Preheat setting on Sony DXC-M3 three tube Camera - UK Vintage Radio Repair and Restoration Discussion Forum

Henenen · 18th Oct 2019, 4:47 pm

I've got a Sony DXC-M3 three tube camera but have never powered it on - until today!

I've read the manual, and looked for info around the web. It seems you have to 'pre-heat' the tubes (with a pre-heat switch) before switching the camera on properly. This is quite foreign to me as I've never used a tube camera before.

My question is how long do you have to pre-heat for, and how do you know when the tubes are ready?
Can you damage the tubes by leaving the preheat switch on too long?
How often do you have to pre-heat - eg if it was off for an hour would you pre-heat again?

Also, it advises to keep the iris closed when not filming so as to protect the tubes - would just leaving the lens cap on achieve the same?

Thanks!

Radio Wrangler · 18th Oct 2019, 5:03 pm

Lens cap would be better. Irises don't usually fully close.

David

beamcurrent · 18th Oct 2019, 9:52 pm

Without digging my manual out, I would suggest that it is, in a roundabout sort of way a battery saving feature.

To explain further, the tubes are thermionic, like valves and take a few seconds (10 or so) to warm up and operate. I think the preheat switch keeps the tube heaters hot so the camera is "ready to go" almost instantly on turning the electronics on so you miss that magic first shot.

The battery saving bit comes in by not having the electronics active, just the heaters. Obviously there is a crossover point as to when to preheat or not from an operational point of view.

There is a view that like valves you should not run the heaters only lest the cathodes become poisoned, but this does, so they say, take a long time days or weeks......

As regards closing the iris or capping, this prevents target burn if exposed to excessive light, don't look at the SUN! or these days powerful led lights. Generally if your eye can tolerate it so will the camera.

Henenen · 19th Oct 2019, 3:49 am

Ah, thanks Beamcurrent, that battery saving analogy makes sense.

In the manual it says:
"Set [the PREHEAT switch] to ON to turn the camera on after setting the POWER switch to ON. When this switch is set to PREHEAT, power is supplied only to the pickup tubes and the viewfinder in order to conserve power. At the PREHEAT position, the iris of the zoom lens is automatically closed to protect the pickup tubes."

It just doesn't say how long to leave it on Preheat for, or anything else much about it at all!

If I'm running the camera from mains power is Preheat even necessary? (assuming I don't want to record from the second it's switched on0.

Vintage Engr · 19th Oct 2019, 5:46 pm

'Beam Current' is quite correct.

Because the DXC-M3 was intended to be operated with portable U-matic VCR's such as the VO-4800, or the later VO-6800, there would be a chance that the saticons would not have warmed up properly, but the VTR would have started up. So the idea of pre-heat was implemented.

When used with a NiCd battery-belt, any unnecessary drain was of course not desirable, but acceptable if you needed an instant start.
The pre-heat was not necessary of course when run from the CCU-M3, or the optional PSU.

I used to work on these way back, happy memories.
I still have a promotional RGB Sony M3 tie that I was given at the product launch!

David.

Phil Reed · 25th Oct 2019, 9:12 pm

Quote:

Originally Posted by Vintage Engr

I still have a promotional RGB Sony M3 tie that I was given at the product launch!

Would that have been the dealer bash in Deauville?

Henenen · 29th Oct 2019, 9:42 pm

Quote:

Originally Posted by Vintage Engr

I still have a promotional RGB Sony M3 tie that I was given at the product launch!.

Cool.

Would love to see a photo of that tie please!

18th Oct 2019, 4:47 pm	#1
Henenen Tetrode Join Date: Mar 2011 Location: London, UK. Posts: 81	Preheat setting on Sony DXC-M3 three tube Camera I've got a Sony DXC-M3 three tube camera but have never powered it on - until today! I've read the manual, and looked for info around the web. It seems you have to 'pre-heat' the tubes (with a pre-heat switch) before switching the camera on properly. This is quite foreign to me as I've never used a tube camera before. My question is how long do you have to pre-heat for, and how do you know when the tubes are ready? Can you damage the tubes by leaving the preheat switch on too long? How often do you have to pre-heat - eg if it was off for an hour would you pre-heat again? Also, it advises to keep the iris closed when not filming so as to protect the tubes - would just leaving the lens cap on achieve the same? Thanks!

18th Oct 2019, 5:03 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,864	Re: Preheat setting on Tube Camera Lens cap would be better. Irises don't usually fully close. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

18th Oct 2019, 9:52 pm	#3
beamcurrent Heptode Join Date: Mar 2008 Location: Camberley, Surrey, UK. Posts: 805	Re: Preheat setting on Sony DXC-M3 three tube Camera Without digging my manual out, I would suggest that it is, in a roundabout sort of way a battery saving feature. To explain further, the tubes are thermionic, like valves and take a few seconds (10 or so) to warm up and operate. I think the preheat switch keeps the tube heaters hot so the camera is "ready to go" almost instantly on turning the electronics on so you miss that magic first shot. The battery saving bit comes in by not having the electronics active, just the heaters. Obviously there is a crossover point as to when to preheat or not from an operational point of view. There is a view that like valves you should not run the heaters only lest the cathodes become poisoned, but this does, so they say, take a long time days or weeks...... As regards closing the iris or capping, this prevents target burn if exposed to excessive light, don't look at the SUN! or these days powerful led lights. Generally if your eye can tolerate it so will the camera. __________________ Regards Brian Visit the Virtual Broadcast TV Camera Museum

19th Oct 2019, 3:49 am	#4
Henenen Tetrode Join Date: Mar 2011 Location: London, UK. Posts: 81	Re: Preheat setting on Sony DXC-M3 three tube Camera Ah, thanks Beamcurrent, that battery saving analogy makes sense. In the manual it says: "Set [the PREHEAT switch] to ON to turn the camera on after setting the POWER switch to ON. When this switch is set to PREHEAT, power is supplied only to the pickup tubes and the viewfinder in order to conserve power. At the PREHEAT position, the iris of the zoom lens is automatically closed to protect the pickup tubes." It just doesn't say how long to leave it on Preheat for, or anything else much about it at all! If I'm running the camera from mains power is Preheat even necessary? (assuming I don't want to record from the second it's switched on0.

19th Oct 2019, 5:46 pm	#5
Vintage Engr Heptode Join Date: Jan 2008 Location: Shrewsbury, Shropshire, UK. Posts: 838	Re: Preheat setting on Sony DXC-M3 three tube Camera 'Beam Current' is quite correct. Because the DXC-M3 was intended to be operated with portable U-matic VCR's such as the VO-4800, or the later VO-6800, there would be a chance that the saticons would not have warmed up properly, but the VTR would have started up. So the idea of pre-heat was implemented. When used with a NiCd battery-belt, any unnecessary drain was of course not desirable, but acceptable if you needed an instant start. The pre-heat was not necessary of course when run from the CCU-M3, or the optional PSU. I used to work on these way back, happy memories. I still have a promotional RGB Sony M3 tie that I was given at the product launch! David.