STE video chip

[exxos]

wow these came fast! Hopefully I can draw my conclusions very shortly!

IMG_0242.JPG

[exxos]

The "S" types were 373, so can't test those :roll:

On with the LS374 tests..

ORIGINAL F374 D3 LOW LEVEL

ORIG_F.JPG

LS374 D3 LOW LEVEL

LS.JPG

So a overall voltage of 1.68V with the F374 against a 1.28V with the LS374.


Zooming in :


LS374 WITHOUT GND WIRE

WO.JPG

LS374 WITH GND WIRE

W.JPG

...And yes the images look almost identical..

I also did a average over 256 samples.


WITHOUT GND WIRE

IMG_0249.JPG

WITH GND WIRE

IMG_0250.JPG

Overall the peak voltages were actually worse with the ground wire. However you can also see there is periods of " quiet" as well.

In order not to confuse things any further (yeah right!) I tested with the CP line, and it is latching on the peaks and the quiet areas so I'm deeming it somewhat irrelevant.

IMG_0251.JPG

I have been flicking backwards and forwards with and without grounds and the overall "high spikes" seem basically the same with the LS374. There does seem to be a slight improvement with the " randomness" of the noise with the ground wire attached. In terms of audible clicks the LS374 solves it with or without the ground wire. Which is what I suspected anyway.

I also believe the F374 is aggravating the grounds inherently and is why it needs the additional ground wire to help it along. The LS does not really seem to care if the extra ground is there or not. But as I said many times, the LS chip is better suited for noisy environments. It is likely not spiking the ground as much is why the additional wire makes little difference.

The bottom line ?

Overall it is just a case of noise on the system as per usual. These machines were barely working out of the factory and age is certainly not helping things. As I said for many years, faults on these machines are just showing up faster than I can investigate and diagnose. Which is again why I opted to abandon original machines and just develop a new motherboard. As people can no doubt tell, one little problem and it turns into days of work. As I am basically the only person who has really investigated issues over the past decade, its just something I cannot really afford to keep spending time on personally.

People also need to understand I am tackling two separate problems here with the 1712 shifter. The primary problem is the corrupt graphics and the machine failing to boot at all with the 1712 shifter. It's relating to the 16Mhz line which I still need to investigate when my buffer boards come. Ironically the STE has not glitched once on the graphics since using the LS chip. Still somewhat " wobbly" picture. But the 16MHz line still needs sorting out anyway yet.

As for the audio crackles. My machine at least, the additional ground wire seems to be enough to get things working with the F374. However without mass testing it is difficult to know if this will solve the problem for others or not. As it is a relatively easy fix to do, and the safest, I would certainly try this first. I would assume in the majority of the cases it would be enough to get things working.

Changing to the LS chip also solves the problems with the audio, but again it would need mass testing to see if this alone is enough to solve the issues. But of course this is also more difficult and in inexperienced hands could trash their machine. I personally would probably go with the LS chips as I am all for chips not spiking the ground as much.

:2k2: :dizzy:

[Badwolf]

Some great research as usual, @exxos !

BW

[exxos]

Some great research as usual, @exxos !

:thanksyellow:

[fenarinarsa]

As for the audio crackles. My machine at least, the additional ground wire seems to be enough to get things working with the F374. However without mass testing it is difficult to know if this will solve the problem for others or not. As it is a relatively easy fix to do, and the safest, I would certainly try this first. I would assume in the majority of the cases it would be enough to get things working.

Changing to the LS chip also solves the problems with the audio, but again it would need mass testing to see if this alone is enough to solve the issues. But of course this is also more difficult and in inexperienced hands could trash their machine. I personally would probably go with the LS chips as I am all for chips not spiking the ground as much.

Thank you for your time! I will try to add a ground wire on my STE first.

[exxos]

Thank you for your time! I will try to add a ground wire on my STE first.

Cool - let us know how you get on!

[exxos]

I have noticed something else past couple of days as well. For the hell of it I fitted the S373, it was pretty odd because one channel worked on the other one did not :shrug: but the video was corrupted again. I changed back to the LS374 which had been running perfectly for some hours playing the tracker music, so the machine was only off for literally a few seconds while I change the chip, but the video was messed up again.

I don't know if it was ever reported if the shifter has any wake-up modes or not ? but something is clearly changing when the machine is powered down and powered up again. It seems very hit and miss if the video is basically perfect or totally trashed. It is not thermal because the video was basically fine for the past few hours. But I have noticed it repeatedly that turning machine off and on seems to have different effects on the video.

So I may look into the phase relationship of the 16MHz and 32Mhz clock when I get chance. Maybe there is a slight timing difference that play there causing the issue.

[derkom]

I don't know if it was ever reported if the shifter has any wake-up modes or not ?

Wasn't @mrbombermillzy talking about some of that here?

[exxos]

I don't know if it was ever reported if the shifter has any wake-up modes or not ?

Wasn't @mrbombermillzy talking about some of that here?

He was talking about a C64 ? Not really sure...

[derkom]

He was talking about a C64 ? Not really sure...

Oh, hah, sorry, I obviously lost the train on that thread back when it was posted. Thought that was still about Closure sometimes not working. :lol: