Yeah and that was the strange thing: I see the filter INSIDE the PTO (i.e., inside the dashed lines of the PTO assembly) on the T-4XB schematic. I haven't checked the T-4X yet. The R-4B has the filter on one of the external boards under the chassis. It just strikes me as funny that they wouldn't have standardized the PTO amongst the transmitter and receiver for any given time period.
I'm stopping by my club room today to borrow the parts cabinets. I'm going to really need them when I start work on the R-4B... 73, Steve, W1ES/4 -----Original Message----- >From: Garey Barrell <[email protected]> >Sent: Aug 21, 2011 10:20 PM >To: Steve Wedge <[email protected]>, drakelist <[email protected]> >Subject: Re: [Drakelist] You just know I'm not going to have any hair left... > >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
