Atari TT power on delay

Hardware, coding, music, graphic and various applications

Moderators: Mug UK, moondog/.tSCc., lp, [ProToS], Moderator Team

damanloox
Atari maniac
Atari maniac
Posts: 99
Joined: Fri Jan 19, 2018 8:45 am

Atari TT power on delay

Postby damanloox » Sun Apr 15, 2018 5:44 am

I've acquired a TT and recapped the PSU with exxos kit. Everything seems to be ok but I noticed a delay of 1-2 seconds between pushing power button and actual psu/TT start (i.e. when I power it on nothing happens for about 1-2 sec and then it starts i.e. fan, leds etc)...
Should I be worried or it normal behaviour of the TT/psu..?

kcr2000
Atari nerd
Atari nerd
Posts: 46
Joined: Sun Aug 19, 2012 8:20 am

Re: Atari TT power on delay

Postby kcr2000 » Sun Apr 15, 2018 2:23 pm

Never seen such behaviour... my TTs always turn on immediately after pushing the switch.
CLAB Falcon MK2 CT60e 14MB/512MB 2x32GB CF FPU, Atari Falcon 030 14MB FPU, Atari TT030 10MB ST 256MB TT Crazy Dots 2 ThunderStorm 8GB IDE CF, Atari TT030 10MB ST 64MB TT Megavision 300, Atari Mega STE 4MB Crazy Dots, Atari Stacy 4 16MHz, Atari 1040 STE 4MB UltraSatan, Atari 520 STE, misc STf, STFM, 1040, 520, 260, Atari PC1, Atari PC5, Portfolio, NetUSBees etc. + misc 8-Bit Ataris

User avatar
frank.lukas
Hardware Guru
Hardware Guru
Posts: 1556
Joined: Tue Jan 29, 2008 5:33 pm
Location: Germany

Re: Atari TT power on delay

Postby frank.lukas » Sun Apr 15, 2018 2:43 pm

Have you solder it well ?
fancy Atari Musik anDA Dance "Agare Hinu Harukana" 1998 ATARI http://www.youtube.com/watch?v=JX10fxb5eYE

damanloox
Atari maniac
Atari maniac
Posts: 99
Joined: Fri Jan 19, 2018 8:45 am

Re: Atari TT power on delay

Postby damanloox » Sun Apr 15, 2018 2:50 pm

Yes I did. That behaviour was the reason for recapping - I was hoping it will solve the issue but it didn't.

czietz
Hardware Guru
Hardware Guru
Posts: 684
Joined: Tue May 24, 2016 6:47 pm

Re: Atari TT power on delay

Postby czietz » Sun Apr 15, 2018 2:59 pm

There is definitively some noticeable delay with my two (recapped) TT/MSTE PSUs as well. It's hard to judge without a stop-watch, but I'd say a little less than one second until the power LED goes on. This can also be explained: For the switching controller to start, its supply voltage has to ramp up over the undervolt lockout threshold. For that, a capacitor (C8) needs to be charged from the rectified mains voltage via two high-value resistors (R1, R2). A little simplified calculation shows that this alone will take ca. 600 ms in countries with 230 V mains and about 1 s in countries with 127 V mains. Before that, the power supply will not even generate secondary side voltages. Add to that some milliseconds for the secondary side to ramp up.

BTW: The spec of the power supply (PSM-5341) does allow for up to 5 seconds power up time.

Side note: A non-recapped PSU with a degraded C8 will even start up faster.

czietz
Hardware Guru
Hardware Guru
Posts: 684
Joined: Tue May 24, 2016 6:47 pm

Re: Atari TT power on delay

Postby czietz » Sun Apr 15, 2018 4:03 pm

PS: I thought this would be a good occasion to test the latest addition to my electronics lab: a differential probe that allows me to safely measure inside a mains powered switch-mode supply.

On the screen shot you can see that it takes about 700 ms for the PSU in my TT to start. The blue trace shows the supply voltage of the switching controller IC slowly rising, like I described above. Only when it reaches about 16 V, the controller starts switching and the 5 V supply voltage (yellow trace) becomes available.
NewFile19.png


damanloox: As to why it takes longer for your PSU to start: If I understand exxos's page correctly, in his capacitor kit he replaced the 100µF C8 by a 220µF one. This of course more than doubles the startup time of your PSU.
You do not have the required permissions to view the files attached to this post.

damanloox
Atari maniac
Atari maniac
Posts: 99
Joined: Fri Jan 19, 2018 8:45 am

Re: Atari TT power on delay

Postby damanloox » Sun Apr 15, 2018 4:28 pm

Ok thanks. I took the psu apart again just to check everything again, installed "dummy" resistors again and double checked all voltages and everything seems ok.
But... when I installed the psu back and powere the TT I didnt get any video... TT seems to start (I can hear a little "squeak" from the speaker but no video at all! I measured voltages on the connector again - all perfectly ok...
Any idea how to start troubleshooting that? What can cause video to fail..?
I think I'm gonna start crying...

czietz
Hardware Guru
Hardware Guru
Posts: 684
Joined: Tue May 24, 2016 6:47 pm

Re: Atari TT power on delay

Postby czietz » Sun Apr 15, 2018 5:57 pm

Oh, man, that sucks! Particularly considering that everything was OK with your PSU; the long startup delay being totally normal with the caps Exxos chose. I feel with you.
TT service manual: https://www.dev-docs.org/docs/htm/searc ... nd=C302483

damanloox
Atari maniac
Atari maniac
Posts: 99
Joined: Fri Jan 19, 2018 8:45 am

Re: Atari TT power on delay

Postby damanloox » Sun Apr 15, 2018 7:10 pm

OK - while crying a little I opened up another TT (which is in perfect working order ready for sale) and connected the PSU to my TT... and it works - every time, no problem. So... my guess it is my PSU that is at fault...
The symptoms so far:
- PSU powers up randomly (sometimes it does power up and produces all correct voltages, some other times it won't power up generating 6V at 12V line and 0.5V at 5v. -5v and -12v seem to be OK and unaffected).
- when the PSU powers up it produces all correct voltages (I don't have oscilloscope so I can only roughly measure voltages etc) but the TT doesn't generate any video. Also - the speaker generates some faint squeeky sounds.
- all caps have been replaced (and they are not at fault as the same behaviour was present before reacapping operation)

Any ideas? What else should I replace on my PSU (I don't have any spare PSU nor I will be able to buy one any time soon unless somebody on this forum has spare one)?

czietz
Hardware Guru
Hardware Guru
Posts: 684
Joined: Tue May 24, 2016 6:47 pm

Re: Atari TT power on delay

Postby czietz » Sun Apr 15, 2018 8:54 pm

Powering up randomly is a strange behavior for a PSU, indeed. Search for cold (i.e. broken) solder joints. They might not be apparent at first glance -- look closely.

damanloox
Atari maniac
Atari maniac
Posts: 99
Joined: Fri Jan 19, 2018 8:45 am

Re: Atari TT power on delay

Postby damanloox » Mon Apr 16, 2018 6:45 am

Does anybody have high res picture of the back of their psu's board (i.e. solder side)? There's a broken ground trace on my (which might have been intentional as it created a loop but just to make sure... Also - it looks like options isolator has floating pin (i.e. No trace connecting to it..)

damanloox
Atari maniac
Atari maniac
Posts: 99
Joined: Fri Jan 19, 2018 8:45 am

Re: Atari TT power on delay

Postby damanloox » Mon Apr 16, 2018 7:56 pm

OK - still crying but trying not to waste my time ;)
Does anybody know what generates "PG" ("power good") signal (on orange wire)? Is it PSU or TT?
I noticed that it all works but... requires patience. Ie. the PSU powers up, all voltages seem to be OK except... PG signal. It takes about 20 seconds and it magically goes to 5v and... TT starts (and works) perfectly OK. So the big question is - what can cause such delay...? That only happens if TT was powered down for long time (and by long I mean 10-15 minutes). Once it starts for the 1st time it then doesn't have that "delay" issue...
And another question - I can see R4 has been removed from my PSU and R5 is about 50 Ohms (instead of 100 Ohms as per PSU diagram)... Does anybody have any idea if that could be the issue...?

czietz
Hardware Guru
Hardware Guru
Posts: 684
Joined: Tue May 24, 2016 6:47 pm

Re: Atari TT power on delay

Postby czietz » Mon Apr 16, 2018 8:20 pm

Power Good is generated by the PSU. If I understand the circuit correctly, the delay for power good is mainly set by C23 and R29. Check that those components have the values specified in the schematics and that their solder joints are OK.

R4 and R5 concern the supply voltage of the switching IC while it is operating. While I have no idea why these components were changed/removed in your
PSU, I don't think they are the cause for a startup delay.

PS: It's correct that the opto-isolator only has four of six pins connected.

damanloox
Atari maniac
Atari maniac
Posts: 99
Joined: Fri Jan 19, 2018 8:45 am

Re: Atari TT power on delay

Postby damanloox » Tue Apr 17, 2018 7:36 am

Double (and triple) checked - C23 and R29 are OK. Back to crying ;)

czietz
Hardware Guru
Hardware Guru
Posts: 684
Joined: Tue May 24, 2016 6:47 pm

Re: Atari TT power on delay

Postby czietz » Tue Apr 17, 2018 5:45 pm

OK, then please check the other components involved in the Power-Good circuit, i.e. in the lower right-hand corner of the schematic. I.e. transistors etc. Does anything look damaged? Are the transistors getting their supply voltages?


Social Media

     

Return to “Professionals”

Who is online

Users browsing this forum: No registered users and 3 guests