Thanks for posting the outcome in the title, I upvoted just because of that. Too many TH-camrs doing clickbait and you are definitely not one of them. Great video!
This wasn't meant to happen , I made a big mistake not placing the line panel in a warm place for a few months and now I cant find a replacement transformer anyware, wont be making this mistake again !
@@michaeldranfield7140 Its the way its all gone. I never did TV repairs but more the audio side of things. We used to use large frame analogue mixing consoles which where great to repair at component level. Now its all gone digital its taken a lot of the fun out of it! Its all become a bit bland i guess.
I had a contract with a hotel in the 80's that had 300 of these mk3 sets that were setup for use on a HF system. They had no tuner and would provide sound even if the set was unplugged from the mains. Back in the day I could repair these with my eyes closed. The 20'' set was very reliable with only a few dry joints, the odd Tripler and an 82 ohm resistor giving any trouble. A friend had a contract with another hotel chain at the time which used 22' sets. He replaced Tripler's on a daily basis. I never has a CRT give trouble on the 20'' sets . They were made by Hitachi. To be honest I made the price of my first home out of these sets. The front panel fitted to the set in the video was a kit that was sold in Ireland to allow sets with 6 buttons etc be used on a cable system. The kit was made in Italy I think. Thanks for the memories.
Glad you liked the video and it's interesting the kit was sold in Ireland as that's where the set came from, I have largely forgotten about these sets now but the trip down memory lane was good.
I remember these TVs as Cable Viewing Terminals the cable version didn't have a tuner just a selector box by the window sill... when it changed over that cable tv had satellite channels everyone was moved over to own aerial system either southern or London tv. and had to have a converter box for the cable only set to receive UHF signals. I remember people complaining about that back then
I did my apprenticeship at Rediffusion back in 1976, there was an earlier MK 1 hybrid colour model using the PL509 and PY500a bottles very similar to the Decca 30 chassis. I always remember the first brand new MK3 arriving in the workshop and the senior apprentice letting the chassis drop and necking the tube. “Panel bashing” was the field repair method at the time the faulty ones being repaired on “the rig” in the workshop so we never had to stick our hands in tight spaces.
I managed to get the other set out after moving a lot of stuff in the hope it would have the same chassis but it turned out to be a valve hybrid and this would have normally excited me as I don't have any other valve hybrid colour sets but it's in very poor condition so not a restoration prospect.
Steve Eardley , Someone had an accident with a Thorn 3000 test jig on a training course , they pushed it too hard against the wall and did the same thing , necked the tube. It was easy to replace it though with a below spec crt.
Saw one or two mk3s and mk4s at Visionhire ex Rediffusion , my friend Pete always fixed them in the field as I think he was ex Rediffusion or British Relay . They were rather rare in our neck of the woods though by the late 80s on rental.
Another excellent video Michael, much appreciated. I too worked for Rediffusion, way back in the '60s. I later worked for Rank, where we had a reciprocal engineering agreement with RVS, & so used their receivers in hotel installations. I think I may have either a MK3 or MK4 somewhere in my workshop, I cant remember which. You could get the LOPT rewound of course, but not cheap. I hope you can get it going again.
I just put it to one side at the moment but in thd meantime the plan is to get a Rank Z718 going but I'm not going to make the same mistake again, the 718 line panel is in the airing cupboard at home for a few weeks to drive out any moisture first.
OMG, been doing a lot of TV sets with that type of line output. We had a lot of Grundig and Luma/Körting sets here in Denmark when I was working in a repair shop in the beginning of the 80s. The normal issues when the line output transformer goes bad, are one of the 3 main caps are faulty, thats the caps between the 2 thyristors. Its seldom the coils that goes wrong. Sometimes it can also be the tripler that has caused the faulty line output transformer, especially if the set has been placed in a damp place. It should be possible to check the thyristors with a ohmmeter, normally they short between Cathode and Anode. A great video, bringing a past time from my youth. Good luck with the repair.
I think this transformer may have also been used in ITT set as well , working on another old set at the moment but going to make sure its well dried out before plugging in , the line panels at home in the airing cupboard at the moment !
I like the way you said at the end of your vid: "If I ever do get this set going". lol!! Now you know the trouble all the Field Service Techs had at Rediffusion with the Mk3 lol 😀 I worked for them at Basildon Essex all through the 70s until 1986,.Granada TV took Redifusion over by then. Yes that discoloured safety resistor on the PSU was common feature Michael. "Apart from stock faults", and there wasn't many, we changed the PCB to cure a problem. As you found out accessibility was not good at all. At the service depot, (if my memory is right) we had a fully working 'open skeleton test jig' with CRT, to fit a faulty PCB into and take diagnostic tests on the boards, we certainly had that for the Rediffusion Mk1 anyway.
I think the modular construction just made life easy for the rental boys so they could do a repair in a few minutes and then take the faulty board back to base for a bench engineer to repair as you say on a skeleton set, Realistically I don't think there is much chance of finding a LOPT, I did dig out the other set I have but it's valve hybrid and in very poor condition.
Reminds me of the time back in 86 me and a friend found a source of Mk 1 Dorics. We used to buy them untested for a tenner and sell them for £30. People bought them as it was world cup football year. We both worked in a telephone exchange so we had access to any test equipment that we might need. Most of them worked OK when we tested them, just needed a bit of setting up. The faulty ones needed the odd valve or caps changing. We had a few scrappers which we could use to repair the other sets. We never had a faulty tube and we must have bought at least 70 or 80 of them. Happy days!
Glad you liked the video, I too started out buying untested ex rental TV s, these were the days when TVs were so expensive a lot of people rented and so like you say there was a big demand for second hand sets, if only we could turn the clock back.
Good luck finding that transformer Michael. Long gone are the days when you could just pop to Wizard distributers and get one off the shelf, sadly. Interesting design though. Reminds me of some Sony sets where the power supply staying up is conditional on the line output stage working. Enjoyed watching the fault-finding process. Not a service friendly set by the look of it.
@@manolisgledsodakis873 I use to deal with Telepart back in the 80 s , not sure if they didn't later re name themselves Economic devices ? long gone now though and they did tend to be more expensive than most suppliers .
@IrishvintageTVRadio @michaeldranfield7140 Excellent video! I have a question: at 39:36 you're using a box that energizes the flyback transformer. Do you have any information on it?
I wish , cant remember the name of the company I bought this from without taking a look in an old Television magazine but inside its filled with epoxy resin to stop anyone copying it sadly.
We had a set which looked just like this one, but it was connected to the Rediffusion cable system. There was a rotary channel switch on the window cill. The sound worked even when the set wasn’t powered. The text under the modification panel read “precision inline”, which intrigued me as an approx ten year old. The previous Rediffusion model we had seemed to have a specific valve changed every six months. The technician used to let me have it.😊
Thanks for the video, I find it really interesting how you work through and fault find. I hope you manage to get a transformer and do another video Regards Mike
It was the Mark 4 that had on off switch with the relay on , the number of ex rental mark 4s with no on off knobs for sale in the trade warehouses was amazing. That mk3 looks like something Heath Robinson modified good luck with that one Michael
Oh. Those Philips/BC blue rectangular caps were quite troublesome, though they generated good repair work for me. Often easy to diagnose when faulty due to the bulge on the casing.
Didn't the Redifusion TV origanaly have what can be called piped (wired) compasit video and chanel selected via a wall switch ? Or was that the monocrome versions, just wondred if tgsts why this set was modified!
This video is absolute gold, I sat here open mouthed as you ran through your encyclopaedic knowledge of that set. Just a thought, perhaps the 150k wasn't open at the time the 27k was fitted?
Very popular in South Africa when I lived there, in fact I was asked to repair as a trade test before starting a new job with a repair company. Power supply/ line and field faults were the usual faults with these and the odd triplet…
@@michaeldranfield7140 No Mike, they were in plentiful supply, along with Thorn 4000’s Philips KT3/K9, other makers sets including Blaupunkt ( featured a thyristor line output stage as well…)Telefunken (711 and 715)Grundig and Sony…Spares backup was second to none, we could even source replacement cabinets, from local suppliers, if needed…
I remember in the late 70s quite a few sets had a Thyristor line output stage, the grundig sets yould get dry joints and suffer massive burn ups on the pcb, happy days.
Another extremely interesting and informative video - thank you for sharing your extensive knowledge with us. I particularly like the way you go through the schematic during the diagnosis explaining your reasoning as you trace down the fault. Is it not possible to strip down the transformer and re-build it correcting the fault?
I used to work on a lot of Rediffusion sets in the nineties, mainly Mk4s which were very easy to swap out boards on and quite easy to fix. I remember a few Mk3s with frame collapse but I think it was always caps. Rediffusion made a MK1 colour set, with valve line output, Mk3 with the thyristor line output, the Mk4 with a more conventional self oscillating SMPSU and line output. The Mk5 was a 14" sharp portable, I don't know about the Mk2.
Great video Michael. It brought back many memories of repairing boards for the mk3 on the rig, which was basically a metal frame with all the wiring, and sliding racks to mount the boards. As previous comments suggested, Rediffusion field engineers tended to just replace the faulty boards, which were then returned to the worshop to be repaired on the rig. Lopts were pretty common failures, as were the triplers, but i think the most common issues i found were related to the tuners and colour related issues on the decoder boards
The modular approach was a good an aid to fault finding and I can see how it would enable the service engineer to do more calls in one day, happy days , sadly now long gone .
I used to fix TVs a few years on from that which used a chip in the vertical deflection circuit. In nearly every case it was just a job of replace the chip and anything else that looked damaged like bad electrolytics or fried resistors. A scope was unnecessary and on one occasion I blew my scope up testing a TV. Scopes and TVs don't mix!.
Nowdays one can only hope,someone leaks the schematics and boardview through the internet.Back then,when buying an appliance,you d recieve the service manual and diagrams inside the package.I dont expect a printed version,but a url on the schematics would be nice.
Conscientious attempt. I'm slightly confused (no change there), although there was frame collapse, the line / EHT side appeared to be working initially. Granted there wasn't much load on the line side. Pure guesswork on my part, but could some of those dodgy looking caps on the line side be responsible for poor starting?
My experience of those blue caps is you can usually tell when they are faulty as the case tends to expand , what I should have done is baked the transformer in the oven before switching the set on , too late now though .
@@michaeldranfield7140 It was the universal thyristors that I used. Badged Konig 15/80H and 15/85R. The original ones were TD3F 900. I still have some here.
You could put out a request on VRAT, in the wanted section. Just a thought. After Saturday's live stream with OjNoj, I remembered that I have a few LOPTs in a box in my container, but having seen this one tonight, I know I don't have one to suit this job - mine are all diode split jobbies. I can see how a Mike Barker rewind would be the answer, but we'd need to know the turns count for the existing TX. I know DB has a lot of LOPT data, but whether this one would be in there would be anyone's guess. Again, an info request might turn up something. You could open a forum thread in this set and see who might be able to help. We have some good'uns on there.
Hi , Yes this will be my next move , I dont see why you cant cut off the old overwinding and place a new one on the other limb of the transformer but replacement overwinding are another think of the past now long gone .
Oh my god, old colour TVs contained so many parts and components. It’s no wonder why they were so expensive back in their day and of course many people would choose to rent instead of buy
A bit disappointing after all the time spent in tracing, but I do remember the 'overwind' in layers of cellulose-like insulation, which I think is slightly hygroscopic. In Australia, Philips (Mullard) made many TV's with this type of transformer, and many were replaced, alongside triplers. Our main suppliers (in the '90's and '00's) were based in Spain called 'HR Diemen', and had many cross-referenced part numbers (FAT ..etc..), so it might be worth trying to find an equivalent.. ('equivalencia')..
@@pauldavies6037 These videos are so enjoyable, they take me back to my time repairing TV's in the 1980's. I found the HR transformers very good quality, I had a lot of G8's on my books and the HR was a good solution for those, I only ever had one HR/G8 failure. Whenever I fitted a genuine 'Philips Service' LOPT to a G8 I always had an unhappy feeling that I'd be back to the same set sometime soon for the same problem. 😐
Lucky a didn't get many mk3 or 4s for repair ideal for the rental market for the field panel swop guys I hated the over complicated circuits and any body using thyrisors in PSU or Line stages
Is there any update on the mk4? Also, is there any way I'd be able to contact you privately to potentially bring my mk4 down to you if that's possible?
@@michaeldranfield7140 Okay thanks Michael I appreciate that. I've made a note of your number. Ill be in touch on Thursday. Might be best to delete your number off of TH-cam comments just in case anybody tries to prank call you or something.
@michaeldranfield7140 Thanks, Michael. I appreciate the help. I'll give you a ring on Thursday, many thanks. I've made a note of your number now, maybe best to delete the number off of the youtube comments so nobody makes any prank calls to you or anything.
JJ atcually brought 5 sets over in his van ! Im working on the next one now , A Murphy Z718 but Im not going to make the same mistake again , the line panels at home in the airing cupboard for a few weeks before I start anything .
I still have a vague recollection of the Mk 4 , I seem to remember dry joints on a Blue chopper transformer mounted on a vertical power board with nothing to hold the transformer apart from its solder connections ?
@@michaeldranfield7140 Also a dry joint on the blue capacitor next to the chopper transistor If you were unlucky This makes the chopper go O/C and takes many components with it .
This transformer looks very similar to soviet TV transformer "твс-110пц15" or "твс-110пц16". Soviet made TV's to the end of USSR used separate transformer and rectifier, also highvoltage rectifier looks like it's soviet counterpart.
thats the biggest problem with crt tvs and keeping them going, lopt failure, i had to scrap a nice nec tv in the late 90s as that had a failed lopt and no supplies of the transformer or any other parts for it anywhere.....if you havent yet done so, see if donberg electronics have a lopt, they still have some types, probably the last place that has any.....
I find it just too much of a coincidence that the set worked for a while, and then dies with this transformer developing a fault. That is an unlikely event. i would expect a capacitor to die when the set is turned on after such a long time, but not the HT transformer.
Thanks for posting the outcome in the title, I upvoted just because of that. Too many TH-camrs doing clickbait and you are definitely not one of them. Great video!
This wasn't meant to happen , I made a big mistake not placing the line panel in a warm place for a few months and now I cant find a replacement transformer anyware, wont be making this mistake again !
TVs with Wood always give me Warm Feeling...
Especially the valve hybrids like the CVC9.
I could just sit and watch these all day long! :)
I know what you mean , if only we could turn the clock back to when sets were repairable , I was so happy in the early days .
@@michaeldranfield7140 Its the way its all gone. I never did TV repairs but more the audio side of things. We used to use large frame analogue mixing consoles which where great to repair at component level. Now its all gone digital its taken a lot of the fun out of it! Its all become a bit bland i guess.
@@gonzinigonz and now everything is software driven so half the time you cant tell if a problem is hardware related , or software related .
I had a contract with a hotel in the 80's that had 300 of these mk3 sets that were setup for use on a HF system. They had no tuner and would provide sound even if the set was unplugged from the mains. Back in the day I could repair these with my eyes closed. The 20'' set was very reliable with only a few dry joints, the odd Tripler and an 82 ohm resistor giving any trouble. A friend had a contract with another hotel chain at the time which used 22' sets. He replaced Tripler's on a daily basis. I never has a CRT give trouble on the 20'' sets . They were made by Hitachi. To be honest I made the price of my first home out of these sets. The front panel fitted to the set in the video was a kit that was sold in Ireland to allow sets with 6 buttons etc be used on a cable system. The kit was made in Italy I think.
Thanks for the memories.
Glad you liked the video and it's interesting the kit was sold in Ireland as that's where the set came from, I have largely forgotten about these sets now but the trip down memory lane was good.
I remember these TVs as Cable Viewing Terminals the cable version didn't have a tuner just a selector box by the window sill... when it changed over that cable tv had satellite channels everyone was moved over to own aerial system either southern or London tv. and had to have a converter box for the cable only set to receive UHF signals. I remember people complaining about that back then
I have heard about a cable version but round here we never got cable so I have never seen that one .
I did my apprenticeship at Rediffusion back in 1976, there was an earlier MK 1 hybrid colour model using the PL509 and PY500a bottles very similar to the Decca 30 chassis. I always remember the first brand new MK3 arriving in the workshop and the senior apprentice letting the chassis drop and necking the tube. “Panel bashing” was the field repair method at the time the faulty ones being repaired on “the rig” in the workshop so we never had to stick our hands in tight spaces.
I managed to get the other set out after moving a lot of stuff in the hope it would have the same chassis but it turned out to be a valve hybrid and this would have normally excited me as I don't have any other valve hybrid colour sets but it's in very poor condition so not a restoration prospect.
I trained at Visionhire
Was very good mainly GEC Philips and Thorn
@@markdunstan8277 I loved the GEC 2010 s back in the 80 s
Steve Eardley , Someone had an accident with a Thorn 3000 test jig on a training course , they pushed it too hard against the wall and did the same thing , necked the tube. It was easy to replace it though with a below spec crt.
Saw one or two mk3s and mk4s at Visionhire ex Rediffusion , my friend Pete always fixed them in the field as I think he was ex Rediffusion or British Relay . They were rather rare in our neck of the woods though by the late 80s on rental.
What a saga! Nice to see the Dranfield homebrew test gear coming out 😀
some home brew stuff I still have I made as a kid !
Another excellent video Michael, much appreciated.
I too worked for Rediffusion, way back in the '60s. I later worked for Rank, where we had a reciprocal engineering agreement with RVS, & so used their receivers in hotel installations.
I think I may have either a MK3 or MK4 somewhere in my workshop, I cant remember which.
You could get the LOPT rewound of course, but not cheap.
I hope you can get it going again.
I just put it to one side at the moment but in thd meantime the plan is to get a Rank Z718 going but I'm not going to make the same mistake again, the 718 line panel is in the airing cupboard at home for a few weeks to drive out any moisture first.
OMG, been doing a lot of TV sets with that type of line output. We had a lot of Grundig and Luma/Körting sets here in Denmark when I was working in a repair shop in the beginning of the 80s.
The normal issues when the line output transformer goes bad, are one of the 3 main caps are faulty, thats the caps between the 2 thyristors. Its seldom the coils that goes wrong. Sometimes it can also be the tripler that has caused the faulty line output transformer, especially if the set has been placed in a damp place.
It should be possible to check the thyristors with a ohmmeter, normally they short between Cathode and Anode.
A great video, bringing a past time from my youth.
Good luck with the repair.
I think this transformer may have also been used in ITT set as well , working on another old set at the moment but going to make sure its well dried out before plugging in , the line panels at home in the airing cupboard at the moment !
Excellent fault finding great video Michael. Love the old school TV workshop reminds of the day I was in the trade. Thanks Michael good health sir
Old school was best, the days when you could atcually repair stuff, sadly now long gone but I'm enjoying the trip down memory lane
I like the way you said at the end of your vid: "If I ever do get this set going". lol!! Now you know the trouble all the Field Service Techs had at Rediffusion with the Mk3 lol 😀 I worked for them at Basildon Essex all through the 70s until 1986,.Granada TV took Redifusion over by then. Yes that discoloured safety resistor on the PSU was common feature Michael. "Apart from stock faults", and there wasn't many, we changed the PCB to cure a problem. As you found out accessibility was not good at all. At the service depot, (if my memory is right) we had a fully working 'open skeleton test jig' with CRT, to fit a faulty PCB into and take diagnostic tests on the boards, we certainly had that for the Rediffusion Mk1 anyway.
I think the modular construction just made life easy for the rental boys so they could do a repair in a few minutes and then take the faulty board back to base for a bench engineer to repair as you say on a skeleton set, Realistically I don't think there is much chance of finding a LOPT, I did dig out the other set I have but it's valve hybrid and in very poor condition.
Ex GTVR field engineer, we ran a mile if a Redifusion set was on the job list,we swapped them out for our more friendly Finlandia's😃
@@TheRogey1 Finlandia, that's a name I haven't heard for a long-time
Great videi Michael Lopt memories from 1990s for me. I really hope you can get part 2 success
Yep, here's hoping, the Internet a big place and who knows someone who watches video may just have one.
Reminds me of the time back in 86 me and a friend found a source of Mk 1 Dorics. We used to buy them untested for a tenner and sell them for £30. People bought them as it was world cup football year. We both worked in a telephone exchange so we had access to any test equipment that we might need. Most of them worked OK when we tested them, just needed a bit of setting up. The faulty ones needed the odd valve or caps changing. We had a few scrappers which we could use to repair the other sets. We never had a faulty tube and we must have bought at least 70 or 80 of them. Happy days!
Glad you liked the video, I too started out buying untested ex rental TV s, these were the days when TVs were so expensive a lot of people rented and so like you say there was a big demand for second hand sets, if only we could turn the clock back.
@@michaeldranfield7140 If you turn the clock back I think it would cause frame instability.
Good luck finding that transformer Michael. Long gone are the days when you could just pop to Wizard distributers and get one off the shelf, sadly. Interesting design though. Reminds me of some Sony sets where the power supply staying up is conditional on the line output stage working. Enjoyed watching the fault-finding process. Not a service friendly set by the look of it.
Yes, it is indeed sad but you never know one may turn up one day.
@@michaeldranfield7140 Just order one from Telepart in Wolverhampton. ;-)
@@manolisgledsodakis873 I use to deal with Telepart back in the 80 s , not sure if they didn't later re name themselves Economic devices ? long gone now though and they did tend to be more expensive than most suppliers .
@IrishvintageTVRadio @michaeldranfield7140 Excellent video! I have a question: at 39:36 you're using a box that energizes the flyback transformer. Do you have any information on it?
I wish , cant remember the name of the company I bought this from without taking a look in an old Television magazine but inside its filled with epoxy resin to stop anyone copying it sadly.
@@michaeldranfield7140 Thank you for the response. I may make my own with a 555 to drive the coil. Keep up the great work!
Thank you for another educational video! Learnt quite a lot from it!
More old TV s to come !
We had a set which looked just like this one, but it was connected to the Rediffusion cable system. There was a rotary channel switch on the window cill. The sound worked even when the set wasn’t powered. The text under the modification panel read “precision inline”, which intrigued me as an approx ten year old. The previous Rediffusion model we had seemed to have a specific valve changed every six months. The technician used to let me have it.😊
I dont know the cable version as we never had cable round here .
Thanks for the video, I find it really interesting how you work through and fault find. I hope you manage to get a transformer and do another video Regards Mike
I think the chances of coming across a replacement LOPT are very slim but you never know someone watching my channel may just have one tucked away.
interesting i repaired many mark 4 but never came across a mark 3 .Look forward to part 2.
Unfortunately unless I can come across a replacement transformer there wont be a part 2 .
It was the Mark 4 that had on off switch with the relay on , the number of ex rental mark 4s with no on off knobs for sale in the trade warehouses was amazing. That mk3 looks like something Heath Robinson modified good luck with that one Michael
Yes I seem to remember something about the knob ejecting when you switched the set off with the handset .
Oh. Those Philips/BC blue rectangular caps were quite troublesome, though they generated good repair work for me. Often easy to diagnose when faulty due to the bulge on the casing.
Dry joints always seem to kill them.
Didn't the Redifusion TV origanaly have what can be called piped (wired) compasit video and chanel selected via a wall switch ? Or was that the monocrome versions, just wondred if tgsts why this set was modified!
I cant remember but I think you are correct as these were for the rental market , you might see this working one day , I have a new transformer now .
Doric was a great set. I had one of those in the 80s. That was my last colour tv
I know , most sets back in the early days were good sets until surface mount started to take over .
@@michaeldranfield7140 were tx 10 worse than dorec then?
I think there would be more chance of repairing a TX 10 as the line transformer and combined chopper split diode transformer very rarely failed.
I keep my fingers crossed that you can locate a LOPT.
You never know , I keep seeing stuff on e bay I never thought I would ever see again .
Very informative Michael, edge of seat stuff I will look out for the next episode ****
Regards
Dave. 😄
No part 2 if I can't find a LOPT, fingers crossed though one may turn up.
This video is absolute gold, I sat here open mouthed as you ran through your encyclopaedic knowledge of that set.
Just a thought, perhaps the 150k wasn't open at the time the 27k was fitted?
Very popular in South Africa when I lived there, in fact I was asked to repair as a trade test before starting a new job with a repair company. Power supply/ line and field faults were the usual faults with these and the odd triplet…
I didn't realize these sets were exported , I assumed they were made just for the British rental market
@@michaeldranfield7140 No Mike, they were in plentiful supply, along with Thorn 4000’s Philips KT3/K9, other makers sets including Blaupunkt ( featured a thyristor line output stage as well…)Telefunken (711 and 715)Grundig and Sony…Spares backup was second to none, we could even source replacement cabinets, from local suppliers, if needed…
I remember in the late 70s quite a few sets had a Thyristor line output stage, the grundig sets yould get dry joints and suffer massive burn ups on the pcb, happy days.
Great video very informative
Another extremely interesting and informative video - thank you for sharing your extensive knowledge with us. I particularly like the way you go through the schematic during the diagnosis explaining your reasoning as you trace down the fault.
Is it not possible to strip down the transformer and re-build it correcting the fault?
I think it would be possible to cut off the overwinding and place one on the other limb but it's where to get a replacement from
I used to work on a lot of Rediffusion sets in the nineties, mainly Mk4s which were very easy to swap out boards on and quite easy to fix. I remember a few Mk3s with frame collapse but I think it was always caps. Rediffusion made a MK1 colour set, with valve line output, Mk3 with the thyristor line output, the Mk4 with a more conventional self oscillating SMPSU and line output. The Mk5 was a 14" sharp portable, I don't know about the Mk2.
I dug the other set out and it was a valve hybrid so no donor there.
I have a vauge recollection on one been a sharp.
This set may have been modified by John buckle he worked at Reddifusion at harrow St Anns road a vey good engineer. I worked there back in the 79/80s.
This is not something I ever remember , converting a set into remote control
Great video Michael. It brought back many memories of repairing boards for the mk3 on the rig, which was basically a metal frame with all the wiring, and sliding racks to mount the boards. As previous comments suggested, Rediffusion field engineers tended to just replace the faulty boards, which were then returned to the worshop to be repaired on the rig. Lopts were pretty common failures, as were the triplers, but i think the most common issues i found were related to the tuners and colour related issues on the decoder boards
The modular approach was a good an aid to fault finding and I can see how it would enable the service engineer to do more calls in one day, happy days , sadly now long gone .
I used to fix TVs a few years on from that which used a chip in the vertical deflection circuit. In nearly every case it was just a job of replace the chip and anything else that looked damaged like bad electrolytics or fried resistors. A scope was unnecessary and on one occasion I blew my scope up testing a TV. Scopes and TVs don't mix!.
That LOPT test gear looks great Have you any links to circuit diagram etc
I was thinking of doing a video on line transistor test sets in the near future.
Nowdays one can only hope,someone leaks the schematics and boardview through the internet.Back then,when buying an appliance,you d recieve the service manual and diagrams inside the package.I dont expect a printed version,but a url on the schematics would be nice.
Conscientious attempt. I'm slightly confused (no change there), although there was frame collapse, the line / EHT side appeared to be working initially. Granted there wasn't much load on the line side. Pure guesswork on my part, but could some of those dodgy looking caps on the line side be responsible for poor starting?
My experience of those blue caps is you can usually tell when they are faulty as the case tends to expand , what I should have done is baked the transformer in the oven before switching the set on , too late now though .
@@michaeldranfield7140 Agree, Apologies, I should have clarified by mentioning the black cap (16:36). As you say, too late now.
Never had a LOPT go on these. You have to fit new LOPT thyristors as they break down under load at switch on.
With hindsight I should have baked the LOPT in the oven first, I still have some universal Thyristor in stock from many years ago.
@@michaeldranfield7140 It was the universal thyristors that I used. Badged Konig 15/80H and 15/85R. The original ones were TD3F 900. I still have some here.
@@philipturner5100 Thats the ones I have , the Konig
You could put out a request on VRAT, in the wanted section. Just a thought.
After Saturday's live stream with OjNoj, I remembered that I have a few LOPTs in a box in my container, but having seen this one tonight, I know I don't have one to suit this job - mine are all diode split jobbies.
I can see how a Mike Barker rewind would be the answer, but we'd need to know the turns count for the existing TX. I know DB has a lot of LOPT data, but whether this one would be in there would be anyone's guess. Again, an info request might turn up something.
You could open a forum thread in this set and see who might be able to help. We have some good'uns on there.
Hi , Yes this will be my next move , I dont see why you cant cut off the old overwinding and place a new one on the other limb of the transformer but replacement overwinding are another think of the past now long gone .
Oh my god, old colour TVs contained so many parts and components. It’s no wonder why they were so expensive back in their day and of course many people would choose to rent instead of buy
Yes , they were expensive in the day compared to wages but big components made everything so easy to test and repair ..
I wonder if part of the reason for the tuning mod was a VHF conversion? Ireland ran 625 on VHF right up to analogue switchoff.
Could be, I'm not sure , they seem to do things differently in Ireland than in the UK .
I didn't think Rediffusion TVs actually had tuners in them, and were fed from the channel switch on the wall, window sill, etc.
A bit disappointing after all the time spent in tracing, but I do remember the 'overwind' in layers of cellulose-like insulation, which I think is slightly hygroscopic. In Australia, Philips (Mullard) made many TV's with this type of transformer, and many were replaced, alongside triplers. Our main suppliers (in the '90's and '00's) were based in Spain called 'HR Diemen', and had many cross-referenced part numbers (FAT ..etc..), so it might be worth trying to find an equivalent.. ('equivalencia')..
Yes in the UK those HR transformers were a God send often better made than the originals and cheap
Yes , I have the HR datasheet for the transformer , the equivalent is HR 1174 but cant find anything for sale on the internet .
there were cracks in the outer insulation , I should have taken more notice of this in the first place .
@@michaeldranfield7140 It could be said, "A trap for young players", but from time to time, it extends to the 'older' ones (players) too...
@@pauldavies6037 These videos are so enjoyable, they take me back to my time repairing TV's in the 1980's. I found the HR transformers very good quality, I had a lot of G8's on my books and the HR was a good solution for those, I only ever had one HR/G8 failure. Whenever I fitted a genuine 'Philips Service' LOPT to a G8 I always had an unhappy feeling that I'd be back to the same set sometime soon for the same problem. 😐
Lucky a didn't get many mk3 or 4s for repair ideal for the rental market for the field panel swop guys I hated the over complicated circuits and any body using thyrisors in PSU or Line stages
In the late 70s quite a few sets had Thyristor line stages, it must have been the new in thing at the time.
I have a mk4 that won't power on. Any advice would be appreciated, also found one of these mk3s dead near an abandoned house once.
Coincidentally someone is suppose to be bringing a Rediffusion Mk 4 in for repair tomorrow , contact me back in a few days time .
Is there any update on the mk4? Also, is there any way I'd be able to contact you privately to potentially bring my mk4 down to you if that's possible?
@@williamfinch2777 no update as it never turned up, give me a ring on Thursday 01298 73989.
@@michaeldranfield7140 Okay thanks Michael I appreciate that. I've made a note of your number. Ill be in touch on Thursday. Might be best to delete your number off of TH-cam comments just in case anybody tries to prank call you or something.
@michaeldranfield7140 Thanks, Michael. I appreciate the help. I'll give you a ring on Thursday, many thanks.
I've made a note of your number now, maybe best to delete the number off of the youtube comments so nobody makes any prank calls to you or anything.
How on earth did you get that TV from Ireland in one piece?
JJ atcually brought 5 sets over in his van !
Im working on the next one now , A Murphy Z718 but Im not going to make the same mistake again , the line panels at home in the airing cupboard for a few weeks before I start anything .
👍 For your effort !!
All that effort for about 10 seconds viewing of a raster.
@@michaeldranfield7140 - I know, I've been their! Thanks...
Not sure about the mk3
But the Mk4 was a brilliant set very reliable
I still have a vague recollection of the Mk 4 , I seem to remember dry joints on a Blue chopper transformer mounted on a vertical power board with nothing to hold the transformer apart from its solder connections ?
@@michaeldranfield7140
Also a dry joint on the blue capacitor next to the chopper transistor
If you were unlucky
This makes the chopper go O/C and takes many components with it .
This transformer looks very similar to soviet TV transformer "твс-110пц15" or "твс-110пц16". Soviet made TV's to the end of USSR used separate transformer and rectifier, also highvoltage rectifier looks like it's soviet counterpart.
Looks very similar to transformers fitted in TTT sets also and some other German sets.
thats the biggest problem with crt tvs and keeping them going, lopt failure, i had to scrap a nice nec tv in the late 90s as that had a failed lopt and no supplies of the transformer or any other parts for it anywhere.....if you havent yet done so, see if donberg electronics have a lopt, they still have some types, probably the last place that has any.....
Tried Donberg already any they dont have the one .
@@michaeldranfield7140 bummer 😢
Can only see one valve in that telly 😂
Shame about the transformer, hopefully you can source a replacement.
Just put the set to one side for now , you never know something may come up .
I find it just too much of a coincidence that the set worked for a while, and then dies with this transformer developing a fault. That is an unlikely event. i would expect a capacitor to die when the set is turned on after such a long time, but not the HT transformer.
sorry, too much beeping in the backbround puts me off watching :o(
security camera , I turned the sensitivity down to minimum but it still detects a fly going past .
Whats that bleeping in the background Michael?
That'll be his carbon monoxide alarm. You get used to 'em, eventually... 🙂
Security camera, triggers if a fly goes past, I have turned the sensitivity down to minium but its still to sensitive.
Great video very informative
hi , Many thanks for that , just a shame it didn't have a happy end !
Great video very informative