Atari psu refurb question

[groppo91]

Hi I am going to try test this psu out and refurb it but wondered what these damaged components are and if they need replacing circled in red. I have included a few images of the psu but not sure they came out good.

 

Anything I need to know for a refurb?

 

Also any recommendations for a modern psu alternative that I can slap into the atari st?

[Forrest]

Others have mentioned the Meanwell RD-50A Link

[masteries]

20 minutes ago, Forrest said:

Others have mentioned the Meanwell RD-50A Link

Yes, the Meanwell RD-50A fits into Atari ST/E case

 

but it barely fits, on one of my STE, the old PSU shield had to be removed, to fit the Meanwell PSU

 

Edited March 21 by masteries

[TZJB]

2 hours ago, groppo91 said:

Hi I am going to try test this psu out and refurb it but wondered what these damaged components are and if they need replacing circled in red. I have included a few images of the psu but not sure they came out good.

 

Anything I need to know for a refurb?

 

Also any recommendations for a modern psu alternative that I can slap into the atari st?

 

This looks like a Mitsumi SR98, a very common Atari ST PSU.

 

Power Supply SR98.pdf

 

Have a look at this and other Atari ST PSU here: - https://www.exxosforum.co.uk/atari/last/psu/index.htm. Due to the heat by this PSU it is generally advisable to replace the electrolytic capacitors.

 

Your PSU looks like it has been mistreated somewhat. It has corrosion and the PCB is damaged and needs a good clean and may need repair. Most of the components look fine and with the exception of D104, look intact.

 

However D104 would not normally expire in isolation, so check related components with an ohmmeter.

 

The damaged resistor R205 should be fine as it is a wire wound component and can be retouched with some varnish of some sort.

 

If you follow Exxos suggestions you should be able to get this going again.

 

As @Forrest suggests, the Meanwell RD-50A or even the RD-35A has sufficient capacity and profile to replace an Atari ST PSU internal unit.

 

RD-35-spec.pdf

[groppo91]

3 hours ago, TZJB said:

 

This looks like a Mitsumi SR98, a very common Atari ST PSU.

 

Power Supply SR98.pdf 4.08 MB · 2 downloads

 

Have a look at this and other Atari ST PSU here: - https://www.exxosforum.co.uk/atari/last/psu/index.htm. Due to the heat by this PSU it is generally advisable to replace the electrolytic capacitors.

 

Your PSU looks like it has been mistreated somewhat. It has corrosion and the PCB is damaged and needs a good clean and may need repair. Most of the components look fine and with the exception of D104, look intact.

 

However D104 would not normally expire in isolation, so check related components with an ohmmeter.

 

The damaged resistor R205 should be fine as it is a wire wound component and can be retouched with some varnish of some sort.

 

If you follow Exxos suggestions you should be able to get this going again.

 

As @Forrest suggests, the Meanwell RD-50A or even the RD-35A has sufficient capacity and profile to replace an Atari ST PSU internal unit.

 

RD-35-spec.pdf 93.9 kB · 2 downloads

Ah many thanks for this useful knowledge. The atari i pulled it from is awful state but i spent a good day tearing it down and cleaning and it came out okay just want a working psu before i test it. The new psu look like good options just I am not sure what cables/connectors I will need to install it.

[TZJB]

21 hours ago, groppo91 said:

Ah many thanks for this useful knowledge. The atari i pulled it from is awful state but i spent a good day tearing it down and cleaning and it came out okay just want a working psu before i test it. The new psu look like good options just I am not sure what cables/connectors I will need to install it.

 

You are welcome.

 

I can't image what the complete Atari ST looked like if the PSU is that bad! Saying that, it was probably little used and just stored badly when the PSU expired.

 

The existing 6 way power lead and socket from the old PSU board would normally be de-soldered and utilised for the new PSU. However you may need to extend the old wires with extension wiring, ensuring it is of similar rating as the original. It is possible to make your own connector but then you would need more parts.

 

Depending on the model of new PSU, you will most likely need to bunch up the COM (common) wires and probably the +5V wires when connecting to the new PSU as it will probably have singular screw terminals with sufficient current capability for the COM and voltages. Obviously the FR (Frame Ground) is separate and should connect to the mains supply earth.

[groppo91]

3 hours ago, TZJB said:

 

You are welcome.

 

I can't image what the complete Atari ST looked like if the PSU is that bad! Saying that, it was probably little used and just stored badly when the PSU expired.

 

The existing 6 way power lead and socket from the old PSU board would normally be de-soldered and utilised for the new PSU. However you may need to extend the old wires with extension wiring, ensuring it is of similar rating as the original. It is possible to make your own connector but then you would need more parts.

 

Depending on the model of new PSU, you will most likely need to bunch up the COM (common) wires and probably the +5V wires when connecting to the new PSU as it will probably have singular screw terminals with sufficient current capability for the COM and voltages. Obviously the FR (Frame Ground) is separate and should connect to the mains supply earth.

Yeah this was the worse out of the three the case is cracked and burned. I have stripped and cleaned the keyboard and motherboard seems okay but cant test until I have a psu I am happy to run it from. The shield plates are in an awful state I had to hit with a hammer to try and flatten them. 

 

What sort of cable would you recommend for extending the existing if I am to desolder and use them?

 

Do you have any guides/resources that can help with wiring up the rd-50a?

 

Lastly if I was to make my own and not reuse cables do the connectors have a name and will I need special tools to terminate them?

 

 

[BJolly]

On 3/22/2024 at 4:41 PM, groppo91 said:

What sort of cable would you recommend for extending the existing if I am to desolder and use them?

 

Do you have any guides/resources that can help with wiring up the rd-50a?

 

 I hope its ok to piggy back my request here. Is there a walk through guide to installing the Meanwhile  rd-50a PSU for the ST especially the wiring so it fits the singular screw terminals? I would appreciate one. I have an STE and possibly STFM I'd like to extend the life of before things fail (including my memory). The less soldering the better! 🙂

[TZJB]

On 3/22/2024 at 4:41 PM, groppo91 said:

Yeah this was the worse out of the three the case is cracked and burned. I have stripped and cleaned the keyboard and motherboard seems okay but cant test until I have a psu I am happy to run it from. The shield plates are in an awful state I had to hit with a hammer to try and flatten them. 

 

What sort of cable would you recommend for extending the existing if I am to desolder and use them?

 

Do you have any guides/resources that can help with wiring up the rd-50a?

 

Lastly if I was to make my own and not reuse cables do the connectors have a name and will I need special tools to terminate them?

 

 

 

Regarding wiring extensions, you can use any low voltage wiring. Personally I use old expired PC ATX PSU low voltage cables. Lots of colours and adequate ratings. If you need to source new wire then possibly eBay or Amazon might help.

 

Making your own connector is possible using Molex KK 254 housings and contacts. They can be crimped, but normally I solder them for reliability.

 

As to guides, the closest I have found is this example:- https://www.atari-forum.com/viewtopic.php?p=355335, where a different Meanwell PSU is used. In this case no wiring extensions were used.

 

Also Jan Beta on Youtube where he shows how to connect the RD-50A.

 

 

You will notice that the three black GND wires are connected to the Common, the blue +12V wire to the 12V terminal and the two red +5V wires to the 5V. That is about all you really need to know.

 

 

[groppo91]

7 hours ago, TZJB said:

 

Regarding wiring extensions, you can use any low voltage wiring. Personally I use old expired PC ATX PSU low voltage cables. Lots of colours and adequate ratings. If you need to source new wire then possibly eBay or Amazon might help.

 

Making your own connector is possible using Molex KK 254 housings and contacts. They can be crimped, but normally I solder them for reliability.

 

As to guides, the closest I have found is this example:- https://www.atari-forum.com/viewtopic.php?p=355335, where a different Meanwell PSU is used. In this case no wiring extensions were used.

 

Also Jan Beta on Youtube where he shows how to connect the RD-50A.

 

 

You will notice that the three black GND wires are connected to the Common, the blue +12V wire to the 12V terminal and the two red +5V wires to the 5V. That is about all you really need to know.

 

 

Ah brilliant this is perfect, thankyou for the time to post this, I will give it a go once the parts arrive.

[TZJB]

16 hours ago, BJolly said:

 I hope its ok to piggy back my request here. Is there a walk through guide to installing the Meanwhile  rd-50a PSU for the ST especially the wiring so it fits the singular screw terminals? I would appreciate one. I have an STE and possibly STFM I'd like to extend the life of before things fail (including my memory). The less soldering the better! 🙂

 

@BJolly, piggy backing is expected and very common in the Atari world!

 

I hope that my previous reply to @groppo91 is sufficient to enable you to proceed with an upgraded PSU and make you into a hardware hacker 🙂.

 

I have not tried it myself, relying solely on repairing the Atari PSU as it's normally cheaper. However the advantage is that modern PSU design is much more efficient than previously, so a lot less heat is generated and wasted.

[BJolly]

@TZJB Many thanks that is just what I was hoping for. Looks like I'm going for a Meanwhile PSU and I'll put the original to one side until I've practised some soldering skills.