So, I could use one 371b in series to drop b+? I never thought of that. So, If I have a LC power supply, where would I put the 371b?
To say with JStewart "Does thinking hurt?"What happened to him, bitten by corona? Emigrated to Sun City?
Think I'm that JStewart, still here . Very busy getting organized for Winter, the property is a few Acres. And helping a neighbor as well, so not much electronics these daze.
Think it was Phil in Australia I asked if thinking hurts. But that would be something more than 10 yrs ago!🙂
Think it was Phil in Australia I asked if thinking hurts. But that would be something more than 10 yrs ago!🙂
You're going to burn 50 watts just to burn some more watts. These tubes simply weren't meant for this voltage range no matter how hard you try. Square peg meet round hole.
Reassuring news then, alte Zigarre. This remark made a lasting impression because it both corrects the other and challenges to perform better. Hope you join us again in the wintertime
Yeah, I think I'm going to save the 371b, maybe a 211 amp or something, the filament transformer I was going to use crapped out on me anyways.I guess I could run two 3b28 and two 5r4wgb (plates in parallel) in a bridge, that should drop some volts. Maybe I will go with 500-600v B+ for the HY69s instead of 400v; I really don't want to resort to using a bunch of series resistance to lower B+ (too much heat).
Last edited:
Reassuring news then, alte Zigarre. This remark made a lasting impression because it both corrects the other and challenges to perform better. Hope you join us again in the wintertime
Easy there war dog - It's actually a snide little comment that makes you seem like a little pompous pri#$k.
Last edited:
True, I have seen the light! I still may breadboard a supply with them in the future to satisfy my own curiosity.
I have 1 or 2 of these around here from estate cleanouts LOL. Nice looking tube! I've tried to find uses for it also.
Professionally, that tube would mainly be used in older high voltage power supplies, dust precipitators, radar modulators, and scientific equipment.
A set of four similar but smaller HV diodes are used here as bridge rectifier circuit in a 0-12KV 100mA supply.
The best hobbyist use today for that tube is in amateur radio, where it can be employed in a high-power plate-modulated AM transmitter, though not as a power supply rectifier because its 300mA rating is too low for that.
It is used there as a clamp tube, to prevent negative overmodulation "splatter" by clamping the modulated plate voltage to a low voltage positive "keep-alive" supply. This allows the operator to achieve positive modulation of 100% or more, without worrying at all about negative overmodulation. This size of tube would usually be found in converted broadcast transmitters and in 'large' homebrew transmitters.
The realm of voltages around the tube in that application are generally 200-300V keep alive voltage, 2500-4000V B+ plate voltage, and 5000-8000V peak to peak AC modulating voltage.
If the modulator pushes the B+ too close to zero on the negative audio swing, the carrier is never cut off making splatter, but clamped more or less gracefully at a few watts. There's plenty of talk about negative peak limiting on amfone.net,
I use the smaller 8020 in my transmitter because the current peaks through the tube seldom reach 500mA.
~~~
It's your amp. Use the 371B as rectifiers if you want, and don't mind the poor voltage regulation with load variations. If you run class A it's moot.
They are scarce, so a soft start should be used on the filament.
If running more than about 25% of the 300mA rating, use AC on the filament or take steps alternate the DC polarity from time to time, such as every time the equipment is turned on.
~~~
If it's just a big rectifier you want for appearance sake and you do not insist on the thoriated tungsten bright filament glow, and 866s are not big enough, try the 872 or 8008, or the xenon equivalents. I have a box of 3B28's, the xenon version of the 866. All these gas and vapor tubes have a voltage drop of only 15V steady over the current range.
~~~
There was some guy making a plug-in night light using an LED and an old 12AX7 built onto a converted consumer plug-in night-light fixture.
A similar but far more tasteful or appealing use could be made of 371Bs, running the filament at 0 to 75% voltage for dimming and long lifetime (no triacs! variac or resistive dimmer only..), and mounting them sticking up out of wall sconces in a small home theater.
Professionally, that tube would mainly be used in older high voltage power supplies, dust precipitators, radar modulators, and scientific equipment.
A set of four similar but smaller HV diodes are used here as bridge rectifier circuit in a 0-12KV 100mA supply.
The best hobbyist use today for that tube is in amateur radio, where it can be employed in a high-power plate-modulated AM transmitter, though not as a power supply rectifier because its 300mA rating is too low for that.
It is used there as a clamp tube, to prevent negative overmodulation "splatter" by clamping the modulated plate voltage to a low voltage positive "keep-alive" supply. This allows the operator to achieve positive modulation of 100% or more, without worrying at all about negative overmodulation. This size of tube would usually be found in converted broadcast transmitters and in 'large' homebrew transmitters.
The realm of voltages around the tube in that application are generally 200-300V keep alive voltage, 2500-4000V B+ plate voltage, and 5000-8000V peak to peak AC modulating voltage.
If the modulator pushes the B+ too close to zero on the negative audio swing, the carrier is never cut off making splatter, but clamped more or less gracefully at a few watts. There's plenty of talk about negative peak limiting on amfone.net,
I use the smaller 8020 in my transmitter because the current peaks through the tube seldom reach 500mA.
~~~
It's your amp. Use the 371B as rectifiers if you want, and don't mind the poor voltage regulation with load variations. If you run class A it's moot.
They are scarce, so a soft start should be used on the filament.
If running more than about 25% of the 300mA rating, use AC on the filament or take steps alternate the DC polarity from time to time, such as every time the equipment is turned on.
~~~
If it's just a big rectifier you want for appearance sake and you do not insist on the thoriated tungsten bright filament glow, and 866s are not big enough, try the 872 or 8008, or the xenon equivalents. I have a box of 3B28's, the xenon version of the 866. All these gas and vapor tubes have a voltage drop of only 15V steady over the current range.
~~~
There was some guy making a plug-in night light using an LED and an old 12AX7 built onto a converted consumer plug-in night-light fixture.
A similar but far more tasteful or appealing use could be made of 371Bs, running the filament at 0 to 75% voltage for dimming and long lifetime (no triacs! variac or resistive dimmer only..), and mounting them sticking up out of wall sconces in a small home theater.
Thanks for all the info, you are right, these are scarce, I'm just going to save them. I got 3B28s on the bench right now, but may go with 5r4 (x2) because I need the voltage drop. I have a lot of tube rectifiers to choose from, so we will see. I want the amp to look as good as it sounds, but I will probably not go with mercury vapor diodes for this build as I have a 3 year old and she likes throwing things (she has an incredible arm lol), which would not be so good if she breaks one. Most of my amps reside in the garage now on industrial shelves
.. just in case.
I am thinking about getting into Ham radios, but don't know if I need another hobby. I work on microwave transmitters all day at work, so I would kinda be at work whilst doing my hobby lol
Last edited:
I think 3B28s look better than mercury vapor rectifiers. Nice near purple glow. There I said it. I said it.
You just need a good choke input supply for them. Also needs to be for a supply higher than maybe 500 volts.
You just need a good choke input supply for them. Also needs to be for a supply higher than maybe 500 volts.