• Please review our updated Terms and Rules here

Superbrain QD repair

All my oscilloscope probes are just pointy tips. I do have those mini claw things on all my logic probes however ( what are they called?) could probably use those?

WP_20190204_09_31_49_Pro_LI.jpg
 
Hah! Just looked at your stardot post - those are traces on a real, modern, trustworthy scope! I use mine more like a continuity test - if there is something more than a flat line on its tiny little screen, it 'means' something!

I will however check the pinout on the 8350 chip, attach my clips to the relevant pins and see what the old crt scope makes of it....
 

Attachments

  • WP_20190204_09_31_49_Pro_LI.jpg
    WP_20190204_09_31_49_Pro_LI.jpg
    89.9 KB · Views: 1
What does the head activity sound like? The SB drive makes a particular sequence of sounds when it boots. Hang on , I'll upload a video..
 
It only does it with your ROM image burned on to an EEPROM with your adapter. Not so with the Blank SB ROMs I have...……

 
Here: https://drive.google.com/open?id=15gRN-S0uT0ZaQdqhLbzWj7v-4vcxUEZI

This is the SB II booting on an HxC emulator. The display shows the track number. Listen to the clicking noises (the HxC is set up to do this each time the host machine changes the track) and match that with the track number. Now, on the board that gave drive activity with your multiplexed drive, listen to the drive. Does it sound similar (in terms of the number of head seeks and their "beat")? If so, it is highly likely the board is booting. Try pressing CRTL-G then RETURN. It should beep. Now try DIR then RETURN. you should hear drive activity.
 
JonB said:
Here: https://drive.google.com/open?id=15gRN-S0uT0ZaQdqhLbzWj7v-4vcxUEZI

This is the SB II booting on an HxC emulator. The display shows the track number. Listen to the clicking noises (the HxC is set up to do this each time the host machine changes the track) and match that with the track number. Now, on the board that gave drive activity with your multiplexed drive, listen to the drive. Does it sound similar (in terms of the number of head seeks and their "beat")? If so, it is highly likely the board is booting. Try pressing CRTL-G then RETURN. It should beep. Now try DIR then RETURN. you should hear drive activity.
Click to expand...

YEEESSSSS!!!! That's exactly what it sounds like!!!!!
 
No, I do not think it is booting having listened to your video. Because the beeper is on constantly, it tells me that the first part of the cold boot is failing. When the machine first powers on, before any CPU activity, the PPI chip's output turns the beeper on. The ROM copies part of itself to C000h then jumps to it, then turns the beeper off.

What happens when you run it with one of the other ROMs? If you hear a very short beep (I mean 100ms long, more like a click really) then you know the PPI is getting initialised. Use that ROM for now.
 
That beep only happened that one time -all the other times, no beep at all. Although if you say a quick beep means PPI is initialising correctly - I got no beep at all.

I had skype - it will take some time to dig it out. I don't do much with social media.
 
Ok, Wild goose chase - it does this drive activity even with a blank/no disk in the drive.

What a Percy!!

Sorry to waste your time :(
 
Last edited:
Ok - I just swapped to the drive that I wrote 'working 25.07.2017' in marker pen along the top

MX is off but now it still does this stepper motor thing when I power up? No disk in the drive. Drive wont spin now with MX off.
 
More tin pot theories - Z71 SN7406 Hex Inverter - all pins tested. Pin 10 says high or floating. That being the case, pin 11, the input to that particular inverter should be low, but it isn't! Its high. If pin 11 is being driven high by something else - then Pin 10 should be low, Motor On?


SN7406.JPG

 
Correct. But for some reason your drive is spinning? Disconnect the drive cable, then test Z71 11 & 10. 11 should always be high (it's pulled up by direct connection to the 5v rail). Thus pin 10 should always be low. I say disconnect the drive cable because you need to be sure the drive isn't pulling it high (i.e., "faulty").
 
Ok, will try in a min. Drive only spins with the MX switched on. With everything as it should be/nit messed with - I just get the drive light coming on, no motor.

Maybe worth the same test on SB2? The drive does spin on that one. If I have a good inverter, maybe worth swapping?
 
You must log in or register to reply here.
Back
Top