I have a stark 9-66 tester and a few stark manuals. The 50B5 tube is not included in any manual but the 50A5 is. Also the 50C5 is included in the onboard tester roll chart.
Can anyone guide me to test a 50B5 tube on a stark 9-66 tester? 😱
Can anyone guide me to test a 50B5 tube on a stark 9-66 tester? 😱
If you look at the data sheet for the 50B5, on page two it states that with exception of the heater characteristics the electrical data is the same as that for 12C5, 12CU5, 17C5, 25C5, and 50C5.
What is a bit strange about that statement is that looking at the two data sheets the heater characteristics seem the same and the difference between the two is that the pin-out of everything except the heater and G2 is changed . Hmmm
50B5 data
50C5 data
Anyway, looking at the controls of the Stark tester, you should be able to test it fine just by setting them to the 'B5 pin-out and following the voltage settings for the 'C5.
What is a bit strange about that statement is that looking at the two data sheets the heater characteristics seem the same and the difference between the two is that the pin-out of everything except the heater and G2 is changed . Hmmm
50B5 data
50C5 data
Anyway, looking at the controls of the Stark tester, you should be able to test it fine just by setting them to the 'B5 pin-out and following the voltage settings for the 'C5.
The 50B5 was the go-to output tube for nearly every tube type table radio made in North America until the UL, and other "safety" agencies created defined "creepage distances" requiring anything connected to line voltage to be spaced a certain distance away from everything else. The UL people dictated that the plate pin was too close to the heater pin, so the 50B5 went extinct overnight and the 50C5 took it's place.
Other than the pin configuration the 50B5 and the 50C5 are identical.
Both, and all of the other heater voltage variants except the 35C5 were derived from the 6W6 by shrinking the guts a bit.
The 50L6, 25L6 and 25W6, 12L6 and 12W6 are all just different heater versions of the 6W6.
The 35C5 and the 35L6 are oddballs with lower powered heaters created for use in AM / FM radios. The output tube gave up some of its heater power to light up the two extra tuner tubes.
If you can find a setting or socket to match the 50B5's pinout, it could be tested with the settings for the 50C5. The 50B5 has the same pinout as the 6AQ5.
Other than the pin configuration the 50B5 and the 50C5 are identical.
Both, and all of the other heater voltage variants except the 35C5 were derived from the 6W6 by shrinking the guts a bit.
The 50L6, 25L6 and 25W6, 12L6 and 12W6 are all just different heater versions of the 6W6.
The 35C5 and the 35L6 are oddballs with lower powered heaters created for use in AM / FM radios. The output tube gave up some of its heater power to light up the two extra tuner tubes.
If you can find a setting or socket to match the 50B5's pinout, it could be tested with the settings for the 50C5. The 50B5 has the same pinout as the 6AQ5.
So the safety police would rather the line-voltage-connected heater be right next to the INPUT pin that you might actually come in contact with instead of the plate voltage (which is already too high to touch with your bare hands)?????
Every one of those radios had one side of the AC line connected to circuit ground. This was often the chassis, or sometimes a cap, known as the death cap, was used between the line and the chassis. These things were
shocking" in many ways, and I found most of them as a kid, but wrong, right, or just plain stupid, the "rules" had to be followed and the 50B5 was abruptly discontinued. This left lots of them in the pipeline and no radios to put them in.
Today the 50C5 is getting scarce, but the 50B5 is cheap, and pretty easy to find. Since we use isolation transformers in our projects today, both are valid choices for DIY amps. Can you get 20 watts from a pair of 50B5's? Yes. Did it run at 20 watts output for 9 hours continuously without issue? Yes.
Stan at ESRC had over 20,000 50B5's in stock and I was about to buy 100 for 50 cents each when Stan passed. For now, that project is dead.
shocking" in many ways, and I found most of them as a kid, but wrong, right, or just plain stupid, the "rules" had to be followed and the 50B5 was abruptly discontinued. This left lots of them in the pipeline and no radios to put them in.
Today the 50C5 is getting scarce, but the 50B5 is cheap, and pretty easy to find. Since we use isolation transformers in our projects today, both are valid choices for DIY amps. Can you get 20 watts from a pair of 50B5's? Yes. Did it run at 20 watts output for 9 hours continuously without issue? Yes.
Stan at ESRC had over 20,000 50B5's in stock and I was about to buy 100 for 50 cents each when Stan passed. For now, that project is dead.
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What about availability of the 12C5? I had zero trouble obtaining the octal version (12W6) in enough quantity to stay stocked up (I won’t need a hundred). It was a 50L6-based hot chassis amp that I needed to work on, and I just used an Antek 50T120 trafo, which has the heater windings too - no more need for a series string. Next one of these I run into I’ll do the same thing. Some 12C5’s might get tacked onto an order, depending on priorities at the time.
Or is it just that three bucks a tube is too much? I know I won’t pay 20 for “experiments” and playing with stone knives and bear skins.
Or is it just that three bucks a tube is too much? I know I won’t pay 20 for “experiments” and playing with stone knives and bear skins.
I was looking at making a super cheap guitar amp based on that 20 watt proto, possibly in kit or board only form. In that case the Triad N68-X power transformer ($16) and the Parts Express 300-040 OPT ($6) make for a low buck amp that must use a series string. As soon as you mention the words "tube" and "transformer" in the same sentence, the price doubles.
I did get a box full of 6DG6GT tubes from Stan a few years ago. They are a 6W6 intended for "audio power amplifier" duty. Oddly, that makes them cheaper, $1 each when I bought a bunch of other stuff at the same time.
I try to stay in the $1 range for experiments that are likely to end badly for the tube. My limit is around $10 each for big sweep tube experiments. I get that stuff working with cheap tubes first.
The 6W6 and its derivatives are like small sweep tubes, and must be treated as such. Despite the triode connection mentioned in the data sheet, do not run them that way for audio, they will eventually runaway when the amp is idle. The vertical sweep section of a TV is never idle.
I did get a box full of 6DG6GT tubes from Stan a few years ago. They are a 6W6 intended for "audio power amplifier" duty. Oddly, that makes them cheaper, $1 each when I bought a bunch of other stuff at the same time.
I try to stay in the $1 range for experiments that are likely to end badly for the tube. My limit is around $10 each for big sweep tube experiments. I get that stuff working with cheap tubes first.
The 6W6 and its derivatives are like small sweep tubes, and must be treated as such. Despite the triode connection mentioned in the data sheet, do not run them that way for audio, they will eventually runaway when the amp is idle. The vertical sweep section of a TV is never idle.
I’m guessing you needed a 160/320 volt supply for that, to get that many watts? That *would* preclude using a toroid because of the half wave load on the 160 volt screen tap. With just a single 160 volt supply you can get away with with running the screen and plate from basically the same rail. Comes down enough under load to stay within rating, but 8 watts is about the practical limit in P-P pentode. A lot of things don’t blow up when you run them on low enough voltages (even fake 2SC5200’s).
I have seen voltage doubled and even tripled hot chassis equipment before - but those take more than any 50VA isolation trafo to make safe. I got the living **** shocked out of me on one when I was 12. I put it aside and didn’t mess with it anymore. Eventually stripped for parts.
I have seen voltage doubled and even tripled hot chassis equipment before - but those take more than any 50VA isolation trafo to make safe. I got the living **** shocked out of me on one when I was 12. I put it aside and didn’t mess with it anymore. Eventually stripped for parts.
On my 122 to 125 volt line I get 170 and 340 volts.
I'm using a triad N68-X because it's the cheapest solution available, but any transformer with a single 120 volt secondary will work, even a toroid because the FW bridge, and the full wave doubler I'm using are completely symmetrical full wave loads. I even run the heaters from rectified, but unfiltered DC in order to achieve a 360 degree conduction angle for the constant resistive load.
I call it the "too many diodes" power supply, but diodes are cheaper than bigger transformers. I don't have a schematic of it or the amp itself as I made it up as I went along. I can draw one if you are interested. I count 9 diodes and 4 caps.
340 volts doesn’t stay 340 volts, unless you use a 1kVA transformer with a 50 watt load. The smaller the trafo, the more it comes down.
That rectifier does look interesting - it was in the HBAC thread. I’ve just put up with a little DC imbalance when using an EI and just 2 diodes, 2 caps.
That rectifier does look interesting - it was in the HBAC thread. I’ve just put up with a little DC imbalance when using an EI and just 2 diodes, 2 caps.