment with winding that on if the LOPT survives
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Old 24th May 2021, 10:36 am   #33
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Default Re: Murphy V659/759 restoration

Original thread reopened to main flow.

Cheers

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Old 25th May 2021, 9:25 am   #34
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Default Re: Murphy V659/759 restoration

Thanks Mike.
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Old 25th May 2021, 3:18 pm   #35
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Default Re: Murphy V659/759 restoration

Attached are some photos of my results so far. I spent a fun afternoon basically playing with different values of S-bend cap trying to get an acceptable balance between width, boost and EHT on both systems. A small change in S bend value makes a big difference- especially to width. As you can see, the results on 405 are almost perfect (although the EHT is a bit high). The results are not so good on 625, with some fold-over on the left and distinct stretch and compression on the picture.

I decided for the moment not to risk putting an extra winding on the LOPT to supply the flywheel line sync board. It would have to go around the main windings and that would bring it perilously near the overwind because the gap between the two would be small. Luckily the set was designed with a flywheel or straight sync option. The components are on a little board which unplugs. so I took out the flywheel board and substituted the two resistors and a cap which make up the direct sync linkage. The lock on 405 is pretty solid. On 625 a small adjustment makes a big difference to the foldover.

It all works well enough for me to try and mount the KB LOPT in the cabinet until the proper LOPT returns. Sadly not enough room in the original LOPT enclosure (which you can see in the photo) so will probably have to go top right above the PY/PL valve bases (these are mounted upside down)
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Old 27th May 2021, 5:15 pm   #36
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Default Re: Murphy V659/759 restoration

I decided before doing anymore with the LOPT I would deal with the issue of low 405 line sound. It turned out that both the detector and noise limiter diodes were o/c. That is 4 o/c germanium diodes so far! So I now have pretty good pictures and sound on both systems.

I have decided to push my luck further with the LOPT. I am going to insulate the overwind with a decent potting silicon, then wind on on some turns over the main bobbin to get the 150-0-150v I need for the flywheel sync panel
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Old 27th May 2021, 6:37 pm   #37
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Default Re: Murphy V659/759 restoration

Quote:
Originally Posted by Niechcial,Steve View Post
I decided before doing anymore with the LOPT I would deal with the issue of low 405 line sound. It turned out that both the detector and noise limiter diodes were o/c. That is 4 o/c germanium diodes so far! So I now have pretty good pictures and sound on both systems.
Those STC GDxx series Germanium diodes don't seem to survive like the glass encapsulated Mullard OAxx series do. I have had to replace many GD types in TVs and radios of the same era as your Murphy Astra TV.
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Old 28th May 2021, 4:36 pm   #38
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Default Re: Murphy V659/759 restoration

Yes, I've not come across those GE ones before Dave. They look nicely sealed but were very o/c (20M+) , so I am not surprised to hear that's a common fault. The sound limiter was of a completely different design and make but that was o/c too.
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Old 28th May 2021, 5:23 pm   #39
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Default Re: Murphy V659/759 restoration

The sound interference limiter is a Q1/5 metal rectifier - also made by STC. It may show o/c in the forward direction, if tested on the diode test range of a DMM.

Whilst I remember, if there is a metal clip around the middle of the U193 valve, remove it - an official mod from Murphy (requested by the valve manufacturer) - it can cause the valve to fail.

Last edited by dazzlevision; 28th May 2021 at 5:28 pm.
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Old 29th May 2021, 1:50 pm   #40
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Default Re: Murphy V659/759 restoration

Yes that clip on the boost diode is there Dave. As a matter of interest how does it cause the valve to fail? When I got this set the first thing I had to do was replace the boost diode valve holder because of internal sparking.
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