Testing D302 russian Ge diodes in series, why the 10-15K ohms limitation?
At the end of this datasheet.
What is the risk if using 30K?
At the end of this datasheet.
What is the risk if using 30K?
I would guess it is for voltage balancing given the high leakage of Ge devices. Ultimately it will depend on the max voltage you apply to the series connected diodes. If the total reverse voltage is approaching the sum of all the individual diodes Vr then you would need the lower resistance values to ensure forced balancing of the volt drops.
That's my best guess 🙂
That's my best guess 🙂
Diode reverse current has to be much smaller than current through parallel resistor. Otherwise reverse voltage will not be shared equally between diodes in a series string.
Thank you for your answers 🙂
It's for a 300Vac PT, 8 diodes for the bridge (twice, in series), it works but 15K on each diode is 60K for 4 diodes but the result is 30K, too much power waisted.
So I have to try 30K on each diode then measure the resistor current to be sure it's much higher than the D302 reverse current at 25°, right?
Or build a bridge with 16 diodes, nice looking 😉
It's for a 300Vac PT, 8 diodes for the bridge (twice, in series), it works but 15K on each diode is 60K for 4 diodes but the result is 30K, too much power waisted.
So I have to try 30K on each diode then measure the resistor current to be sure it's much higher than the D302 reverse current at 25°, right?
Or build a bridge with 16 diodes, nice looking 😉
...or just use Si 🙂 Sometimes the trade offs are just not worth the hassle, no matter how much we want to use the older technology.
of course, Si diodes are the logical way.
But I wanted this time to do a different looking amplifier, ok I'll go with 16 x D302 B+ bridge rectifier. And D303 bridge for positive bias of the 805 grids.
Didn't measured yet voltage across D302 bridge, maybe 20K on each diode will do it, they won't be stressed at all.
Finished yesterday manual winding for the two 805 heaters (made from a 0.68mH mundorf aircore inductor for speaker crossover).
Recycled wood... in the woods near a river and copper from an old heating setup.
Takes a lot of time to paint everything with a small pencil 🙂
But I wanted this time to do a different looking amplifier, ok I'll go with 16 x D302 B+ bridge rectifier. And D303 bridge for positive bias of the 805 grids.
Didn't measured yet voltage across D302 bridge, maybe 20K on each diode will do it, they won't be stressed at all.
Finished yesterday manual winding for the two 805 heaters (made from a 0.68mH mundorf aircore inductor for speaker crossover).
Recycled wood... in the woods near a river and copper from an old heating setup.
Takes a lot of time to paint everything with a small pencil 🙂
Attachments
Well I can see the visual appeal I suppose 
One thing to be aware of is whether you have spares (diodes) in case any fail in the future.
One thing to be aware of is whether you have spares (diodes) in case any fail in the future.
I bet it took ages to paint all the resistors and stuff with that brown paint. 😀
Are the component values a guarded secret?
Joking aside, it needs a flywheel and governor to complete the steampunk look!
Are the component values a guarded secret?
Joking aside, it needs a flywheel and governor to complete the steampunk look!
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Great looking amplifier!
30s, 40s, and 50s look.
All except for the Toroid, Lundahl transformer and [modern caps?]
30s, 40s, and 50s look.
All except for the Toroid, Lundahl transformer and [modern caps?]
Thanks all 😉
Very good idea.
Nothing really special, cheap metal oxide 5W resistors, Solen SCR caps for positive grid fixed bias, Wima DC-LINK PS caps, Hammond 3.5H 150mA choke.
PT & OPT are from a Quicksilver amplifier.
I may cover the toroids but first be sure they don't heat too much, it should be fine (160VA core).
These monoblocs will be driven by another smaller amplifier.
Hope it will work fine.
Yes, it took a lot of time for the painting job, and that's not finished 😱
Very good idea.
Nothing really special, cheap metal oxide 5W resistors, Solen SCR caps for positive grid fixed bias, Wima DC-LINK PS caps, Hammond 3.5H 150mA choke.
PT & OPT are from a Quicksilver amplifier.
I may cover the toroids but first be sure they don't heat too much, it should be fine (160VA core).
These monoblocs will be driven by another smaller amplifier.
Hope it will work fine.
Yes, it took a lot of time for the painting job, and that's not finished 😱
We don't want the old tech, we just want better sound. Imho minor trade offs are very much worth it in this particular case. Used Ge myself before discovering the LT4320.