TT030 with PSU issue.. but not sure what.

[Bikerbob]

Hey all, not been around for a bit. I have been playing with my TT030 this Spring/Summer - now into fall.

Mine is a very modded machine, so I figure it is pulling a lot more than most.

Here is the description of what its doing as best as i can describe it.

**System:**
- Atari TT030 with original Phihong PSU
- Nova VME graphics (ATI Mach64 4 MB)
- Lightning / Thunder / Storm upgrades
- 10 MB ST-RAM + 256 MB TT-RAM
- FreeMiNT/XaAES, MagiC and TOS

This seems to be a power on OR more accurately a power DRAW problem

**Symptoms:**
- Atari video always works correctly - so system as listed using just the regular VGA out.
- When switching to Nova video, the display sometimes fails to initialize properly.
- Under TOS, the Nova display can be completely white.
- Under MiNT, the desktop background may appear, but icons, text, menu bars and other screen elements are missing or incorrectly drawn.
- Once the problem occurs, resets, warm boots and waiting at the boot menu do not resolve it.
- Leaving the machine completely powered off for an extended period (sometimes 24–48 hours) has restored normal operation.
- Once Nova initializes correctly, the machine can operate for many hours or days, including warm and cold resets, without the problem returning. As long the power to the machine is never off - resets work (THIS HAS BEEN ON NOW FOR 14 Days continuous.. working fine)
- The rest of the TT030 appears to operate normally.

**Observations:**
- The issue appears related to the transition to Nova video rather than general system stability.
- The original PSU is still installed. ( I have yet to recap - I have the caps)
- I suspect a PSU startup, voltage regulation or Power Good timing issue, but this has not yet been confirmed by measurements.

**Next steps:**

I'm considering replacing or recapping the Phihong PSU. A Mean Well RQ-85B, which provides all four required voltage rails. However, it lacks the original PSU's Power Good output.

The original Phihong specification requires Power Good to assert 100–500 ms after the outputs stabilize and deassert at least 1 ms before +5 V falls below 4.8 V.

Any thoughts?? IDEAS?? I could create a PG circuit for the Mean Well. Exxos since you have so much experience I am very interested in your thoughts. I am in Canada - so simply buying a replacement out of UK or EU is VERY expensive, but an option.

James

[exxos]

Have you tried holding the reset button in while powering up for several seconds?

BTW I don't sell any TT replacement PSUs. IMHO the original psu is fine just with a recap.

[HigashiJun]

Yup, you should recap your original PSU or get a beefier one from here:

https://www.16-32bit.eu/product-page/po ... rrency=JPY

Cyril makes good stuff, so you won't regret your purchase.

[Bikerbob]

Yup, you should recap your original PSU or get a beefier one from here:

https://www.16-32bit.eu/product-page/po ... rrency=JPY

Cyril makes good stuff, so you won't regret your purchase.

Yes I know that one.. but it will cost me close to $250 after shipping to Canada.

I will try the recap then - I see in the Exxos kit the octo coupler is also replaced.. really good idea? just suggested because of some failures?

Funny thing is.. the machine would be on for a good 2mins if I let the memory test run - and it passes.. but when it tries to init the VME NOVA card.. it does not resolve.. as per the descriptions above.. THE machine still run.. but does not init the card properly.. This might be a VME or Video card issue.. but I have no idea how to troubleshoot it.

[Bikerbob]

Have you tried holding the reset button in while powering up for several seconds?

BTW I don't sell any TT replacement PSUs. IMHO the original psu is fine just with a recap.

I am pretty sure I followed your values when I bought all the caps with other stuff from Digikey.. have to haul all that out of storage.

Do these symptoms seem PSU to you?? or maybe just poor connections? if I power it off completely - trying to restart is when this happens.. If I go back 30m 2h 6h - it still happens.. if I wait 24 or 48h usually thats long enough it works again.. but thats WAAAY too long to be a heat related issue, and besides if it was heat -- Ive been power on now for 15 days.. and every RESET or software COLD Boot the machine works fine in VME NOVA.. so this seems to be as long as the psu is warm. its ok.. otherwise it needs all that time to "reset"

[HigashiJun]

Yes I know that one.. but it will cost me close to $250 after shipping to Canada.

[jwd]

Bypass the PSU, get an ATX PSU off a non used PC you might have lying around and hook up directly to the original PSU motherboard connection.

That will tell you if the original PSU is the problem

[WDB]

Best had some upgraded power supplies for the TT and MegaSTE last time I looked.

[Bikerbob]

Best had some upgraded power supplies for the TT and MegaSTE last time I looked.

So im in Canada, Best sells the upgraded PSU at $198 USD before shipping. I would be looking at way more than bringing one of the new PSU from EU for that kinda money.. hard pass.

An ATX is missing -5v and PG - so its not a straight swap. I also think the issue is more a ripple or something else. I have a MEgaSTE here - so if I was so inclinded I could rip everything apart and start swapping. Trying to avoid that.

Thanks for the responses though guys.

James

[HigashiJun]

@Bikerbob

So a recap is the way to go then, and it won't cost you an arm and a leg...

You can even buy a recap kit from here:

https://console5.com/store/atari-mega-s ... -5341.html