Author Topic: What more i can do?  (Read 36935 times)

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Online drhex

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Re: What more i can do?
« Reply #400 on: December 06, 2024, 06:05:24 pm »
Data and address are shared buses connected from the CPU to all chips providing/getting data. The CE signals (amongst others) control, who owns the bus at a given moment. So make sure that there is continuity on all lines between CPU and EPROMs/RAM at least.
 

Offline Harry_22

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Re: What more i can do?
« Reply #401 on: December 06, 2024, 07:53:22 pm »
What shall we do next?
Where are we heading towards, its all dark ahead, we need some candles or some lights.

You are not the only one with your problem. There is also my son this week.
Sorry for being off-topic, but I couldn’t even upgrade his computer with the new ROG STRIX Z790-H mother and 8GHz memory. The motherboard can update the BIOS without a processor and memory, do prestart diagnosis. The only thing it couldn’t do was simply come to an agreement with the monitor. It just  turned on the white VGA LED and remain silent.
Today we solved this problem by simply connecting another monitor for the first start. Everything works now but it cost me another set of DDR5 memory.
Anyway there are more benefits. Thanks to remote work my son can rebuild his own computer now.

You were also able to learn something, right?
 

Offline Harry_22

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Re: What more i can do?
« Reply #402 on: December 06, 2024, 09:35:43 pm »
Could you check that the address and data of the processor and EPROM match.
As you can see on the picture CPU address bus consist of two components: 30 address lines (A2-A31) and 4 byte enable lines (BE0#-BE3#)

I cannot understand why is start instruction fetching begins from 3FFF8H.


PS
I would like to say that it was not in vain that you film the data.
I found something.
« Last Edit: December 06, 2024, 10:18:46 pm by Harry_22 »
 

Online fzabkar

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Re: What more i can do?
« Reply #403 on: December 06, 2024, 10:22:02 pm »
The slow EPROM would at some time be unpacked into RAM, especially when MS-DOS boots. That necessitates remapping the address lines by the chipset. Perhaps you are seeing the result of remapping?
 

Offline asis

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Re: What more i can do?
« Reply #404 on: December 07, 2024, 09:20:03 am »
Hello,

In my practice, I once encountered a similar problem while repairing printing equipment
VEB Polygraph Buchbindereimaschinenwerke Leipzig -
VEM NUMERIK "KARL MARX" Karl-Marx-Stadt, a country that no longer exists - GDR.
In practice, I had to reverse engineer all the boards, including the six-layer CPU board (U880 - Z80).
EPROM was made on UV U2716 24 pieces (MC2716)
During the repair, dumps were taken from all EPROMs.
And, the programmer that I recommended to you (Advantech LabTool 48) allows you to do final verification of the EPROM contents, using a check when increasing and decreasing the power supply from the nominal value.
As it turned out, - a very effective verification method that identifies vulnerable UV ROM cells.

-

And so.

I would like to offer you a method that involves supplying additional power to the PCB in the +5V circuit with an acceptable excess of +5.5V, in parallel with the already present - from the standard PSU.
If, of course, you have a reliable laboratory power supply.
The goal is to provoke a change in the situation or reaction, including TTL and everything else.
In this case, you can manipulate the "virtual RESET button" that @Harry_22 talked about.
-
In fact, you do not risk anything if you do everything consciously and carefully.
If there is a result, then a further strategy can be developed.

@222Lab_Test222 I do not insist on anything.
It's up to you.

Good luck.
 

Offline Harry_22

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Re: What more i can do?
« Reply #405 on: December 07, 2024, 12:05:40 pm »
The slow EPROM would at some time be unpacked into RAM, especially when MS-DOS boots. That necessitates remapping the address lines by the chipset. Perhaps you are seeing the result of remapping?

May be. Then remapping must be done by Tornado-T chip.
But what is the point of placing EPROM between the 80486DX2 and the Tornado-T?
I would place Tornado-T close to CPU.

And, the programmer that I recommended to you (Advantech LabTool 48) allows you to do final verification of the EPROM contents, using a check when increasing and decreasing the power supply from the nominal value.
As it turned out, - a very effective verification method that identifies vulnerable UV ROM cells.

I would like to offer you a method that involves supplying additional power to the PCB in the +5V circuit with an acceptable excess of +5.5V, in parallel with the already present - from the standard PSU.


We need to work out your version with undervoltage.
It is clearly seen from old traces that unworking machine has a bit lower power supply. Please see the attached picture).

@222Lab_Test222,
please draw us a wiring diagram for LT1085 and the trimmer. What voltages are coming to the board CN10?

PS
Unfortunately you have attached data only from High EPROM. I confused them with Low ones and was already glad that I had found the reason.
Could you attach them as well as missed D3 for working board.
« Last Edit: December 07, 2024, 12:19:30 pm by Harry_22 »
 

Online drhex

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Re: What more i can do?
« Reply #406 on: December 08, 2024, 04:14:15 pm »
And maybe establish if address lines are remapped or on the bus.
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #407 on: December 08, 2024, 11:28:23 pm »

Could you attach them as well as missed D3 for working board.

 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #408 on: December 08, 2024, 11:34:54 pm »

Unfortunately you have attached data only from High EPROM. I confused them with Low ones and was already glad that I had found the reason.


Here,

 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #409 on: December 08, 2024, 11:38:06 pm »

What voltages are coming to the board CN10?

Here
 
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Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #410 on: December 08, 2024, 11:52:36 pm »
Here LT1587CT is used instead of LT1085.
Vin is 4.75V and Vout is 3.5V and adj with 2.3V.
More Images below
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #411 on: December 08, 2024, 11:54:36 pm »

I would like to offer you a method that involves supplying additional power to the PCB in the +5V circuit with an acceptable excess of +5.5V, in parallel with the already present - from the standard PSU.
If, of course, you have a reliable laboratory power supply.
The goal is to provoke a change in the situation or reaction, including TTL and everything else.

Clarify me more to it, How to provide more Voltages, is there any diagram?
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #412 on: December 09, 2024, 12:38:02 am »
Could you check that the address and data of the processor and EPROM match.
As you can see on the picture CPU address bus consist of two components: 30 address lines (A2-A31) and 4 byte enable lines (BE0#-BE3#)

I cannot understand why is start instruction fetching begins from 3FFF8H.

I do not see any sorting between them. The EPROM are connected to ICs and Tornado.
Check Reply #283
 

Offline Harry_22

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Re: What more i can do?
« Reply #413 on: December 09, 2024, 12:47:03 am »
Here LT1587CT is used instead of LT1085.
Vin is 4.75V and Vout is 3.5V and adj with 2.3V.
More Images below

Could you measure both Vout by multimeter on working and not working.
Also please measure +5volts at the same EPROM pins on both.
« Last Edit: December 09, 2024, 12:52:55 am by Harry_22 »
 

Offline asis

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Re: What more i can do?
« Reply #414 on: December 09, 2024, 01:42:54 am »
Hi,

1. Vin LT1587CT allows +7V and probably the Vin circuit is connected to the +5V bus (check this).
2. The Adjustable resistor (varactor) is a weak point, because over time, its carbon layer has the property of losing its stability.

(This often manifests itself in audio devices, causing a characteristic crackle when adjusting the volume).

LT1587CT, in fact, is the power supply of the processor core, and, depending on the tasks, the dynamic range of CPU consumption can vary greatly.
Moreover, the varactor itself is installed in the OUT circuit.
For prevention purposes - visually fix (mark) the position of the adjustment slot or measure the resistance of the middle point relative to the extreme terminals, so that later it can be returned to the nominal value (!) and turn the slider from edge to edge several times (you can use alcohol).
-
Check the pulsation level of all voltages by setting the scope input to the closed mode (i.e. with a capacitor) and increasing the input sensitivity.
 

Offline asis

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Re: What more i can do?
« Reply #415 on: December 09, 2024, 03:00:11 am »

Clarify me more to it, How to provide more Voltages, is there any diagram?
[/quote]

The idea is simple.

If you have a LAB PSU with the ability to set the output voltage >/= +5.5V and the output current, about - 0.5~1A, just connect GND and +5.5V to the PCB power connector, which is already powered by a standard power source.
Connecting two sources with the same or close voltage values ​​in parallel should not cause anything fatal.
You can connect the LAB PSU through a suitable diode.
The goal is to raise the voltage of the common +5V bus and see how the device reacts using the "RESET button".
During the experiment, you can disconnect and connect the LAB PSU.
-
The +/- 12V voltages are probably used only to power the RS232 IC19/ IC20/ IC79 (GD75232D) and RS485/422 IC81 (SN751177N) drivers.
Check it out.
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #416 on: December 09, 2024, 06:34:26 am »
Hi,

1. Vin LT1587CT allows +7V and probably the Vin circuit is connected to the +5V bus (check this).
2. The Adjustable resistor (varactor) is a weak point, because over time, its carbon layer has the property of losing its stability.

I install a new LT11587CT couple of weeks ago so its good..
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #417 on: December 09, 2024, 06:42:21 am »

If you have a LAB PSU with the ability to set the output voltage >/= +5.5V and the output current, about - 0.5~1A, just connect GND and +5.5V to the PCB power connector, which is already powered by a standard power source.
Connecting two sources with the same or close voltage values ​​in parallel should not cause anything fatal.
You can connect the LAB PSU through a suitable diode.


I have 2 PSU..
CKT like this is good? Whats the didode requirement?
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #418 on: December 09, 2024, 07:07:32 am »

Could you measure both Vout by multimeter on working and not working.
Also please measure +5volts at the same EPROM pins on both.
Working Board
-Vout 3.57V
-EPROM High 5V
-EPROM Low 5V

Non Working Board
-Vout 3.61V
-EPROM High 5V
-EPROM Low 5V



« Last Edit: December 09, 2024, 07:09:12 am by 222Lab_Test222 »
 

Offline Harry_22

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Re: What more i can do?
« Reply #419 on: December 09, 2024, 07:11:38 am »
And 5.00 ?
Reduce 3.61 up to 3.45
 

Offline asis

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Re: What more i can do?
« Reply #420 on: December 09, 2024, 10:37:38 am »
here
-

Could you measure both Vout by multimeter on working and not working.
Also please measure +5volts at the same EPROM pins on both.
Working Board
-Vout 3.57V

Non Working Board
-Vout 3.61V
[/quote]
=
The CPU has no dynamic load, so Vout is 3.61V (it consumes almost nothing).
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #421 on: December 09, 2024, 11:07:49 am »
And 5.00 ?
Reduce 3.61 up to 3.45
I would say 4.9 and some points
How to reduce it?
If i reduce 5V to around 4.5 it beeps in working board, the minimum volt is 4.6.
« Last Edit: December 09, 2024, 11:11:49 am by 222Lab_Test222 »
 

Offline Harry_22

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Re: What more i can do?
« Reply #422 on: December 09, 2024, 09:19:26 pm »
So I have completed a comparative analysis of the Addresses supplied to the EEPROM and the Data read.
On the faulty board identical Chip Select, Read and Address signals are traced within eight clock cycles but the output data is different.

On the working machine the data sequence is ODE9h, 00F8h, 0000h, 0000h...
On the not-working is 0D0Dh, 0000h, 0000h...

Colleagues, what are your thoughts?
 
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Offline Harry_22

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Re: What more i can do?
« Reply #423 on: December 10, 2024, 06:41:19 pm »
Remove IC16 (Low EPROM) and look the signals on the data bus.
Please post here the tracks D0, D2 and D5.

We check for the presence of extraneous signals on the data bus freed from IC16.

PS
Try diagnosing another board using our experience.
« Last Edit: December 10, 2024, 08:50:14 pm by Harry_22 »
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #424 on: December 11, 2024, 02:10:26 am »
Remove IC16 (Low EPROM) and look the signals on the data bus.
Please post here the tracks D0, D2 and D5.

We check for the presence of extraneous signals on the data bus freed from IC16.

PS
Try diagnosing another board using our experience.

IC16 removed, here are outputs of DO D2 and D5. Its the working board.
 


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