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 22nd Apr 2019, 3:30 pm   #1
Sean Williams
Dekatron
 
Sean Williams's Avatar
 
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,517
Default Emiscope 3/1 Testing, and value?

Hello All,

Having a bit of a pre Freidricschafen tidy up (and fund raiser ) - Big Amateur Radio rally in Germany....

I have come across an unmarked CRT that looks to me to be an Emiscope 3/1.

I have tested the heaters for continuity, and operation - 4v applied to the heater terminals results in the heater lighting, and 1.35A being drawn from the PSU.

I do not have anything here that will drive this CRT, so is there anything else I can do to test it?

I am looking to sell the tube in any case, but have no idea of it's value - Pre War TV stuff is a little beyond my means, so I very much doubt that a 904 will come my way for a few tens of pounds

Could the assembled experts suggest any non destructive or potentially non damaging test methods, and some indication of a fair market value?

Cheers
Sean
Attached Thumbnails
Click image for larger version

Name:	20190422_151544.jpg
Views:	444
Size:	78.2 KB
ID:	181648  
__________________
Engineers make things work and have spare bits when finished

Last edited by Sean Williams; 22nd Apr 2019 at 3:38 pm.
Sean Williams is offline  
Old 22nd Apr 2019, 4:47 pm   #2
Jac
Heptode
 
Jac's Avatar
 
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 640
Default Re: Emiscope 3/1 Testing, and value?

Hello Sean,

I would be interested in this tube to try it out in my Marconiphone set, but somehow I doubt that it is a 3/1.
All 3/1's that I have seen photo's of, seem to have a much longer aquadag layer on the inside. See attached picture.

Jac

p.s. photo is part of a photo by Catkins on this forum
Attached Thumbnails
Click image for larger version

Name:	3-1 CRTs.jpg
Views:	255
Size:	18.2 KB
ID:	181656  
Jac is online now  
Old 22nd Apr 2019, 5:17 pm   #3
Panrock
Nonode
 
Panrock's Avatar
 
Join Date: Feb 2005
Location: Worcestershire, UK.
Posts: 2,525
Default Re: Emiscope 3/1 Testing, and value?

Hi Sean,

That looks quite a find! I guess you could illuminate the screen with a pocket U/V torch in a dark room if you want to check the phosphor for ion burns and check its colour, especially if it's not a 3/1.

The 3/1 often seems to suffer from temporary inter-electrode leaks on warm-up, so try connecting an Avo, on its high resistance measuring range, between the grid and cathode, with the lead bearing the negative test voltage on the grid, and then apply 4v to the heater. If there's an intermittent 'warm-up' leak, this will show it. Check also between heater and cathode.

Hope the tube is a good 'un!

Steve
Attached Thumbnails
Click image for larger version

Name:	3-1.gif
Views:	72
Size:	5.4 KB
ID:	181668  

Last edited by Panrock; 22nd Apr 2019 at 5:44 pm.
Panrock is offline  
Old 22nd Apr 2019, 9:07 pm   #4
peter_scott
Dekatron
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,273
Default Re: Emiscope 3/1 Testing, and value?

I learnt from Jac a good test to see ion burn on 6/6s. Supply the heater as normal, keep cathode and grid at zero volts, apply something in the 200 volt range to A1 and something like 1000 volts to the final anode. (Experiment with the A1 voltage for best results.) I didn't have a convenient high voltage source but paid about about £5 for a little module that generates a nice safe 1000 volts. A permanent magnet can then be used to steer the defocused beam to the centre of the screen.

Peter
Attached Thumbnails
Click image for larger version

Name:	P1050679 (Small).JPG
Views:	212
Size:	34.3 KB
ID:	181677  
peter_scott is offline  
Old 22nd Apr 2019, 9:33 pm   #5
Sean Williams
Dekatron
 
Sean Williams's Avatar
 
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,517
Default Re: Emiscope 3/1 Testing, and value?

Thanks All,

From the digging I have currently managed, I cannot find any other EMISCOPE tube other than a 3/1 that matches the physical arrangement of this one.

I do not have a UV light source here, have tried various torches and LED sources to exploit the UV content to no avail.

Will give the method Peter describes a bash - I have plenty of PSUs that will provide the required voltages, al be it at a quite low impedance, so will be keeping the fingers well away
__________________
Engineers make things work and have spare bits when finished
Sean Williams is offline  
Old 22nd Apr 2019, 9:43 pm   #6
Argus25
No Longer a Member
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Emiscope 3/1 Testing, and value?

I think that 3/1 you have is a valuable CRT, they are practically unobtainium.

It also looks pretty good cosmetically, it has a known good heater and the getter looks great.

I would suggest not tinkering with it applying voltages, it won't tell you anything useful about it, the thing you want to know especially, that is if the emission is good enough to display a reasonable TV picture. With CRT's that run around 2kV EHT, the overall beam energy is very low on a full TV raster and they have to be in fairly good order (low gas and good cathode emission and good phosphor) to get a reasonable focused image. A blob of a de-focused beam won't help you asses that. Plus, without scanning coils running there is always a chance of a phosphor burn, even applying lower voltages. Also don't put permanent magnets anywhere near its gun structure.

The safer and better move is to find somebody with a working set, drop it into the set and check the TV image.

Last edited by Argus25; 22nd Apr 2019 at 9:49 pm.
Argus25 is offline  
Old 22nd Apr 2019, 9:45 pm   #7
Sean Williams
Dekatron
 
Sean Williams's Avatar
 
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,517
Default Re: Emiscope 3/1 Testing, and value?

Ah, a slight flaw in the method described Peter, this is a triode, so no A1 to play with.

I guess the same approach will work with the triode, just need to be careful to keep the beam intensity low to save burning the phosphor
__________________
Engineers make things work and have spare bits when finished
Sean Williams is offline  
Old 22nd Apr 2019, 9:47 pm   #8
Sean Williams
Dekatron
 
Sean Williams's Avatar
 
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,517
Default Re: Emiscope 3/1 Testing, and value?

Quote:
Originally Posted by Argus25 View Post
I think that 3/1 you have is a valuable CRT, they are practically unobtainium.

It also looks pretty good cosmetically, it has a known good heater and the getter looks great.

The safer and better move is to find somebody with a working set, drop it into the set and check the TV image.
Yes, good points well made.

I wonder if anyone localish to me has a suitable set and would be happy to test the tube on my behalf?
__________________
Engineers make things work and have spare bits when finished
Sean Williams is offline  
Old 22nd Apr 2019, 10:08 pm   #9
Argus25
No Longer a Member
 
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Emiscope 3/1 Testing, and value?

If it is excellent on testing in a set, the person who tests it will probably want it as it may be better than their own 3-1 ! I would want it, especially if it tested well and I lived in the UK, but I would not like to take the risk shipping it to Australia, just in case it got damaged / broken. That would be a real loss and I'm not talking just about financial loss, it cannot be replaced. It is better to avoid shipping at all for this rare part (unless you hand carry it in good packing) and hand it directly to the person who wants it.
Argus25 is offline  
Old 23rd Apr 2019, 8:35 am   #10
peter_scott
Dekatron
 
peter_scott's Avatar
 
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,273
Default Re: Emiscope 3/1 Testing, and value?

Sean, Testing in a set would certainly be best but if you decide to test it with a defocused beam I think you might find that with the 3/1 the burnt area may not be the concentrated centre spot but rather a much larger circular area with a well defined edge in which case you might need to explore a rather larger sweep with the magnet.

Peter
peter_scott is offline  
Old 23rd Apr 2019, 8:48 am   #11
Jac
Heptode
 
Jac's Avatar
 
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 640
Default Re: Emiscope 3/1 Testing, and value?

To illustrate this, a photo of the 3/1 in my 706.

Hope this helps.

Jac
Attached Thumbnails
Click image for larger version

Name:	2017-01-08 706 266 ionenvlek.jpg
Views:	302
Size:	12.0 KB
ID:	181692  
Jac is online now  
Old 23rd Apr 2019, 9:07 am   #12
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
Default Re: Emiscope 3/1 Testing, and value?

I have never seen a 3/1 with a side evacuated seal on the bulb. It may well be a very early tube possibly experimental. I believe the 3/1 were manufactured like it's big brother the 6/6 from Pyrex hard glass.

1000v will not burn the screen and 500V may well give an indication on a 5" tube. Due to zero focusing field the unfocused beam will show the familiar 'moon' pattern on the screen and will give a good indication as to the tube's condition. I have done this many times as a test.
When working on an early receiver with mains derived EHT, one of the first tests I carry out is to determine the make of the EHT smoothing capacitor/s. If they are the the Bakelite TCC Visconol type I disconnect them.

Next the HT rectifier valve/s are removed and the set powered up. You can do this with a variac/limiter if you feel nervous. The focus arrangement with these early receivers is almost universally electromagnetic so there is no danger of producing a sharply focused spot that would burn a mark on the tube if there is no HT to activate the focus coil.
A quick visual check will prove for certain that a focus coil is fitted.

It works very well with triode tubes typically Mazda CRM types but will also give a fair indication with tetrodes such as the MW22-7 employed in the Pye D16T. Even without the A1 voltage a patch is produced but of lower brightness.

Of course care has to be taken but this rough test will often prove the viability of an unknown tube and the condition of the EHT transformer.

I carried this out recently with a 3/32 EMI tube and posted the outcome on a recent thread.

Good luck with your tube and I hope it is a good one! John.
Heatercathodeshort is offline  
Old 23rd Apr 2019, 10:14 am   #13
Jac
Heptode
 
Jac's Avatar
 
Join Date: Jun 2006
Location: Eindhoven, Netherlands.
Posts: 640
Default Re: Emiscope 3/1 Testing, and value?

Hi John,

My 3/1 in the Marconiphone 706 also has no evacuation pip on the bulb, but if the photo by Catkins (2015) and a photo of the CRT booklet (also by Catkins) are any indication, both with and without pip on the bulb were made.
Please see attachments.

Jac
edit: added a photo of the 3/1 on my CRT tester at 2 kV anode voltage.
In reality brightness is much less than it appears to be on the photo.
Attached Thumbnails
Click image for larger version

Name:	2015-04 Catkins 06 BBen.JPG
Views:	203
Size:	35.8 KB
ID:	181696   Click image for larger version

Name:	2015-04 Catkins 09 BB spec.JPG
Views:	182
Size:	16.0 KB
ID:	181697   Click image for larger version

Name:	2015-04-28 706 45 BB Diffusionsbild @ 2kV.jpg
Views:	198
Size:	8.1 KB
ID:	181699  

Last edited by Jac; 23rd Apr 2019 at 10:19 am.
Jac is online now  
Old 23rd Apr 2019, 6:07 pm   #14
draenog
Tetrode
 
draenog's Avatar
 
Join Date: Oct 2009
Location: Chepstow, Monmouthshire, UK.
Posts: 60
Default Re: Emiscope 3/1 Testing, and value?

Quote:
Originally Posted by Jac View Post
My 3/1 in the Marconiphone 706 also has no evacuation pip on the bulb, but if the photo by Catkins (2015) and a photo of the CRT booklet (also by Catkins) are any indication, both with and without pip on the bulb were made.
The CRT with the side evacuation in that picture is from my Marconi 706. This tube is o/c so I would be very interested in a new one! A 3/1 appeared on ebay a few years ago which also turned out to be dud. This also had side evacuation...
draenog is offline  
Old 23rd Apr 2019, 6:47 pm   #15
draenog
Tetrode
 
draenog's Avatar
 
Join Date: Oct 2009
Location: Chepstow, Monmouthshire, UK.
Posts: 60
Default Re: Emiscope 3/1 Testing, and value?

Without a working CRT I never got far with my restoration (I have since obtained a 5FP4 so I've been intending to start on it again for at least the last year). My brother's HMV 904 was in working order 3 years ago, but hasn't been turned on since. We're also not quite round the corner, being 2.5 hours drive away.
draenog is offline  
Old 23rd Apr 2019, 10:14 pm   #16
Sean Williams
Dekatron
 
Sean Williams's Avatar
 
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,517
Default Re: Emiscope 3/1 Testing, and value?

Well, I put the brave pants on tonight - et voila! A white phosphor!

I moved the beam around with a magnet as Peter suggested, and there appears to be no Ion burn to speak of other than the pinprick in the centre of the tube face.

EHT was around 900v and heater at 4v at the CRT base.
Attached Thumbnails
Click image for larger version

Name:	emiscope 2.jpg
Views:	318
Size:	28.0 KB
ID:	181749  
__________________
Engineers make things work and have spare bits when finished
Sean Williams is offline  
Old 24th Apr 2019, 12:41 am   #17
linescan87
Heptode
 
linescan87's Avatar
 
Join Date: Mar 2014
Location: Meath, Ireland
Posts: 547
Default Re: Emiscope 3/1 Testing, and value?

Great stuff, I'm sure that crt will make someone very happy!
linescan87 is offline  
Old 24th Apr 2019, 12:17 pm   #18
draenog
Tetrode
 
draenog's Avatar
 
Join Date: Oct 2009
Location: Chepstow, Monmouthshire, UK.
Posts: 60
Default Re: Emiscope 3/1 Testing, and value?

Hi Sean,

Could you provide a close-up picture of the gun assembly?

Thanks.
draenog is offline  
Old 25th Apr 2019, 10:25 pm   #19
draenog
Tetrode
 
draenog's Avatar
 
Join Date: Oct 2009
Location: Chepstow, Monmouthshire, UK.
Posts: 60
Default Re: Emiscope 3/1 Testing, and value?

No response to my post and no response to a PM so I guess this is now sold.
draenog is offline  
Old 26th Apr 2019, 5:29 am   #20
Sean Williams
Dekatron
 
Sean Williams's Avatar
 
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,517
Default Re: Emiscope 3/1 Testing, and value?

No, not sold, just away with work, and this isnt a selling thread
__________________
Engineers make things work and have spare bits when finished
Sean Williams is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 6:00 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.