From: Paul
Date: Tue, 09 Jan 2001 13:07:03 +0000
Subject: Re: [TSSP] Top voltage testing
I asked: > >Did you happen to note the base input current or the V drop > >across your pad resistor - not essential but useful for > >autopsy if the gain prediction doesn't match. Terry wrote: > I drove directly from the low Z (<1 ohm) signal generator. > Putting a 1 ohm surface mount resistor in the signal path with > the HP meter would be easy if needed. Looks like we might need that base current reading as we have a discrepancy (dont we always :)) to sort out. There's a problem with the voltage gains. The voltage gain should (according to pn2511 theory and the model) be a little higher than the Q factor, eg for test #1, Q=93 and the predicted vgain is 96.1, your measurement with the P6015 probe gives only 76.2, a 26% difference. Similar for test #2 also. Test #3 does better, with a Q of 73 the predicted vgain is 74.5 and measured is 76.2, a 2.3% difference, which is reasonable. Also, going back to your NSVPI terminated coil results, your total voltage gradient after adding 0.12v for the diode drops, comes to around 155.4 volts - a vgain of 155.4 for a predicted 168.5 volts. Again the vgain should have been slightly higher than the measured Q of 163.8, thats a discrepancy hard to account for at either my end or yours. So far the only vgain comparisons that match are your NSVPI bare coil results, and the test #3 data from the regular scope probe. Can you check that the P6015 and YT5060 probes agree on the voltage when they simultaneously measure the same voltage. Could your P6015 be open circuit somewhere, so that we only got a capacitive pickup perhaps? I might have a problem with the predictions, but if so its a serious one, as the vgain > Q trend is a fairly basic result which is expected for all coils with medium or large h/d. The comparisons for tests #1 and #3 are in http://www.abelian.demon.co.uk/tssp/pn0801.html Maybe you can check the probes and also obtain a base current readings - they should be consistent with the input resistances given in pn0801. Cheers, -- Paul Nicholson, Manchester, UK. --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.