Hi Dennis:
Yep...the DC values do not suggest saturation. Is the feedback you
refer to the base bypass cap? I thought that to be a part of the
detector (the charge cap). I guess I dont see anything else on my
schematic that looks to be feedback. Straight voltage dividing for bias
and collector, just the diode in series with the base source.
Pretty sure I have tried all variants of the pinouts and checked the
devices on the Huntron to be sure.
I'm really betting on the Gain-Bandwidth issue now. Old devices/vs new
ones.
Curt
On 2/26/2013 9:31 PM, Dennis Monticelli wrote:
The saturation you are seeing should not be happening based upon
simple DC specs. Either the pinout is not correct as has been
suggested or perhaps the new transistor is oscillating due to a higher
gain-bandwidth product. The circuit does use a feedback connection.
Dennis AE6C
On Tue, Feb 26, 2013 at 12:06 PM, Tom Holmes <thol...@woh.rr.com
<mailto:thol...@woh.rr.com>> wrote:
:-).
I wonder if there is an asterisk on the schematic next to some
bias resistor
that says hand chosen.
Oh well. Have fun!
Tom Holmes, N8ZM
Tipp City, OH
EM79
> -----Original Message-----
> From: drakelist-boun...@zerobeat.net
<mailto:drakelist-boun...@zerobeat.net>
[mailto:drakelist-boun...@zerobeat.net
<mailto:drakelist-boun...@zerobeat.net>]
> On Behalf Of Curt Nixon
> Sent: Tuesday, February 26, 2013 12:30 PM
> To: drakelist@zerobeat.net <mailto:drakelist@zerobeat.net>
> Subject: Re: [Drakelist] R4A-B Detector Amp Q5
>
> 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>
> > [mailto: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 <mailto: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>
> >>> [mailto: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
> >>>>
> >>>> _______________________________________________
> >>>> Drakelist mailing list
> >>>> Drakelist@zerobeat.net <mailto:Drakelist@zerobeat.net>
> >>>> http://mailman.zerobeat.net/mailman/listinfo/drakelist
> >>>
> >>> _______________________________________________
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