Atari STE needs to "warm up" first

[Atari8guy]

Hi All,

 

I'm hoping someone has experienced this before and its a really easy fix. I pulled my STe out of the closet today and it requires considerable time to "warm up" for a lack of a better word.

 

It does the following, in fairly consistent fashion:

 

1) Upon powering up, I get a black screen.

2) After 60-120 secs I get a white screen.

3) After 5-7 mins it finally boots to my Ultra-Satan, or from floppy.

 

Sometimes after step 2 I get 4 bombs for a bit before I get full boot up.

 

Once it appears to be warm however it seems to reboot without issue.

 

The system has 4MB Ram (which tests okay when it gets there) and an Adspeed card in it.

 

Thoughts and/or suggestions....any help appreciated.

[GadgetUK]

Very likely your PSU needs replacement capacitors.

 

You can order them from maplin, and you can do this yourself if you know how to solder, but you've got to be careful not to electrocute yourself. The capacitors can hold a mains voltage type charge so dont touch any of the contacts when removing them - even after you've removed them.

 

Here's a quick kit (top of list):-

 

http://exxos.www.idnet.com/IMPULSE/atari/last/store.htm

 

[GadgetUK]

You can discharge them whilst they are still on the PCB using something metal (this will create a large spark as it instantly dissipates) - but don't be touching the metal when you do it, you need to be isolated from whatever you use to short the contacts. A better way is with something like a 1 mega ohm resistor for 5 mins or something - that drains them slowily.

 

Again - DO NOT ELECTROCUTE YOURSELF. Remove power lead from the ST before you start, switch power on then (with no power lead - this drains some of the caps.) Then remove the PSU and be carefull what you touch - contact with any of the solder points or components could result in shock,

 

PSU's are also on EBAY. Alternatively, if you are in the UK I could do this for you.

 

Edit: Electrolytic capacitors go one way around, make sure the dashed side goes to the - on the board. Pay attension when removing them as to which way they are fitted.

Edited February 16, 2013 by GadgetUK

[Atari8guy]

I think I can handle that. Warnings appreciated too, I have discharged capacitors before...so I will be sure NOT to electrocute myself.

 

I guess plunking in another power supply from another ST would only buy time. Eventually they will have to be replaced too?

[GadgetUK]

Yes, they all go eventually. That kit I've linked above is good as it uses better higher rated caps, and provides a better bridge rectifier.

[Atari8guy]

And those caps are the same in a North American power supply?

[GadgetUK]

And those caps are the same in a North American power supply?

 

Hmmm, good question... Not sure how US PSU may differ but the caps are likely to be the same. Take PSU out first to have a look at some of them first I guess.

[Atari8guy]

Anyone out there from this side of the pond use the kit above?

[GadgetUK]

Just wanted to post an update here. I re-capped my STe and STFM on Monday and I found that the list of caps in that 'kit' didn't correspond to the caps on either of my PSU's. Instead of 47uF 350 / 400v caps I had 2 x33uF in each PSU and the physical size you need to consider - whilst my 47uF replacements fitted the PCB they were 1cm too high so I ended up putting the 33uF's back in after checking them with my capacitance meter - they were both OK in my case, measuring 35uF each.

 

I also counted 3 x 330uF caps (25v I think) in each PSU - not mentioned in that cap kit. Mine all measured 330uF so didnt need to replace. I did replace the 2200uF cap in each PSU with 4700uF.

 

Iv'e had a slighter rippling on video of the STe for first 3 mins until warmed, I had expected caps in the PSU to be causing this but apparently not... When I get chance I will swap the 2 PSU's around just to rule the PSU out entirely. I suspect it could be a dodgy bridge on my STe causing those ripples, or it could be other caps related to video out - STe seem to have tonnes of caps on the mobo.

 

In your case the crashes etc are likely PSU related as your first port of call. You may have video issues related to warm up to deal with seperately later - like mine.

[31336haxx0r]

You'll need low-ESR capacitors in the PSU. It's a switch mode power supply and it can fry "normal" caps. Check if they get hot while in operation (safety rules regarding electricity apply ).

[Atari8guy]

I'm going to have to pull it out this weekend and look at the caps, if I have trouble identifying them I'll post some photos but should be straight forward. This is my favourite machine and I hate that its not aging well.

[carmel_andrews]

You could always try best electronics, I guess they do ST parts/components as well (since you are in canada), alternatively you could try rs components, I think they might do some US/North Am. psu components

[krupkaj]

Just wanted to post an update here. I re-capped my STe and STFM on Monday and I found that the list of caps in that 'kit' didn't correspond to the caps on either of my PSU's. Instead of 47uF 350 / 400v caps I had 2 x33uF in each PSU and the physical size you need to consider - whilst my 47uF replacements fitted the PCB they were 1cm too high so I ended up putting the 33uF's back in after checking them with my capacitance meter - they were both OK in my case, measuring 35uF each.

 

I want to change capacitors in my power supply too. And I have found there is several types of power supplies from several vendors. I have found four different supplies in my and friend's STs.

Here is a table of capacitors I made. It is the 1st version, I have to work on it.

caps.zip

[Atari8guy]

I replaced the questionable power supply with a known good one and the problems were instantly fixed!!! I will still have to replace the caps at some point but I'm glad to have found the problem and fixed the issue. Thanks GadgetUK, your input was spot on and appreciated.

[GadgetUK]

Excellent, glad you've sorted it! It won't be difficult to remove the caps and replace them. Just do what you've said and examine them first, make notes as to the voltage and uF rating, and the way they are around on the PCB (+ and -) - if you note all that down you could remove them all and take them to radio shack or somewhere like that where they can match up replacement parts for you. If you can get low ESR capacitors that's great as they may last a lot longer, but to be honest i've always just swapped them out for normal ones - provided they are higher voltage rating or higher temperature rating they will last for years and years. I did one for a friend 15 years ago, he still doesn't need new caps yet!

[31336haxx0r]

BTW, what's the culprit when the capacitors on the low voltage side of the PSU get hot? I have replaced them with new low ESR ones and even those still warm up dramatically.

[krupkaj]

I think they are near a big radiator, so maybe this is a reason. Did you measure the temperature?

BTW did you use caps for 105°C or for 85°C?

[GadgetUK]

I think its the heat sinks, and general load on the low voltage lines. I always use 105 degree caps. I am not an expert on PSU's so I am not sure if there's an inherent design flaw there or not, but switch mode PSU's always hammer the balast caps.

 

I've just fixed a dehumidier 12v PSU - same problem, 2 x 220uF balast caps burnt out through the switching - 12v line measured 4v.

Edited February 26, 2013 by GadgetUK

[31336haxx0r]

The voltages measure fine and everything stays cool on that PSU. Just the caps oh the secondary side get hot. For whatever reason.

[atarian63]

gently press down on mmu & glue

[GadgetUK]

gently press down on mmu & glue

 

Hahahaha, I love it when someone doesnt read the whole thread!! I think this is a suggestion to fix the original problem which was the PSU, but yes its always worth making sure socketed chips are in properly. If the MMU and Glue isnt socketed you would need the chip resoldering.