Featured
Latest
Pye Lynx TVC/1A Cam...
 
Share:
Notifications
Clear all

Forum 141

Pye Lynx TVC/1A Camera.

37 Posts
10 Users
0 Likes
2,834 Views
Marc
 Marc
(@marc)
Posts: 2753
Noble Member Registered
Topic starter
 

Hi all,

A while ago I found a Pye Lynx TVC/1A camera at a steam fair (web photo of camera type below) and for the princely sum of a fiver it was mine. Any way it's been sat on a shelf collecting dust ever since so I thought I would give it a quick once over.

Powering up and running the camera through a modulator produced a big fat nothing so with the case removed and power reapplied I noticed that there was no glow coming from the tube heater (if tube is the correct term). A dab across the heater pins shows 6.7v, a bit high but there, now checking for continuity across the heater...nothing ! So duff tube.

My first question is, do I continue with this project and fit a tube ? And the second question....where the heck would I find a tube ?

Marc.

PYE-LYNX-CCTV-CAMERA-TCC-1-PICT3716.JPG

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 31/03/2017 9:42 pm
Katie Bush
(@katie-bush)
Posts: 4884
Famed Member Registered
 

Definitely worth having a go!

You might just find a compatible tube on eBay. Tubes do turn up quite often, but you may need to be a little bit creative to make one work. Otherwise, you might even find another Lynx for spares.

Just a though.... If the heater is truly O/C you could try the EHT welding trick - nothing to lose?

Have you got a pic of the tube?

 
Posted : 31/03/2017 9:50 pm
Marc
 Marc
(@marc)
Posts: 2753
Noble Member Registered
Topic starter
 

Katie_Bush said
Just a though.... If the heater is truly O/C you could try the EHT welding trick - nothing to lose?

Have you got a pic of the tube?  

Hi Marion,

Yep, the tube is well and truly O/C heater so the EHT welding trick may be worth a go. hmm_gif I'll try and post a photo of the tube tomorrow.

Marc.

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 31/03/2017 10:27 pm
PYE625
(@pye625)
Posts: 5121
Famed Member Registered
 

I wonder what the intended application would have been for the camera....schools, college or industry?

Surely not a CCTV camera as it looks like it's meant to carry around or to fit a tripod.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 31/03/2017 10:36 pm
Nuvistor
(@nuvistor)
Posts: 4594
Famed Member Registered
 

Is this of any use?

http://www.tvcameramuseum.org/pdfs/pye/pyelynxcircuittvc1a.pdf

Later FET version brochure

http://www.tvcameramuseum.org/pdfs/pye/fetlynxbroc.pdf

Frank

 
Posted : 31/03/2017 10:45 pm
Marc
 Marc
(@marc)
Posts: 2753
Noble Member Registered
Topic starter
 

PYE625 said
I wonder what the intended application would have been for the camera....schools, college or industry?

Surely not a CCTV camera as it looks like it's meant to carry around or to fit a tripod.  

Hi Andrew,

According to the 'Museum of the Broadcast Television Camera' it's for general purpus CCTV. 

http://www.tvcameramuseum.org/pye/pyethumb.htm#lynx

Marc.

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 31/03/2017 10:57 pm
Marc
 Marc
(@marc)
Posts: 2753
Noble Member Registered
Topic starter
 

nuvistor said
Is this of any use?

http://www.tvcameramuseum.org/pdfs/pye/pyelynxcircuittvc1a.pdf

Later FET version brochure

http://www.tvcameramuseum.org/pdfs/pye/fetlynxbroc.pdf  

Cheers Frank, at least I now know the tube type, 9677P vidicon.

Marc. 

EDIT....Oops ! looks like the tube is C938 Staticon.....

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 31/03/2017 11:02 pm
Marc
 Marc
(@marc)
Posts: 2753
Noble Member Registered
Topic starter
 

Hi all,

Well would you believe it..... Whilst unsuccessfully trawling the web for camera tubes I found an add from eBay from a few weeks ago showing that someone sold a NOS C938 Staticon tube and it was less than 6 miles from me and even worse it went for 99p. waa_gif

I reckon i'll have to put the Lynx back on the shelf until either a tube or a donor camera turns up.

Marc.

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 01/04/2017 2:27 pm
Cathovisor
(@cathovisor)
Posts: 6390
Famed Member Registered
 

Well, it does show that tubes are out there. Pop it back on the shelf, one will turn up sooner or later.

 
Posted : 01/04/2017 2:46 pm
Marc
 Marc
(@marc)
Posts: 2753
Noble Member Registered
Topic starter
 

Cathovisor said
Well, it does show that tubes are out there. Pop it back on the shelf, one will turn up sooner or later.  

Very true, and it' already back on the shelf....wonder how many years for this time hmm_gif wink

Marc.

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 01/04/2017 2:55 pm
occiput
(@occiput)
Posts: 117
Estimable Member Registered
 

If I recall correctly, "Staticon" was simply the Cathodeon brand name for a vidicon.  I suspect that any vidicon which will physically fit ought to be enough to "get you going" and find out whether there are any more faults.

 

6.7V is a bit high for a nominally 6.3V tube and this will shorten tube life, though not to the "switch on and it goes pop" stage.  It may simply be that the mains transformer taps need adjusting appropriately.  Although, personally, I am very wary indeed of the various "folk" means of remotely welding o/c heaters, as Marion points out, you seem to have a dead tube at the moment and therefore little enough to lose if it doesn't work.  Before taking this step, however, it might be worth cleaning the pins, if you have not done so already.  There isn't much contact area at the best of times, and it doesn't take much tarnishing to produce an apparent o/c reading.

 

The Lynx was one of the first cameras small and light enough to be one-person portable and to mount on a standard photographic tripod.  They were very popular with the amateur television fraternity at one time, and I remember seeing piles of them at amateur rallies for, typically, about ten pounds each (late seventies/early eighties).  For this reason, you may find that various modifications have been applied.

 

Looking at the circuit diagram, at first sight it appears that the field timebase is mains-locked but the line-timebase free-runs, so the interlace is random and there is no guarantee that there will even be 625 lines in a picture.  This was very common in this class of equipment when new, but was regarded as a bit crude by the mid-seventies, so you may find mods to make the timebases lock to an external source.  Equally, I wouldn't expect to find any equalising pulses on the output signal.  However, these features also mean that it should be relatively easy to slow the line timebase down to produce sort-of 405 line pictures, if you have any thoughts of doing this.

 

The other thing you will find, of course, is low laggy vidicon pictures are.

709379

 
Posted : 01/04/2017 3:18 pm
Marc
 Marc
(@marc)
Posts: 2753
Noble Member Registered
Topic starter
 

Hi occiput,

Thanks for the info, all very useful to know.

The tube heater is definitely O/C cleaning the pins was one of the first things I did whilst checking. The camera voltage tappings only go to 235v max which may explain the 6.7 at the heater with our house voltage drifting anywhere between 238v and 254v it's not surprising.

Also looking at the PCB's and comparing them to the data I have it appears that the camera was set for 405 line use.

http://www.tvcameramuseum.org/pdfs/pye/lynx405mod.pdf

I shall keep my eyes peeled for a 25mm tube.

Marc.

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 01/04/2017 3:54 pm
wd40addict
(@wd40addict)
Posts: 74
Trusted Member Registered
 

I have the original TVC1 (no a). It arrived with a whole bunch of tubes, but only 2 actually worked after a fashion. The TVC1 supplies the tube heater via resistor from the 11.5v line so the heater voltage is only correct with the original Cathodeon tube and its 0.4A current. Staticons from other makes can vary between 0.09A & 0.6A, the previous owner didn't appear to realise this.

Your TVC1a has a proper heater winding so you could probably try any of them. Remember your 6.7v is unloaded so will go down with a working tube.

In the end I fitted an East German silicon target type from eBay. This can virtually see in the dark, presumably good for the Stasi. For outdoor use an RCA 7735 might be better.

My camera had the 405 components factory fitted despite being badged as 625.

405 Selfie attached to inspire you, looks much better in real life!405-Selfie.jpg

 
Posted : 01/04/2017 5:57 pm
Marc
 Marc
(@marc)
Posts: 2753
Noble Member Registered
Topic starter
 

wd40addict said

In the end I fitted an East German silicon target type from eBay. This can virtually see in the dark, presumably good for the Stasi.   

Thanks for all the info, it's appreciated. Do you know what the model number was for the East German tube you got from eBay was ?

Marc.

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 01/04/2017 6:53 pm
wd40addict
(@wd40addict)
Posts: 74
Trusted Member Registered
 

It was the "TGL39121 F2,5 M51B". with 0.3A heater, trouble is the seller only has a different type now and I don't know if this would work.

The RCA 7735 should give a good result if your transformer can cope with the 0.6A heater load. Maybe try loading with a 10R power resistor and see what the voltage falls to?

As an aside for TVC1 (not a) models with modulators if you want to swap the modulator to positive modulation for 405 use then reverse diode V9 (cathode to transformer). I have never seen this mentioned among the normal 405 component changes.

 
Posted : 01/04/2017 8:39 pm
wd40addict
(@wd40addict)
Posts: 74
Trusted Member Registered
 

I should also add that if you did fit a silicon target Vidicon (sometimes known as a Sidicon) then you would have to disable the automatic biasing fitted to the TVC1a. 

 
Posted : 01/04/2017 10:36 pm
Marc
 Marc
(@marc)
Posts: 2753
Noble Member Registered
Topic starter
 

Again thank you for all the info, I have spotted a TGL 39120 F2.5 M31B on eBay, I wonder if that would be suitable ?

Marc.

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 01/04/2017 10:58 pm
wd40addict
(@wd40addict)
Posts: 74
Trusted Member Registered
 

I'm afraid I don't know, I couldn't find any data. Si target vidicons have the advantages that they don't suffer from burn in, but they are extremely sensitive, have a gamma of 1 and seem prone to burn out a bit on highlights.

In your position I'd load the tube LT with a 10R resistor and see how much it droops. If it's OK check all other voltages and ensure timebases are correct with a scope. If all is well fit a 7735. otherwise you'll have to find something with lower heater current.

I've never seen any data on the C938 so I've used the 7735 data as my reference when comparing others.

Note later Vidicons had an extra terminal bought out to pin 3, this needs to be strapped to pin 5. This mod appeared to be factory fitted to my camera.

Some faults on my camera included failure of the -11.5v pass transistor. Failure of the focus regulator zener and broken pots etc.

 
Posted : 02/04/2017 12:04 pm
Marc
 Marc
(@marc)
Posts: 2753
Noble Member Registered
Topic starter
 

Putting a 10Ω resistor across the heater supply gives a more comfortable voltage of 6.22

I think I'll stick with the 7735 tube you mentioned.

Marc.

Marc
BVWS member
RSGB call sign 2E0VTN

 
Posted : 02/04/2017 1:38 pm
wd40addict
(@wd40addict)
Posts: 74
Trusted Member Registered
 

Tube order in mine was:

EMI 9677C this just gave no real picture only sensitive to extreme black or white. Heater voltage way too high due to TVC1 resistor heater feed. Has a 95ma heater!

Miscellaneous other tubes which all did not a lot.

Finally tried the Cathodean C938 which gave a recognisable picture, but lots of burnt in sparkly damage.

This success returned me to the 7735. Having realised it was a 0.6A heater I powered it externally and got the best picture so far, but still a few sparklies. 

If the TVC1 could power a 7735 I would have got another one, but I couldn't figure out a way of getting enough current without an external wall wart.

So finally this lead on to the East German RFT Sidicon with its 0.3A heater, I changed the series resistor to suit and got the best picture so far, but you'd need an extreme neutral density filter to use it outside!

7735 gives good indoor and outdoor pictures.

All heater circuit comments relate to the TVC1 NOT the TVC1a

 
Posted : 02/04/2017 5:13 pm
Page 1 / 2
Share: