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Old 28th October 2011, 06:38 PM   #1
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Default Updating 555 timer chip.

Would there be any benfit to replacing an older 555 timer chip with a more modern unit?

This unit in question is in a mid seventies reciever, and I believe is part of the tuner section. (At the very least, I can't imagine what it would do for the pre or power amp section )
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Old 28th October 2011, 06:48 PM   #2
Mooly is online now Mooly  United Kingdom
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I can't imagine what it does in the tuner either...

I would say no, leave it be. Reason why, it may be used as a pulse generator/monostable etc and replacing with a low power version would alter it's characteristics slightly maybe needed a realignment of something else.

You need to know what it does ?

I have never come across commercial kit that used a 555 tbh. Could it be used as a negative rail generator (charge pump) ?
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Old 28th October 2011, 06:59 PM   #3
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It's not hugely important, really. This is an old, low-power reciever (Lafayette Lr310)I've had my eye on to refresh once I got the money to do so. The goal here would be to improve performance.

Thanks for the answer though. I never realized that there were so many different variations of this chip. The one in question is a metal can type, something I've never seen done with an IC. "C555a 2"
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Old 28th October 2011, 07:57 PM   #4
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It is most likely not a timer IC! It is an rf IF IC also called a 703 originally by Fairchild!
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Old 28th October 2011, 08:14 PM   #5
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by simon7000 View Post
It is most likely not a timer IC! It is an rf IF IC also called a 703 originally by Fairchild!
Never mind, replacing it with a plain 555 might have interesting results, like converting an old analogue tuner into a top class DAB receiver. You never know.
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Old 28th October 2011, 11:56 PM   #6
Enzo is offline Enzo  United States
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I'm willing to believe Simon, but if we have to have a 555 timer IC, I could see it as a delay for a speaker relay or similar application. Or as a blinker for some indicator light.
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Old 29th October 2011, 05:26 PM   #7
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Well well, this has turned out to be an interesting discussion.

I took another look at it, and it is on the edge of the tuner, where it ends and the amp begins (they're on the same board). I opened up my little tiny Integrated amp, which is also a Lafayette, and it does not have one of these.

The little metal can chip in question was made by NEC, and the reciever itself was made between 74 and 78.
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Old 29th October 2011, 05:38 PM   #8
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The original NE555 timer was Signetics, not Fairchild. I don't remember a TO5 like can version. I remember P & D(ceramic) dips. I do have an original Signetics catalog but can't reach it.
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Old 29th October 2011, 06:30 PM   #9
Mooly is online now Mooly  United Kingdom
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Supply on pin 8 and ground on pin 1 would go some way to identifying it for sure.

There are only a few configurations the 555 is used in normally so easy to tell from the parts around it.

Close up pic of the chip and surrounding area maybe...
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Old 1st November 2011, 02:42 AM   #10
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It's quite strange that there's a NE555 in a receiver. Maybe it's configured as a trigger, or flip-flop, controlling buttons :-P
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