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What more i can do?
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222Lab_Test222:
Here LT1587CT is used instead of LT1085.
Vin is 4.75V and Vout is 3.5V and adj with 2.3V.
More Images below
222Lab_Test222:

--- Quote from: asis on December 07, 2024, 09:20:03 am ---
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.


--- End quote ---
Clarify me more to it, How to provide more Voltages, is there any diagram?
222Lab_Test222:

--- Quote from: Harry_22 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.


--- End quote ---
I do not see any sorting between them. The EPROM are connected to ICs and Tornado.
Check Reply #283
Harry_22:

--- Quote from: 222Lab_Test222 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

--- End quote ---

Could you measure both Vout by multimeter on working and not working.
Also please measure +5volts at the same EPROM pins on both.
asis:
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.
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