Rebuilt MW22-7 Tube in Bush TV1 - Page 5 - UK Vintage Radio Repair and Restoration Discussion Forum

neon indicator · 16th Jul 2011, 1:27 pm

Quote:

Originally Posted by chipp1968

Maybe he means at no cost except the post and insurance ?
My pre war tube is to go there soon , so Im hoping that will run smoothly !!!

I thought that's what he meant.

I still have a vague memory from megalithic era that certain operating condition can affect phosphor secondary emissions. Since the phosphor is supposed NOT to be a mix it would not hurt to re-check all electrode voltages and currents, taking into account any loading due to meter.

It's also possible for organic contamination I think to cause something like this.

geoff999 · 16th Jul 2011, 2:18 pm

While these remoter possibilities are being considered I presume there is no doubt that the tube exhibiting these phenomena is the one overhauled by RACS.

Heatercathodeshort · 16th Jul 2011, 2:30 pm

Secondary emission will not cause an afterglow as observed with this tube. The effect can be seen as demonstrated by shining a torch at the screen face without any voltages applied to the tube. Secondary emission produces a halation of the main raster that can be seen as a duplicate raster but at a much lower intensity. It does not have the 'drag' factor and is exactly the same colour as the screen phosphor. It is very rare and I last observed it with a 14" Samsung colour tube but that is a different story. Hope you get the tube sorted, I'm sure you will. Regards, John.

FRANK.C · 16th Jul 2011, 3:36 pm

neon
I spent months insuring that all voltages around the tube were OK. Even going to the lengths of rewinding the overwind on the LOPT because it was about 1 kV too low. RACS is a highly respected company and I needed to be absolutely sure that every thing else was OK before I would even consider that there may be a problem with the tube.
I didn't know then what I know about tubes, I have learnt a lot along the way and still have a lot to learn.

Geoff999
This tube is totally unique it is a Mullard MW31/74 tube that I got fitted with a Mazda CRM123 type gun. There is no other one like it in the world. It is not possible to mistake it for another tube.

Frank

jhalphen · 17th Jul 2011, 11:50 am

Good day Gentlemen,

Yes you are 100% correct - and a big typo on my part (serves me right for answering Mails too fast and not proof-reading before getting up at 5AM to go to London yesterday).

Read of course: if Frank so wishes, his unique CRT will be entirely rebuilt again for FREE except for shipping & insurance cost.

The delay in reply was caused by RACS having to sift through the paperwork to review the details of Frank's tube when it was at the processing plant 2 years ago. They found nothing unusual, P4 phosphor used was the usual supplier's standard mix and the QC post-rebuild tests which include generating a raster + video content display was A-OK.

So this begs for the following question: can phosphors "go sour" i.e. be normal after rebuild and transform into some weird P7 type 2 years later? - they do not know, never seen "that" before in 35 years of B&W CRT phosphor recoating.

The UK company supplying the phosphor mix was PTL - Phosphor Technology Ltd, Norton Park, Norton Road, Stevenage, Hertfordshire SG1-2BB.

http://www.phosphor-technology.com/

OT:
You have a big BVWS meeting on Nov 6th in London, i intend to come over for a couple of days and get to meet some of the friendly people here whom i only know via Mail & phone chats.

Best Regards

jhalphen
Paris/France

radioredcat · 17th Jul 2011, 11:58 am

Hi Jerome the link works ok for me so the company looks like it's still in business.

Andy

jhalphen · 17th Jul 2011, 12:07 pm

Hello Radioredcat,

yes, works for me also. Server was probably down when i tested on friday morning.

Case closed.

Thanks!

JH/Paris

Panrock · 17th Jul 2011, 12:24 pm

Quote:

Originally Posted by jhalphen

You have a big BVWS meeting on Nov 6th in London, i intend to come over for a couple of days and get to meet some of the friendly people here whom i only know via Mail & phone chats.

I shall be there Jerome, so I too look forward to meeting you then! Also, thank you for your PM, to which I have replied.

Steve

FRANK.C · 17th Jul 2011, 2:17 pm

Hi Jerome
Thanks for clearing that up. I would be delighted to take RACS up on there offer, it is better than I could have hoped for.
I am happy that RACS will get an opportunity to inspect the tube, as seeing it up close may shed more light on what happened. It is practically impossible to diagnose a problem at long distance.

Frank

jhalphen · 17th Jul 2011, 2:27 pm

Hi Frank,

indeed, when i asked them if higher resolution re-shots of your two YouTube clips would help IDying the problem, the answer was no.

I suspect they might scrape a sample of your P4 before rebuild and have a chemical analysis done to understand what happened.

Please inform me & RACS when you intend to ship your CRT as they are closed for annual holidays in august. You can ship from august 20 onwards as the factory will be manned in preparation for the 2011-2012 season.

Quiz: if anyone looked at the CRT Phosphor section of the mixes offered by PTL, i can't locate the P4 mix - anyone less of a nitwit like me:

http://www.phosphor-technology.com/

Best Regards

jhalphen
Paris/France

Maarten · 17th Jul 2011, 5:18 pm

I'm sure you're not a nitwit, or I'd be one as well (which off course is fully possible). The closest phosphor I can find on that site is P45-WB, a rare earth white phosphor. Probably quite useable but not the same as P4.

FRANK.C · 17th Jul 2011, 7:18 pm

Hi Jerome
I will get the CRT packaged for shipping in the next day or two and will PM you then.

Frank

FRANK.C · 25th Jul 2011, 10:47 pm

Just a quick update.
I shipped the tube on Wednesday last, and it was delivered today to RACS, hopefully in one piece.

Frank

chipp1968 · 7th Aug 2011, 4:55 pm

Mathewhouse came yesterday and we had a look at the Bush.
The eht was tested to 4 so a bit low. also there has been a crackling noise with horizontal sparking across the picture lately when the set is cold .It goes away when warm.But is a bit worrying`Fortunately the font of the cabinet is removable so we removed the tube and Matty had a look at the EHT cap .which was redundant , but after some dismantling of the inner front panel which was also possible in situ we found that there were modern replacement hidden .He tested the resisters in series in that area and one was completely open! so this was replaced .The others were spot on. After replacing the tube the picture appears to be slightly brighter and the EHT is up to 4.5 as it is supposed to be .The brown spot is still visible .
Other than the slight fold-over ,the apparent faults still there are a whistle wind noise on the sound that fluctuates on it own and with the use of controls .When quiet this is acceptable for now , but it has been quite loud in recent past.We checked the sound section and one of the red coated valves needed it screening wire replaced as it was corroded, but it made no difference .The noise could be made to fluctuate if the top cap screen wire on this first valve was pushed with a pen. The sparking when cold is still there which is worrying , and the picture curves inwards a bit at the top corners which isn't noticeable except on text.
here are some pics.

murphyv310 · 7th Aug 2011, 5:08 pm

The fold over may just be down to the design of the set but also could be that the flyback time is slightly too long due to a fault. It may be an idea to check everything in the line timebase.

chipp1968 · 7th Aug 2011, 5:27 pm

I think the fold-over is the only thing we know what the problem is .I believe the fact it has the wrong lopt. which was replaced sometime in its early life , a non standard part .The original was in two parts .The smaller winding is still in situ. I hope the crackling when cold isnt the replacement giving up !

murphyv310 · 7th Aug 2011, 5:48 pm

Try taking the back off and having a look in darkness if there is any little sparks or flashovers

chipp1968 · 7th Aug 2011, 6:20 pm

I will have to try that next, when its cold . We thought we could hear snik noises but by that point it stopped doing it . I have been running this set the last 2 hours so another day.

Panrock · 8th Aug 2011, 3:22 pm

A quick note for chipp1968 and jhalphen. I'm now expecting to visit RACS on 13 September. I'll be going by air - there and back in a day! I'll be travelling with a customer, but will also be taking your Emiscope 3/3 tube along for refurbishment, Chipp.

Steve

chipp1968 · 8th Aug 2011, 11:07 pm

Hopefully all will run smoothly and we get a decent working example ! cant wait !

16th Jul 2011, 2:18 pm	#82
geoff999 Rest in Peace Join Date: Jun 2007 Location: Croydon Posts: 92	Re: Rebuilt MW22-7 Tube in Bush TV1 While these remoter possibilities are being considered I presume there is no doubt that the tube exhibiting these phenomena is the one overhauled by RACS. Last edited by geoff999; 16th Jul 2011 at 2:19 pm. Reason: Typo

16th Jul 2011, 2:30 pm	#83
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Rebuilt MW22-7 Tube in Bush TV1 Secondary emission will not cause an afterglow as observed with this tube. The effect can be seen as demonstrated by shining a torch at the screen face without any voltages applied to the tube. Secondary emission produces a halation of the main raster that can be seen as a duplicate raster but at a much lower intensity. It does not have the 'drag' factor and is exactly the same colour as the screen phosphor. It is very rare and I last observed it with a 14" Samsung colour tube but that is a different story. Hope you get the tube sorted, I'm sure you will. Regards, John.

16th Jul 2011, 3:36 pm	#84
FRANK.C Heptode Join Date: Feb 2006 Location: Roscommon, Ireland Posts: 732	Re: Rebuilt MW22-7 Tube in Bush TV1 neon I spent months insuring that all voltages around the tube were OK. Even going to the lengths of rewinding the overwind on the LOPT because it was about 1 kV too low. RACS is a highly respected company and I needed to be absolutely sure that every thing else was OK before I would even consider that there may be a problem with the tube. I didn't know then what I know about tubes, I have learnt a lot along the way and still have a lot to learn. Geoff999 This tube is totally unique it is a Mullard MW31/74 tube that I got fitted with a Mazda CRM123 type gun. There is no other one like it in the world. It is not possible to mistake it for another tube. Frank Last edited by FRANK.C; 16th Jul 2011 at 3:37 pm. Reason: typo

17th Jul 2011, 11:50 am	#85
jhalphen Hexode Join Date: Jul 2004 Location: Paris, France Posts: 350	Good day Gentlemen, Yes you are 100% correct - and a big typo on my part (serves me right for answering Mails too fast and not proof-reading before getting up at 5AM to go to London yesterday). Read of course: if Frank so wishes, his unique CRT will be entirely rebuilt again for FREE except for shipping & insurance cost. The delay in reply was caused by RACS having to sift through the paperwork to review the details of Frank's tube when it was at the processing plant 2 years ago. They found nothing unusual, P4 phosphor used was the usual supplier's standard mix and the QC post-rebuild tests which include generating a raster + video content display was A-OK. So this begs for the following question: can phosphors "go sour" i.e. be normal after rebuild and transform into some weird P7 type 2 years later? - they do not know, never seen "that" before in 35 years of B&W CRT phosphor recoating. The UK company supplying the phosphor mix was PTL - Phosphor Technology Ltd, Norton Park, Norton Road, Stevenage, Hertfordshire SG1-2BB. http://www.phosphor-technology.com/ OT: You have a big BVWS meeting on Nov 6th in London, i intend to come over for a couple of days and get to meet some of the friendly people here whom i only know via Mail & phone chats. Best Regards jhalphen Paris/France Last edited by jhalphen; 17th Jul 2011 at 12:09 pm. Reason: Corrective info supplied

17th Jul 2011, 11:58 am	#86
radioredcat Hexode Join Date: Apr 2009 Location: Billinge, Wigan, UK. Posts: 492	Re: Rebuilt MW22-7 Tube in Bush TV1 Hi Jerome the link works ok for me so the company looks like it's still in business. Andy __________________ http://www.youtube.com/user/radioredcat

17th Jul 2011, 12:07 pm	#87
jhalphen Hexode Join Date: Jul 2004 Location: Paris, France Posts: 350	Re: Rebuilt MW22-7 Tube in Bush TV1 Hello Radioredcat, yes, works for me also. Server was probably down when i tested on friday morning. Case closed. Thanks! JH/Paris

17th Jul 2011, 2:17 pm	#89
FRANK.C Heptode Join Date: Feb 2006 Location: Roscommon, Ireland Posts: 732	Re: Rebuilt MW22-7 Tube in Bush TV1 Hi Jerome Thanks for clearing that up. I would be delighted to take RACS up on there offer, it is better than I could have hoped for. I am happy that RACS will get an opportunity to inspect the tube, as seeing it up close may shed more light on what happened. It is practically impossible to diagnose a problem at long distance. Frank

17th Jul 2011, 2:27 pm	#90
jhalphen Hexode Join Date: Jul 2004 Location: Paris, France Posts: 350	Re: Rebuilt MW22-7 Tube in Bush TV1 Hi Frank, indeed, when i asked them if higher resolution re-shots of your two YouTube clips would help IDying the problem, the answer was no. I suspect they might scrape a sample of your P4 before rebuild and have a chemical analysis done to understand what happened. Please inform me & RACS when you intend to ship your CRT as they are closed for annual holidays in august. You can ship from august 20 onwards as the factory will be manned in preparation for the 2011-2012 season. Quiz: if anyone looked at the CRT Phosphor section of the mixes offered by PTL, i can't locate the P4 mix - anyone less of a nitwit like me: http://www.phosphor-technology.com/ Best Regards jhalphen Paris/France

17th Jul 2011, 5:18 pm	#91
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,199	Re: Rebuilt MW22-7 Tube in Bush TV1 I'm sure you're not a nitwit, or I'd be one as well (which off course is fully possible). The closest phosphor I can find on that site is P45-WB, a rare earth white phosphor. Probably quite useable but not the same as P4.

17th Jul 2011, 7:18 pm	#92
FRANK.C Heptode Join Date: Feb 2006 Location: Roscommon, Ireland Posts: 732	Re: Rebuilt MW22-7 Tube in Bush TV1 Hi Jerome I will get the CRT packaged for shipping in the next day or two and will PM you then. Frank

25th Jul 2011, 10:47 pm	#93
FRANK.C Heptode Join Date: Feb 2006 Location: Roscommon, Ireland Posts: 732	Re: Rebuilt MW22-7 Tube in Bush TV1 Just a quick update. I shipped the tube on Wednesday last, and it was delivered today to RACS, hopefully in one piece. Frank

7th Aug 2011, 4:55 pm	#94
chipp1968 Rest in Peace Join Date: Jul 2006 Location: Somerset, UK. Posts: 2,356	Re: Rebuilt MW22-7 Tube in Bush TV1 Mathewhouse came yesterday and we had a look at the Bush. The eht was tested to 4 so a bit low. also there has been a crackling noise with horizontal sparking across the picture lately when the set is cold .It goes away when warm.But is a bit worrying`Fortunately the font of the cabinet is removable so we removed the tube and Matty had a look at the EHT cap .which was redundant , but after some dismantling of the inner front panel which was also possible in situ we found that there were modern replacement hidden .He tested the resisters in series in that area and one was completely open! so this was replaced .The others were spot on. After replacing the tube the picture appears to be slightly brighter and the EHT is up to 4.5 as it is supposed to be .The brown spot is still visible . Other than the slight fold-over ,the apparent faults still there are a whistle wind noise on the sound that fluctuates on it own and with the use of controls .When quiet this is acceptable for now , but it has been quite loud in recent past.We checked the sound section and one of the red coated valves needed it screening wire replaced as it was corroded, but it made no difference .The noise could be made to fluctuate if the top cap screen wire on this first valve was pushed with a pen. The sparking when cold is still there which is worrying , and the picture curves inwards a bit at the top corners which isn't noticeable except on text. here are some pics. Attached Thumbnails

7th Aug 2011, 5:08 pm	#95
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 5,422	Re: Rebuilt MW22-7 Tube in Bush TV1 The fold over may just be down to the design of the set but also could be that the flyback time is slightly too long due to a fault. It may be an idea to check everything in the line timebase. __________________ Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

7th Aug 2011, 5:27 pm	#96
chipp1968 Rest in Peace Join Date: Jul 2006 Location: Somerset, UK. Posts: 2,356	Re: Rebuilt MW22-7 Tube in Bush TV1 I think the fold-over is the only thing we know what the problem is .I believe the fact it has the wrong lopt. which was replaced sometime in its early life , a non standard part .The original was in two parts .The smaller winding is still in situ. I hope the crackling when cold isnt the replacement giving up !

7th Aug 2011, 5:48 pm	#97
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 5,422	Re: Rebuilt MW22-7 Tube in Bush TV1 Try taking the back off and having a look in darkness if there is any little sparks or flashovers __________________ Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

7th Aug 2011, 6:20 pm	#98
chipp1968 Rest in Peace Join Date: Jul 2006 Location: Somerset, UK. Posts: 2,356	Re: Rebuilt MW22-7 Tube in Bush TV1 I will have to try that next, when its cold . We thought we could hear snik noises but by that point it stopped doing it . I have been running this set the last 2 hours so another day.

8th Aug 2011, 3:22 pm	#99
Panrock Nonode Join Date: Feb 2005 Location: Worcestershire, UK. Posts: 2,533	Re: Rebuilt MW22-7 Tube in Bush TV1 A quick note for chipp1968 and jhalphen. I'm now expecting to visit RACS on 13 September. I'll be going by air - there and back in a day! I'll be travelling with a customer, but will also be taking your Emiscope 3/3 tube along for refurbishment, Chipp. Steve __________________ https://www.radiocraft.co.uk

8th Aug 2011, 11:07 pm	#100
chipp1968 Rest in Peace Join Date: Jul 2006 Location: Somerset, UK. Posts: 2,356	Re: Rebuilt MW22-7 Tube in Bush TV1 Hopefully all will run smoothly and we get a decent working example ! cant wait !