pre65 wrote:When looking for alternative diodes they seem either to be high voltage/low current or low voltage/high current.
I looked at FRED diodes before, but could not find the ideal parameters.
Any one know of a diode that does 2KV and 2 amp ?
In a bridge you need 1.414 times rms of secondary so 1,018 PIV.. Admittedly you want a margin of error.
In a centre tapped transformer with the single diode on each peak you need 2 times RMS of that peak so if you had a 720-0-720 transformer you would need a piv of 1,440.
You are using a bridge aren't you? 600v FRED's are plentiful, two in series per side of the diamond shaped bridge rectifier. 8 FRED's in all. 8 pieces 1 meg 2 resistors watt.
Where is this need for 2 amp suddenly coming from? your TV damper diodes were only 1/2 an amp. I have yet to see the 1kv valve amp which needs 2 amps. But either you or Steve had to try it some day!
Last edited by Paul Barker on Sun Jan 06, 2013 11:35 am, edited 1 time in total.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
Paul Barker wrote:Where is this need for 2 amp suddenly coming from? your TV damper diodes were only 1/2 an amp. I have yet to see the 1kv valve amp which needs 2 amps. But either you or Steve had to try it some day!
His 1 Amp SS diodes blew up. (literally)
Still need to find out what caused that.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
Paul Barker wrote:The English rectifier made for the job is the U19. But there would be series resistance and first cap criteria to observe. If you want to try them I can send you two, or is it dual mono? Do you need 4? Your power transformer probably has virtually no resistance this data sheet shows R source minimum 500ohm tdsl says 600 ohm. first cap 4uF.
That's a good point actually. Note also the note about flash over.
I looked up GZ37/U54, that's 'only' 4uF as well!
These often need series current limiting resistors added, which value includes the winding DCR by the way. If you're lucky the winding DCR is adequate.
Re the heater supply question, note the GZ family have one end of the heater internally connected to cathode, so you have no other options.
What is the value of the first supply capacitor?
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
No, you are wrong, they have not failed. your tv damper diodes failed and due to the short circuit inside them the solid state diodes were xpected to handle much greater current than they were designed for.
Remove the dodgy parts check the transformer and perhaps the capacitors, if all good, build up again with your 1300v piv diodes with confidence.
As Mike said on the 6d22s thread
Mike H wrote:
So I'm not convinced "problem is sorted"
Edit: what I mean is, highly likely the replacements will just do the same again.
The solid state diode is not your faulty component through faults elsewhere you have stressed it beyond it's limits. the answer is not to double up on the good component. It is to find the fault.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
Paul Barker wrote:you see the problems your evoke when you don't take my advice and go choke input
Normally I would.
When I mentioned about raising the HT of the 833a (after the 833a day at Owston) I was advised (by Nick from memory) that choke input above 1000v was more of a problem, but I forget the reasons why.
The only thing necessary for the triumph of evil is for good men to do nothing.
