Hi there,
I got 2 NOS RCA 82 on hand, wanted to use one of them in my 6C45 single stage amp....
Last night I hooked up the heater to warm it up, as I've read somewhere that old mercury tubes probably need it.
2.5V AC for the heater is not readily available. So I took a 220V primary / 5V secondary and plugged it in 110V main. Unloaded, I got 2.7V on the secondary, seemed OK.
Plugged the tube into the socket, switched on, the filament was lighted up dimly (like my 5R4 & 5Y3). Measured the voltage on filament, only 2.2V, then drop to 2.1, not very stable.
Suddenly, 2 or 3 flashes popped out, seemed from inside the plate, blueish flashes. Then the filament faded out quickly.
Switched off, & on again, nothing.
1A slo-blo main fuse blew. I changed it to 3A fast-blo. Switched on, lighted up, few seconds later, popped & flashed again. (yes, the pops were audible from inside the glass)
Fuse blew again. This time I had yet to get the chance to monitor the heater voltage. Probably no good.
In the process, I saw some white to light grey vaper growing inside the tube & attached on the inner wall. Just like the mist on the bathroom's mirror.
I didn't try anymore. Pulled the tube out, I measured the 2 pins of heater, they were short.
Is the tube still alive? Or it's gone?
Was it because the voltage dropped? So the heater was not heated enough?
PS. From the very beginning to the end, no high voltage was applied to the plates. Only heater was powered.
I got 2 NOS RCA 82 on hand, wanted to use one of them in my 6C45 single stage amp....
Last night I hooked up the heater to warm it up, as I've read somewhere that old mercury tubes probably need it.
2.5V AC for the heater is not readily available. So I took a 220V primary / 5V secondary and plugged it in 110V main. Unloaded, I got 2.7V on the secondary, seemed OK.
Plugged the tube into the socket, switched on, the filament was lighted up dimly (like my 5R4 & 5Y3). Measured the voltage on filament, only 2.2V, then drop to 2.1, not very stable.
Suddenly, 2 or 3 flashes popped out, seemed from inside the plate, blueish flashes. Then the filament faded out quickly.
Switched off, & on again, nothing.
1A slo-blo main fuse blew. I changed it to 3A fast-blo. Switched on, lighted up, few seconds later, popped & flashed again. (yes, the pops were audible from inside the glass)
Fuse blew again. This time I had yet to get the chance to monitor the heater voltage. Probably no good.
In the process, I saw some white to light grey vaper growing inside the tube & attached on the inner wall. Just like the mist on the bathroom's mirror.
I didn't try anymore. Pulled the tube out, I measured the 2 pins of heater, they were short.
Is the tube still alive? Or it's gone?
Was it because the voltage dropped? So the heater was not heated enough?
PS. From the very beginning to the end, no high voltage was applied to the plates. Only heater was powered.
An 82 should draw about 3 amps in normal conditions. It sounds like there is some condensed mercury around the filament / plate which is causing the pops and flashes (probably due to the tube being stored for a while). The grey vapour is normal - you should see this on every mercury rectifier as it warms up.
The tube needs to be in its normal vertical operating position when you heat it. I would try again and hopefully the flashing should stop after a few minutes.
If there really is a short across the heater pins (should be a very low resistance even when working fine) its probably down to a splash of mercury in the wrong place. Before writing the tube off as faulty I would keep it somewhere warm for a few days (in vertical position) to allow the mercury to settle to the base of the tube envelope.
The tube needs to be in its normal vertical operating position when you heat it. I would try again and hopefully the flashing should stop after a few minutes.
If there really is a short across the heater pins (should be a very low resistance even when working fine) its probably down to a splash of mercury in the wrong place. Before writing the tube off as faulty I would keep it somewhere warm for a few days (in vertical position) to allow the mercury to settle to the base of the tube envelope.
useful info here
You will need to use a choke input power supply as mercury rectifiers don't like big capacitors
You will need to use a choke input power supply as mercury rectifiers don't like big capacitors
Thanks a lot for reply, and good to hear there're still chances.
I've read somewhere that such mercury tubes should be stored & shipped in vertical postition, all the way, to prevent the condense in "wrong" place. I thought, gee, how is that possible? It's already dacades!! It has been probably somersaulting forward/backward/sideways big time.
If warmth helps, I think I'll put it on top of other amps to speed up the inner vaporization
Will get back when I have further progress.
I've read somewhere that such mercury tubes should be stored & shipped in vertical postition, all the way, to prevent the condense in "wrong" place. I thought, gee, how is that possible? It's already dacades!! It has been probably somersaulting forward/backward/sideways big time.
If warmth helps, I think I'll put it on top of other amps to speed up the inner vaporization
Will get back when I have further progress.
Still no good
It just kept flashing & popping & blowing the main fuse
I gave up I think it's gone. And I almost lost the courage to try another one...
Just curious, anyone try NOS mercury tube?
The reading about " keeping the tube vertical all the time from storage to delivery to handle to use... " is from RCA handbook. I really doubt how many of these old stuff can hold that position throughout the years.
It just kept flashing & popping & blowing the main fuse
I gave up
I think it's gone. And I almost lost the courage to try another one... Just curious, anyone try NOS mercury tube?
The reading about " keeping the tube vertical all the time from storage to delivery to handle to use... " is from RCA handbook. I really doubt how many of these old stuff can hold that position throughout the years.
I got an 866 rectifier from the local surplus place,to play with..
I've no idea it's age,I suspect it was a "pull",and it was stored in a box,in who-knows-what-position, with some other tubes.
I brought it right home and put it in my tube tester to look at the glow,hardly waited for the filament to warm up before I hit the "test" button to see the pretty colors..
It seemed fine,no sparks or anything.
I've no idea it's age,I suspect it was a "pull",and it was stored in a box,in who-knows-what-position, with some other tubes.
I brought it right home and put it in my tube tester to look at the glow,hardly waited for the filament to warm up before I hit the "test" button to see the pretty colors..
It seemed fine,no sparks or anything.
Mercury vapor rectifier tubes need about one minute warm-up time before B+ is applied. So, I suspect you did perform the one minute warm-up time. I would limit first cap on a capacitor input PS design to 5uF. Or, as stated choke input is best. Small MV tubes do not care for any input capacitance & the 82 is tiny by MV tube rectifier standards. Try an 83 MV tube, more robust.
Anyways, perhaps the MV tube filament broke & is touching the plate or the tube was received broken inside due to rough handling from the carrier. Don't you own a tube tester?
IMHO, I do not like Mercury Vapor rectifiers beyond the cool color when operating. MV tubes are known to produce a lot of RF noise when operating & perhaps some lower frequency noise will mix with your audio downstream creating additional IMD products. That is why a vacuum type tube rectifier usually makes for a better audio amp.
Anyways, perhaps the MV tube filament broke & is touching the plate or the tube was received broken inside due to rough handling from the carrier. Don't you own a tube tester?
IMHO, I do not like Mercury Vapor rectifiers beyond the cool color when operating. MV tubes are known to produce a lot of RF noise when operating & perhaps some lower frequency noise will mix with your audio downstream creating additional IMD products. That is why a vacuum type tube rectifier usually makes for a better audio amp.
Thanks for the info.
I did warm it up on the heater only, NO high voltage on plates. (I don't have tube tester, just using "part of the amp" for the job. )And I did also configure it as a choke input rectifier, but not yet have the change to make it work.
About the RF noise, I read in the hand book, too. Make sense. Funny enough, I have many other readings indicate that the MV tube is excellent for audio amp. Hmmm......
Years ago, I bought 2* 82, no more MV tube other then that. They kept unused for all these years. Finally I built an amp which the current draw seems suitable for it, but unfortunately it didn't work out.
I guess I won't try them any more.
I did warm it up on the heater only, NO high voltage on plates. (I don't have tube tester, just using "part of the amp" for the job. )And I did also configure it as a choke input rectifier, but not yet have the change to make it work.
About the RF noise, I read in the hand book, too. Make sense. Funny enough, I have many other readings indicate that the MV tube is excellent for audio amp. Hmmm......
Years ago, I bought 2* 82, no more MV tube other then that. They kept unused for all these years. Finally I built an amp which the current draw seems suitable for it, but unfortunately it didn't work out.
I guess I won't try them any more.
hi CLS
sorry to hear about your stash of 82 tubes. check out the below schematics to see how they did it.
sakuma-san has been using mv tubes in quite a few of his designs.
josh stippich uses mv tubes in his designs too. check out that linked big image which has a writeup of his 826 drive 2a3 power amp. notice that the pair of 816 mv rects for the 2a3 B+ is placed very close to the driver and power tubes.
cheers
garbage
sorry to hear about your stash of 82 tubes. check out the below schematics to see how they did it.
sakuma-san has been using mv tubes in quite a few of his designs.
josh stippich uses mv tubes in his designs too. check out that linked big image which has a writeup of his 826 drive 2a3 power amp. notice that the pair of 816 mv rects for the 2a3 B+ is placed very close to the driver and power tubes.
cheers
garbage
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