Booster V4sm problem

[exxos]

You don't say if you tried removing the ROM CE wire ?

But also I would suggest not having any physical switch on the ROM board while debugging. If there is a bad contact it could be causing problems.

[zfrenchy]

sorry, yes I tried, no success, still black screen sometime in 32Mhz mode.


I will take a break on that for now, may be put back the STE to factory setup but keep the DualTOS, which was working very well.

[exxos]

Do you have a scope to make your both sides of the 32Mhz wire ?

You could also try soldering the 32mhz wire direct to pin1 of the GAL..As it sounds like the booster is not seeing the 32mhz at all..

[zfrenchy]

yes, I have a scope, Tektronix 222.

My knowledge on using a scope is very limited, using the auto button is my best skill

[exxos]

using the auto button is my best skill

Mine also

[zfrenchy]

I will found a way to connect the scope on pin4 of U405, under the PSU.

I measure the resistance from pin4 U405 and the wire solder joint is 0.1 Ohm, from the wire solder joint to pin1 of the GAL is 68.1 Ohm.

Is it normal to you ?

[exxos]

I will found a way to connect the scope on pin4 of U405, under the PSU.

I measure the resistance from pin4 U405 and the wire solder joint is 0.1 Ohm, from the wire solder joint to pin1 of the GAL is 68.1 Ohm.

Is it normal to you ?

Yes because there is a 68R in series with that wire..

This is why I suggest connect the wire directly to pin1 of the GAL, because it bypasses that resistor..

I'm working on the assumption that for some reason the board does not "see" 32Mhz..

So if you measure with your scope what you see on U405 end of the wire.. then measure pin1 of the GAL , we can see if there is to much voltage drop there... I assume there is..

[zfrenchy]

I cannot make it to fail this morning !!!! But still not having the ATARI logo and RAM test at boot.

Top trace is from the wire, bottom is the GAL pin1

20260119-084640.JPG (162.64 KiB) Viewed 1056 times

[zfrenchy]

STOP THE TRAIN, I HAVE A FAIL !!!!

here the scope, same settings, black screen in 32Mhz mode !!!

20260119_085736.jpg (155.42 KiB) Viewed 1055 times

sorry, for some reason the photo is displaying like that in the forum.

[exxos]

I cannot make it to fail this morning !!!! But still not having the ATARI logo and RAM test at boot.

You know you only get the logo with TOS206 ?

Top trace is from the wire, bottom is the GAL pin1
20260119-084640.JPG

Looks fine then..

I assume you changed U405 for the FAST series as the S version won't work.