I have a depth finder that uses this tube. The display is getting very dim. Anyone have the pinout on the tube? Or a source for a new one?

Thanks,

Mike

Its a Japanese tube. see if its marked for brand. That may help track one down.
For pin out run the set & measure the pins. This is the most likely........
filament one side ground other 6 or 12 VDC.
cathode higher DCv that varies with brightness control. High dc = black px, low
DC = brite pix
G1 usually about 0 VDC
G-2 is focus & often goes to taps from zero VDC up.
Hope that helps some.

73 Zeno
LFOD !

There were certainly some small portable B&W TV's back in the day which used a 150mm CRT. Identifying which ones could potentially interchange with your tube might take some significant research.

Finding a new one will probably require patience, but one may eventually turn up.

A quick search shows a posting where someone claims the 150BGB4 is a drop in replacement for the original CRT in the Panasonic TR-005 which is a highly collectible, and therefore quite valuable set. But there may be other common TV sets of the same age which have very little value today, once you know which CRT's can interchange, you could look for one which was functional enough to be able to determine the CRT is still brighter than your old one.

The 150BGB31 (a green phosphor type (P31= green) was used in the common garden Panasonic model M-C5001A VDU.

I know because I have a number of these VDU's that I converted to White, by fitting the 150BGB4 , which I got from NEWTUBES (in Canada) via eBay, though I'm not sure if any are left there.

Here is a link to a project:

www.worldphaco.com/uploads/Autodetectin ... nitor..pdf


In all probability, your unit was fitted with one of these Panasonic industrial VDU units and fitted with the B4 CRT. These industrial CRT's are very hardy with a long life.

Here is some good news. These VDU's were fitted with both sub-brightness and sub-contrast controls.

Have you tried adjusting those yet ?

Thanks for all of the information.

I have not figured out how to reply to individual posts yet, so if someone can advise me on how to do that, I would appreciate it...didn't see anything in the FAQs, but must be missing something.

Anyone have a schematic of this tube in a unit would be helpful, it's been too many years since I worked on TV's to remember the details.

I also located my old Beltron Picture Tube checker, but did not find the tube in the listings and don't seem to have a plug that would fit the socket, although I could probably patch it in. Although someone noted that the filament voltage is 6-12 VDC, not sure the checker could be used as I believe it is only capable of producing AC voltage for the filament.

I also searched ebay and other places in hopes of finding a new one, but did not find anything.

I have not seen a cross-reference for tubes in 40 years...

If anyone can offer any additional information, it would be appreciated.

Best,

Mike

Here is the schematic of the Panasonic unit. So, you can see the location of the sub-contrast and sub-brightness controls, in this model at least.

I changed a capacitor value in these units to kill the power off afterglow spot, which occurs when the 12V power collapses too rapidly at turn off. A common problem in many industrial VDU's unless they went to the trouble to add a spot killer.

In addition, I placed a resistor in series with the CRT heater, the reason for this is that if the VDU is powered from a very low internal resistance 12V power source, such as a car battery where it is often less than a few hundred milli-Ohms, and the CRT heater is cold, its resistance is very low and the initial peak currents cause a bright flash from the heater at turn on. It is better to have the resistor to limit the peak current.

One other thing about these small VDU's, as you can see from the video amplifier design, they have a true Black Level clamp where a delayed H pulse is used to drive the clamp transistor to clamp the back porch of the video signal just after the H sync pulse.

I'd caution against using the tube tester as it poses a risk to the tube, the tube is better tested in the VDU that was designed to run it.

If you can post a video showing the picture as you turn the brightness from minimum to maximum, I (and others) could tell you if the problem is the tube or something else.
There are numerous other reasons for low brightness other than the tube.

It might be just a resistor in the G2 circuit gone high.

On the lower right corner of the individual post, hit the "quote" button.

I was looking through my stuff and I found some new 150BGB31 (green)CRT's. I could sell one if you got stuck and had no other solution.