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 13th Sep 2020, 9:11 pm   #1
1100 man
Octode
 
1100 man's Avatar
 
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 1,377
Default HMV 1807- BVWS Bulletin

As soon as the Bulletin arrives, I always have a quick scan through to see if there are any TV related articles- naturally, I read these first!

Matt Spanner has come up trumps again with the restoration of an 1807. From what I've gathered from the forum over the last few years, this has to rate as the worst TV chassis of the 1950's.

I've long been fascinated by the sets that Manufacturers got so, so wrong and that were real 'lemons'. There is a lot of insightful information from Heatercathodeshort and others who knew these sets at the time detailing exactly why they were so bad. The list is very long!!

It's well worth reading these two threads:
https://www.vintage-radio.net/forum/...d.php?t=118099

https://www.vintage-radio.net/forum/...ad.php?t=83897

Consequently, having read how bad they were, its really interesting to see one being restored and to see if they can be made to work reasonably well.

The problems at the time were many, but very poor quality capacitors & resistors, valve bases & slider presets seem to have been big issues. Add to that a tube that seemed to suffer O/C heaters and some very odd design quirks such as altering the focus by altering the EHT and some very odd valve choices.

It's amazing that the sets actually got into production but it must have been very embarrassing for the dealers dealing with irate customers. I wonder how many were sold?

Well done to Matt for taking one of these sets on and showing that they can be made to work, at least tolerably well!

All the best
Nick
1100 man is offline  
Old 13th Sep 2020, 10:17 pm   #2
peter_scott
Dekatron
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,273
Default Re: HMV 1807- BVWS Bulletin

+1

I really enjoyed the article too. That (well the console version) was the first set I ever owned (and never got working.)

Peter
peter_scott is offline  
Old 14th Sep 2020, 2:36 pm   #3
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 230
Default Re: HMV 1807- BVWS Bulletin

Thanks Nick, Peter!
It's always nice to get a bit of feedback about my antics with these lovely old tellies.
I very much enjoyed bringing the HMV 1807 back to life and trying to improve it a bit.
I love a challenge with oddities such as this, and sets that are a bit different or obscure. Or just super rare!
It's all great fun as we know.
Thanks & regards
Matt

https://m.youtube.com/channel/UCGj4m..._kMowcA/videos
matspar is offline  
Old 14th Sep 2020, 3:40 pm   #4
beery
Heptode
 
beery's Avatar
 
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 988
Default Re: HMV 1807- BVWS Bulletin

Hi Matt,
Yes I loved the article too.

I bought one once at the NVCF when it was at the NEC.
It had a slightly wormy cabinet and no back. When I got it home it turned out to have a heater transformer connected to a 9" Mullard MW22-7, which was flat. It had a 9" mask behind the 10" one. Needless to say I scrapped it.

I'm not really a fan of the 1807's looks, though I do like the looks of the console versions, however the 10" crt's reputation has put me off from buying another one.

Anyway, I'm glad you got a good one.

I wonder if a couple of zener diodes back to back across the crt heaters would help protect it as the other valves warm up.

Cheers
Andy
beery is offline  
Old 14th Sep 2020, 4:15 pm   #5
peter_scott
Dekatron
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,273
Default Re: HMV 1807- BVWS Bulletin

Believe it or not after 56 years of storing it I still have the 3/16 from mine and the heater is intact but wait for it.....
It has absolutely zero emission!

Peter
peter_scott is offline  
Old 14th Sep 2020, 5:36 pm   #6
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: HMV 1807- BVWS Bulletin

Yes Matt's article is an excellent one that covers the faults in the 1807 and 1807A versions. The original 1807 has a number of differences mainly to the frame output stage involving high impedance scanning coils fed directly from the anode of the frame output valve via an electrolytic cap, similar to the Ultra models of the period. No transformer required of course. The 1807A employs a frame output transformer in a conventional circuit.

When I was a kid in 1960 I used to bring both versions home from jumble sales in the hope that I could get one working but I never did! Most other makes such as the Ekco T161, PYE B18T/LV/FV series and the later models such as the V4 stood a good chance of a picture but never the EMI's! The exception was of course the 1805/6 series, in my opinion the best and most reliable models ever produced by EMI.

I remember wheeling a 15" 1806 that I had just bought for 2/6d from a jumble sale held at the the old Raynes Park library hall on the corner of Kingston Road and Approach Road along the cycle path of the Kingston by pass spur [Bushey Road] in 1961 but that is another story.

EMI were also restricted by the use of MOV valves. The only dedicated .3amp line output valve available was the KT36, a cumbersome thing similar in construction to the Mullard PL38 but on the whole, quite reliable. The boost diode is a U31 borrowed from the AC/DC radio dept. The KT33C was another AC/DC radio/amplifier valve and in it's position as the frame output valve gave a good performance.

The RF strip employed the then new B7G based Z77 valves the MOV equivalent to the excellent Mullard EF91. These miniature valves ran very hot with the MOV Z77's often developing internal shorts burning out their screen grid supply resistors. They also lost their emission. The Z77 was also put to work as the audio output valve.

The capacitors used for decoupling were of poor quality causing many faults such as instability, sound on vision, vision on sound, low and intermittent gain.

EMI suggested locating the faulty ones by warming the receiver up until the fault appeared and then blowing through a drinking straw at each one until the duff one was located! It took them a while to issue a mod kit of capacitors that replaced the whole lot in one go. Think of all the aggro this would have saved if they had done this as soon as problems arose.

The cheap and nasty B7G Paxolin valve holders must have been the worst ever produced. They were very lossy causing low gain together with yet more instability problems.

The resistors were also of poor quality that drifted high in value and were often of insufficient wattage rating. This required constant adjustment of both line and frame hold controls being mostly of EMI manufacture, fell apart causing yet more frustration.

The infamous MOV B36 valve caused endless problems and was a disgrace to it's maker. There were never two the same specification and as many as four to eight new valves would have to be tried before both timebases would lock. As Matt discovered the replacement of the B36 with the American/Brimar 12SN7 cleared up all these problems.

The 1807 was also very sensitive to mains fluctuations. I few years ago I carried out a simple experiment. I connected three receivers of the same period to a variac and a good signal. The models used were a Ferguson 941T A Bush TV12A [both 1949]and the 1807. On full mains [240v] the three performed well producing stable pictures. Reducing the mains input to 230V had no effect on the Ferguson or the Bush but the line sync on the 1807 was triggering slightly at the top. Reducing the input to 220V resulted in slight lack of picture size on the first two but complete loss of picture on the 1807.

H.T. was supplied by a large metal rectifier that soon lost it's efficiency then sat at this lower voltage for an extended period until eventually being replaced. I have no doubt that the B36 valve was also sensitive to slight heater fluctuations.

As Matt has mentioned the Emiscope 3/16 10" tube suffered it's own problems. Like the B36 valve they varied in quality control and consistency. The screen colour on the early examples had a sort of sepia dull appearance and this added to the low EHT potential required for focusing, produced a very poor picture. The tubes were aluminised requiring around 7kv for a bright picture but the 1807 with it's variable EHT focus control resulted in focus being obtained with only around 4kv at the anode. Later 3/16s produced better pictures but unfortunately suffered from O/C heaters. EMI were aware of this and increased the heater voltage in steps, 8.5v 10.5v and 13.5v but they still developed O/C heaters! The annoying thing was they never marked on the tube bowl which gun was fitted.

They must have had terrible problems with the tubes during manufacture. Some versions mainly the Marconi branded ones had 3/20 tubes fitted that had a much better life and gave excellent pictures. They had the classic Cossor four pin base, the connections to which were wander plugs. I have no doubt that these were produced by Cossor for EMI.

The 1807 series were produced in a large variety of styles. 10" and 12" table models and consoles some complete with a radio unit that has all the looks of Plessey about it. The London models were TRF but models for the other regions 2/3/4/5/807 were superhet employing the curious B7G based X78 frequency changer. The cathode connection is internally connected to one side of the heater..

I expect that many of this series worked reliably in districts where the mains remained constant and a good signal was available. The problem in 1949 and the 50's was that the mains varied considerably due to lack of generating capacity caused by enemy action during WW2. It took around 20 years to clear this up.

Gerry once said that they worked well if the mains was 240 v and never varied by 1 volt, the receiver was installed within sight of Alexandra Palace and the wind was blowing in the right direction!

It is interesting to note that the 1807 series was working well at considerable distances from AP. I have some well thumbed EMI manuals that originated from a large dealer at Bognor Regis in West Sussex. They must have worked with a pre amp!

The 1807 did have a few good points. The LOPT was 100% reliable as was the mains dropper and the large U35 octal based EHT rectifier.

The 1807 was a sad end to a company that had designed and built the first public television service in the World. Subsequent models were only slightly better with very short life Emiscope tubes and most of these later models to 1955/6 were soon scrapped by their owners. Only a tiny handful were brought in for service when I was 16 working at D&B television in 1964 and from what I can remember were all written off. It's a bit spooky..I was born 18-07 1948 just months before the release of the infamous 1807..

Thorn/Ferguson took production of EMI brands around 1956, the first chassis being the HMV 1864 fitted with the Ferguson 306T chassis. This was a very smart and reliable receiver and sold in large numbers.

The Thorn/EMI arrangement worked very well producing many models over the years that I suspect Alan Blumlein would have approved of.

The pictures show my Marconi VC53DA version. The tube takes about 15mins to reach an acceptable emission and after all the mods were carried out gives a reasonable picture but it's still susceptible to mains variations with a custom picked new B36! The picture is nowhere near as good as Matt's 1807.
Regards, John.
Attached Thumbnails
Click image for larger version

Name:	VC53DA.jpg
Views:	201
Size:	29.2 KB
ID:	215681  

Last edited by Heatercathodeshort; 14th Sep 2020 at 5:48 pm. Reason: Picture added.
Heatercathodeshort is offline  
Old 15th Sep 2020, 6:40 pm   #7
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: HMV 1807- BVWS Bulletin

HKS wrote: "The 1807 was also very sensitive to mains fluctuations."

Hi John,
perhaps that's why my Marconi VRC54 had a heater chain rheostat so any variation in the mains supply could be corrected during the course of viewing.
The only good thing about these sets is the standard of construction of the cabinets. As solid as any other EMI models gone before.
It just shows how bad things had gone when EMI had to go to arch rival Cossor for a 10" CRT. Many 12" models were fitted with a Mullard MW31-16 CRT. The service manual reminds us when the Mullard tube needs replacing fit an Emiscope 3-18 instead. I'd imagine the Mullard tube outlasted the rest of the receiver and was fitted into something else.
Sobell showed EMI how to make a reasonably priced set which didn't break down. In fact Sobell made certain models for EMI under the Columbia brand name. The model C501 for example, same chassis as the Sobell T121.

DFWB.
FERNSEH is offline  
Old 16th Sep 2020, 7:06 pm   #8
mark pirate
Dekatron
 
mark pirate's Avatar
 
Join Date: Mar 2008
Location: Worthing, West Sussex, UK
Posts: 5,185
Default Re: HMV 1807- BVWS Bulletin

I actually quite like the 1807, I now own four examples

Once restored with modern caps, they are very reliable, the first set I tackled really led me a merry dance, but dim CRT aside, has needed no further attention. https://www.vintage-radio.net/forum/...d.php?t=113547
If anyone has a reasonable 10" Emiscope tube, please let me know!


Mark
mark pirate is offline  
Old 16th Sep 2020, 8:06 pm   #9
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: HMV 1807- BVWS Bulletin

Well I suppose you need 4 to get through a 30 min programme. Line lock fails on 1, Frame hold on 2, Bursts into oscillation 3 and for a final finale, O/C tube heaters on 4.
As Mark says, with modern caps, a decent tube and 240v steady mains it would be just about passable but when compared with many of it's contemporaries it's just a terrible excuse for a television produced by a manufacturer with such a long standing pedigree. Regards, John.
Heatercathodeshort is offline  
Old 16th Sep 2020, 10:25 pm   #10
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: HMV 1807- BVWS Bulletin

It's worth noting the GEC BT2147 and BT5144 employed a similar timebase circuit and in those receivers the line and frame hold is dead steady. Like the HMV 1807 and the Marconi VT53 the timebase oscillator valve is a B36, although it should be mentioned as in the 1807 a better replacement for the B36 is the American 12SN7GT.

DFWB.
FERNSEH is offline  
Old 17th Sep 2020, 8:53 am   #11
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: HMV 1807- BVWS Bulletin

Yes David, I have two BT2147s and they are both rock steady. I've often wondered what causes the widespread drift in the 1807? Probably just a mass of poor quality caps and resistors plus a too critical B36.

Even with good quality components fitted both timebases drift if you drop the mains input, a common occurrence in the 1950's at a time that stability with mains variations was everything. All water under the bridge as they say. John.
Heatercathodeshort is offline  
Old 18th Sep 2020, 12:01 am   #12
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 230
Default Re: HMV 1807- BVWS Bulletin

This is all really interesting and thought provoking stuff. It's always intriguing to hear about others accounts and experiences. John I very much enjoyed reading about your own one also, along with the wealth of knowledge you possess about the ill fated 1807. It really is one of those truly fascinating sets that are still remembered for their shortcomings even now.
matspar is offline  
Old 18th Sep 2020, 7:16 am   #13
Duke_Nukem
Octode
 
Duke_Nukem's Avatar
 
Join Date: Jan 2003
Location: Birmingham, West Midlands, UK.
Posts: 1,268
Default Re: HMV 1807- BVWS Bulletin

I have the Marconiphone and HMV versions.

With the Marconiphone playing next to a Ferguson 954, the picture on the Marconi I would say was better than the Fergy (and the Fergy wasn't bad) ... often for many many minutes at a time.

The HMV version is in fact the ultra rare dual standard version which includes a very early primitive version of Alexa which forms an important part of the standards switch; when in 240 line mode (you can hear the timebase is half speed), switch off/on a few times whilst thumping it** _AND_ you have to swear profusely then when the set's primitive Alexa determines you've reached the point that you are about to burst a blood vessel it finally concedes and switches to 9.75Khz which you correct by removing the back so you can access the rotary pots used to replace the sliders but before you touch the controls it locks at the correct frequency (until you sit back in your chair obviously).

Way better than boring TV22's; you haven't ran it for years and cant even be bothered to service it first (i.e. polish the control knobs), you just switch it on and it works. Boooorrrrrrrrrring ! Think about it, do people buy classic cars for trouble free motoring or do they really want something they can enjoy tinkering with on a Sunday afternoon?

TTFN,
Jon

** - Having to thump these sets is why the CRTs have an un-justified reputation for heater fractures
Duke_Nukem is offline  
Old 18th Sep 2020, 10:13 pm   #14
1100 man
Octode
 
1100 man's Avatar
 
Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 1,377
Default Re: HMV 1807- BVWS Bulletin

It makes you wonder what it was like in the factory when these things were coming off the production line. Even with brand new components, they must have had major problems getting any of them to work. Maybe they gave up and just sent them out to dealers non working and hoped they could coax some life into them!

Presumably, they were compelled to design it with Osram valves, rather than being able to select more suitable types which would have worked better?

Of course, when they designed it, they would not have known how quickly the resistors would change in value or the capacitors go leaky or open. Also problems with the CRT would not have shown up at that stage, and maybe, when the CRT's were new, they would focus at a reasonable EHT level?

Was there a lack of a suitable Osram HT rectifier valve? Is that why they used a metal rectifier I wonder? Surely, though metal rectifiers were tried and tested technology by this time and so should have been reliable!

Strangely, the main weakness in a TV is usually the LOPT and by all accounts they managed to make this reliable. Mind you, 3-4KV of EHT is hardly much of an effort and possibly the sets did not work for long enough for the LOPT to fail!

Where is the EHT rectifier by the way? Surely not in the LOPT can? I've not spotted it in any of the pictures.

Cheers
Nick
1100 man is offline  
Old 18th Sep 2020, 11:52 pm   #15
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: HMV 1807- BVWS Bulletin

The octal based U35 EHT rectifier is in the can next to the line output valve. It's heater is fed from the LOPT. MOV did not have a .3amp series operation H.T. rectifier that would deliver enough HT for a television receiver.

Mullard had the PZ30 and Mazda had the less reliable U801.

Metal rectifiers were on the whole unreliable. They developed high resistance reducing the HT level by at least 30% after just a few years. The STC RM4 was one of the worst! The only exception was the AUTOMAT used by EKCO. 100% reliable.

A bit of fun now but must have caused endless problems for those 1950's service guys.
Regards, John.
Heatercathodeshort is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 12:02 pm.


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.