[time-nuts] HP 5245L Question

[paul swed]

Good points. But I have the 4000 series, so thats what gets used.
Also have 74LS but then I would need voltage regulators and level
conversion...


On Sun, Jan 10, 2010 at 12:19 PM, Bob Camp <lists at cq.nu> wrote:

> Hi
>
> I would be very careful with the reference conversion.
>
> Your rubidium probably puts out 10 MHz and the counter needs 1 MC ....
>
> The 4000 series CMOS gates probably have quite a bit more jitter than some
> of the more modern parts. Stuff like the 74AC series will beat them on
> jitter.
>
> Bob
>
>
> On Jan 10, 2010, at 11:48 AM, paul swed wrote:
>
> > 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 <paulswedb at gmail.com> wrote:
> >
> >> Arie,
> >>
> >>
> >> On Sun, Jan 10, 2010 at 7:14 AM, arie schellaars <
> >> arie.schellaars at yahoo.com> 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.
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
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> >>
> >>
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