If the problem is an intermittant connection somewhere (i.e. a bad solder joint) the point application of heat or cold can change the problem (either aggravate or improve) thus allowing you to isolate the troublesome region. Have you tried the point application of cold spray? Often those cans come with a needle tip.
Dennis AE6C On Sun, Aug 21, 2011 at 7:20 PM, Garey Barrell <[email protected]> wrote: > Steve - > > NONE of the T-4X(any) had the low-pass filter on the output of the PTO. > Only the receivers used the filter, and only in version 2 of the R-4A and > up. > > It would be OK to just bypass the LP filter in the receiver for testing > purposes. Also, don't gloss over the possibility of a bad, (cracked?), or > just noisy resistor at R49. Or even poor solder on those associated > connections. > > Also, don't overlook the possibility of erratic or intermittent operation > of the BAND oscillator (listen at 18.1 MHz on 40M). > > Possible other resistors associated with V8 are noisy. Since you have no > jitter in TRANSCEIVE (XMTR control) the problem is in the BAND, PTO or > PreMixer, as these are all disabled in XMTR mode. > > > 73, Garey - K4OAH > Glen Allen, VA > > Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line > and TR-4/C Service Supplement CDs > <www.k4oah.com> > > > Steve Wedge wrote: > >> I'm going to have to look again. I did swap the VR tube. >> >> Something Garey mentioned made me check the T-4XB schematic. If that >> schematic is accurate, Drake put the filter inside the PTO at some point or >> just for the T-4XB. I'm suspecting this was done for all PTO's at some >> point, as I couldn't imagine Drake building different versions of the PTO at >> the same time (of course, not everything follows what I or anyone else would >> consider logical...). This could allow me to try temporarily bypassing the >> filter board. I did notice that shielded cable went directly to the PTO >> when I removed it. Given these differences, it also looks like I'll be >> ripping the receiver apart (again!) to put the original PTO back in. >> >> Arrrggggghhhhh... >> >> >> Steve Wedge, W1ES/4 >> >> "I can't complain, but sometimes I still do." >> - Joe Walsh >> >> If the above message appears, it came from Steve's Son of Laptop! >> ----- Original Message ----- From: <[email protected]> >> To: <[email protected]> >> Sent: Sunday, August 21, 2011 6:11 PM >> Subject: Re: [Drakelist] You just know I'm not going to have any hair >> left... >> >> >> Did you put a scope on the voltage to the PTO and watch it carefully? >> As it fails? >> 73, >> Lee, KC9CDT >> >> >> >> -----Original Message----- >> From: Steve Wedge <[email protected]> >> To: Eddy Swynar <[email protected]> >> Cc: drakelist <[email protected]> >> Sent: Sun, Aug 21, 2011 5:30 pm >> Subject: Re: [Drakelist] You just know I'm not going to have any hair >> left... >> >> >> That's the thing: it's a different PTO that was working properly before >> I transplanted it. >> >> Looks like I've got to try replacing the components on the filter >> board. Something is pulling the frequency... >> >> Steve Wedge, W1ES/4 >> >> > ______________________________**_________________ > Drakelist mailing list > [email protected] > http://mailman.zerobeat.net/**mailman/listinfo/drakelist<http://mailman.zerobeat.net/mailman/listinfo/drakelist> >
_______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
