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Old 19th January 2004, 12:22 PM   #1
protos is offline protos  Greece
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Default BZLS PS limits?

I have been experimenting with lower voltages and increased bias on BZLS. However I was surprised that the Pass BZLS recommended PS could not supply 500ma at +- 15v.The voltage sagged down to something like +- 3v.Looking at the circuit I can't understand why.The irf 610 and 9620 should handle a couple of amps or not?
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Old 23rd January 2004, 07:40 AM   #2
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Hi,

wenn youŽve got the 22ohm resistors in place youŽll lose 0,5x22=11Volts (on plus and minus rails). To change this you must use smaller resistors.

William
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Old 23rd January 2004, 01:41 PM   #3
protos is offline protos  Greece
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No the resistors have nothing to do with it.I did take them out anyway.I know the problem now but I don't know why it's happening.Let me explain:
Since I wanted to go to +- 15v I of course shorted the necessary zeners in the original 60v ps.But I wanted a lower tx voltage as well for dissipation purposes.So I connected the existing two 55v tx primaries (two txs , one primary each) in series and when I measured the secondaries they were as expected about half as much as before.But it seems that under any but the lightest loads (under 10ma) the voltage on the tx sags to something like a couple of volts.
I know I have done something wrong with txs here but it doesn't make any sense.There is something about the series connection of the txs that I am missing.Each tx on its own works perfectly.
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Old 23rd January 2004, 02:09 PM   #4
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Hello,

There is no reason to not have +- 15 V/500mA from modified
BOSOZ power supply.
Did you connect the tx's in phase ?
This could be only problem I can see, assuming that your
power supply is not blown.

Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip
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Old 23rd January 2004, 03:06 PM   #5
protos is offline protos  Greece
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The Ps works at +-15v with normal lower voltage tx 120va 18v (actually does sag to about +-13.5v, why that much?).
I don't see a phase problem appearing since the secondaries are not connected to each other at all.I did change the phase of one tx primary just in case but the same problem appeared unchanged.
It really stumped me in the beginning because as I said the secondaries measured correctly with a multimeter so I had no suspicion that the problem was in the tx and so I obviously thought it was in the PS.
Any semi-realistic load on the tx and the voltage goes way down.
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