How to: recapping the Mega STe power supply

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Pacman
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Re: How to: recapping the Mega STe power supply

Post by Pacman »

I just logged after getting an email alert about a new posting here!
Yup, have been clogged down with other things and haven't had the time to pop into here for a while.

I'll need to re-read the thread to catch up, but what exactly needs updating/fixing in the thread (sorry for the clueless question) without having to go through all the details?
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Re: How to: recapping the Mega STe power supply

Post by mikro »

See my previous post - Exxos was so kind to edit the picture to correct C14 but you can still add the mention about the central screw. Your picture (and I assume the physical PSU, too) still has it, it shouldn't be there.
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Re: How to: recapping the Mega STe power supply

Post by Pacman »

mikro wrote: Tue May 12, 2020 6:54 am See my previous post - Exxos was so kind to edit the picture to correct C14 but you can still add the mention about the central screw. Your picture (and I assume the physical PSU, too) still has it, it shouldn't be there.
Thanks, Exxos for editing the C14 polarity!
I compared the photo in the first posting with the actual PSU board and C14 now looks correct.

I don't have time to go through entire threads and immerse myself fully into the subject at the moment, but my understanding from all this is that there are two versions of the Mega STe PSU board:
one with 4 screws (one at each corner)
and a different PCB version with 5 screws (one at each corner and one in the middle).
So the problem is that the middle screw shouldn't be there at all? Did Atari make a mistake in their design or is it to be removed for some other reason?
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Re: How to: recapping the Mega STe power supply

Post by mikro »

Pacman: yes. It is explained in the quoted text in the first post of yours. :) The screw must be removed and the hole insulated.
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Re: How to: recapping the Mega STe power supply

Post by Pacman »

OK, I've taken a look at it and this is what I've found out.

1) my board has neither a -001 nor -002 designation but "Rev A1", specifically this is what it says on the PCB:

PHIHONG
PSM-5341
29203-102A
REV- A1

It does however have a centre screw, so I assume it's a -001 version, or a derivative of it.

2) I removed the PCB from its metal frame, then found out that the PCB area joined to the centre screw also joins to the rightmost screw (screws 5 and 2 in the photo below). There's a jumper next to #2 which allows for this.
Furthermore, when the PCB is mounted to the metal frame then screws #3 is also joined together with #2 and #5 because of the frame itself.
20200513-100552__MG_7236-Edit.jpg
20200513-100552__MG_7236-Edit.jpg (383.24 KiB) Viewed 5352 times
20200513-100418__MG_7231-Edit.jpg
20200513-100418__MG_7231-Edit.jpg (520.67 KiB) Viewed 5352 times

On a sidenote, look at the "fried" area on the frame (underneath where the AC wires go in/the fuse). Any cause for concern?:
20200513-100442__MG_7232.jpg
20200513-100442__MG_7232.jpg (268.76 KiB) Viewed 5352 times
So which signal exactly is the removal of screw #5 (and insulating the PCB at this point -probably best done by removing the screw post entirely, along with cutting the jumper wire near #2) supposed to eliminate?


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Re: How to: recapping the Mega STe power supply

Post by exxos »

So are we saying the 001 has screw 5 and is fine, and 002 also has the screw but should be isolated ?

In that case, who has a 002 version to check this then ?

EDIT:

This is the version I had on my site with the screw...

PSM-5341rc.jpg
PSM-5341rc.jpg (105.66 KiB) Viewed 5344 times
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: How to: recapping the Mega STe power supply

Post by czietz »

exxos wrote: Wed May 13, 2020 10:11 am So are we saying the 001 has screw 5 and is fine, and 002 also has the screw but should be isolated ?
The text from Chips'n'Chips (quoted above) is quite specific: The screw needs to be removed in the 001 model. However, given the jumper link I'm also not sure what this will achieve. Break a ground loop?

http://tho-otto.de/hypview/hypview.cgi? ... 8&index=64
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Re: How to: recapping the Mega STe power supply

Post by exxos »

czietz wrote: Wed May 13, 2020 12:00 pm The text from Chips'n'Chips (quoted above) is quite specific: The screw needs to be removed in the 001 model. However, given the jumper link I'm also not sure what this will achieve. Break a ground loop?

http://tho-otto.de/hypview/hypview.cgi? ... 8&index=64
hmmm... hold up, wasn't there a cut track on some of these boards ? I'm sure I saw it somewhere.... Sure it was on the LV side..as I am sure I thought WTF when I saw it.. but I half remember it was a grounding point issue on the board.. the cut track just changed the GND route somewhere or something.. was a long time ago now so don't remember much about it :roll:
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
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Re: How to: recapping the Mega STe power supply

Post by exxos »

ah found it https://www.exxosforum.co.uk/forum/viewt ... 5433#p1900

and from the post...

Icky wrote: Sat Nov 11, 2017 1:17 am I have come across these two versions of PHIHONGS PSUs:

One is a REV-A1 which has the cut track and the centre post is isolated with cloth tape. This one the opto isolator is a CNY17-3Z and it is from an Atari TT REV H.

The other a REV-02 which does not have the cut track and the centre post is not isolated. This one has the PC111 opto isolator and is from and Atari MegaSTE.

I'll add pictures shortly as I am in the process of re-capping the REV-A1, the REV-02 is already recapped
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
mikro
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Re: How to: recapping the Mega STe power supply

Post by mikro »

Pacman wrote: Wed May 13, 2020 10:03 ammy board has neither a -001 nor -002 designation but "Rev A1", specifically this is what it says on the PCB:
FYI, "-001" or "-002" is written on the metal case, not PCB. It's a paper sticker.
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