6 Nov
2014
6 Nov
'14
10:47 p.m.
Tony, All,
On Thu, Nov 6, 2014 at 11:55 PM, tony duell <ard at p850ug1.demon.co.uk> wrote:
That base amplitude sounds a bit low to me, I would have expected about
0.6V. But without
seeing the waveform it's hard to be sure..
I don't have enough experience to rate it one way or the other. All I'll
say, is that (again) these readings were taken when I knew I had precious
little time to take +any+ kind of measurement, before things went away -
and I was neglecting / ignoring any spiky / HF components. Didn't have time
to analyze the minutiae of the signal to any depth.
My primary goal was to establish an easily-acquired reference to compare
with any changes that might (well, that I knew would) occur. Oh, and it's
like a 10MHz scope (Telequipment D54). Limited bandwidth and capability,
but it does have a really excellent trigger setup..
BUT...
Remember that the forward voltage drop of a semiconductor junction -- like
the B-E junction of
the HOT -- depends on temperature. Diodes have actually been used as
temperature
sensors due to this effect.
Sure, alongside output transistors in audio amps, for example.
So if the HOT is overheating for any reason the base
drive
may appear to increase.
Yes, it's worth replacing the HOT. But don't be too surprised if it
doesn't cure it.
I will. And no, nothing will really surprise me at this juncture, lol. But
I do suspect that a new HOT will more than likely cure what ails it..
Time will tell. Anyone got a spare? =) Otherwise, I'll hit up eBay or
whatnot.. I'll also check with the local electronics jobber, but they tend
to have mad markups on this stuff. Wouldn't be surprised if they wanted $20
for a simple NTE 379.