Hi Everyone,

My Global Specialties 6000 frequency counter counter died on me, it
powers up, but does not count.

I wonder if anyone has a manual/schematics and could guide me through
the repair. I looked around and found no documentation available.

The counter itself was made around the '80s, and it uses an LS7031
counter/driver chip, National MM5369 based time base, and a bunch of
CMOS glue logic. The first two digits of the counter are implemented off
the LSI chip for speed, in this case two chips of dual J-K flip-flops,
74S112, and a 74LS90.
The signal gets through the input stage, but the J-K flip-flops are
already not counting.
I would really appreciate if someone could help me out with the
schematics, it would save me reverse engineering the circuit.

Thanks for listening, Peter

If this is anything like some other "Global Specialities" instruments, it
may have been made by Tabor in Israel - try looking on their web site.

David
"Peter Orban" wrote in message
...
Hi Everyone,

My Global Specialties 6000 frequency counter counter died on me, it powers
up, but does not count.

"Peter Orban" wrote in message
...
Hi Everyone,

My Global Specialties 6000 frequency counter counter died on me, it powers up,
but does not count.

I wonder if anyone has a manual/schematics and could guide me through the
repair. I looked around and found no documentation available.

The counter itself was made around the '80s, and it uses an LS7031
counter/driver chip, National MM5369 based time base, and a bunch of CMOS glue
logic. The first two digits of the counter are implemented off the LSI chip
for speed, in this case two chips of dual J-K flip-flops, 74S112, and a
74LS90.
The signal gets through the input stage, but the J-K flip-flops are already
not counting.
I would really appreciate if someone could help me out with the schematics, it
would save me reverse engineering the circuit.

Thanks for listening, Peter



Your counter is probably similar to the DSI 3550 counter. It also uses the
LS7031 counter/multiplexer LSI chip, similar to your counter. It uses LSTTL
logic instead of CMOS, but it is probably quite similar in construction. I
suggest that you start by downloading the datasheet for the LS7031 from
http://www.datasheetarchive.com/sear...ExactDS=Starts
and look at the suggested application schematic. It will give you a starting
point for the circuit surrounding the LSI chip. I have the schematic for the
DSI counter, if you can't find the problem with your counter, I can scan the
3550 schematic and send it to you. It may give you some ideas as to where to
look.
But since you say that you know that the flip-flops aren't counting, you need to
identify the main signal gate. It will be a NAND or AND gate, and will be
enabled by some derivative of the time base oscillator. If the oscillator is
running, follow its signal string down to the main gate. The signal string will
be a series of decade dividers. If the time base is getting to the main gate,
and the input signal is getting to the main gate, your chase is nearly over. If
the signal is being gated properly, follow it to the flip-flops and see where
the counting stops.
If the signal isn't getting to the main gate, start following the signal from
the input. It will probably go through a Schmitt trigger to square it up, and
then to the main gate. If it isn't getting to the main gate, you have to find
where it stops.

Cheers!!!

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Never take a laxative and a sleeping pill at the same time!!

Hello Everyone,

Many thanks for the replies!

Here is an update: I did find the datasheets for the main functional
chips and made some more measurements in the counter.
There is no clock signal coming out of the time-base chip! The
oscillator stage is running, but no signal at the end of the divider
chain, even if the next stage is disconnected.
Now I just have to find an MM5369AA locally. I hoped to get a sample
from National, but the chip is now obsolete ;-(

I also looked up Tabor Electronics in Israel as suggested, and will ask
them about documentation. Their current counters are 6020, 6030 etc.

Thanks again for the help!

Regards, Peter