Electronics > Repair
ADVANTEST R9211B
<< < (38/39) > >>
stfjohn:
Also pin 12 of HC148 is only connected to R35 and nothing else.
I will try to replace HC148, but I have little hope...
m k:
Have you checked pin 13 connection to GND, is it shorted?

Take a picture when it's off, then you never forget what is under it.

Pin 12 as a spare also is a good sign.
It sort of strengthens the probability that pin 13 really is a spare and that turns it probable that HC148 is the problem.

Interrupt level we have means that pin 13 is low, being pulled up and nothing more means it permanently is not.

The I/O map we have, with very old 8245B CRTC controller indicates that the PCB is a new design.
So HC148 just missing few traces from initial design is very plausible.

So only practical reason why the problem is not HC148 is that there is a secret trace to somewhere or the problem is the other end of interrupt lines, the CPU.
If you like you can test CPU by cutting those legs near PCB level or make them float otherwise.
You can also lift HC148 pins 7 and 9, then only interrupt level 4 is possible, it should make a difference if the chip is a problem.
stfjohn:
I disconnected pins 7 and 9 of the HC148. I disconnected pins 24 and 25 of the CPU. I reassembled the device. The result is that the self test starts (Photo 1), but, at the end, the same message reappears (Photo 2). Then I re-soldered pins 24 and 25 of the CPU, leaving pins 7 and 9 of the HC148 disconnected: the result is that, once the self test is finished, it tells me "all pass", but, immediately after, the message in photo no. 3 appears. I tried to disconnect the CD player, but nothing changes.
m k:
First and second pictures mean that interrupt Level is random, CPU pins 25 and 24 are off.
So you were lucky that you got the result you got, something good for a change.

When CPU pins are back and HC148 pins off only interrupt level 4 line is active, IPL2 pin 23.

Last picture, something prevents random interrupts and self test can continue.
(when TTL output drives CMOS input it may be necessary to use a pull-up resistor, TTL high is not enough for CMOS)
Then finally normal operation tries to start but fails.

Assuming
'code = 8' privilege violation
'pc' program counter
'sr' status register
'usp' user stack pointer
'D' data
'C' code

Privilege violation, software does something it is not allowed to do.
It can be either way, disk access creates a wrong situation or something else creates a false disk situation.

When HC148 pins are off and interrupt level is less than 4 nothing happens, all CPU side pins stay up.
When interrupt level is higher than 3 the result is level 4, the only active line goes down.
Fingers crossed that HC148 is the only fault.
stfjohn:
I ordered the HC148 chip: as soon as it arrives, I will disassemble everything again, replace it, and see what happens. In the meantime, thanks for your precious and competent availability.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod