Help with 7D15 Tek logic gates


Dave Peterson
 

I'm trying to debug a 7D15. I think I'm on the right path in that I'm able to follow the circuit description, set up the device, trace inputs, and get waveforms. I'm not getting any frequency or period measurements.

I think there's an issue in the Gating and Control Logic as there is no signal coming from the main gate to the 8 Decade Counter. See 7D15 Instruction Manual 070-1433-00, page 3-2, "Fig 3-1. Signal flow for FREQ and Frequency Ratio modes."

I've setup the counter as prescribed by the Voltage and Waveform Test Conditions portion of the Block Diagram fold-out page. That is, set up frequency mode and apply a 4vpp 1kHz square wave from a PG506.

Looking at the Gating & Control Logic schematic <2>, I'm able to trace waveforms to U287C, a 2-input NOR gate of type 1662. In the table on the lower right of the schematic it says Vee is on pin 8. I measure -4v.

What's tripping me up are these Tek logic gates. They are not TTL, and I don't know what the logic is. I'm currently getting no output from U287C and it is stuck "high" at 0v. The input on pin 11 is switching between a low of -3v and high of 0v. Pin 10 is at -1.2v, which is 0.6v down from the Q429 base of -0.6v. The collector is at about the same level as the emitter -1.2v, so I presume Q429 is in saturation and ON. Therefor the voltage at pin 10 is the result of the network of Q424, Q427, Q429, and associated resistors. The voltages seem near enough to the values in the schematic that I think that network is ok. On the other hand, if I apply the PG506 to the A input instead of B I get a good, but relatively small signal: -1.7v to -1.0v on pin 10. Seems like it should be larger. Is the failed U287 pulling out of range?

I suspect U287 is bad. If pin 10's ambiguous level was interpreted as a 1/high, then the NOR output should be low: about -3v (or -4?). If pin 10 was interpreted as a 0/low, then the signal on pin 11 should be going through. So it seems bad either way. But not knowing the circuit design of the logic, and the input levels to pin 10 make me uncertain.

The Tek part number is 156-0226-00. Consider this my introduction to Tektronix logic families. I'm sure there's plenty of documentation out there. I'll keep searching this forum, the TekWiki, Google, etc. But a swift kick in the right direction would be greatly appreciated.

Thanks,
Dave


Bruce Griffiths
 

That's a MECLIII part number.
ECL has a logic level swing of about 0.8V ssymmetrical about 1.3V below the VCC (typically 0V).
That is it swings from 0.4V above to 0.4V below 1.3V below Vcc.
The swing is more thna adequate to switch an emitter coupled transistor pair.
MECLIII is much faster than TTL.

Bruce

On 12 October 2021 at 13:06 "Dave Peterson via groups.io" <davidpinsf=yahoo.com@groups.io> wrote:


I'm trying to debug a 7D15. I think I'm on the right path in that I'm able to follow the circuit description, set up the device, trace inputs, and get waveforms. I'm not getting any frequency or period measurements.

I think there's an issue in the Gating and Control Logic as there is no signal coming from the main gate to the 8 Decade Counter. See 7D15 Instruction Manual 070-1433-00, page 3-2, "Fig 3-1. Signal flow for FREQ and Frequency Ratio modes."

I've setup the counter as prescribed by the Voltage and Waveform Test Conditions portion of the Block Diagram fold-out page. That is, set up frequency mode and apply a 4vpp 1kHz square wave from a PG506.

Looking at the Gating & Control Logic schematic <2>, I'm able to trace waveforms to U287C, a 2-input NOR gate of type 1662. In the table on the lower right of the schematic it says Vee is on pin 8. I measure -4v.

What's tripping me up are these Tek logic gates. They are not TTL, and I don't know what the logic is. I'm currently getting no output from U287C and it is stuck "high" at 0v. The input on pin 11 is switching between a low of -3v and high of 0v. Pin 10 is at -1.2v, which is 0.6v down from the Q429 base of -0.6v. The collector is at about the same level as the emitter -1.2v, so I presume Q429 is in saturation and ON. Therefor the voltage at pin 10 is the result of the network of Q424, Q427, Q429, and associated resistors. The voltages seem near enough to the values in the schematic that I think that network is ok. On the other hand, if I apply the PG506 to the A input instead of B I get a good, but relatively small signal: -1.7v to -1.0v on pin 10. Seems like it should be larger. Is the failed U287 pulling out of range?

I suspect U287 is bad. If pin 10's ambiguous level was interpreted as a 1/high, then the NOR output should be low: about -3v (or -4?). If pin 10 was interpreted as a 0/low, then the signal on pin 11 should be going through. So it seems bad either way. But not knowing the circuit design of the logic, and the input levels to pin 10 make me uncertain.

The Tek part number is 156-0226-00. Consider this my introduction to Tektronix logic families. I'm sure there's plenty of documentation out there. I'll keep searching this forum, the TekWiki, Google, etc. But a swift kick in the right direction would be greatly appreciated.

Thanks,
Dave





 

Dave,

I expect that they are ECL, but that's the depth and breadth of my wisdom on this.

-- Jeff Dutky


Dave Peterson
 

Thanks Bruce,

Quickly found the cross reference to MC1662 in the TekWiki Semiconductor Cross Reference. But haven't found electrical specs yet. The input levels described helped my understanding of what the pin10 input is doing.

Glad to see there are some of these available out there. I'm not dead in the water with unobtanium.


Mark Vincent
 

Dave,

I see there are a number of the 151-0367-00 transistors in this plug-in. Replace them with KSP10BU. These have a BEC pinout. I had to replace all of these in my piece as well as any others I saw in other items. They will be leaky from C to E as a diode. Q429 is one of these 0367 transistors. Being leaky, conduction will occur from C to E. Those leaky transistors have caused problems until I replaced them. Your chip may not be bad.

There are resistors that should be raised in wattage. In mine, the replaced resistors above the board still are warm enough.

Mark


 

Dave,

BitSavers has the Motorola MECL data book available on-line (http://www.bitsavers.org/components/motorola/_dataBooks/1978_Motorola_MECL.pdf) which includes the MC1600 series chips. The also have the MECL Integrated Circuits Semiconductor Data Library (http://www.bitsavers.org/components/motorola/_dataBooks/1974_Motorola_MECL_Integrated_Circuits_Series_A_Vol4.pdf)

Here is the data sheet for the MC1662 https://rocelec.widen.net/view/pdf/nslk2yp4uy/MOTOS13352-1.pdf?t.download=true&u=5oefqw

There is also the MECL System Design Handbook (http://bitsavers.trailing-edge.com/components/motorola/_dataBooks/1989_Motorola_MECL_System_Design_Handbook_4ed.pdf) that appears to be full of all kinds of useful information. It might have been better to have learned about his book BEFORE the three-day weekend.

-- Jeff Dutky


Dave Peterson
 

Thanks for the replies. It's pretty clear what these devices are and the characteristics.

I've been doing a little looking for availability. I have to say I'm a little surprised there aren't contemporary suppliers of ECL gates. Or I'm not finding them. I've tried looking on Mouser, eBay, and Duck-Duck-Go. There's a couple of sources on eBay for either the original Tek number 156-0226(*) or MC1662. But I'm not finding ECL DIP packages on Mouser, and generally not with web searches. I'm still quite naive when it comes to the world of discrete components. Is ECL DIP logic dead?


Dave Seiter
 

The only place I ever did work for that used ECL actively was MIPS in the early 90's.  I know On Semi still makes some family members, but I doubt anyone has made them in DIP packages for a fairly long time.
-Dave

On Monday, October 11, 2021, 08:18:18 PM PDT, Dave Peterson via groups.io <davidpinsf=yahoo.com@groups.io> wrote:

Thanks for the replies. It's pretty clear what these devices are and the characteristics.

I've been doing a little looking for availability. I have to say I'm a little surprised there aren't contemporary suppliers of ECL gates. Or I'm not finding them. I've tried looking on Mouser, eBay, and Duck-Duck-Go. There's a couple of sources on eBay for either the original Tek number 156-0226(*) or MC1662. But I'm not finding ECL DIP packages on Mouser, and generally not with web searches. I'm still quite naive when it comes to the world of discrete components. Is ECL DIP logic dead?


cmjones01
 

On Tue, 12 Oct 2021, 05:18 Dave Peterson via groups.io, <davidpinsf=
yahoo.com@groups.io> wrote:

Is ECL DIP logic dead?
Yes, except for very specialist replacement applications. The speed of CMOS
logic caught up with ECL and overtook it, and in any case discrete gates
are hardly ever used these days. In any design for about the last 20 years,
the logic is almost all in programmable devices (CPLDs and FPGAs). Even
run-of-the-mill FPGAs will cheerfully handle speeds of several hundred MHz
today.

Chris


Dave Peterson
 

I found this interesting perspective: https://www.quora.com/Is-Emitter-Coupled-Logic-in-use-today

I've been working in the industry for some 30+ years now. I'm well aware of modern circuit performance. I didn't really think of it as a speed thing as much as a support and backward compatibility question. I don't know why so many relatively obsolete components are still mass produced. The likes of DIP packaged TTL logic gates. We can certainly pack vastly more circuitry into a 16 pin DIP, but manufacturers are still producing simple logic gates that are compatible with, for example, the circuit boards I worked on in the Army. Things designed and built in the 60's and 70's. Such as components in Tek equipment.

Don't get me wrong! I'm sure glad they do. I'm just surprised there's still a large enough market for it. Considering the electrical I/O specs of ECL, I thought maybe there would be enough demand for it as well. But clearly the market is not there. I guess the discrete component logic on a board is not a speed critical part of any current design. So there's no call for ECL. If speed is important you  start going FPGA, or ASIC, etc.

On Monday, October 11, 2021, 11:06:31 PM PDT, cmjones01 <chris@stumpie.com> wrote:

On Tue, 12 Oct 2021, 05:18 Dave Peterson via groups.io, <davidpinsf=
yahoo.com@groups.io> wrote:

Is ECL DIP logic dead?
Yes, except for very specialist replacement applications. The speed of CMOS
logic caught up with ECL and overtook it, and in any case discrete gates
are hardly ever used these days. In any design for about the last 20 years,
the logic is almost all in programmable devices (CPLDs and FPGAs). Even
run-of-the-mill FPGAs will cheerfully handle speeds of several hundred MHz
today.

Chris


Dave Seiter
 

One exception to discrete gates is the Tinylogic series from OnSemi; many companies I worked for added pads for them "just in case" in much the same manner that extra gates in x4 and x6 devices were used decades ago, the ability to add/correct logic without a board spin.
-Dave

On Monday, October 11, 2021, 11:06:33 PM PDT, cmjones01 <chris@stumpie.com> wrote:

On Tue, 12 Oct 2021, 05:18 Dave Peterson via groups.io, <davidpinsf=
yahoo.com@groups.io> wrote:

Is ECL DIP logic dead?
Yes, except for very specialist replacement applications. The speed of CMOS
logic caught up with ECL and overtook it, and in any case discrete gates
are hardly ever used these days. In any design for about the last 20 years,
the logic is almost all in programmable devices (CPLDs and FPGAs). Even
run-of-the-mill FPGAs will cheerfully handle speeds of several hundred MHz
today.

Chris


cmjones01
 

On Tue, Oct 12, 2021 at 9:51 AM Dave Seiter <d.seiter@att.net> wrote:

One exception to discrete gates is the Tinylogic series from OnSemi; many companies I worked for added pads for them "just in case" in much the same manner that extra gates in x4 and x6 devices were used decades ago, the ability to add/correct logic without a board spin.
Yes, they're really handy. I use them for all sorts of odd jobs that
don't fit in to a microcontroller or FPGA, like signal conditioning or
taking signals in to odd power domains.

Chris


Tom Gardner
 

On 12/10/21 08:51, Dave Seiter wrote:
One exception to discrete gates is the Tinylogic series from OnSemi; many companies I worked for added pads for them "just in case" in much the same manner that extra gates in x4 and x6 devices were used decades ago, the ability to add/correct logic without a board spin.
A wide range of new such devices are being introduced by several manufacturers, because they have significant advantages apart from those you mention.

For example DigiKey lists TI 74LVC*04 inverters where there are 1, 2, 3, and 6 devices in a single package.

Good features are the wide voltage range (1.65-5V), high current output (+-32mA @5V), small size, and high speed. That makes them very suitable for line driving purposes. Some even have internal resistors for source terminating 50ohm transmission lines.

I've use three (74LVC1G14+143ohm resistors) in parallel to drive a 50ohm line with ~300ps transition times.


Jim Ford
 

Yep, I used to call them Oh Shit parts!        Jim FordSent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Dave Seiter <d.seiter@att.net> Date: 10/12/21 12:51 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Help with 7D15 Tek logic gates One exception to discrete gates is the Tinylogic series from OnSemi; many companies I worked for added pads for them "just in case" in much the same manner that extra gates in x4 and x6 devices were used decades ago, the ability to add/correct logic without a board spin.-Dave    On Monday, October 11, 2021, 11:06:33 PM PDT, cmjones01 <chris@stumpie.com> wrote:  On Tue, 12 Oct 2021, 05:18 Dave Peterson via groups.io, <davidpinsf=yahoo.com@groups.io> wrote:> Is ECL DIP logic dead?>Yes, except for very specialist replacement applications. The speed of CMOSlogic caught up with ECL and overtook it, and in any case discrete gatesare hardly ever used these days. In any design for about the last 20 years,the logic is almost all in programmable devices (CPLDs and FPGAs). Evenrun-of-the-mill FPGAs will cheerfully handle speeds of several hundred MHztoday.Chris>