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Split Diode LOPT Testing: Diemen STVDST-01 Flyback tester

 
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10839

Over the years when a LOPT was under suspicion I've used the age old method of ringing with a scope and occasionally using the JABCO LOPT tester to see if all is well or not!

loptst

The split diode LOPTS found in later sets I've not had much dealing with but do now have a few sets in the collection that have them installed. Those that know me will know I have an interest in test equipment, even if it is infrequently used, so in to the fray steps the HR Diemen flyback tester. I've occasionally seen these turn up on e-bay but never really considered buying one. Norman however whilst clearing out all his kit, kindly passed one on to me with the box of service data, it came boxed with all its leads, manual and technical data.

Now other than the handful of sets in the collection with these split diode LOPTS installed, I only had a couple of loose ones in stock. One is a brand new one I bought for one of the B&O sets and the data book does not have it listed for connections to the tester. The other is a manky pull from what appears to be a Ferguson TX80, its code being HR 7527, now that was in the book.

Consulting the data I connected all the leads to the specified pins. The manual shows the kV value I should expect to be displayed upon testing a good LOPT. For this LOPT '27kV' but instead all I get is the red LED lit and a first segment error code of '5'.

This means there is a direct short circuit in the primary feed terminal or in the initial coil of the primary winding near the feed terminal. This can be verified with an  oscilloscope showing no return pulse only continuous feed voltage but pulses being present in auxiliary windings.

Bored yet? Sorry just thought it might be of interest and I suspect there might be a few old hands ( R2B, JCB, etc) who may have used one in the past and enjoyed seeing one again.

stvdst
hr7527
tst2
tst1
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Topic starter Posted : 08/08/2019 5:06 pm
Cathovisor
(@cathovisor)
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Posts: 5477

D'you know, I'm sure I have one of those buried in a store...? Turned up in a mixed box of junk from a Chas Miller auction, I think. 

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Posted : 08/08/2019 6:26 pm
Norman-Raeburn
(@norman-raeburn)
Trusted V-Ratter Registered
Posts: 174

Hi Chris, Glad everything arrived ok, it will keep you amused for a while. Now I have a box of about 20 nos lopt's all split diode type. Do you or anyone else want them before they go to the tip. Norman

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Posted : 08/08/2019 7:28 pm
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crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10839

@norman-raeburn

I will offer them safe harbour in crusty stores. I'll catalogue them and should myself or anyone be in need in the future, well we will be sorted. We can't have rocking horse doo doo's being lost to landfill now can we. ? 

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Topic starter Posted : 08/08/2019 7:38 pm
Norman-Raeburn
(@norman-raeburn)
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Posts: 174

@crustytv

Hi Chris, I will look for a suitable box and get them off to you in the next few days. Now what else do I want rid off!!! Norman

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Posted : 08/08/2019 7:40 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10839

I'll have that 19" GEC 2028 you forgot about lurking under your desk ? ? 

Don't suppose you have a Betamax eccentricity alignment tool?

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Topic starter Posted : 08/08/2019 7:47 pm
Norman-Raeburn
(@norman-raeburn)
Trusted V-Ratter Registered
Posts: 174

@crustytv

Hi Chris, I had a 2028, it was our first tv when we got married. I got it from the place I worked it came in as a trade in. My boss was tight as the proverbial duck backside and wouldn't let me have for free, it was on the scrap pile. I got it for £20 but the tube was poor. I fitted a regun which I acquired for free from work and used it for many years. I later sold it to an aunt who also had it for years. It was very reliable and always had a great picture.

On the subject of vcr's I don't have any tools for the Betamax range but I will have some bits and pieces for vhs. You may have them in your service kits. I will have a proper look and see what I have left. All the best, Norman

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Posted : 08/08/2019 9:09 pm
Doz
 Doz
(@doz)
Noble V-Ratter Registered
Posts: 1329

Hi Chris, @crustytv

There's a DTI on a heavy base here if you'd like a borrow to set your eccentricity.

It's what  I used back in the day.

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Posted : 08/08/2019 9:24 pm
Doz
 Doz
(@doz)
Noble V-Ratter Registered
Posts: 1329
Posted by: @crustytv

Over the years when a LOPT was under suspicion I've used the age old method of ringing with a scope and occasionally using the JABCO LOPT tester to see if all is well or not!

loptst

The split diode LOPTS found in later sets I've not had much dealing with but do now have a few sets in the collection that have them installed. Those that know me will know I have an interest in test equipment, even if it is infrequently used, so in to the fray steps the HR Diemen flyback tester. I've occasionally seen these turn up on e-bay but never really considered buying one. Norman however whilst clearing out all his kit, kindly passed one on to me with the box of service data, it came boxed with all its leads, manual and technical data.

Now other than the handful of sets in the collection with these split diode LOPTS installed, I only had a couple of loose ones in stock. One is a brand new one I bought for one of the B&O sets and the data book does not have it listed for connections to the tester. The other is a manky pull from what appears to be a Ferguson TX80, its code being HR 7527, now that was in the book.

Consulting the data I connected all the leads to the specified pins. The manual shows the kV value I should expect to be displayed upon testing a good LOPT. For this LOPT '27kV' but instead all I get is the red LED lit and a first segment error code of '5'.

This means there is a direct short circuit in the primary feed terminal or in the initial coil of the primary winding near the feed terminal. This can be verified with an  oscilloscope showing no return pulse only continuous feed voltage but pulses being present in auxiliary windings.

Bored yet? Sorry just thought it might be of interest and I suspect there might be a few old hands ( R2B, JCB, etc) who may have used one in the past and enjoyed seeing one again.

stvdst
hr7527
tst2
tst1

I had one at the shop. Worked well 

 

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Posted : 08/08/2019 9:26 pm