UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Closed Thread
 
Thread Tools
Old 17th Apr 2007, 6:23 pm   #1
ALANS ANITAS
Rest in Peace
 
Join Date: Jun 2006
Location: North West Northamptonshire, UK.
Posts: 346
Default Infallible Line Output Transformers?

In another thread Michael Maurice says that the Philips cp110 LOPT is not infallable. What sets have LOPTS that are not likely to require replacement?

ALAN
ALANS ANITAS is offline  
Old 17th Apr 2007, 6:40 pm   #2
Steve_P
Dekatron
 
Steve_P's Avatar
 
Join Date: Sep 2003
Location: Bolton, Greater Manchester, UK.
Posts: 6,644
Default Re: Infallable Line Output Transformer

No LOPT can be described as 100% fail-proof, but the BRC1400 / BRC1500 come closest to this. The triplers tend to die though.

Cheers,

Steve P
__________________
If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?
Steve_P is offline  
Old 17th Apr 2007, 6:57 pm   #3
Mike Phelan
Dekatron
 
Mike Phelan's Avatar
 
Join Date: Nov 2003
Location: Near Leeds, West Yorkshire, UK
Posts: 4,609
Default Re: Infallable Line Output Transformer

Yep - I'd say the BRC jelly-pots are about the best ones, but any of them of any make can fail!
__________________
Mike.
Mike Phelan is offline  
Old 17th Apr 2007, 7:16 pm   #4
Michael Maurice
Moderator
 
Michael Maurice's Avatar
 
Join Date: Feb 2006
Location: Wembley, Middlesex
Posts: 7,219
Default Re: Infallable Line Output Transformer

I've never had to change a Pansonic LOPT on any of their modern TV's save for the Alpha 4 range.

Hitachi LOPT's (not the Vestell version) are also very reliable, same goes for Mitsubishi TV's made after 1990.

What is disheatening is that of all the Manufacturers listed on my repair Database, I can only think of THREE manufacturers who make reliable LOPT's.
Michael Maurice is offline  
Old 17th Apr 2007, 9:29 pm   #5
Welsh Anorak
Dekatron
 
Welsh Anorak's Avatar
 
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,884
Default Re: Infallable Line Output Transformer

Hi
Yes, the Hitachi LOPTs from 1990 onwards were all very reliable. However the earlier G6 (Hitachi, not Philips) (then again...) failed frequently, as did the 2044 series.
Like Mr Maurice, I have ratrely changed a recent Panasonic except the Z7 and Alpha 4. Sony have a way of indicating a faulty transformer - they put a label 'Made in Slovenia' on it so you know!
It does tend to be down to transformer manufacturer - Eldors tend to arc over spectacularly, Oregas tend to hiss and spit and Philips ones tend to soldier on. The problems come when the majors buy their transformers in - HR transformers when used as replacements are pretty good, but can fail oddly in Sharp TVs, dishing out all sorts of unlikely voltages!
It's odd how a different version of a chassis can cause LOPT failure - remember the TX100? The green spot one would die on sight, but the yellow spot one wouldn't. Likewise the TX90 - the 14" would never die, but the similar looking 20" used to virtually explode!
I assume we're talking about diode-splits here, and I assume most faults are due to tripler failure or insulation breakdown, but that wouldn't explain why some fail more than others.
At least the LCDs don't have LOPTs! No, they have inverter transformers which are even LESS reliable - and there are up to twelve! Onwards and downwards....
Glyn
Welsh Anorak is offline  
Old 17th Apr 2007, 9:47 pm   #6
Focus Diode
Octode
 
Focus Diode's Avatar
 
Join Date: Jan 2006
Location: Borough of Gateshead, UK.
Posts: 1,420
Default Re: Infallable Line Output Transformer

Surprisingly in view of Rank's usual reputation, the LOPT in the A823 solid state colour chassis from 1969 onwards has a good reputation for reliability, unlike the later T20 series.

I agree that the Jellypot LOPTS as used in the BRC 1400 & 1500s are amongst the most reliable, yet they can easilly be destroyed by careless handling, as I once discovered many years ago, ie: too much heat from the iron on the tags when replacing the disc capacitor.

Brian R
Focus Diode is offline  
Old 18th Apr 2007, 1:01 am   #7
Hybrid tellies
Nonode
 
Hybrid tellies's Avatar
 
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,965
Default Re: Infallable Line Output Transformer

I agree with Brian ref the RBM A823 Line Output Transformer, I've never known one to fail. The same can be said about the BRC 1400'S and 1500 as well as the small screen 1580 and 1590's which were also jellypot loptx's.
Surprisingly I have never had to replace a Line Output Transformer on the GEC 2038/2043 dual standard mono's or the later single standard (625) mono sets either. If I remember correctly I think the Line Output Transformer on both the GEC single standard hybrid and the solid state 2110 colour chassis's was also very reliable with replacements virtually unknown.
__________________
Simon
BVWS member
Hybrid tellies is offline  
Old 18th Apr 2007, 9:11 am   #8
flyingtech55
Octode
 
Join Date: Nov 2005
Location: Ayrshire, UK.
Posts: 1,096
Default Re: Infallable Line Output Transformer

For what it's worth, I remember changing only a couple of LOPTxs in ITT CVC5/8/9s and we did a lot of that chassis, both retail and rental. On the ones I had go it was pretty obvious they'd gone because they burned up.

I never remember renewing any LOPTxs on the RBM A823 chassis either (fortunately because it would have been a major stripdown to get at it) and very, very rarely the tripler. However, we didn't supply a lot of those sets so I might be representative.

TimR
flyingtech55 is offline  
Old 18th Apr 2007, 1:17 pm   #9
Stewart
Retired Dormant Member
 
Stewart's Avatar
 
Join Date: Jul 2003
Location: N.E. Surrey, UK.
Posts: 361
Default Re: Infallable Line Output Transformer

Indeed the ITT CVC5-9 enjoyed a good reputation for LOPT (and CRT) life. Nothing lasts forever it seems though - and my own sets have got through three transformers in quite a short space of time. No visable signs of distress and no pattern to which windings fail.. :-( If anyone knows of spares....
Stewart is offline  
Old 18th Apr 2007, 9:50 pm   #10
stuie319
Pentode
 
stuie319's Avatar
 
Join Date: Jan 2007
Location: Stockport, Greater Manchester, UK.
Posts: 229
Default Re: Infallable Line Output Transformer

Hi All,

Despite the hundreds of G11's that passed through our workshop, I can't ever recall one needing a new Loppy, we saw a lot of B&O 7700 series as well and apart from going dry enough to fall off the PCB I can't ever remember replacing one of these either, though the EHT lead assemblies gave trouble ISTR.
KT3's as well. loads of reccy trays, but think the transformers were pretty hardy.

Regards Stu
stuie319 is offline  
Old 19th Apr 2007, 10:00 am   #11
flyingtech55
Octode
 
Join Date: Nov 2005
Location: Ayrshire, UK.
Posts: 1,096
Default Re: Infallable Line Output Transformer

Hi Stu

Yes, you're right about the EHT cable on the 55/77/89xx B&Os. It was a common fault. However, while not wishing to appear a smart a**e, the thing that looked like the LOPTx was actually the chopper transformer and EHT generator. The LOPTx was in fact a small wound component on the timebase panel mounted on the bottom of the cabinet. This threw a lot of engineers who couldn't make head nor tail of the arrangement and ordered up the 'line output transformer' only to receive this small choke looking thing.

The rather complex looking circuit diagrams didn't help of course but once you got used to them they were in fact very logical.

But having said that, the chopper/EHT generator transformer was very reliable but I did have to renew a couple of the line output transformers which cooked up and developed shorted turns. But I do remember when I ordered them up the spares lady asked if I was sure that I knew what I was ordering was what I actually wanted.

Great days.

TimR
flyingtech55 is offline  
Old 20th Apr 2007, 7:47 am   #12
Mike Phelan
Dekatron
 
Mike Phelan's Avatar
 
Join Date: Nov 2003
Location: Near Leeds, West Yorkshire, UK
Posts: 4,609
Default Re: Infallable Line Output Transformer

Things change as time goes on - when I worked for British Relay, for several years after the G8 first appeared, LOPTX failure was completely unknown, then, within a few months, they started to go, and continued so.
By then, the G6s and K70s often needed one, but the König replacements we used seemed to be OK - anyone used them?

Never had to change a G11 or RBM A823, but maybe after a few decades it is a different matter.
__________________
Mike.
Mike Phelan is offline  
Old 20th Apr 2007, 8:55 am   #13
Studio263
Octode
 
Studio263's Avatar
 
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,574
Default Re: Infallable Line Output Transformer

Not strictly a line output transformer, but what about the 30AX-based B&O? I've never changed one. The BRC TX10 is very similar, they never "go" either.

The 20AX-based B&O is also good, I think the transformer is the same as the one in the Philips G11, also no failures to report.

The BRC TX9 and Philips KT3 are very good, I remember one TX9 failure out of many sets, it was still working but flashing over to the core.

You don't get much LOPT trouble in early Sony sets, but they soon made up for that later...

Finally the BRC 1400 and 1500, the LOPT is the best bit!
Studio263 is offline  
Old 20th Apr 2007, 4:02 pm   #14
Hybrid tellies
Nonode
 
Hybrid tellies's Avatar
 
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,965
Default Re: Infallable Line Output Transformer

I am tempting fate here but here goes. As many of us would know, the Decca Bradford Lopt was not the most reliable, but my CS1910 still has the original one fitted and still going strong. I hope I don't live to regret telling everyone about this
__________________
Simon
BVWS member
Hybrid tellies is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 7:41 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.