Diodes, silicon that is....
I've got a bunch of different kinds, and I really don't grasp their practical application as much as I'd like. Here's a few I'm considering using in the power supply of my next tube amp; a PP 1625 amp.
BY228 damper diode - 1500V/5A (axial, Phillips)
BYW95 fast soft-recovery controlled avalanche - 600V/3A (axial, Phillips)
RU3A fast recovery - 600V/1.5A (axial)
FMU16S fast recovery - 600V/5A (TO-220)
FR805 600V/8A (TO-220)
In past builds I've always been overly cautious and have never used diodes under 1000V rating. However, the PT I'll be using has a B+ of 300V using a FWB. So a 600V diode would be fine for this circuit; right?
What about these damper diodes, controlled avalanche, or fast recovery?
I've never seen these types used in tube amps. It would be great to hear from some of you in the know about the practical application of such devices.
Thank You in advance....
TT
I've got a bunch of different kinds, and I really don't grasp their practical application as much as I'd like. Here's a few I'm considering using in the power supply of my next tube amp; a PP 1625 amp.
BY228 damper diode - 1500V/5A (axial, Phillips)
BYW95 fast soft-recovery controlled avalanche - 600V/3A (axial, Phillips)
RU3A fast recovery - 600V/1.5A (axial)
FMU16S fast recovery - 600V/5A (TO-220)
FR805 600V/8A (TO-220)
In past builds I've always been overly cautious and have never used diodes under 1000V rating. However, the PT I'll be using has a B+ of 300V using a FWB. So a 600V diode would be fine for this circuit; right?
What about these damper diodes, controlled avalanche, or fast recovery?
I've never seen these types used in tube amps. It would be great to hear from some of you in the know about the practical application of such devices.
Thank You in advance....
TT
For a 600V diode, you must ensure that the voltage it sees never exceeds that number.
If you have a non centre tapped transformer winding that gives 300V B+ after rectification, then the diodes would be fine. If you are using a centre tapped winding, you can't use 600V - go for 1000V.
If you have a non centre tapped transformer winding that gives 300V B+ after rectification, then the diodes would be fine. If you are using a centre tapped winding, you can't use 600V - go for 1000V.
Lately i have been using HEXFRED diodes, HFA06TB120 from Vishay,
mostly because i got a bunch from a friend, they are suitable for both HV and most filament regulating
1200V/6A and the curves are....curvy 🙂 -no sharp spikes anywhere!
edit: found the datasheet here http://www.vishay.com/docs/94038/hfa06tb1.pdf
mostly because i got a bunch from a friend, they are suitable for both HV and most filament regulating
1200V/6A and the curves are....curvy 🙂 -no sharp spikes anywhere!
edit: found the datasheet here http://www.vishay.com/docs/94038/hfa06tb1.pdf
If you have a non centre tapped transformer winding that gives 300V B+ after rectification, then the diodes would be fine. If you are using a centre tapped winding, you can't use 600V - go for 1000V.
The PT I'm using is from a Leslie 102. It has a non-center tapped B+ that yields 300VDC (at least on the schematic) This PT is powering four pairs 7189's so I figure it will be a breeze for a pair of 1625's. (the 12VAC filament winding helps too)
The really wacky thing the Leslie PS does is float a 100V center-tapped winding on top of the 300V output. Then uses a FW SS rectifier to feed 400V to the plates while the 300V source feeds the screens and the rest of the preamp.
I'm planning on using that same circuit for the 1625's. (this is going to be for a Standel guitar amp circuit)
Damper diodes, or efficiency diodes as they also are called are OK to use as rectifiers for audio.
They are used in horizontal outputstages in TV´s.
BY228 is a fast recovery diode, but the maximum average current is max 3A @1500V.
Datasheet can be found here:
http://skory.z-net.hu/alkatresz/by228_86003.pdf
They are used in horizontal outputstages in TV´s.
BY228 is a fast recovery diode, but the maximum average current is max 3A @1500V.
Datasheet can be found here:
http://skory.z-net.hu/alkatresz/by228_86003.pdf
Interesting..... so it looks like damper diodes and controlled avalanche diodes are the same type of device.
Just for kicks I compared the reverse recovery times of these diffrent diodes with a 1N4007 and a UF4007.
TYPE trr
UF4007 - 75 nS
RU3A - 180nS
BYW95 - 250nS
FMU16S - 400nS
BY228 - 2 uS
1N4007 - 30 uS
Looks like the UF4007 is a pretty good little diode for the money; now those CREE diodes, zero recovery; that's pretty cool but dang they're expensive... can't really justify with all the surplus I've got laying around
Thanks for the info...
Just for kicks I compared the reverse recovery times of these diffrent diodes with a 1N4007 and a UF4007.
TYPE trr
UF4007 - 75 nS
RU3A - 180nS
BYW95 - 250nS
FMU16S - 400nS
BY228 - 2 uS
1N4007 - 30 uS
Looks like the UF4007 is a pretty good little diode for the money; now those CREE diodes, zero recovery; that's pretty cool but dang they're expensive... can't really justify with all the surplus I've got laying around
Thanks for the info...
While digging thru some old files I stumbled across a report about avalanche diodes...check this out...
So it looks like avalanche diodes would be the best choice for that power spike protection circuit some use of 3 1N4007's in series connected between each plate and ground......
Applications for Avalanche Diodes
Avalanche type diodes can result in increased reliability in many applications, particularly those where voltage transients are expected. Due to its high speed and ability to withstand large numbers of transients, avalanche diodes are used to protect circuits against surges, lightning and other transients. They are faster than MOV’s, zeners, and gas tubes.
Avalanche diodes are the diode type of choice in high voltage circuits, such as high voltage multipliers, due to possibility of transients caused by arcs, pulses, etc.
Another usage for rectifiers with avalanche capability is putting individual diodes in series to obtain higher reverse voltage capability. The voltage normally divides in proportion to the reverse resistance of each diode. Since there could be large variation in the reverse resistance, the voltage may not divide equally across the series string of diodes. A transient of sufficient amplitude will drive the voltage across one or more diodes into the breakdown region. A typical diode will exhibit catastrophic failure when this occurs. However, avalanche type diodes will cause the voltage to divide much more evenly. Also, the avalanche diode is capable of protecting itself by handling transient energy, providing it does not exceed the energy rating of the diode. Thus, whenever diodes are connected in series to increase the voltage rating, avalanche diodes should be used.
So it looks like avalanche diodes would be the best choice for that power spike protection circuit some use of 3 1N4007's in series connected between each plate and ground......
I've used damper diodes for B+ in my SCA35 amp. Works fine.
The coil between the diodes and the power resistor (used to lower the B+ some) isn't really needed.

The coil between the diodes and the power resistor (used to lower the B+ some) isn't really needed.
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