:-). 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: [email protected] [mailto:[email protected]] > On Behalf Of Curt Nixon > Sent: Tuesday, February 26, 2013 12:30 PM > To: [email protected] > 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: [email protected] > > [mailto:[email protected]] > >> On Behalf Of Curt Nixon > >> Sent: Tuesday, February 26, 2013 11:43 AM > >> To: [email protected] > >> 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: [email protected] > >>> [mailto:[email protected]] > >>>> 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 > >>>> [email protected] > >>>> http://mailman.zerobeat.net/mailman/listinfo/drakelist > >>> > >>> _______________________________________________ > >>> Drakelist mailing list > >>> [email protected] > >>> http://mailman.zerobeat.net/mailman/listinfo/drakelist > >>> > >> _______________________________________________ > >> Drakelist mailing list > >> [email protected] > >> http://mailman.zerobeat.net/mailman/listinfo/drakelist > > > > > > _______________________________________________ > > Drakelist mailing list > > [email protected] > > http://mailman.zerobeat.net/mailman/listinfo/drakelist > > > > _______________________________________________ > Drakelist mailing list > [email protected] > http://mailman.zerobeat.net/mailman/listinfo/drakelist _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
