STE V1.5 32MHz BOOSTER - STATUS

[exxos]

The 1K resistor pull-up did not seem to change anything. So I added a 100pF across it and so far so good.. Fast approaching loop 50 in GB6. It wasn't getting past around 10-20 before. So seems the oscillation on the low part of BR is causing the issue somehow. Not really sure how or why..

I will leave it running for another hour and then I will try diode clamp on the pin instead. If I can clamp the huge negative undershoot then maybe the oscillation will be a lot less anyway. Then I can leave the 1K pull-up to get a faster rise time without it being counteracted by the capacitor is currently in place..

Nothing like waiting endless hours for something to maybe crash or not

[rubber_jonnie]

So this one worked first time.. see how it goes.. got the new firmware in it...

It it seems OK, will sell it cheaper for someone to beta test it Will have a second one when I get more bits..

As usual, I would be very interested in beta testing.

[exxos]

As usual, I would be very interested in beta testing.

There will be much angular velocity involving a sledgehammer if it locks up again

[rpineau]

[exxos]

At some point the ROM CS wire had snapped off I soldered it back on and now just getting rows of bombs pretty soon after GB6 starts. Removing the wire and it did not bomb. So this seems yet another problem which has only just started to show up

So I have tweaked the code and added in a wait state onto the ROM CS line. I have also put back the 40MHz OSC.

Now to leave it running again... oh it died on ROM access test ... So now 2WS on ROM.. so now ROM speed is just 267% (normally 309% or 368%) .. See how long it runs for this time... oh nope, second loop.. So god knows why its started acting up really odd all of a sudden.

It also looks like my monitor is developing the fault it looks like there is some noise and odd scaling issues for some reason. Has been fine for years and always gave a really sharp image. I guess the heat and constant use lately has pushed it over the edge so at some point how have to take it apart start changing the capacitors I guess

[Stimpy]

Sometimes a slow slew rate can causes issues, stronger pullup as you tried. Depends on the logic family. Also that signal is not monotonic, likely caused by reflections. Especially nasty if it happens between the logic thresholds as it looks like it does. More modern faster logic is more sensitive to this. How do you measure the signal? Your ground is clipped close to the receiver or driver and not on the ground ring around the motherboard?

[exxos]

Sometimes a slow slew rate can causes issues, stronger pullup as you tried. Depends on the logic family. Also that signal is not monotonic, likely caused by reflections. Especially nasty if it happens between the logic thresholds as it looks like it does. More modern faster logic is more sensitive to this. How do you measure the signal? Your ground is clipped close to the receiver or driver and not on the ground ring around the motherboard?

The scope is on the outring gnd, but all other signals look really good, just BR is all over the place. The gnd oscillation is a lot less now.. probably spikes up to 0.3V.. so should be ok at that, but still having some odd issues with something else.

I've put back the 38MHz osc.. see if things look to improve.. I'm starting to wonder if the CPU's simply can't run at these speeds at all. I seem to be getting a lot of screwy problems with no real apparent causes

Even more annoying as it has gone back to the odd fault now where won't reset, that always seem to be bad soldering somewhere.. But this board has been fine two days

EDIT:
..and that is odd as it boots without the ROM_CS line connected.. Bizarre..

[exxos]

So the board I have been using isn't booting at all now there just must be some bad connection on it still.. (This is the board I put double solder paste on the pins on the CPU). It just seemed to get progressively worse as the day go on until the point it stopped booting altogether.

Went back to my previous test board and that one has booted up.. So I will leave this one running for a while and see if this one locks up... This is the board I heated up with the heat gun to re-solder the CPU..

I think when my new PCBs arrive, I will use a hotter profile in my PCB oven.. Generally I always use the same one, because any hotter, PCB starts to burn, that is a problem I had with some of the earlier V1 STE boosters. Though I think it could be possible as the CPU is large, it is not actually getting up to hot enough temperature to melt the solder onto the pins correctly.

The thing is the original board I made was running for several hours several days without issue, so it's not like there's huge issue with the booster design itself. It is pretty much based on the tried and tested V1 STE booster anyway. So I think am just wasting my time trying to find faults which are probably not even there...

[PhilC]

Do you have a thermocouple you can place on the CPU when the board is in the oven to check the temps?

Could it also be that the pins you push into the socket are moving with heat? Am I correct in thinking that the previous set booster required removal of the CPU socket etc?

Of course I'm sure you've already checked all of this.

[exxos]

Do you have a thermocouple you can place on the CPU when the board is in the oven to check the temps?

Only a IR one, doesn't much help with the small oven window

Could it also be that the pins you push into the socket are moving with heat?

The pins on the PCB I solder by hand after the CPU (and other bits) have been soldered to the board in the oven. The plastic on the pins tends to melt in the oven.. some images in another thread here... https://www.exxosforum.co.uk/forum/viewt ... 2056#p2056