Hi,

Does anyone know of a source for the electonic version of the 50A1 ballast tube used in the some of the Transoceanics? AES used to sell them (50A1TR), but apparently doesn't anymore.

Jeff S.

Jeff: I tried AES's solid-state version, but it didn't work. I wonder if AES pulled them from its catalog because of too many returns?

The 50A1 was perhaps more necessary back when utility voltage variations were worse than now (and Commander McDonald, who was Zenith's chief sponsor of the T/O program, wanted the sets to work in all kinds of third-world countries). Most T/O models didn't use a voltage regulator tube, anyway.

I wound up subsitituting fixed power resistors to get the desired voltage, and then stuck in my dud 50A1 for ornamental purposes. Works fine.

:Hi,
:
:Does anyone know of a source for the electonic version of the 50A1 ballast tube used in the some of the Transoceanics? AES used to sell them (50A1TR), but apparently doesn't anymore.
:
:Jeff S.
:
:

One more comment. The 50A1 replacement sold by AES, aside from not working at least for me, was quite ugly - looked like a .410 shotgun shell, nothing like a real 50A1. Of course, if I remember correctly, the 50A1 tube was hidden out of view from the rear of the set.

:Jeff: I tried AES's solid-state version, but it didn't work. I wonder if AES pulled them from its catalog because of too many returns?
:
:The 50A1 was perhaps more necessary back when utility voltage variations were worse than now (and Commander McDonald, who was Zenith's chief sponsor of the T/O program, wanted the sets to work in all kinds of third-world countries). Most T/O models didn't use a voltage regulator tube, anyway.
:
:I wound up subsitituting fixed power resistors to get the desired voltage, and then stuck in my dud 50A1 for ornamental purposes. Works fine.
:
:
::Hi,
::
::Does anyone know of a source for the electonic version of the 50A1 ballast tube used in the some of the Transoceanics? AES used to sell them (50A1TR), but apparently doesn't anymore.
::
::Jeff S.
::
::

Doug: Thanks for the info. I have a pristine NOS 50A1 in my R600 T/O, and I hate to think about it burning up. I'm curious about the power resistor arrangement you used as a subsititue. How'd you do it? Jeff S.

:One more comment. The 50A1 replacement sold by AES, aside from not working at least for me, was quite ugly - looked like a .410 shotgun shell, nothing like a real 50A1. Of course, if I remember correctly, the 50A1 tube was hidden out of view from the rear of the set.
:
::Jeff: I tried AES's solid-state version, but it didn't work. I wonder if AES pulled them from its catalog because of too many returns?
::
::The 50A1 was perhaps more necessary back when utility voltage variations were worse than now (and Commander McDonald, who was Zenith's chief sponsor of the T/O program, wanted the sets to work in all kinds of third-world countries). Most T/O models didn't use a voltage regulator tube, anyway.
::
::I wound up subsitituting fixed power resistors to get the desired voltage, and then stuck in my dud 50A1 for ornamental purposes. Works fine.
::
::
:::Hi,
:::
:::Does anyone know of a source for the electonic version of the 50A1 ballast tube used in the some of the Transoceanics? AES used to sell them (50A1TR), but apparently doesn't anymore.
:::
:::Jeff S.
:::
:::

I do not have one of these radios, so I do not know exactly how the 50A1 normally glows, and what stresses are put upon it. However, if you replace all of your condensers with new ones, you will less likely burn up the 50A1 due to a shorted condenser. In all of my Zenith portables, the electrolytics are actually the originals, and they work extremely well. This may be an exception to the rule, especially if you live in a dry environment. My portables use regular wire wound resistors, and function quite well. However, line voltage fluctuations do exist. My appartment is at 125 volts, whereas the electric company measures only 121 at the meter (so they say). My parents' current varies with season and with load. If you live in a house with a so-so ground system, voltage could fluctuate quite a bit whenever a large device is turned on. It'll go up if the device is on the opposite phase, and down if it's on the same phase.

Also, you would be amazed at how well a lightbulb can regulate. Like I said before, I don't know what a 50A1 looks like when it's running. However, Norm Leal suggested a while back that a 40 watt bulb could be used to regulate just about any size .3 ampere tube. It's true, too. I can hook it up to a 6Q7 and the tube will glow normally. I can also hook it to a 25L6, and the tube will glow normally. In each case, the lightbulb makes up for the difference. When the lightbulb is hooked to a greater load (6Q7, which has low resistance), it heats up more, which raises its resistance, which automatically compensates. It's amazing that something so simple could act much like a high quality regulator. Perhaps, if you ever have a 50A1 failure, you can use a very low wattage lightbulb. Old C7 Christmas tree lamps are about 10 watts. The newer ones are 7, and some nightlights sold in stores are only 4. Experiment and see if one of these doesn't match the current requirements of a .06 ampere tube. Maybe I'll try it for myself. If you want to experiment, hook a tube in series with a bulb and hook it to your tube tester or a variac. Slowly increase the voltage until the tube lights or you can read 1.5 volts with your meter. If you can increase the voltage all the way to 120, then you're halfway there. If you can add more tubes to the string and still have them glow properly, then you're in business.

Thomas

Jeff

The 50A1 can be replaced with a 1300 to 1400 ohm 10 watt resistor, wire it across the socket pins 2 and 7. You can install this above the chassis, just push the resistor leads down through the socket pin holes 2 and 7 and solder them under the chassis.

Dave

The resistor idea works fine. I put mine underneath the chassis, but above the chassis would be good.

Most T/Os didn't use a 50A1, anyway. Commander McDonald perhaps ordered the addition of a 50A1 after receiving reports that a T/0's oscillator wouldn't run in Timbuktu, or some remote place, where the line voltage was very low?

In my opinion, the 50A1 was a marginally successful kludge, at best. I can imagine Zenith engineers rolling their eyes when instructed to add the 50A1.

:Jeff
:
:The 50A1 can be replaced with a 1300 to 1400 ohm 10 watt resistor, wire it across the socket pins 2 and 7. You can install this above the chassis, just push the resistor leads down through the socket pin holes 2 and 7 and solder them under the chassis.
:
:Dave

When I found this R600 at a flea market nearly 8 years ago (I paid $4 for it), I didn't realize what it was going to take to get it working. The 1L6 was bad, and that cost plenty to replace. Among other things I recapped it, replaced the selenium rectifier, and replaced one side of the cabinet that warped itself right off (the side where the cord comes out; that was fun to build!!). About a week after it came back to life, the 50A1 (which was questionable to begin with) fried. That tube cost as much or more than the 1L6. I figured it might be wise to save the 50A1 for a rainy day by using a suitable replacement system.

Thanks for all your help!

Jeff S.

:The resistor idea works fine. I put mine underneath the chassis, but above the chassis would be good.
:
:Most T/Os didn't use a 50A1, anyway. Commander McDonald perhaps ordered the addition of a 50A1 after receiving reports that a T/0's oscillator wouldn't run in Timbuktu, or some remote place, where the line voltage was very low?
:
:In my opinion, the 50A1 was a marginally successful kludge, at best. I can imagine Zenith engineers rolling their eyes when instructed to add the 50A1.
:
:
::Jeff
::
::The 50A1 can be replaced with a 1300 to 1400 ohm 10 watt resistor, wire it across the socket pins 2 and 7. You can install this above the chassis, just push the resistor leads down through the socket pin holes 2 and 7 and solder them under the chassis.
::
::Dave

Jeff

I hope you added a resistor when you replaced the selenium, if not you will have to put one in series with the silicon diode, the value will be between 47 and 100 ohms depending on the filament voltage.

Dave

_________________________________________________________________
:When I found this R600 at a flea market nearly 8 years ago (I paid $4 for it), I didn't realize what it was going to take to get it working. The 1L6 was bad, and that cost plenty to replace. Among other things I recapped it, replaced the selenium rectifier, and replaced one side of the cabinet that warped itself right off (the side where the cord comes out; that was fun to build!!). About a week after it came back to life, the 50A1 (which was questionable to begin with) fried. That tube cost as much or more than the 1L6. I figured it might be wise to save the 50A1 for a rainy day by using a suitable replacement system.
:
:Thanks for all your help!
:
:Jeff S.
:
:
::The resistor idea works fine. I put mine underneath the chassis, but above the chassis would be good.
::
::Most T/Os didn't use a 50A1, anyway. Commander McDonald perhaps ordered the addition of a 50A1 after receiving reports that a T/0's oscillator wouldn't run in Timbuktu, or some remote place, where the line voltage was very low?
::
::In my opinion, the 50A1 was a marginally successful kludge, at best. I can imagine Zenith engineers rolling their eyes when instructed to add the 50A1.
::
::
:::Jeff
:::
:::The 50A1 can be replaced with a 1300 to 1400 ohm 10 watt resistor, wire it across the socket pins 2 and 7. You can install this above the chassis, just push the resistor leads down through the socket pin holes 2 and 7 and solder them under the chassis.
:::
:::Dave

Perhaps the 50A1 fried because you installed the diode backwards. If you did so, the electrolytics will short out the circuit and fry the 50A1. Make sure that your polarity is correct. The diode should feed positively towards the positive sides of the electrolytics.

T.

The original 50A1 in the radio fried shortly after I got it working back in 1999, but it did work for awhile. I had already replaced the rectifier (to include adding the resistor). As I remember, it didn't look healthy to begin with as the filaments would move around inside the tube like a Slinky held in one hand and allowed to dangle. I bought a NOS 50A1 at considerable cost, but I haven't used this radio much -- I recently took a renewed interest in it after fixing up an "8G" T/O for a friend. Based on the condition of the radio when I bought it, I was probably lucky any of the tubes worked. BTW, the original selenium rectifer still worked when I got it. I replaced it based on the advice of an "old time" radio repairman who worked at the local Radio Shack. I wish I still lived close to that particular RS...

Thanks for the input!

Jeff S.

:Perhaps the 50A1 fried because you installed the diode backwards. If you did so, the electrolytics will short out the circuit and fry the 50A1. Make sure that your polarity is correct. The diode should feed positively towards the positive sides of the electrolytics.
:
:T.

A lot of people say that you should replace them for prevention. Truth is, though, that they won't likely go as long as they aren't overloaded or exposed to moisture. I still have quite a bit of equipment that has original seleniums, and they all work fine. I had one phonograph that had a leaky selenium. This caused hum and warm electrolytics. I replaced it with another selenium we had in stock where I worked, and the phonograph went right back to work (this was in 1998). A portable radio of mine had fried seleniums. I don't know what happened to them. The radio was stored in a basement, and all of the electrolytics were bad, so what happened to the selenium is anyone's guess. It now has some hat shaped diodes that I had lying around. They're from the 1940s or 1950s, and I don't know what they're made of.

I have several battery chargers that are almost as old as I am, and one that is definitely older than I am (from the 1960s or 70s). All have seleniums. All are stored in the garage. All have had their leads shorted together. ....And all work fine.

A friend of mine has a Leslie rotary speaker that kept blowing fuses. Turned out all of the silicon diodes had shorted out. He replaced them with new silicons, and the thing works beautifully.

....So....either device can go bad. Make sure everything else is fine first. Then test the device. If it's good, try it out. Whatever it is, it can fail in its own way. Keep it in a good environment and it probably won't. Fuse it for added protection. If you increase the values of the electrolytics (you really shouldn't do this for either kind of diode, because both don't like surges), be sure to fuse the circuit. Silicons are less susceptable to environmental problems, though heat can kill them. They are more prone to problems when they are underrated to begin with, which is also true of seleniums.

Thomas

Good info. Thanks!