Search found 5134 matches

by exxos
Mon Oct 02, 2017 3:16 pm
Forum: HARDWARE DISCUSSIONS
Topic: Switch between 4mb and 1Mb on STe
Replies: 5
Views: 743

Re: Switch between 4mb and 1Mb on STe

MMU -> R454 -> simm normally.

MMU -> nothing (lift one end of R454)
Simm side of R454 connect to gnd.



Looks like R454 anyway...
20171002151429.jpg
20171002151429.jpg (6.86 KiB) Viewed 722 times
by exxos
Mon Oct 02, 2017 12:57 pm
Forum: EVERYTHING ELSE
Topic: Boosting the Mega ST motherboard
Replies: 11
Views: 2555

Re: Boosting the Mega ST motherboard

LS being slower acts as a noise filter. F series is fast enough to react to the noise and will cause glitches and oscillations.
by exxos
Mon Oct 02, 2017 8:18 am
Forum: HARDWARE DISCUSSIONS
Topic: Switch between 4mb and 1Mb on STe
Replies: 5
Views: 743

Re: Switch between 4mb and 1Mb on STe

Isolate MAD9 and GND the simm side pin.
by exxos
Sun Oct 01, 2017 11:08 pm
Forum: HARDWARE ISSUES
Topic: STE video synchronisation problem
Replies: 35
Views: 3710

Re: STE video synchronisation problem

I thought that too and have even bought more MC1377s, but if I just measure pin 9 on socket without the IC, then I should see something like >5-6VDC, but I see only this: I would confirm your IC's are "blown" on your other machine before anything else.. or try a brand new IC (never before being use...
by exxos
Sun Oct 01, 2017 10:57 pm
Forum: HARDWARE ISSUES
Topic: STE video synchronisation problem
Replies: 35
Views: 3710

Re: STE video synchronisation problem

Hold up.. SDS00008.jpg If that is 6.7V there, then the IC is getting a external DC bias somewhere. Like Q404 C-B short.. feeding 12V into 1377 pin 9... I think you need to try one of the IC's like you are using now in your working ST and see if you have composite there.. I have a feeling now that ev...
by exxos
Sun Oct 01, 2017 10:48 pm
Forum: HARDWARE ISSUES
Topic: STE video synchronisation problem
Replies: 35
Views: 3710

Re: STE video synchronisation problem

Number_Nine wrote:
Sun Oct 01, 2017 10:44 pm
But only this on pin 9:
SDS00008.jpg
are you using x10 probe and 100mV/DIV on your scope ? If so , try 10mV and see if you can see anything..

I also assume you have pin 9 still bent upwards out of the socket ?
by exxos
Sun Oct 01, 2017 10:33 pm
Forum: HARDWARE ISSUES
Topic: STE video synchronisation problem
Replies: 35
Views: 3710

Re: STE video synchronisation problem

I see it, but it's very unstable and jerky. Is it fairly stable on your machine? It's not great no. Though the scope will be loading the signal and causing some issues anyway. So I think your input to pin 17 is just fine by the looks for it. .. As for pin 9, I see this... again with 100mV/DIV X10 p...
by exxos
Sun Oct 01, 2017 10:18 pm
Forum: HARDWARE ISSUES
Topic: STE video synchronisation problem
Replies: 35
Views: 3710

Re: STE video synchronisation problem

Number_Nine wrote:
Sun Oct 01, 2017 10:09 pm
Output C427:
You need to be in x10 mode with your probe, and 100mV/div on scope...

c3.png
c3.png (3.42 KiB) Viewed 975 times
I don't think you will see it with the modes you are using.
by exxos
Sun Oct 01, 2017 10:07 pm
Forum: HARDWARE ISSUES
Topic: STE video synchronisation problem
Replies: 35
Views: 3710

Re: STE video synchronisation problem

Yep, no signal, I was blaming that from the beginning, but then I've checked on a good Atari and that was the same flat signal. Both input and output of R469 have clock, output has it much weaker (~300mV), though, regardless of the IC side soldered or desoldered. On schematics R469 is 5.0K, but on ...
by exxos
Sun Oct 01, 2017 9:53 pm
Forum: HARDWARE ISSUES
Topic: STE video synchronisation problem
Replies: 35
Views: 3710

Re: STE video synchronisation problem

This is what I get "left side input" of R469..
c2.png
c2.png (3.85 KiB) Viewed 978 times
3V p-p. Bias 0v.

Output side of R469 (IC side).
c1.png
c1.png (3.9 KiB) Viewed 978 times
about 0.2V p-p (200mV) with 0.4V (400mv ). DC offset.