Joosemachine wrote on 2024-07-25, 11:45:

Hi all,

I wanted to try connect a 4 AA battery pack to the external battery header on my 386 motherboard because I have seen quite a few old motherboards where there were 4 AA's connected and they all seemed fine.. but when I connected the battery pack, this diode on the board got very hot and started smoking! I unplugged it immediately, and the diode seems to have survived (passed the diode test on my multimeter). But obviously the 6.4v from the 4 AA batteries was way too much for this circuit.. so how did other motherboard get away with also using the same battery pack without damage? And how much power should I connect to the external battery connector? 2 x AA (3v) seems like too little, while 3x AA (4.8v) seems like too much..

I use 3x 1.2v Eneloop rechargeable AAA’s (https://www.ebay.com.au/itm/280532941508) on most of my 386’s with this holder https://www.ebay.com.au/itm/164638079293

FWIW I have been using 3x1.5v battery packs with regular alkaline batteries in probably 20 different boards ranging from 286 to 486 and I've never experienced any issue with the voltage being too powerful...

Sounds more like the battery was shorted to ground rather than any issue with the voltage (although anything more than 5V is probably not a good idea). Was the board set correctly to use an external battery? What does the jumper shown in the screenshot do?

jmarsh wrote on 2024-07-25, 12:36:

Sounds more like the battery was shorted to ground rather than any issue with the voltage (although anything more than 5V is probably not a good idea). Was the board set correctly to use an external battery? What does the jumper shown in the screenshot do?

I suppose that could be the case, yes.. I am not sure what the jumper does because I have been unable to find a manual for this board.. all I have found is if I move the jumper to the other setting - the board wont post. If I remove it completely and put in a new barrel battery, it will post.

jmarsh wrote on 2024-07-25, 12:36:

Sounds more like the battery was shorted to ground rather than any issue with the voltage (although anything more than 5V is probably not a good idea). Was the board set correctly to use an external battery? What does the jumper shown in the screenshot do?

I did check the pins on the header though - pins 3 and 4 are connected to ground, but there is no connection to ground on pins 1 or 2

Can you post a picture of the whole board?

Hi Zuldan, I am not able to take a pic right now (at work) but its pretty much this exact board:

https://theretroweb.com/motherboards/s/jetway … 6dx-opti-495slc