[Amps] Resistor Types

[Peter Chadwick]

The comments about equalising resistors on diodes are interesting. The guys who manufactured and did the applications on diodes, SCR's, triacs and IGBTs at my employer's plant in Lincoln (before it was sold it to someone!)  told me that it's OK doing without equalising resistors if the diodes are from the same diffusion batch, but warned that diodes from different batches shouldn't be mixed without equalisation because the avalanche voltage can be high enough in some of them for the dissipation to become a problem when they avalanche. Now this was from people making diodes all the way from microwave detector diodes through small signal, small rectifier and up 5000 Amp devices for electric trains....
This suggests that if you have to replace a modern diode, you should replace the string.........OTOH, you might just get away with it for years without problems. But these guys did have a good track record of knowing what they were talking about.....
73
Peter G3RZP