selection of output power tr

[arthur]

for my amplifier with +/- 60v power supply, may i use 100v rating power tr, or the higer voltage rating the better?
thanks

[sakis]

is not enough ....wise would be to use 160 volt devices each device will see almost 120 volt at some times ....so yes 100 volt is not enough

[arthur]

as i have the 100v rating power trs, are they safe if in amps with +/- 50 volt supply?
thanks

[PeteMcK]

100 V AC rectified gives 141 V DC, i.e. +/- 70v

for +/- 60V DC you'll need a transformer that is 42-0-42 V ac

[arthur]

soory i have lots of 100v rating power transister pairs(npn and pnp),
are they safe in power amplifiers with +/- 50v dc supply?
thanks

[ostripper]

Properly derated , 100V devices would be best for no more than a 35-0-35v DC supply (might survive 40-0-40VDC). DX amp , symasym , most of the 50-60 watt amps , even a P3a (elliot sound - esp) might be best. If they are small (to-220) , you might need 2 pair at OP. i f they are big (to-3 metal) ,1 pair will do.
OS

[Wavebourn]

Originally Posted by arthur

soory i have lots of 100v rating power transister pairs(npn and pnp),
are they safe in power amplifiers with +/- 50v dc supply?
thanks

100V rating means that they have higher than 100V break-down voltage collector-base and collector-emitter. How much you don't know; you know that more than 100V. May be much more!
To test them you can use some 300V power supply, one 300K 2W resistor, and a high ohm input voltmeter.
Collect base and emitter together, and apply voltage to collector through the 300K resistor. Measure voltage between collector and emitter. It is a rough method, but it should work well for modern transistors that have low inverse currents.
Such a way you will get real breakdown voltage of each of your transistors. Select some with higher voltages, and be happy!

+/-50V power supply can give more, depending on power conditions in your outlet. For safety I would use transistors with 120V break-down voltages at least.

[wg_ski]

Originally Posted by Wavebourn

Such a way you will get real breakdown voltage of each of your transistors. Select some with higher voltages, and be happy!

Second-breakdown ratings are uncertain, however. If you do this be conservative. If the original design calls for two parallel pairs, use three. Or four. If you already have them, you won't be out anything but some inexpensive emitter resistors.

[arthur]

as the origial design use bdv64c/65c darlington trs,as they are difficult to source nowaday
please suggest newer devices to replace
thanks

[sakis]

since darligtons is a quiet strange story for starts i could advice you to trush the design and work with something better


serch the forum for a post called "a darling....ton story " there you will find plenty of info regarding designs based on these devices

though there is many other posts related to this ....read carefully and then decide if you like to play arround this devices

your first option will be ON SEMI 11015-16 extremelly rowbust allready been working in Marshal amplifiers but packadge might be a problem TO3

kind regards sakis

PS if your concept is to push the amplifier by lifting the rails higher for more power just skip it it will never work