ATARI STF Power Supply problem

[derkom]

To adjust the 5 volt trimmer, can I keep the power supply on without problems for a few seconds?

Yes. Just be careful of live electrics, and don't forget your resistors are getting hot.

[exxos]

To adjust the 5 volt trimmer, can I keep the power supply on without problems for a few seconds?

Yes carefully adjust and measure 5V rail with your meter as you turn the trimmer until you get 5.00V.

[demonlg]

I have moved trimmer to left and now i have minimum possible value on 5 volt (exactly 5,06 volt)is not possible to have 5,00, and on a 12 vol rail now i have 11,05 volt.

[exxos]

I have moved trimmer to left and now i have minimum possible value on 5 volt (exactly 5,06 volt)is not possible to have 5,00, and on a 12 vol rail now i have 11,05 volt.

Probably about as good as it will get now then.

[demonlg]

Nothing, i have connected psu on my 520ST and it's not boot, led with low light, little ultrasonic sound from power supply when i power it on, and i have 1,90 volt on 5 volt rail.

[exxos]

Just a question which I just thought, you are running the power supply on 230VAC ?

[demonlg]

Yes, correct, 230vac.

[demonlg]

Of all elctrolytic capacitors i only haven't replaced the little one of 1uF 50v at the top center right in my photo.

All not polarized capacitor, resistors and main switching transistor are original.

Then for the bridge diode I have used a KBF04 (400v 2,5A), it is good for this application?

Emanuel

[demonlg]

Another test i have to make on it?

I have ordered new primary transistor on ebay, 4-5 days to arrive, but the problem of this voltage drop is very strange, i don't know if it is caused from ad new capacitor or not good type of it.

I have only one ELNA RE2J4700uF and i try to replace the 2200Uf con 12 volt rail only.

[exxos]

It sounds like the PSU is shutting down like overcurrent protection. It works with 0.5A but not higher on the ST. But I don't know what would really cause that problem.

Probably lift all resistors and check values . https://www.exxosforum.co.uk/atari/last/ ... 20SR98.pdf