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Forum Index : Microcontroller and PC projects : Old Philips PM6668 counter to 1 GHz --- in trouble

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plover

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Joined: 18/04/2013
Location: Australia
Posts: 305

Posted: 10:54am 23 Jun 2025

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I would just like to know if anybody have the PM6668 freq ccounter

Mine is showing problem with the display when I powered up, as it has a battery unit it could be the problem it seems, working my way through the manual.

However somebody may know the answer, there are two counters PM667, no battery unit and PM6668 with battery options.

The counters are 1985 abouts vintage, be interesting so see how far I can get with repair.

Marcel27

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Joined: 13/08/2024
Location: Netherlands
Posts: 89

Posted: 11:17am 23 Jun 2025

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Hi plover,

I've seen someone with also a Philips device with LCD troubles. It seemed that after years the contacts will erode. Those little rubber strips with laminated carbon between the display and the pcb.

Marcel

Marcel27

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Joined: 13/08/2024
Location: Netherlands
Posts: 89

Posted: 09:45am 24 Jun 2025

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Plover, could you post some pictures?

Marcel27

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Joined: 13/08/2024
Location: Netherlands
Posts: 89

Posted: 12:27pm 24 Jun 2025

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https://github.com/MagicSmokeBlog/Philips-PM2535-Kermit

plover

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Joined: 18/04/2013
Location: Australia
Posts: 305

Posted: 01:43pm 24 Jun 2025

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Yes I will do but not sure when I can find time. I just had a quick look at your link

The concept will be perfect for my unit, though the amount of programming needed may be too much for me.

Thank you it is great start

You may have a look at the counter in a project, not mine, giving the PM6668 a heart transplant, this was my starting point 15 years ago when I got the unit, it got put on the storage shelf until recently a major clean out started.

https://www.sbprojects.net/projects/sb6668/index.php

Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 5023

Posted: 07:29pm 24 Jun 2025

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Hi,

Can't you replace the LCD with something like this.

Looks like the 6668 has a 8 numeric display.

I am convinced we could replace the 8048 with a pico, driving that display.

The pico's PIO can do the counting. All software in MMBasic.

Volhout
Edited 2025-06-25 05:32 by Volhout

PicomiteVGA PETSCII ROBOTS

plover

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Joined: 18/04/2013
Location: Australia
Posts: 305

Posted: 01:00pm 25 Jun 2025

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Volhout

Very good idea, but personally I will be unable to handle the programming I am just getting too slow, think it has something to do with being 81 years old, bit disappointing but hey lets see.

I have just managed to get the battery unit removed, during taking counter out of the case I must have stirred something up. While checking operation I turns out when pushing the ON button, display went through very quick check showing all segments and then settling down to showing all digits zero.

I will come back on the replacement displays, I would at least like to check out theoretically what would be needed. In case it is just a new battery I need.it looks like being open circuit, the charge current then sent the voltage up to 7V 'over voltage limit' which stepped in and stopped operation.

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