Author Topic: Replacing a vintage +8vcc shift register  (Read 1196 times)

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Offline gkmaiaTopic starter

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Replacing a vintage +8vcc shift register
« on: July 14, 2019, 09:10:52 am »
I got a bit of a problem. Got two 74 logic 164 shift registers that are faulty.

The issue is. These registers run on a +8V rail and on the market today I can only find shift registers that will take 5V or 6V VCC.

Has anyone had the same issue replacing these old shifters? Any tip?!





 

Offline oPossum

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Re: Replacing a vintage +8vcc shift register
« Reply #1 on: July 14, 2019, 09:19:14 am »
CD4094 / HEF4094 / MC14094
 

Offline tggzzz

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Re: Replacing a vintage +8vcc shift register
« Reply #2 on: July 14, 2019, 09:27:46 am »
I assume this is a one-off replacement. You have several options, but none are trivial...

Find a secondhand supplier. There are several such dedicated companies on the web, but they will be expensive.

See if there are 4000 series devices that have suitable timings and pinouts. Pinout could be dealt with using a carrier board.

Use a modern small outline device on carrier board, together with a voltage regulator and level shifters. Be careful of the risetime of a 5V->8V shifter; some can be good up to 5V, and anaemic from 5V to 8V

Timing: most people will verify the tPD and tS timing in their circuit, but tH is equally important and can be less tractable.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline gkmaiaTopic starter

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Re: Replacing a vintage +8vcc shift register
« Reply #3 on: July 14, 2019, 11:12:45 pm »
I assume this is a one-off replacement. You have several options, but none are trivial...

Find a secondhand supplier. There are several such dedicated companies on the web, but they will be expensive.

See if there are 4000 series devices that have suitable timings and pinouts. Pinout could be dealt with using a carrier board.

Use a modern small outline device on carrier board, together with a voltage regulator and level shifters. Be careful of the risetime of a 5V->8V shifter; some can be good up to 5V, and anaemic from 5V to 8V

Timing: most people will verify the tPD and tS timing in their circuit, but tH is equally important and can be less tractable.

Yes, I was afraid that was the case. I will get some NOS ones instead of tweaking another one as it is a precision device.

But interesting. Half of the circuit uses 5v logic and other half uses 8v logic. Was that a common thing back in the past? What are the benefits of 8v logic?
 

Offline tggzzz

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Re: Replacing a vintage +8vcc shift register
« Reply #4 on: July 14, 2019, 11:57:17 pm »
What are the benefits of 8v logic?

Nothing per se.

There may be advantages in the surrounding circuit, of course.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline Neomys Sapiens

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Re: Replacing a vintage +8vcc shift register
« Reply #5 on: July 15, 2019, 12:23:10 am »
I did not even know this 40H series. It seems to be 74nnn devices converted into standard CMOS. Did anyone except Toshiba make those?
 

Offline oPossum

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Re: Replacing a vintage +8vcc shift register
« Reply #6 on: July 15, 2019, 12:52:00 am »
74C series. Fairchild made the 74C164, but it is obsolete just like the 40H164.
 

Offline gkmaiaTopic starter

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Re: Replacing a vintage +8vcc shift register
« Reply #7 on: July 15, 2019, 01:01:26 am »
The C164 can go to up 15v. But the thresholds are diferent. From what I can see only toshiba did those.
I have a guy in china who I buy these old things directly and he is cheap and sell one or two.
If anyone need I can share his contact.
 


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