Arie Still working on the a26 board. It works but I want to improve the 10 mc in. Most likely a schmitt trigger CD 4093 I might guess. The boards very simple. Since I have 10 mc in the shack from a RB standard I simply square it up and send it to a CD4050 buffer IC to the 10 MC systems in the 5248M. Then take the same 10 MC divide with a CD 4018 to get 1 MC feed this to 3 CD4050 inverters. I strongly suspect actually one buffer is more then enough in the package just have not had time to try it.
I also found some HP sloppy work. HP no way. But evidently it does happen. There is a 7474 on the A35 board that has open set and reset inputs. Good practice is to tie those high. These are floating and as I had seen with age they become slightly erratic. Replaced that chip and will tie the spare leads high. I have indeed isolated my issue to the tunnel diode gate section. Inject a signal just beyond that and the counter counts. Though incorrectly because no gate action. I have another 5248 thats been working for years and had never been in it. Well I figured I would borrow the A21 card to confirm the issues and measure voltages. Son of a gone someone else had the same section issue and cleverly replaced the tunnel diode with a ecl 10116. I don't see how they are gating that yet. But I do understand how the 10116 works to amplify and clip the signal. So I may indeed copy that circuit if I can not recover the gate section of A21. Regards On Sun, Jan 10, 2010 at 11:38 AM, paul swed <[email protected]> wrote: > Arie, > > > On Sun, Jan 10, 2010 at 7:14 AM, arie schellaars < > [email protected]> wrote: > >> >> >> >> >> Hi folks, >> My 5245L had faulty nixies and my approach was to use Russian replacements >> available from a Canadian outfit. >> The "snags" are. >> These nixies , though a direct socket fit , have a glass extrusion at the >> back to >> "suck out" or let in the neon gas during manufacture. >> I drilled the socket ,slow and carefully here, to allow this extrusion to >> fit into the >> socket . There is some room to spare for this on the socket and no >> disassembly of the readout card is needed. >> The second "snag " is that the figure 5 is in fact an inverted (upside >> down) fig 2 but >> in practice it's not a problem. >> BTW never had a problem with any of the "innards" of the counter boards! >> Would be interested in your details of the oscillator board as , like you, >> mine came without the crystal. The oven container was there but empty! >> Have since obtained a crystal in its oven but still not happy with the A26 >> board. >> performance AND have run out of Germanium transistors as per on that >> board. >> >> Just had a thought. Ever since I purchased my 5245L many years ago, I have >> been on this Time nut treadmill . I guess I should have known better at the >> time !!! >> Now with a shack full of HP and Tek gear and the inevitable rubidiums , >> GPS thunderbolts and plain old oxco's , time to call "CQ' is at a premium. >> (Hi) >> Cheers from OZ >> Arie >> VK3DBF >> >> >> Been troubleshooting a 5248 M someone grabbed teh oscilator and A26 board >> from it. >> The a26 board was replced with 2 cmos chips and 1 transistor. >> Now I am at the counter gate. Darned if I don't have an issue in the >> dreaded >> tunnel diodes area. Such a lucky day for me. >> Need to cleanup and solder in the pseudo a26 board so I can more easily >> work >> on the gate. >> >> >> >> >> >> >> __________________________________________________________________________________ >> See what's on at the movies in your area. Find out now: >> http://au.movies.yahoo.com/session-times/ >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
