Hi Tom:
The collector goes to hard saturation value. Less than .2V. I did the
test using a Huntron on a few of the swaps just to be sure.
I also carefully watched the base voltage established thru the detector
diode. It stays right around .5-.6V. Even repalced the diode to see if
that might be the case but same result.
At this point, I guess I am going to try to find a genuine 3394 and call
it a day. It all works fine when I put in a working device from another
R4 so suspect something particular about the device. Transistors were a
lot less controlled in 1968 so it may not be close. Dont have a curve
tracer and not going to remove it again to do an Hfe test on it the hard
way.
It is just a curiosity now. I taught solid-state design and theory in
Navy and later in college and thought I had seen most issues. ;)
Curt
KU8L
On 2/26/2013 12:02 PM, Tom Holmes wrote:
Well, it was worth a shot. Since I don't have the circuit in front of me I
can't make a more educated guess.
Since you caught the lead issue, I'll assume that you also did the diode
test on the replacement parts. I have seen a few cases where the NTE doc's
are wrong about the leads though. When the collector voltage goes to near
zero, is it .2 V or .6 V? The first case is a saturated transistor; the
second is a diode junction, which would suggest the pinout info is wrong.
When I get back from some errands, I'll look in my NTE book to see if I can
find any other clues.
Happy hunting!
Tom Holmes, N8ZM
Tipp City, OH
EM79
-----Original Message-----
From: drakelist-boun...@zerobeat.net
[mailto:drakelist-boun...@zerobeat.net]
On Behalf Of Curt Nixon
Sent: Tuesday, February 26, 2013 11:43 AM
To: drakelist@zerobeat.net
Subject: Re: [Drakelist] R4A-B Detector Amp Q5
Hi Tom:
Yes...there are the lead arrangement issues but I accounted for them.
The typical EBC Vs ECB issue. Easy in this case because they used the
triangular hole pattern instead of the inline pattern on both the R4A and
B version
modules.
Curt
On 2/26/2013 10:49 AM, Tom Holmes wrote:
HI Curt..
It almost sounds like there is a different lead arrangement on the
3393. Any well designed circuit of that era would have had to tolerate
the typical high variability of Hfe to avoid tedious hand picking of
parts, although that may have been done in this case.
Tom Holmes, N8ZM
Tipp City, OH
EM79
-----Original Message-----
From: drakelist-boun...@zerobeat.net
[mailto:drakelist-boun...@zerobeat.net]
On Behalf Of Curt Nixon
Sent: Tuesday, February 26, 2013 10:40 AM
To: Drake Forum
Subject: [Drakelist] R4A-B Detector Amp Q5
GM All:
Has anyone else had trouble getting a general purpose sub working in
the
Q5 AM
detector amp position?
I tried several close NTE GP subs and also a 3393 which is same
parameters
ex
Hfe which is slightly different.
The transistor comes on but with the grounded emitter, pulls the
collector
voltage
to near zero. As soon as I put in a "real" orignal
3394 from a R4A, it works as it should--good fidelity and collector
voltage at about
5V from the supply rail of 10V.
Is this design so sensitive to Hfe as to be marginal or need to be
hand
selected?
Certainly the 3393 is well within the spec range of the 3394.
Thanks
Curt
KU8L
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