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Global Specialties 6000 frequency counter

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

Reply to
Peter Orban
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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.

Reply to
David C. Partridge

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

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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!!
Reply to
DaveM

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

Reply to
Peter Orban

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