Aui wrote on 2024-05-22, 07:27:

Would a 10k do as well ?

Technically no, because a tolerance interval of 5% allows an upper limit of no more than 9.56K.
9.1K resistors are quite common. They are in the E24 table.

https://www.newark.com/c/passive-components/r … istance=9.1kohm

On the other hand a rule of thumb says that you can generally replace a resistor with the next higher / lower value in the same (or higher) E-row. That would be 8.2K or 10K here.

No luck unfortunately with my attempt to fix the board. I cleaned everything and retinned traces as good as possible and also added a few new wires (+ the new replacement resistors). Continuity was ok on all damaged traces but the board is not waking up. CPU, chips and VGA chip are getting warm though. I wonder if it is missing a battery. There is a 4pin connector close to the site where the Varta was sitting and I am wondering if thats the connector for an external battery. However, in that case there should also be a jumper to set it to external. Which brings me to my question - can anyone identify the board - I had no luck.

On the backside there is a little icon that could be a company logo ? Thanks already in advance.

The writing "FTK-A253" suggests it´s some FTK mainboard.

There´s probably one of the traces / vias still interrupted. To get at least some information about any ongoing activity and where the the start up process stops, you should buy yourself an "ISA POST-card". (They cost no more than $10.)

I‘m using an external battery on 6 or 7 mainboards, 386 and 486. Only one of them has a jumper for it so you‘re probably good.

I see, but will these board wake up even without the battery?

Nearly all do, very few don´t.

Aui wrote on 2024-05-24, 04:22:

Continuity was ok on all damaged traces but the board is not waking up.

Do you have a POST card? It's very useful in repairs like this. In fact it's very difficult to diagnose a "black screen" problem otherwise, you don't know if the mobo is completly dead or just failing the initial self-test.
Also make sure that RAM is in the correct bank. These early mobos usually can't work with RAM just in bank 1, first you need to populate bank 0. I can't tell from the photo which is which.

I ordered one, but it will take time until it arrives. I will post an update from my post card once I got it.

thanks

Ok - I got the POST card and gave it a try - but I dont get any code readings (nor any beeps).
It seems all the LED's are lighting up correctly - so any idea what that means ?
Is there any meening to not receiving any POST codes (e.g. no BIOS access etc ?)
- CPU gets warm
- chips get warm
- BIOS gets warm
- Chips on VGA card get warm

any ideas ? - Thanks

First of all, the KBC socket (U36) is empty so you have no Keyboard Controller installed. No wonder you get nothing. That would be suspect 1.

Suspect 2 would be the BIOS EEPROM (U58), seeing as the battery damage is very close to the BIOS EPROM socket. I would start looking there first. Remove, spray some contact cleaner into socket and reseat the EPROM, then test continuity between each pin and the respective solder joint on the bottom of the PCB. Then check to make sure that the EPROM gets voltage on the Vcc pin.

I checked with a spare keyboard controller - nothing.

Suspect 2 - Yes - that is what I am afraid too - several traces (also inside the board on a lower layer) look quite bad and go under the BIOS EPROM socket. I thought I can get away without removing the BIOS EPROM socket as this is something a bit beyond my skill. Especially, if there really are bad traces under the socket you cant just add more wires as the socket wont sit flat any longer. There are also more chips under this socket - It's a mess! I may have to put it aside for a while to regain patience and then start over again.

Make sure to try at least a few KBCs, not all KBC ICs are equal..