1000 series "logic" gates - UK Vintage Radio Repair and Restoration Discussion Forum

dominicbeesley · 11th Oct 2009, 12:44 am

Evening all,

My sig-gen (Logimetrics 925A) has gone on the blink again, this time the frequency display has stopped working.

I've managed to track this down to a chip marked N1027A which turns out to be a "funny" j-k flip-flop, in that it will aparently accept AC coupled signals at high frequencies. This seems to be used to divide the frequency by 2 (I've pulled it and coupling the input to the output the display starts working and produces a display that is double what it should be)

My questions are:

- anyone likely to have one of these?
- if not any ideas how to knock up a replacement - it needs to work upto 80MHz!
- any more information on the 1000 series, this is the first time I've come across them and I've only managed to find out a tiny amount

Cheers

Dom

Brian R Pateman · 11th Oct 2009, 7:31 am

Hello Dom,

These are ECL (Emitter Coupled Logic) chips, but you may already know that. I do have a copy of a Signetics data sheet on the "1000" series but it doesn't give much additional information.

RS components list some ECL in the 1000 series but I couldn't see anything directly equivalent to a 1027. You may be able to produce a replica using gates from the types available from RS.

Sorry not to be more help!

Regards,

Dickie · 11th Oct 2009, 9:14 am

Hi,

ECL used to categorised as "non-saturating" logic (cf. TTL which is saturating) which is how it manages to be so fast. As such it has a linear operating point halfway between its logic levels so if its input is biased correctly and ac coupled, it will quite happily work OK with a sine wave, albeit being very sensitive to noise on the signal.
It sounds as if the 1027 is being used in a classic divide by 2 prescaler application used in many frequency counters. If you can't find an exact replacement there are several devices that would do the job, depending on supply rails, space available, etc. Googling "prescaler ic" is a good start.

If all else fails, I've probably got a MC10131P which is an ECL double D type flip -flop that could be wired as a divide by 2.

dominicbeesley · 11th Oct 2009, 11:50 am

Aha, thanks lads, thats got me a bit further on! The key is knowing what to search for! Now I know its "Emitter Coupled Logic" I've got somewhere to start.

It might not be as simple as I'd hoped (just dividing by two) as there are some other inputs from the gating circuit to the j-k as well. I'll see if I can work out what they're trying to do.

I think I may be able to bodge this by cutting tracks and using a different input. These gates have four paralleled j and k inputs, one seems to have gone very low impedance but the others seem ok. will give it a go....

Anyway thanks for the pointers, I'm now closer to being in business! And now know that the dodgy looking logic levels are deliberate!

Cheers

Dom

11th Oct 2009, 12:44 am	#1
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	1000 series "logic" gates Evening all, My sig-gen (Logimetrics 925A) has gone on the blink again, this time the frequency display has stopped working. I've managed to track this down to a chip marked N1027A which turns out to be a "funny" j-k flip-flop, in that it will aparently accept AC coupled signals at high frequencies. This seems to be used to divide the frequency by 2 (I've pulled it and coupling the input to the output the display starts working and produces a display that is double what it should be) My questions are: - anyone likely to have one of these? - if not any ideas how to knock up a replacement - it needs to work upto 80MHz! - any more information on the 1000 series, this is the first time I've come across them and I've only managed to find out a tiny amount Cheers Dom

11th Oct 2009, 7:31 am	#2
Brian R Pateman Nonode Join Date: Jun 2005 Location: Western Lake District, Cumbria (CA20) - UK Posts: 2,136	Re: 1000 series "logic" gates Hello Dom, These are ECL (Emitter Coupled Logic) chips, but you may already know that. I do have a copy of a Signetics data sheet on the "1000" series but it doesn't give much additional information. RS components list some ECL in the 1000 series but I couldn't see anything directly equivalent to a 1027. You may be able to produce a replica using gates from the types available from RS. Sorry not to be more help! Regards, __________________ Brian

11th Oct 2009, 9:14 am	#3
Dickie Octode Join Date: Sep 2004 Location: St. Albans, Hertfordshire, UK. Posts: 1,478	Re: 1000 series "logic" gates Hi, ECL used to categorised as "non-saturating" logic (cf. TTL which is saturating) which is how it manages to be so fast. As such it has a linear operating point halfway between its logic levels so if its input is biased correctly and ac coupled, it will quite happily work OK with a sine wave, albeit being very sensitive to noise on the signal. It sounds as if the 1027 is being used in a classic divide by 2 prescaler application used in many frequency counters. If you can't find an exact replacement there are several devices that would do the job, depending on supply rails, space available, etc. Googling "prescaler ic" is a good start. If all else fails, I've probably got a MC10131P which is an ECL double D type flip -flop that could be wired as a divide by 2. __________________ Regards, Richard, BVWS member Last edited by Dickie; 11th Oct 2009 at 9:22 am.

11th Oct 2009, 11:50 am	#4
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	Re: 1000 series "logic" gates Aha, thanks lads, thats got me a bit further on! The key is knowing what to search for! Now I know its "Emitter Coupled Logic" I've got somewhere to start. It might not be as simple as I'd hoped (just dividing by two) as there are some other inputs from the gating circuit to the j-k as well. I'll see if I can work out what they're trying to do. I think I may be able to bodge this by cutting tracks and using a different input. These gates have four paralleled j and k inputs, one seems to have gone very low impedance but the others seem ok. will give it a go.... Anyway thanks for the pointers, I'm now closer to being in business! And now know that the dodgy looking logic levels are deliberate! Cheers Dom