View Full Version : Beltron Bulbs?


wb2mep
01-21-2008, 07:14 PM
A few months ago I bought a Beltron CRT tester/rejuvinator off Flea-Bay.
It was in OK shape, but it looked like it got a lot of use by its original
owner. It also had a musty smell to it, like it had bee stored in a
damp environment. When I plugged it in, I got a nice Snap as the
plug made contact with the outlet, so either this unit has some big
caps in its power supply, or something may be shorted, so I immediately
unplugged it and put it in the closet until I had some time to open it up
and see what's inside.

There's a big Hamfest coming to Orlando in 2 weeks, so I figured it would
be a good time to see what parts I might need for the Beltron.
Out of curiosity, I pulled the bulbs to see what type they were,
and all 3 of the Cleaning Lamps were open. Really open - like no
trace of the filaments left. Either there is a fault in the unit that
took out the bulbs (one of the socket harnesses was wrapped with
electrical tape, so could have been a short at one time), or the bulbs
were the wrong type. The bulbs were #49, which is an odd type.
Can anyone with a working Beltron check what type bulbs are used
in the cleaning lamps, so I can try to track some down? Thanks-
Mike

andy
01-21-2008, 08:11 PM
...

dgwojo
01-21-2008, 10:08 PM
I've had good luck selling the vintage GE 49's on eBay, the folks across the sea buy the entire 10 packs, Dave. dgwojo (http://search.ebay.com/_W0QQfgtpZ1QQfrppZ25QQsassZdgwojo)

refill233
01-22-2008, 08:05 AM
I have just about anything you need to repair your Beltron . What model do you have ? PM me if you need anything i have.

Thanks. Don


Cleaning lamps--49

Restoring lamps--10S6 10watt 250 volts

wb2mep
01-22-2008, 10:25 PM
Thanks for the info, guys. It looks like I'll have to hunt down some #49s
at the Hamfest. My 2005 Mouser catalog shows those to be 2.0 V, 60 mA
bulbs. Just wanted to be sure that's what belongs there.

Don - not sure what model I have, it's at home and I'm at work.
I plan on opening it up this weekend to check for shorted diodes/caps-
I'll post again if I have any more questions.

Mike

wb2mep
03-29-2008, 12:31 AM
Sorry for letting this thread drop for so long, but I wanted to get a
couple other projects started so I could put together a shopping list for
the Big Hamfest (3 days long, 1 building of indoor swap tables, 2
buildings of commercial vendors, and loads of outdoor swap tables).
Hamfests are great for finding parts for old equipment, but they
only have one a year.

Anyway, good news and bad news on my Beltron (model 2972-E.)
Good news is that my Cleaning Lamps are OK. The #49 bulbs are
2.0 volts 60 mA and the filaments are hair-thin. I didn't see them
until I held the bulbs against the fluorescent tube of my bench lamp.

Bad news is that the Blue gun emission meter has an open coil, and
the Green meter has a sticky pointer, but I can live with that.
These are a common 0-1 mA rating, but are an odd size, made by
Modutec (now Jewell Instruments), wider/shorter than common
panel meters (sort of a 16:9 aspect ratio). I had no luck finding
one at the hamfest, or at Skycraft Surplus (a local Industrial/Electronics
surplus house.) It appears that Jewell/Modutec still make this
style of meter, but their on-line catalog doesn't give the physical
dimensions. The meters are mounted side-by-side on the Beltron,
with no gaps between adjacent meters, so getting the right size
meter is critical. It looks like I'll be PMing Refill233...

Regarding the spark I got as I first plugged the unit in, the Beltron
uses a voltage-doubler right off the AC line for the Restore circuit.
There is no current limiting resistor ahead of the rectifier diodes,
and there are two 160 uF electrolytics to charge up.
I'm going to change the caps - the rubber seal on the output filter
looks kind of pimply, and has 370 volts on a 350 V. rated cap, and
add a 22 ohm wirewound resistor in series with the AC input to
the doubler. Also, there is normally no load on this power supply,
so the caps stay charged. There was still 40 volts left on one cap
a day later. I'm going to add a 470 K 1 watt bleeder resistor across
the output cap.

I know this post is getting kind of long, but have any of the Beltron
owners out there tried removing one of the Restore lamps and doing
a rejuvenation? The two bulbs are in parallel with each other, and in
series with the output of the voltage doubler, and serve to limit the
current during rejuvenation. Taking one bulb out would cut the max.
restore current in half, reducing the chance of damaging a CRT.

Mike

kbmuri
04-03-2008, 04:07 PM
The indicator lamps in the Beltron CRT Restorer serve two purposes. The obvious purpose is to provide the operator some visual indication of what's going on. The not-so-obvious purpose of the lamps is to act as fuses to protect the meters and internal components (and the customer's CRT) from overcurrent. The lamps are designed to be the weakest link. This is why most of the used Beltrons for sale have burned out bulbs in them.

The two Restore Lamps do limit current to some degree, but not to the degree necessary to prevent damage to the tube. The "current limiter" for the restoration process is the person operating the equipment. When you first apply restoring current to the tube, the lights are not lit, and the meter reads zero or very low. Over the course of a couple of seconds, the meter rises and the lamps slowly increase in brilliance. What's going on in the tube at this point is things are ionizing between the grid and cathode and as more ions occur, more current flows, causing more ions to occur, causing more current to flow... It feeds on itself exponentially. This is the beauty of the Beltron process vs. other CRT rejuvenators. You don't just blast a fixed current through the tube and blow away half the cathode's chemicals. You softly build up the current until the tube itself tells you it's had just the right amount, and then you stop. This is why the Beltron is so successful at restoring picture tubes.

So like I said, the current limiter is the operator. It's his job to watch the meter and lamps and hit the cutoff switch at the appropriate moment (when the lamps reach a brightness level and the meter reads 85). When the meter drops to a certain level (65), he repeats the process once or twice to make sure the cathode is completely clean. Any more times than that is overkill and could strip the cathode unnecessarily of it's ion-producing chemicals.

So long story short, if you took one lamp out, you might limit the current to a certain degree, but the result would be that the exponential-curve rise of the meter would just take longer to reach 85. But more than likely the single bulb, taking the current load meant for two bulbs, would just burn out first. This is the Beltron's failsafe so that you don't smoke the customer's picture tube (as a serviceman in the field) by goofing up and looking at the wrong meter, or by being distracted by the pretty customer.

I haven't actually tried it, but that's my theory. They put two bulbs in for a reason, and I'm sure the engineers balanced everything correctly when they designed it. Pulling one bulb would be a mistake. My 2 cents.