My rectifier has been arcing. I made a couple of changes (diodes in series w/ plates, and changed input cap). Now it usually starts fine, but occasionally (maybe 1 in 5 pwer cycles) there's a tiny spark that Ive noticed falls down the tube. I thought what I saw falling was some coating coming off the filament, but several days ago I noticed one fell to the bottom of the tube and bounced across to the other side and then up towards the top before it disappeared!!
So, lately Ive been watching closely every time I turn it on, and it did it again today. Not such a dramatic bounce, but it was definitely a tiny ball of plasma.
(ive got a different post about what could be causing the rectifier to spark, and am waiting on some parts to arrive to try to fix it.. just wanted to mention the interesting thing it's doing)
So, lately Ive been watching closely every time I turn it on, and it did it again today. Not such a dramatic bounce, but it was definitely a tiny ball of plasma.
(ive got a different post about what could be causing the rectifier to spark, and am waiting on some parts to arrive to try to fix it.. just wanted to mention the interesting thing it's doing)
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I doubt this is a plasma ball, but crazier thing have happened. But what you could have happening is some serious heating and a little bit of molten metal flying around in there. At any case you need to replace that tube before you have it catastrophically and take something else with it.
Nick
Nick
One thing I failed to mention in the other thread about this, is that I have a negative supply coming off the same 2ndary of the power tx. That goes through a couple of diodes and 100uf-R(forget what)-100uf. Maybe those charging quickly is causing or helping the surge.
Well, it doesn't matter. I know the design of the amp is good (it's a tubelab SE, so there are plenty of them out in the world.. I used default values for everything). I think my power tx or choke are somehow causing it. They are literally the only components that haven't been replaced.
(well I didn't replace every resistor, but I did test them while trying to solve this issue)
Well, it doesn't matter. I know the design of the amp is good (it's a tubelab SE, so there are plenty of them out in the world.. I used default values for everything). I think my power tx or choke are somehow causing it. They are literally the only components that haven't been replaced.
(well I didn't replace every resistor, but I did test them while trying to solve this issue)
Can you reduce the capacitance behind the choke temporarily to approximately 1/3 or 1/4 of what it is now and test it again with those different rectifier tubes you mentioned ?
I have, and I got no sparks (But, I don't always get sparks even with the normal capacitance). I left it like that for several days, maybe 10 power cycles, and it seemed fine.
But otherwise the choke tests fine (has the DCR it should), and seems to function properly after the initial surge.
My power TX is a hammond, and has never been right.. It's supposed to be 250-0-250, but I get about 300-0-300 out of it! Even under full load, it's putting out way more power than it should. So, it's definitely a suspect too.
I hope the problem is just the initial surge, and I have some cl-90's on the way to hopefully fix that.
Once I have some extra money, I guess I'll purchase a new power tx and choke.. Then I will have replaced every single component in this amp.. (always w/ better parts, so Im not complaining)
But otherwise the choke tests fine (has the DCR it should), and seems to function properly after the initial surge.
My power TX is a hammond, and has never been right.. It's supposed to be 250-0-250, but I get about 300-0-300 out of it! Even under full load, it's putting out way more power than it should. So, it's definitely a suspect too.
I hope the problem is just the initial surge, and I have some cl-90's on the way to hopefully fix that.
Once I have some extra money, I guess I'll purchase a new power tx and choke.. Then I will have replaced every single component in this amp.. (always w/ better parts, so Im not complaining)
I did notice when I turned the amp on this morning, I didn't get a spark today, but the filament that usually sparks had an strange blue glow for 1/2 second as the filament started to glow. It looked like photos of mercury rectifiers Ive seen! It was a strange aqua blue, but the blue glow faded as the filament heated.
Unfortunately all my 5u4g's are the cheap ones AES has. But actually, I shouldn't say unfortunately.. even with these issues this one keeps on going! I would have killed 10 or more 5ar4's by now if I was still using them!
Unfortunately all my 5u4g's are the cheap ones AES has. But actually, I shouldn't say unfortunately.. even with these issues this one keeps on going! I would have killed 10 or more 5ar4's by now if I was still using them!
This indicates a pretty significant level of voltage stress when the power is applied.. (Big cap, long time constant, very big voltage drop across the rectifier along with a demand for substantial current.)
My 300B amp uses a single 5U4 providing > 200mA of dc at 600V and it is the original one I installed after completing the amp back in the summer of 2004. (>2K hours of use at this point)
I have had no problems with the CLC input filter which uses a 50uF input cap, 5H choke with dcr 50 ohms, and a 50uF output cap. ESR of these caps is around 5 ohms (2 100uF caps stacked). This is actually a bit beyond the short term rating of the rectifier, but the dcr of the secondary windings was carefully specified in the original transformer design - you might try measuring the dcr and determine whether adding a small amount of series resistance is required to reduce inrush to a safer value. I use active voltage regulation to get the source impedance and ripple performance I am looking for.
You might want to consider reducing the size of the cap after the choke as well.
My 300B amp uses a single 5U4 providing > 200mA of dc at 600V and it is the original one I installed after completing the amp back in the summer of 2004. (>2K hours of use at this point)
I have had no problems with the CLC input filter which uses a 50uF input cap, 5H choke with dcr 50 ohms, and a 50uF output cap. ESR of these caps is around 5 ohms (2 100uF caps stacked). This is actually a bit beyond the short term rating of the rectifier, but the dcr of the secondary windings was carefully specified in the original transformer design - you might try measuring the dcr and determine whether adding a small amount of series resistance is required to reduce inrush to a safer value. I use active voltage regulation to get the source impedance and ripple performance I am looking for.
You might want to consider reducing the size of the cap after the choke as well.
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I initially assumed you're stuck with choke filtering because your power transformer gives you to low a voltage. Now that you mentioned you're getting way more out of it than required I would definitely suggest you to follow advice given by others and put some resistors at the anodes of the rectifier.
This way you'll decrease the stress your rectifier takes significantly, plus you'll have some extra supply filtering.
How to determine what kind of resistors to use ? First you need to figure out how much a voltage drop you desire (or can afford; dU) and what the average current draw (I) of your amplifier is. R = dU / I then, and its power rating should be appropriate for continuous dissipation of at least (dU * I) * 1.25 (and better make that factor 1.5 to be on the safe side).
"Better" isn't always better if it means things such as nice grossly overspecced iron and way more capacitance without any compensation for the disproportions by adjusting other elements in the chain appropriately (this would be the rectifier tube in your particular case, you'd need one that is way beefier so it could cope with the initial surge those filtering "goodies" cause at powerup).
Dear folks,
Am a new member to this site so forgive me if sound stupid!
How does post a question/request. Below is details
I have a problem with the disc reading on the above unit. It will load the 5 cds into the multichanger and then change each one as requested. But the tells me "No Disc". What is most likely the problem? Is it that the cd reader is bust or is it that some other mechanism is not "notifying the cd reader of the disc and so giving the all clear to start".
Would be pleased to hear from you and if you which is broken where I can get a replacement part.
Thank you for your help.
Look forward to hearing.
Am a new member to this site so forgive me if sound stupid!
How does post a question/request. Below is details
I have a problem with the disc reading on the above unit. It will load the 5 cds into the multichanger and then change each one as requested. But the tells me "No Disc". What is most likely the problem? Is it that the cd reader is bust or is it that some other mechanism is not "notifying the cd reader of the disc and so giving the all clear to start".
Would be pleased to hear from you and if you which is broken where I can get a replacement part.
Thank you for your help.
Look forward to hearing.
Stephen this is the wrong part of the forum to post this sort of question - this is a very specific thread about an issue one of the guys is having with a rectifier tube. You should start a new thread here: Digital Source - diyAudio Click on "New Thread"
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