Electronics > Repair

What more i can do?

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asis:

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.

222Lab_Test222:

--- Quote from: asis 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.


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

222Lab_Test222:

--- Quote from: asis on December 09, 2024, 03:00:11 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.


--- End quote ---

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

222Lab_Test222:

--- Quote from: Harry_22 on December 09, 2024, 12:47:03 am ---
Could you measure both Vout by multimeter on working and not working.
Also please measure +5volts at the same EPROM pins on both.

--- End quote ---
Working Board
-Vout 3.57V
-EPROM High 5V
-EPROM Low 5V

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



Harry_22:
And 5.00 ?
Reduce 3.61 up to 3.45

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