Old vidicon TV camera - Page 1
Forum section: electronics / repair

author: Unknown
author_rank: Unknown
timestamp: July 23, 2015, 01:32:58 am
content: I'm trying to get an old pre-CCD (vidicon tube) black-and-white CCTV camera working.It's from about 1979 (GBC Mark XV). It worked when I put it away around 1982.Now, no picture.On an oscilloscope I see something vaguely like NTSC composite video (roughly 1v peak-to-peak). Except the base level (blanking level, lowest voltage of the signal) is around +4.5 volts. Line period is a little long - around 70 uS (should be 63.5). Front and back porch area of signal looks fine, as does vertical retrace.When I wave a light bulb in front of the lens I see the signal level on each line (on the oscilloscope) move a tiny bit - barely noticeable.This thing has a separate power supply box and a long cable with 9 wires in it. As best as I can tell:Pin 1: Chassis groundPin 2: Can't tell. At 0v.Pin 3: Seems to have something to do with audio. I can unplug it and still get the video signal.Pin 4: Seems to have something to do with audio. I can unplug it and still get the video signal.Pin 5: Video Ground (reference)Pin 6: Video (composite NTSC)Pin 7: +16 volts (from a transformer, full-wave bridge, and some filter caps)Pin 8: Connected to a button on the camera (otherwise does nothing).Pin 9: +12 volts (from a 7812 regulator in the box).That's about all I know. There are about 10 pots in the thing, I twiddled all of them - only one seems to affect the output at all (seems to change the amount of noise in the output video signal).Any suggestions re where to start?

author: BennVenn
author_rank: Regular Contributor
timestamp: July 23, 2015, 02:01:56 am
content: Any Pics?

author: poot36
author_rank: Frequent Contributor
timestamp: July 23, 2015, 05:07:34 am
content: Check and test all of the capacitors in the power supply as well as the video camera itself. I am willing to bet that some have dried out or otherwise failed.

author: SL4P
author_rank: Super Contributor
timestamp: July 23, 2015, 06:00:56 am
content: Quote from: Dave92F1 on July 23, 2015, 01:32:58 amThat was probablynota good starting point.You say itwasworking before you stored it...Chances are it can be salvaged (check the caps as above), but if there is any damage caused to the optical surfaces or heaters of the vidicon - well...To get it back in spec - assuming you get everything working - you'll need a scope and some idea of what the pots were set to before you corrected them.

author: Unknown
author_rank: Unknown
timestamp: July 23, 2015, 03:30:53 pm
content: Quote from: SL4P on July 23, 2015, 06:00:56 amI didn't twiddle them until AFTER I saw it wasn't working.And I did note where they started and put them back as close as I could.I read online (can't find the link now) that vidicon tubes should be run for a few hours every few months to allow the getter to absorb any stray gas molecules - otherwise the tube becomes contaminated and doesn't work. I suspect that's what happened - it wasn't run at all for 30 years.But based on that idea I left it powered on overnight - now I get a picture that syncs with the monitor, but it's still just noise...I'll leave it powered for a week or two and see if that helps anything.

author: SeanB
author_rank: Super Contributor
timestamp: July 23, 2015, 04:22:22 pm
content: You probably have a damp tube front face from storage, so leaving on for a week should dry it so the first stage amplifier works again, as it has a very high impedance JFET input stage to do the first stage video amplification.Check that you have video coming from the head amplifier, but do not open the front of the tube where the amplifier is, as it will be soldered together and glued down during manufacture. You can measure the signals on the connector though, there will be some power supplies, a high voltage bias ( depends on tube as to what it is) for the tube and the amplified video signal. If you have video there, most likely on a screened cable, then you look on the main boards for dead caps and resistors that have drifted high in value.

author: Unknown
author_rank: Unknown
timestamp: July 25, 2015, 08:46:41 pm
content: Been 3 days now, no improvment.But I know you guys - you want those super-sexy pictures. I will oblige.Here's the case:Left side:Right side:Power supply box (front):Power supply box (back):Left side with the guts hanging out (and vidicon visible):Business end of the vidicon:Right side with the guts hanging out (and those many pots):A better view of the vidicon:And finally, the picture I get from it (yes, lens cap is off):Interesting white spot in the vertical retrace (made visible by fiddling with Vertical Hold on the monitor):

author: N2IXK
author_rank: Frequent Contributor
timestamp: July 25, 2015, 10:27:43 pm
content: Do you get any sign of hum bars or noise in the video if you touch your finger lightly to the face of the vidicon (not the electrical contact ring, the actual glass faceplate)? You should if the video amp is at least somewhat working.If so, does shining a light source near the tube face give any result on screen? If the beam and target controls are set incorrectly (or one of the associated bias voltage supplies is out), the tube won't sense light AT ALL. It also needs proper scanning signals and focus current driving the various coils mounted around it.All the small aluminum electrolytics would be suspect just from age. Do you have access to a schematic? Pretty much going to need one if you haven't worked on these things before.Vidicons are pretty easily available and cheap for these things on eBay and similar. A bad tube isn't the end of the world if you really want to resurrect this thing. Looks nicely enough constructed (for a CCTV grade camera) and pretty easy to work on. Analog video stuff in general is lots of fun to play around with, and with the digital takeover, actual broadcast grade kit is available for scrap prices.

author: SeanB
author_rank: Super Contributor
timestamp: July 26, 2015, 09:26:08 am
content: Do you see the capacitor in the left above the DIP14 in a white spocket? The one with a shrinking sleeve. I would suspect that one.Where does the target wire ( grey one in the fron t of the vidicon) attach, I would guess somewhere near this area.

author: mikerj
author_rank: Super Contributor
timestamp: July 26, 2015, 09:51:39 am
content: Quote from: SeanB on July 26, 2015, 09:26:08 amThe two large caps on the upper right hand side also look suspicious, the upper one especially looks a bit bulged at the top.It's also worth re-seating all the socketed ICs.

author: Unknown
author_rank: Unknown
timestamp: July 26, 2015, 02:48:36 pm
content: Quote from: N2IXK on July 25, 2015, 10:27:43 pmWill touching the vidicon surface damage it? @SL4P seemed to think so (above).Quote from: N2IXK on July 25, 2015, 10:27:43 pmNothing visible on the monitor, but on an oscilloscope I can see a very slight increase in average voltage when I shine a light at it.Quote from: N2IXK on July 25, 2015, 10:27:43 pmNo, and I can't find one online either..Quote from: N2IXK on July 25, 2015, 10:27:43 pmNo kidding - look at this!http://www.ebay.com/itm/Ikegami-HK-357A-Vintage-1980-Broadcast-Studio-Color-Video-Camera-Movie-TV-3Tubes-/131563065700They're asking $68 for it (will consider lower offers).My real goal here is to get a black-and-white vidicon camera that I can play with. I want to experiment with non-standard scanning patterns, by driving the vidicon (and a CRT display) with a microcontroller and DAC.If this one is too hard to get going, I may just sell it on eBay (with flaws disclosed, of course - I'm not that kind of scum) and buy another one.

author: N2IXK
author_rank: Frequent Contributor
timestamp: July 26, 2015, 03:23:16 pm
content: Quote from: Dave92F1 on July 26, 2015, 02:48:36 pmNo. The part that can be damaged is the photoconductive coating on the INSIDE surface of the tube faceplate. Bright light and/or improper bias settings can do that.The front of the tube is just a piece of flat glass. The worst that touching it will do is leave a fingerprint, which will clean right off.Quote from: N2IXK on July 25, 2015, 10:27:43 pmQuoteGBC appears to still be around in some form. They were a pretty big name in CCTV gear at one point. Maybe you can get one from them?http://www.securityinfowatch.com/company/10213165/cctv-corporation-gbcQuote from: N2IXK on July 25, 2015, 10:27:43 pmQuoteA good buy if you need parts, but without a lens and the separate rackmount control unit (CCU) and cable that plugs into that zillion pin connector, what they are selling is pretty much a doorstop.QuoteThose sorts of cameras were everywhere, and are still pretty common on eBay and at hamfests/flea markets. Used to fix a lot of them back in the day.Lacking a schematic, I would probably shotgun all the electrolytics (shouldn't cost more than a few bucks), and check that all the power supplies are good.

author: Unknown
author_rank: Unknown
timestamp: July 30, 2015, 04:13:36 pm
content: I've decided this is too much trouble - I'm going to put it on eBay (in a few days).If anybody here wants it, let me know before it goes on eBay - I'll let it go pretty cheap (free, if you'll pick it up and save me the trouble of packing it up). It's in Boston USA.

author: poot36
author_rank: Frequent Contributor
timestamp: August 01, 2015, 04:19:19 am
content: If you replace the electrolytic caps that have the blue shrink pulling away from the top of the can I think that it should work again.

author: Unknown
author_rank: Unknown
timestamp: August 03, 2015, 03:01:33 am
content: You think? I see maybe four with that problem - all in the "Left side with the guts hanging out" photo - the three at the top left, the other just to the left of the UA7570C chip.Do you agree? If you think it's just those four, I'll give it a try.

author: miguelvp
author_rank: Super Contributor
timestamp: August 03, 2015, 05:11:40 am
content: Quote from: Dave92F1 on July 30, 2015, 04:13:36 pmDefine cheap, I'm interested since I like to work on video signals, even the obsolete NTSCHow much to ship it to Chicago IL?

author: Unknown
author_rank: Unknown
timestamp: August 03, 2015, 03:00:14 pm
content: Quote from: miguelvp on August 03, 2015, 05:11:40 amI PM'ed you.

author: miguelvp
author_rank: Super Contributor
timestamp: August 03, 2015, 03:18:28 pm
content: Quote from: Dave92F1 on August 03, 2015, 03:00:14 pmCool, I'll take it off your hands and try my best to bring it back.

author: Unknown
author_rank: Unknown
timestamp: August 04, 2015, 12:23:05 am
content: If you get it working, please post here...I'd like to know. It will be picked up tomorrow.

author: miguelvp
author_rank: Super Contributor
timestamp: August 04, 2015, 01:13:15 am
content: I will most definitely do so.

author: miguelvp
author_rank: Super Contributor
timestamp: August 07, 2015, 03:36:40 pm
content: According to FedEx it should get here today.As soon as I have some time I'll do some scope captures of the signal. Since it's B&W there might not be a color burst signal, but I can use the HSynch as a reference to figures out the output levels.

author: miguelvp
author_rank: Super Contributor
timestamp: August 10, 2015, 01:43:58 am
content: So when I got it, I did power it up and hooked the composite output to my scope.I was able to see just the VSync (about 4 lines) and the rest of the blanking period (17 lines) didn't look good at all since it was stuck high at just 0.2V from reference and no HSync present at all.Also if I turn the camera on or off but leave the power supply on I get the same signal.Today I had more time so I left it on for a while and HSynch started to work, I even see the color burst, but I don't see any changes even if I put a 300 lumens flashlight in front.The color burst seems a bit low in comparison to other composite signals I've seen:I would expect it to be more like this with no video in:This is a capture of the VSync (4 lines followed by 17 more lines):And here is a full frame:So I will have to dig into the camera to see if I can get any video out of the vidicon itself after checking if all the voltages to the tube are ok. I've seen replacements on ebay but they are the longer ones.But with summer, and the wife wanting to go out because it's nice I might not get a lot of time to work in this just yet.Also I didn't measure the timings much, but looks like the Vertical Front Porch is non existent (not a concern really).

author: ccs46
author_rank: Regular Contributor
timestamp: August 10, 2015, 02:22:23 am
content: If you get it working you got to show us some sexy photos of it. The Geek-Gasm will be really strong if we see that thing working.

author: miguelvp
author_rank: Super Contributor
timestamp: August 10, 2015, 04:51:48 pm
content: The view finder is optical I believe and I don't see anything through it.Maybe the light path is obstructed, I'll try to shine the light directly to the vidicon.

author: Unknown
author_rank: Unknown
timestamp: August 11, 2015, 06:17:18 pm
content: Quote from: miguelvp on August 10, 2015, 04:51:48 pmYes, it's a half-silvered mirror thing - the light goes in the lens, then a portion of it is diverted to the viewfinder, while the rest goes straight to the vidicon.

author: miguelvp
author_rank: Super Contributor
timestamp: August 11, 2015, 06:21:42 pm
content: I guess I wasn't looking right, because I can see fine through the window.Audio works for what is worth.Maybe this weekend I can look at the power levels on the vidicon tube.

author: hef
author_rank: Newbie
timestamp: June 13, 2016, 01:47:45 am
content: Sadly, MiguelVP was not able to complete repairs on the camera. Would anyone like it?