Currently, I am not confident in any of the "soldered" pins of the total 84 in IC W83C201P. I decided to revise one by one. This was a very bad repair and probably is the cause of the motherboard malfunction. It will take me some time to revise the pins connections, at least, those pins accesible to be checked. Thanks and regards.

Rwolf wrote on 2024-02-18, 17:56:

Looking at the pics of U7, the 83C201P, it might be a ripped via near pin4, going down into the board. It might be worth checking continuity to where it leads.

Yes, your suggestion was already done by other user but I do not Know how to get it. I will check my motherboards to see if any has the better RTC

rasz_pl wrote on 2024-02-19, 15:51:

So this bios is incapable of generating lower number error code for bad/missing cmos. I would source another RTC chip, preferably one like in the retroweb photo

jnemo2004 wrote on 2024-02-19, 16:24:

Yes, your suggestion was already done by other user but I do not Know how to get it. I will check my motherboards to see if any has the better RTC

https://shop.tvsat.com.pl/pl/searchquery/HM68 … ot/5?url=HM6818
Seller has ebay shop.

but definitely first desolder W83C201P to check whats under it, and the via above it

jnemo2004 wrote on 2024-02-19, 15:47:

In this situation, should I make the test with the 4k7 resistor?

Please do. If the issue is with a dead RTC chip, or improper addressing but the data bus still works this might just fool the mobo into thinking the CMOS is powered. I'm not sure if it's enough but it sure is easy and worth a try. Just a note here, do not leave that resistor connected for too long as this connection will drain the battery in a day or so.

You are right, the most professional solution is to remove the IC and see what damage there is, try to repair it and solder it again but I have my limitations and I am going to first try to see if all the pins are well soldered. I have to think how to do it.

rasz_pl wrote on 2024-02-19, 16:49:

https://shop.tvsat.com.pl/pl/searchquery/HM68 … ot/5?url=HM6818 Seller has ebay shop. […]
Show full quote

jnemo2004 wrote on 2024-02-19, 16:24:

Yes, your suggestion was already done by other user but I do not Know how to get it. I will check my motherboards to see if any has the better RTC

https://shop.tvsat.com.pl/pl/searchquery/HM68 … ot/5?url=HM6818
Seller has ebay shop.

but definitely first desolder W83C201P to check whats under it, and the via above it

With the resistor I got the same error.
The seller told me that he removed the chip to see if there was any broken track.
I will follow with to check if all the pins are connected and I will look in my other motherboards for another RTC.
This is all by the moment.
Thank to all for the suggestions. Regards

Deunan wrote on 2024-02-19, 14:52:

If you want something to try, I have 2 experiments in mind: […]
Show full quote

jnemo2004 wrote on 2024-02-19, 14:37:

Thank you very much for your info. I have already checked the voltage in pin 24 and it was OK (4,78 mobo ON and 3,47 mobo OFF). I will check the voltage in pin 22 (PS). Regards.

If you want something to try, I have 2 experiments in mind:

1) Please remove the RTC chip and see if the mobo powers up with the same error. Or is it different now.
2) With the RTC removed please attach 4k7 resistor between pins 11 and 24. You could try sticking the resistor leads into the socket but it might damage it, you can also do a temporary solder to the socket pins on the backside of the mobo. Power the mobo with the resistor (but without RTC chip) and see if anything changes.

If you don't have 4k7 resistor then 10k down to maybe 1k should also work. But do not use resistor smaller than 1k for this.

This is what I am doing.

jnemo2004 wrote on 2024-02-22, 14:57:

With the resistor I got the same error.

It was worth a try, a pity it didn't do anything. Since you are now checking all the connections please make sure the data bus (pins with D0 to D7) on the RTC/NVRAM chip are connected to one of the big chipset parts on the mobo. I would also assume that both the RTC and keyboard controller share the same data bus (in fact it might also be shared with the ISA slots lower 8 bits of data) - but don't assume the bus is OK just because there is a connection between the slots or the KBC. There must be a good connection to the chipset for any of that to work.

Same with /CS and R/W signals on the RTC, these must have some conenction to the chipset.

Good morning. I am still working with this motherboard.
I am working also with other issues but time to time go back to this motherbard.
I have to investigate if all pins are connected.
I did the following sketch but please think that I have not professional tools.
Now, it is the time to try to find the tracks under the chip.
I will keep you updated.
Regards

Hello, good afternoon.
I have checked the pin and hole connections and have found the following errors:
a) Hole M is not connected to any pin of the W83C201P chip or any hole under it. Hole M is connected to pin 65 of the W83C202AP chip.
B) Pin 11 is not connected.
C) There are 3 broken tracks, pin 3, 10 and hole X in the front side.
The broken tracks can be repaired but I don't know where pin 11 and hole M connect on the W83C201P chip.
Can you help?
Thank you so much.

jnemo2004 wrote on 2024-03-03, 13:39:

The broken tracks can be repaired but I don't know where pin 11 and hole M connect on the W83C201P chip.

I think the only option is to use hot air to desolder W83C201P and see what goes where. This would also be an opportunity to fix the M via with a thin wire.
If you don't have a hot air soldering station than hot air gun can also be used but that needs some practice - or you will melt and burn stuff. Aluminum foil and kapton tape should be used to protect the mobo, so that you only heat the opening with the chip in it. In general I would advise to try it first on some other PCB.

Alternatively, if you have access to good quality X-ray machine, you might be able to figure out track layout that way.

I full agree with you.
I have a hot air soldering station but not a professional one (could be enough for this job).
I will remove the chip but I have to practice before do it. I will protect the sorrounding components with ahesive silicon tape.
I asked the seller for the pictures taken after desoldering the chip but he told me that pictures were deleted (????). What a pitty!
Thank you very much for your help.

Deunan wrote on 2024-03-03, 15:29:

I think the only option is to use hot air to desolder W83C201P and see what goes where. This would also be an opportunity to fix […]
Show full quote

jnemo2004 wrote on 2024-03-03, 13:39:

The broken tracks can be repaired but I don't know where pin 11 and hole M connect on the W83C201P chip.

I think the only option is to use hot air to desolder W83C201P and see what goes where. This would also be an opportunity to fix the M via with a thin wire.
If you don't have a hot air soldering station than hot air gun can also be used but that needs some practice - or you will melt and burn stuff. Aluminum foil and kapton tape should be used to protect the mobo, so that you only heat the opening with the chip in it. In general I would advise to try it first on some other PCB.

Alternatively, if you have access to good quality X-ray machine, you might be able to figure out track layout that way.

jnemo2004 wrote on 2024-03-03, 18:54:

I have a hot air soldering station but not a professional one (could be enough for this job).
I will remove the chip but I have to practice before do it. I will protect the sorrounding components with ahesive silicon tape.

If I can offer some suggestions:
- Find a way to lift the chip up, this is usually done with suction tools but the professional ones are expensive and the cheap ones are not worth the money (they cause more problem than they solve). Perhaps a thin wire hooked under the corner pins would help you do that. You want to lift the chip up and not move it to sides, where it can "grab" a colder piece of solder pad and get stuck again, or even rip the pad.
- The chip should lift up with very little resistance. If you think a corner or a pin is still stuck then stop pulling and heat that spot. PLCC type pads don't rip off that easily but you don't know what kind of heat cycle was done to this mobo during previous desoldering, so the pads might now be weaker.
- Get some soldering flux for SMD work and put it around the chip pins. It will evaporate due to heat so have some fumes extractor or just open a window - but it's way easier with the flux, so don't be afraid to put too much. It can be cleaned afterwards with 90%+ IPA.
- This is a big PCB so depending on your hot air nozzle you might need to be very patient. For this job the bigger the nozzle, the better, but even with a small one you can just move it around to apply heat evenly.
- Try to pre-heat the mobo with a hair dryer from the bottom. Make sure it's hot, ideal target temperature would be 60-80C. Preheating will greatly reduce the PCB stress and desoldering time. On the other hand be careful if you want to apply bottom heating along with desoldering without temperature control, this can quickly create hot-spots so I would not recommend it. BTW even solder station with preheater will usually overshoot the temperature after cold power-on so don't put any PCB on cold preheater. Set it to 80-100% and let the temperature control kick in once or twice, then put the PCB on it.

If you have any kind of thermometer that can be used here - a thermocouple, or maybe IR sensor - do use it. Place it very close to the pads, preferably closer to the PCB center then to edge. It will be much easier to figure out how much heat still needs to be applied rather then guessing.

Thank you very much for your recommendations.
The problem is that some tracks are weaks or complety damages by the very bad first desoldering and later soldering.
Also some pins they does not look very well.
Probably after desoldering many tracks will be full damaged and some pins very close to broken.
I attach a picture of my hot air gun.
I have bad experience with old motherboards. With the hot air the inner layers of ground (and maybe other +5v) make a bubble that is not a risk for the motherboard funcioning but the bubble bend the motherboard.
I have flux (the well known chinese fake amtech) and I believe it is good enough.
For sure tracks will be damaged and probably the chip also.
I have to think how to do it
Regards

Deunan wrote on 2024-03-03, 20:15:

If I can offer some suggestions: - Find a way to lift the chip up, this is usually done with suction tools but the professional […]
Show full quote

jnemo2004 wrote on 2024-03-03, 18:54:

I have a hot air soldering station but not a professional one (could be enough for this job).
I will remove the chip but I have to practice before do it. I will protect the sorrounding components with ahesive silicon tape.

If I can offer some suggestions:
- Find a way to lift the chip up, this is usually done with suction tools but the professional ones are expensive and the cheap ones are not worth the money (they cause more problem than they solve). Perhaps a thin wire hooked under the corner pins would help you do that. You want to lift the chip up and not move it to sides, where it can "grab" a colder piece of solder pad and get stuck again, or even rip the pad.
- The chip should lift up with very little resistance. If you think a corner or a pin is still stuck then stop pulling and heat that spot. PLCC type pads don't rip off that easily but you don't know what kind of heat cycle was done to this mobo during previous desoldering, so the pads might now be weaker.
- Get some soldering flux for SMD work and put it around the chip pins. It will evaporate due to heat so have some fumes extractor or just open a window - but it's way easier with the flux, so don't be afraid to put too much. It can be cleaned afterwards with 90%+ IPA.
- This is a big PCB so depending on your hot air nozzle you might need to be very patient. For this job the bigger the nozzle, the better, but even with a small one you can just move it around to apply heat evenly.
- Try to pre-heat the mobo with a hair dryer from the bottom. Make sure it's hot, ideal target temperature would be 60-80C. Preheating will greatly reduce the PCB stress and desoldering time. On the other hand be careful if you want to apply bottom heating along with desoldering without temperature control, this can quickly create hot-spots so I would not recommend it. BTW even solder station with preheater will usually overshoot the temperature after cold power-on so don't put any PCB on cold preheater. Set it to 80-100% and let the temperature control kick in once or twice, then put the PCB on it.

If you have any kind of thermometer that can be used here - a thermocouple, or maybe IR sensor - do use it. Place it very close to the pads, preferably closer to the PCB center then to edge. It will be much easier to figure out how much heat still needs to be applied rather then guessing.

From what I recall, professionally, the pad/rework could be done about 4 times if you were good at it, but after that the tracks & vias were at severe risk of delaminating and the board was usually scrapped if it didn't look good enough.

jnemo2004 wrote on 2024-03-03, 22:19:

The problem is that some tracks are weaks or complety damages by the very bad first desoldering and later soldering.
Probably after desoldering many tracks will be full damaged and some pins very close to broken.

if they are already damaged there is no point worrying about ripping them off 😀

jnemo2004 wrote on 2024-03-03, 22:19:

I attach a picture of my hot air gun.

typical "858" with new controller, good enough for older stuff

jnemo2004 wrote on 2024-03-03, 22:19:

I have bad experience with old motherboards. With the hot air the inner layers of ground (and maybe other +5v) make a bubble that is not a risk for the motherboard funcioning but the bubble bend the motherboard.

moisture inside pcb, you need to bake whole board before proceeding, 100-120C in the owed for at lest few hours, requires good thermal controlled owen otherwise all plastics might melt if it gets hotter

jnemo2004 wrote on 2024-03-03, 22:19:

I will protect the sorrounding components with ahesive silicon tape

use alu foil, or better yet thicker pieces of metal

jnemo2004 wrote on 2024-03-03, 22:19:

For sure tracks will be damaged and probably the chip also.

not if you dont overdo temperature, you can also put additional good old leaded solder on all legs with regular soldering iron before you start, additional solder will help by providing extra thermal capacity so you have more time going around the chip with nozzle

Thank you very much.
In a few days I will remove the chip and post some photos of the disaster.
Regards

rasz_pl wrote on 2024-03-04, 05:17:

if they are already damaged there is no point worrying about ripping them off :) […]
Show full quote

jnemo2004 wrote on 2024-03-03, 22:19:

The problem is that some tracks are weaks or complety damages by the very bad first desoldering and later soldering.
Probably after desoldering many tracks will be full damaged and some pins very close to broken.

if they are already damaged there is no point worrying about ripping them off 😀

jnemo2004 wrote on 2024-03-03, 22:19:

I attach a picture of my hot air gun.

typical "858" with new controller, good enough for older stuff

jnemo2004 wrote on 2024-03-03, 22:19:

I have bad experience with old motherboards. With the hot air the inner layers of ground (and maybe other +5v) make a bubble that is not a risk for the motherboard funcioning but the bubble bend the motherboard.

moisture inside pcb, you need to bake whole board before proceeding, 100-120C in the owed for at lest few hours, requires good thermal controlled owen otherwise all plastics might melt if it gets hotter

jnemo2004 wrote on 2024-03-03, 22:19:

I will protect the sorrounding components with ahesive silicon tape

use alu foil, or better yet thicker pieces of metal

jnemo2004 wrote on 2024-03-03, 22:19:

For sure tracks will be damaged and probably the chip also.

not if you dont overdo temperature, you can also put additional good old leaded solder on all legs with regular soldering iron before you start, additional solder will help by providing extra thermal capacity so you have more time going around the chip with nozzle

Hello, good morning (in Zaragoza).
I have removed the IC W83C201P. To remove components I do it from the back of the motherboard.
I think it is very fast and there is little risk of damaging components although it is the board that suffers.
The typical bubble has been made but it is not very big since it has many metal inserts in that area.
A diode has also been desoldered.
I have used a hot air gun which is used to remove the old paint layer on the wood.
It works very well, 300/600ºC. I use 600ºC directly and in a few seconds the chip falls by itself.
I have no experience desoldering by applying heat to the IC pins.
I have seen that the two elements without connection, hole M and pin 11, should have been connected to each other but the track is cut.
Well, now I have to see if I am able to clean and restore that entire area and solder the IC. I don't think I'll be able to do it since I don't have enough experience, but I'll think about how to do it.
I will always put the results here whether they are positive or negative.
Rgards

What I'm thinking of doing is the following:
1.- Desolder all the surrounding components to work well.
2.- Sand the tracks so that the cut ones can be seen clearly.
3.- The tracks that are broken below the IC and are connected to a pin of the IC, I will join the track to the pin with fine cable. I will need to drill a hole in the plate to pass the cables from one side to the other. I don't think it's important to make the hole and just make sure there is no contact between the internal ground and positive plates.
4.- I think I don't have the means to do better.

dont drill any holes
thin strand of wire + nail polish is the way https://youtu.be/hJOcxf_xzHk?feature=shared&t=563 nail polish secures wire in place and insulates from accidental shorts
for corroded vias plug a wire thru and solder on both ends https://youtu.be/YGGyQ1RHEfo?feature=shared&t=734