Sorry to hear this particular board is proving to be more difficult than you expected. It seems a lot of you guys seem to like the challenge of replacing barrel batteries with either new ones or CR2032... Personally I'm all in for using external battery packs and not having to solder anything! I've managed to make every board that had a suitable connector work thanks to a 3xAA or 3xAAA pack (and I've tried with maybe 15-20 boards ranging from 286 to 486.) Only once have I encountered the problem of the clock not ticking when powered off, and I assumed it was due to a faulty crystal.

Hopefully you'll be able to make this board work!

MMaximus wrote on 2020-07-11, 20:02:

Sorry to hear this particular board is proving to be more difficult than you expected. It seems a lot of you guys seem to like the challenge of replacing barrel batteries with either new ones or CR2032... Personally I'm all in for using external battery packs and not having to solder anything! I've managed to make every board that had a suitable connector work thanks to a 3xAA or 3xAAA pack (and I've tried with maybe 15-20 boards ranging from 286 to 486.) Only once have I encountered the problem of the clock not ticking when powered off, and I assumed it was due to a faulty crystal.

Hopefully you'll be able to make this board work!

Me too ! I prefer to use externals on all the XT, 286, 386 that had a barrel battery and have the ext. header. Have read that Tunnel/Schottky diodes have a much less V. drop (~.2-.3v, similar to In34 Germ. type) at the typical 10uA draw of most CMOS, better than standard In4001 silicon type diodes of .7v drop

I think the same. Germanium diodes have little voltage drop (~0.2V) and were often used in crystal radios.

This is very interesting !
Sure I can do the external battery mod, but I feel like the internal mod is more convenient in the end when dealing wiht the motherboard itself though this is just my personal opinion.
Are the germanium diodes still made ? can see lots on ebay and such, but I feel like they could easily be fakes x)

What kind of diode would you recommend the most ? Any of them as long as they have a smaller drop ?
Can I replace other diodes that end up in the circuit to reduce even more the voltage drop ?

Deksor wrote on 2020-07-11, 21:41:

This is very interesting ! Sure I can do the external battery mod, but I feel like the internal mod is more convenient in the en […]
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This is very interesting !
Sure I can do the external battery mod, but I feel like the internal mod is more convenient in the end when dealing wiht the motherboard itself though this is just my personal opinion.
Are the germanium diodes still made ? can see lots on ebay and such, but I feel like they could easily be fakes x)

What kind of diode would you recommend the most ? Any of them as long as they have a smaller drop ?
Can I replace other diodes that end up in the circuit to reduce even more the voltage drop ?

Yes you should be able to swap out one of the other diodes once you draw up the schematic of the circuit. On one of my very cheaply built old soc 3 - 486 it has a very simple resistor + diode circuitry for the batteries. It used a 3.6v NiCad (not rechargeable Lithium) so did not need a transistor based V & I limiting circuit to charge the NiCad. I attached how it runs, it has 5 diodes but it is a bit diff than many others. It looks like you could have 4 native diodes around the Batt + Cmos RTC feed from the picture. I would check to see your circuit is like in my ugly drawing..if your D1 does feed the CMOS (it appears to) then it could be swapped out with a Germanium or Schottky to gain about .3v more feed and still protect the circuit. .if the Tranny below batt is connected that would be for V+I limiting in the charge circuit to old battery.
edit fixed a boo-booo

I use the similar method a laptop uses for mine, I take 2 cr2032, a speaker wire stripped and put red to + and black to - electrical tape it then heat shrink and then on my 386 I let it just sit on the board since it's a desktop not a tower. Works well, has the convince of cr2032 but connected to ext but comes out with the board. If you want to solder it I'm sure you could add a double cr2032 to attack to the external header