Nice 40MHz grey top fasmath.

mkarcher wrote on 2022-08-31, 18:52:

You need to find out where the power is interrupted. You need to understand that your mainboard consists of four layers of trace […]
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biessea wrote on 2022-08-31, 17:29:

Thanks a lot, I am thinking about that, the keyboard has no power. And problably mess around the motherboard.
How can I fix if it has no power?

You need to find out where the power is interrupted. You need to understand that your mainboard consists of four layers of traces. You can easily see the traces on the top and on the bottom of the board. The two inner layers actually are power planes. They are solid areas of copper with small holes in them. One of the inner layers is connected to ground and the other one is connected to +5V. As you get beeping, +5V and ground are definitely getting around on the board, so the power planes themselves seem to be powered.

For the keyboard supply, the outer edge of the wire labelled "F1" is connected to the +5V plane. On the back of the board, a trace from other end of F1 runs to one end of L1, and the other end of L1 is connected to one pin of the keyboard connector. Also, the end of L3 that is farther away from the keyboard connector is connected to the ground plane. The end of L3 that is closer to the keyboard connector is connected to a pin of the keyboard connector via a trace on the top of the board. That trace might be broken right next to the keyboard connector. You need to check continuity between +5V on the power plane (e.g. a +5V connector of the AT power supply) and the pin and the keyboard jack that should carry +5V. You also need to check continuity between GND (e.g. one of the center pins of the AT power supply connector) and the keyboard jack pin that is connected to L3. If you don't have a tool to check continuity, go buy any multimeter. While there are a lot of deficiencies on budget ($5-$10) multimeters, they generally work for continuity tests and probing around in low voltage circuits like computers.

If you find the place where the power delivery is interrupted, you need to fix the trace or solder a wire to the board as replacement for the broken trace.

Here I am! With big news I suppose!

The keyboard connector is OK, no problem to the trace.

I read with my father this message and we slowly understand it all. It was very exciting understand and test. We have continuity in all the traces.

Then my father said me to connect the board to the power supply and give it power and test with the multimeter the keyboard connector if the 5v was effective present: and here we are, 5.00V perfect at those pins!
We saw better and at begin when I give power the led in the keyboard blink. Last time probably we didn't see it cause it is so fast.

I attach the photo of the measurement of 5.00V.

For the crystal oscillator I can say the 40MHZ is present yes, as you can see in the photos in the first post, and the other one is labelled 50/66MHZ. And it's empty.

Anyway, after about 30 seconds the PC speaker always beep repeating until I power off the mobo.

Can this be good for any other advice?

PS: yes I know, I really need a VGA card now, perhaps I could have the signal and I have to see what it's write in the monitor.

PPS: We checked the continuity from the power supply connector to the 80MHZ crystal oscillator. Yes, a pin have the positive and another pin has the GROUND.

biessea wrote on 2022-08-31, 21:34:

PS: I am buying a VGA ISA card.

If the market didn't change a lot the last days, getting an ET4000AX card at 30 bucks (€ or USD) in the USA or (western) Europe is a great price. If you are located in that region or a region with similar pricing, and you need an ISA VGA card, go get it
[/quote]

Ok, just to update you about the video card.

I just paid the Et4000ax, It will arrive probably tuesday.

If you have any ideas or advice meanwhile I'm here to listen you.

Thanks

Until you plug the video card it will be difficult to make next steps.
Once at that point:
Getting a picture from not getting a picture will make all the difference. Impossible to tell what the outcome of that first check will be.
If no picture - remove battery, L2 cache, FPU and leave only the first 4 SIMM modules. Basically strip the motherboard from as much components as possible in case one of them is the problem.
If still no picture - swap the first 4 SIMM modules with the second one to minimize chance of failing RAM chips.

The fact that you are getting beeps is a good sign.
It means that mobo (at least its vital components), BIOS and CPU are functional.

pshipkov wrote on 2022-09-02, 16:20:

If no picture - remove battery, L2 cache, FPU and leave only the first 4 SIMM modules. Basically strip the motherboard from as much components as possible in case one of them is the problem.
If still no picture - swap the first 4 SIMM modules with the second one to minimize chance of failing RAM chips.

I don't expect an AMI-based board to do a continous beep if all that is missing is a video card. The procedure suggested is not a bad one, but I would start with a slightly different approach: Try to remove all RAM modules first. Leave the cache chips and FPU as they are now. The expected symptom of a standard AMI BIOS when there is no RAM is two or three short distinguished beeps after a couple of seconds at most. Not a long continous beep after 30 seconds. Test whether you get a valid "no RAM" beep.

If nothing changes, there are different possiblities. Maybe the support for your mainboard chipset placed a "RAM intialization" step before where the BIOS tries to detect the size of SIMMs installed and initializes the chipset before the standard AMI basic RAM test. As this is a custom step provided by the chipset manufacturer, symptoms on failure vary, and a single continous beep is possible. On the other hand, maybe the beep is not supposed to be indefinitely long. This might indicate problems with the timing. The timing of many steps in the POST is often performed by referencing a clock in the keyboard controller. There is a status bit in the keyboard controller that toggles at around 10kHz even without any initialization by the processor. If either the keyboard controller doesn't run or the host processor can't access the keyboard controller correctly, an endless beep might just be the computer hanging while it tries to make a short beep.

So if anything changes if you remove RAM, we know that the mainboard is actually able to make use of the RAM once it is installed, which is in itself a great thing to know.

I was talking a lot about how the keyboard controller provides a clock that is used by the BIOS. The keyboard controller is also used in various parts of the POST very early when you turn the computer. I noticed in the picture with the AT supply and the keyboard connected that cleaning the board after the vinegar therapy seems to have left some dirt at the pins of the keyboard controller (but that part isn't that clear on the picture). If there is grime near the pins of the socket of the keyboard connector left, give it a good wash. Water and possibly a little bit of soap should be good enough.

pshipkov wrote on 2022-09-02, 16:20:

Until you plug the video card it will be difficult to make next steps. Once at that point: Getting a picture from not getting a […]
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Until you plug the video card it will be difficult to make next steps.
Once at that point:
Getting a picture from not getting a picture will make all the difference. Impossible to tell what the outcome of that first check will be.
If no picture - remove battery, L2 cache, FPU and leave only the first 4 SIMM modules. Basically strip the motherboard from as much components as possible in case one of them is the problem.
If still no picture - swap the first 4 SIMM modules with the second one to minimize chance of failing RAM chips.

The fact that you are getting beeps is a good sign.
It means that mobo (at least its vital components), BIOS and CPU are functional.

Super, probably tuesday will finally arrive that nice ISA VGA and I will make some trying. And I let you all know, thanks a lot for the partecipation.

We all love old computer I know.

mkarcher wrote on 2022-09-02, 18:46:

I don't expect an AMI-based board to do a continous beep if all that is missing is a video card. The procedure suggested is not […]
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pshipkov wrote on 2022-09-02, 16:20:

If no picture - remove battery, L2 cache, FPU and leave only the first 4 SIMM modules. Basically strip the motherboard from as much components as possible in case one of them is the problem.
If still no picture - swap the first 4 SIMM modules with the second one to minimize chance of failing RAM chips.

I don't expect an AMI-based board to do a continous beep if all that is missing is a video card. The procedure suggested is not a bad one, but I would start with a slightly different approach: Try to remove all RAM modules first. Leave the cache chips and FPU as they are now. The expected symptom of a standard AMI BIOS when there is no RAM is two or three short distinguished beeps after a couple of seconds at most. Not a long continous beep after 30 seconds. Test whether you get a valid "no RAM" beep.

If nothing changes, there are different possiblities. Maybe the support for your mainboard chipset placed a "RAM intialization" step before where the BIOS tries to detect the size of SIMMs installed and initializes the chipset before the standard AMI basic RAM test. As this is a custom step provided by the chipset manufacturer, symptoms on failure vary, and a single continous beep is possible. On the other hand, maybe the beep is not supposed to be indefinitely long. This might indicate problems with the timing. The timing of many steps in the POST is often performed by referencing a clock in the keyboard controller. There is a status bit in the keyboard controller that toggles at around 10kHz even without any initialization by the processor. If either the keyboard controller doesn't run or the host processor can't access the keyboard controller correctly, an endless beep might just be the computer hanging while it tries to make a short beep.

So if anything changes if you remove RAM, we know that the mainboard is actually able to make use of the RAM once it is installed, which is in itself a great thing to know.

I was talking a lot about how the keyboard controller provides a clock that is used by the BIOS. The keyboard controller is also used in various parts of the POST very early when you turn the computer. I noticed in the picture with the AT supply and the keyboard connected that cleaning the board after the vinegar therapy seems to have left some dirt at the pins of the keyboard controller (but that part isn't that clear on the picture). If there is grime near the pins of the socket of the keyboard connector left, give it a good wash. Water and possibly a little bit of soap should be good enough.

My dear, the RAM proof I have already done.

Two days ago I tried removing ALL RAM modules, and the Speaker beeped with a different tone and if I rememeber correcty, three beeps.
I put only one module, and the same happens.
With two modules at least the situation returned the actual, after about 30 secs PC Speaker emits beeps until I power off the system. BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP Etcetera.

PS: not a single continuos bip, lot of high tones "bip" until I remove power. Continuos meant that it will bip forever until I power off all the system.

biessea wrote on 2022-09-04, 08:39:

Two days ago I tried removing ALL RAM modules, and the Speaker beeped with a different tone and if I rememeber correcty, three beeps.

Great. So the computer works fine at least until it makes sure that at least 64KB of RAM are kind of working.

biessea wrote on 2022-09-04, 08:39:

I put only one module, and the same happens.

That's expected. The RAM modules need to be inserted in chunks of four, because the 386DX needs to get 32 bits at once, and one module only provides 8 bits. So they use four modules at the same time, each providing 8 bits for a total of 32 bits. A set of four modules is called a bank in this system.

biessea wrote on 2022-09-04, 08:39:

With two modules at least the situation returned the actual, after about 30 secs PC Speaker emits beeps until I power off the system. BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP Etcetera.

PS: not a single continuos bip, lot of high tones "bip" until I remove power. Continuos meant that it will bip forever until I power off all the system.

Oh, I misunderstood that. Symptoms like that are typical for RAM problems. With just two modules, you do not get any reliably working memory, but it is quite possible that the BIOS "forgets" to check all 32 bits and passes the early "Is there at least 64KB RAM" check, if only the low 16 bits are working. Getting the same symptom with two modules (is expected to fail quite early) and four modules (is expected to work until the missing graphics card is noticed) points to something more involved with the memory seems to be failing.

As I see, you have two sets of 4 modules each. Possibly one of the modules is damaged, so you should try with one set or the other set of modules installed in the sockets for bank 0. If you get the 8-beep signal, that set of modules works mostly fine and you need the graphics card to continue. If you keep getting the continous beeps, there likely is another problem on your board.

I noticed that the 74F245 chip (U10) right next to the battery is involved in generating the address signals for the RAM. Anything so close to the leaked battery is kind of suspect. The outputs of that chip are sent to the address signals A0-A7 of the SIMM slots via 33 Ohm resistors. I recommend you to check "continuity" (i.e. expected 33 Ohm resistance, which might cause the continuity tester to not beep) between the following pins to make sure that none of the addressing signals are missing:

• U10, pin 10 to SIMM slots, pin 15 (A7)
• U10, pin 11 to SIMM slots, pin 14 (A6)
• U10, pin 12 to SIMM slots, pin 12 (A5)
• U10, pin 13 to SIMM slots, pin 11 (A4)
• U10, pin 14 to SIMM slots, pin 8 (A3)
• U10, pin 15 to SIMM slots, pin 7 (A2)
• U10, pin 16 to SIMM slots, pin 5 (A1)
• U10, pin 17 to SIMM slots, pin 4 (A0)

As a secondary test, whether all address pins are actually connected to the silicon inside the chip (the corrive battery electrolyte might have damaged U10 internally), put your meter into "diode check" mode, connect the black lead to +5V and probe all the address pins I mentioned with the red lead. You should read approximately the same number on the meter for 8 pins. Repeat the procedure with the read lead connected to ground and probing the address pins with the black lead. Again, the number should be the same for all 8 pins. It might be that one of the checks provides "OL" or "1" for all of the pins (i.e. "no conductivity"). If it happens for all of the 8 pins, this is fine, too.

mkarcher wrote on 2022-09-04, 10:07:

Great. So the computer works fine at least until it makes sure that at least 64KB of RAM are kind of working. […]
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biessea wrote on 2022-09-04, 08:39:

Two days ago I tried removing ALL RAM modules, and the Speaker beeped with a different tone and if I rememeber correcty, three beeps.

Great. So the computer works fine at least until it makes sure that at least 64KB of RAM are kind of working.

biessea wrote on 2022-09-04, 08:39:

I put only one module, and the same happens.

That's expected. The RAM modules need to be inserted in chunks of four, because the 386DX needs to get 32 bits at once, and one module only provides 8 bits. So they use four modules at the same time, each providing 8 bits for a total of 32 bits. A set of four modules is called a bank in this system.

biessea wrote on 2022-09-04, 08:39:

With two modules at least the situation returned the actual, after about 30 secs PC Speaker emits beeps until I power off the system. BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP-BIP Etcetera.

PS: not a single continuos bip, lot of high tones "bip" until I remove power. Continuos meant that it will bip forever until I power off all the system.

Oh, I misunderstood that. Symptoms like that are typical for RAM problems. With just two modules, you do not get any reliably working memory, but it is quite possible that the BIOS "forgets" to check all 32 bits and passes the early "Is there at least 64KB RAM" check, if only the low 16 bits are working. Getting the same symptom with two modules (is expected to fail quite early) and four modules (is expected to work until the missing graphics card is noticed) points to something more involved with the memory seems to be failing.

As I see, you have two sets of 4 modules each. Possibly one of the modules is damaged, so you should try with one set or the other set of modules installed in the sockets for bank 0. If you get the 8-beep signal, that set of modules works mostly fine and you need the graphics card to continue. If you keep getting the continous beeps, there likely is another problem on your board.

I noticed that the 74F245 chip (U10) right next to the battery is involved in generating the address signals for the RAM. Anything so close to the leaked battery is kind of suspect. The outputs of that chip are sent to the address signals A0-A7 of the SIMM slots via 33 Ohm resistors. I recommend you to check "continuity" (i.e. expected 33 Ohm resistance, which might cause the continuity tester to not beep) between the following pins to make sure that none of the addressing signals are missing:

• U10, pin 10 to SIMM slots, pin 15 (A7)
• U10, pin 11 to SIMM slots, pin 14 (A6)
• U10, pin 12 to SIMM slots, pin 12 (A5)
• U10, pin 13 to SIMM slots, pin 11 (A4)
• U10, pin 14 to SIMM slots, pin 8 (A3)
• U10, pin 15 to SIMM slots, pin 7 (A2)
• U10, pin 16 to SIMM slots, pin 5 (A1)
• U10, pin 17 to SIMM slots, pin 4 (A0)

As a secondary test, whether all address pins are actually connected to the silicon inside the chip (the corrive battery electrolyte might have damaged U10 internally), put your meter into "diode check" mode, connect the black lead to +5V and probe all the address pins I mentioned with the red lead. You should read approximately the same number on the meter for 8 pins. Repeat the procedure with the read lead connected to ground and probing the address pins with the black lead. Again, the number should be the same for all 8 pins. It might be that one of the checks provides "OL" or "1" for all of the pins (i.e. "no conductivity"). If it happens for all of the 8 pins, this is fine, too.

Oh my God, ok I will do that. I hope to have understand good, I will read lot of times, english for me is not my mother language.

Anyway I try this now, without power I think isn't it?

Thanks a lot

biessea wrote on 2022-09-05, 12:29:

mkarcher wrote on 2022-09-04, 10:07:

I noticed that the 74F245 chip (U10) right next to the battery is involved in generating the address signals for the RAM. Anythi […]
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I noticed that the 74F245 chip (U10) right next to the battery is involved in generating the address signals for the RAM. Anything so close to the leaked battery is kind of suspect. The outputs of that chip are sent to the address signals A0-A7 of the SIMM slots via 33 Ohm resistors. I recommend you to check "continuity" (i.e. expected 33 Ohm resistance, which might cause the continuity tester to not beep) between the following pins to make sure that none of the addressing signals are missing:

• U10, pin 10 to SIMM slots, pin 15 (A7)
• U10, pin 11 to SIMM slots, pin 14 (A6)
• U10, pin 12 to SIMM slots, pin 12 (A5)
• U10, pin 13 to SIMM slots, pin 11 (A4)
• U10, pin 14 to SIMM slots, pin 8 (A3)
• U10, pin 15 to SIMM slots, pin 7 (A2)
• U10, pin 16 to SIMM slots, pin 5 (A1)
• U10, pin 17 to SIMM slots, pin 4 (A0)

As a secondary test, whether all address pins are actually connected to the silicon inside the chip (the corrive battery electrolyte might have damaged U10 internally), put your meter into "diode check" mode, connect the black lead to +5V and probe all the address pins I mentioned with the red lead. You should read approximately the same number on the meter for 8 pins. Repeat the procedure with the read lead connected to ground and probing the address pins with the black lead. Again, the number should be the same for all 8 pins. It might be that one of the checks provides "OL" or "1" for all of the pins (i.e. "no conductivity"). If it happens for all of the 8 pins, this is fine, too.

Oh my God, ok I will do that. I hope to have understand good, I will read lot of times, english for me is not my mother language.

Anyway I try this now, without power I think isn't it?

Yes. You perform voltage and current measurements when the circuit is powered on, but you use resistance, diode check and continuity check when power is off.

mkarcher wrote on 2022-09-05, 12:34:

biessea wrote on 2022-09-05, 12:29:

mkarcher wrote on 2022-09-04, 10:07:

I noticed that the 74F245 chip (U10) right next to the battery is involved in generating the address signals for the RAM. Anythi […]
Show full quote

I noticed that the 74F245 chip (U10) right next to the battery is involved in generating the address signals for the RAM. Anything so close to the leaked battery is kind of suspect. The outputs of that chip are sent to the address signals A0-A7 of the SIMM slots via 33 Ohm resistors. I recommend you to check "continuity" (i.e. expected 33 Ohm resistance, which might cause the continuity tester to not beep) between the following pins to make sure that none of the addressing signals are missing:

• U10, pin 10 to SIMM slots, pin 15 (A7)
• U10, pin 11 to SIMM slots, pin 14 (A6)
• U10, pin 12 to SIMM slots, pin 12 (A5)
• U10, pin 13 to SIMM slots, pin 11 (A4)
• U10, pin 14 to SIMM slots, pin 8 (A3)
• U10, pin 15 to SIMM slots, pin 7 (A2)
• U10, pin 16 to SIMM slots, pin 5 (A1)
• U10, pin 17 to SIMM slots, pin 4 (A0)

As a secondary test, whether all address pins are actually connected to the silicon inside the chip (the corrive battery electrolyte might have damaged U10 internally), put your meter into "diode check" mode, connect the black lead to +5V and probe all the address pins I mentioned with the red lead. You should read approximately the same number on the meter for 8 pins. Repeat the procedure with the read lead connected to ground and probing the address pins with the black lead. Again, the number should be the same for all 8 pins. It might be that one of the checks provides "OL" or "1" for all of the pins (i.e. "no conductivity"). If it happens for all of the 8 pins, this is fine, too.

Oh my God, ok I will do that. I hope to have understand good, I will read lot of times, english for me is not my mother language.

Anyway I try this now, without power I think isn't it?

Yes. You perform voltage and current measurements when the circuit is powered on, but you use resistance, diode check and continuity check when power is off.

Please, I read hundres of times but here I am with my multimeter and don't sure to understand what to have to measure. I begin with measure continuity between chip u10 pins, but I understood I was wrong.
I think you want to me that I point a stick of the multimeter on the u10 chip and the another stick one the SIMM slots?
Please try to explain me better or in another way the procedure that I have to do, because I am not understanding, probably I lack a lot of Electronics knowledge, sorry.

But with you help I will try to understand and fibally solve this 386 motherboard situation.

Thanks, I here waiting.

I really don't understand where to put my multimeter sticks..

U10, pin 10 to SIMM slots, pin 15 (A7)
U10, pin 11 to SIMM slots, pin 14 (A6)
U10, pin 12 to SIMM slots, pin 12 (A5)
U10, pin 13 to SIMM slots, pin 11 (A4)
U10, pin 14 to SIMM slots, pin 8 (A3)
U10, pin 15 to SIMM slots, pin 7 (A2)
U10, pin 16 to SIMM slots, pin 5 (A1)
U10, pin 17 to SIMM slots, pin 4 (A0)

I cannot understand this scheme.

There are TWO commas, so I have to measure three point? U10 you mean the chip, yes, but which pin? What do you mean with a0-a7 inside the ()?
I am really not understanding, sorry.

biessea wrote on 2022-09-05, 16:14:

I really don't understand where to put my multimeter sticks.. […]
Show full quote

I really don't understand where to put my multimeter sticks..

U10, pin 10 to SIMM slots, pin 15 (A7)
U10, pin 11 to SIMM slots, pin 14 (A6)
U10, pin 12 to SIMM slots, pin 12 (A5)
U10, pin 13 to SIMM slots, pin 11 (A4)
U10, pin 14 to SIMM slots, pin 8 (A3)
U10, pin 15 to SIMM slots, pin 7 (A2)
U10, pin 16 to SIMM slots, pin 5 (A1)
U10, pin 17 to SIMM slots, pin 4 (A0)

I cannot understand this scheme.

There are TWO commas, so I have to measure three point? U10 you mean the chip, yes, but which pin? What do you mean with a0-a7 inside the ()?
I am really not understanding, sorry.

I use the comma to separate the component (chip, SIMM slot) from the pin number. "U10, pin 10" means "pin 10 of U10". I use the word "to" separate one point of the measurement to the other point of the measurement.

So you have to read the first line like: One probe of the meter to pin 10 of U10 (which is a chip near the keyboard connector). See https://en.wikipedia.org/wiki/Dual_in-line_pa … _lead_numbering on information on how to count the pins on a dual in-line package IC. The other probe to pin 15 of the SIMM slot. Pin 1 is next to the AT connector, Pin 30 is next to the cache RAM. Because of its function, pin 15 of the SIMM slot is called A7 (address bit number seven). Put your meter in the "Ohms" range (top position of the switch). It should read slightly above 33.0 for all 8 of these pairs.

Later where I suggested "diode check" mode, you put the switch in the same position, but then you push the yellow button two times, so a diode symbol appears in the multimeter screen.

I'm sorry but, how could be pin 10 the pin near the keyboard connector?

If we start counting pin from the little hole on the chip, the pin 10 is the last one near the resistor line and near the u11 right?

I put a photo of that.

Thanks for all this support.

Anyway I am having problems to understand.

I try to measure and have always a number of resistance of about 7 mega ohm. This is what multimeter says me. And expecially I have this measurement through various pins if I change pin of measurement on the RAM slots, for example if I point the stick to the pin 10 of the chip I can measure this 7 megaohm in the pin 15,in the pin 14,in the pin 13...how could it be?

Probably I am not understanding how to measure and I am wrong, I don't know how to do, please help.

Anyway I think this is the pdf datasheet of the octavial transceiver u10.

Can you see the pin number?

biessea wrote on 2022-09-06, 11:49:

I'm sorry but, how could be pin 10 the pin near the keyboard connector?

That's a misunderstanding. I didn't mean to say that pin 10 is near the keyboard connector. I did say that the complete chip is near the keyboard connector. Anyway, I marked the first three pairs you are supposed to test with different line colors. The two pins you should connect the probes to are marked by colored rectangles.

Ok, thanks to the image I understand better.

Anyway in the image you ask me to measure pin 11 on u10 to pin 15 on simm sockets. (not pin 10 to pin 15). Pin 10 on the chip u10 is GROUND.

Probably you made a little mistake on the scheme you gave me before.
Anyway measurement are successful, I read about 33ohm (only in the pin 4 I can read about 34ohm but I think is correct so.)

The strange thing is that I can confirm measurement only in the first FOUR Simm socket near the resistances, the four socket upper give me 0.0.

Is four simm socket gone?

Now I try measure diodes.

I am sorry, but for the diode test, where I put the black lead you said me on 5v?? Where is this 5v pin?

I have other updates, I try to explain me better as I can.

The ISA video card arrived today, but in sustance, nothing has changed.

But let explain with steps.

As I told you before the lower four slot of simm gave me correct measurement on multimeter, the four upper not, gave me ZERO.

Infact, when I populate the four lower slot system arrive to bip-bip-bip-bip-bip-bip-bip... Etcetera after about thirty seconds from my power on.
When I populate the four upper simm slot the pc speaker soon gave me Three low tone beep (ram problem). Probably the upper slot are gone, or the chip u10 is fault with addressing the upper four simm slot. Am I right?

Anyway I put the VGA on the ISA slot and I have no image at all. I tried to switch the video card in ALL ISA slot. Always the same result. No video signal.

I wait your answer to diode test, where I can take the 5v that you ask me.

Other ideas now?
I am fighting with a bigger things than me, but if you could help me further I will be so happy.

I'm here to test all you ask me.