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BGE's take on the Quadra 900/950 ATX PSU Mod


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It's been a while since I last posted anything here but I haven't given up. Far from it actually.

I've made some board mock ups, identified the old original parts (reverse engineering connectors isn't easy, plus some of those parts are old and not manufactured anymore... but I've found some alternatives). I also found footprints for all the new parts and I am currently working on updating the AC board schematic to include some filtering (I took apart the Becker, and just like Geekdot's Maxsilent unit, some components are soldered to the plug...). I'll replace those components and completely bypass the Becker's switch and plug. It has some spade/blade connectors for its board's AC input. I'll connect the new AC board (with its upcoming filtering 'circuit') to those. That way it'll be even more plug and Play!

Anyway, here are the mock ups. Those only include the 'critical' dimensions (ie where the original screw holes were, where the molex 4 pin 5556 connectors need to be in relation to the board etc... the rest of the mounting system with the screws/standoffs isn't included). Also, those aren't professional grade. They will be replaced by the Eagle board layout document. I created those parts/drawings in Catia just to test the dimensions with a 1:1 mock up and as a reference for later. 


One problem I didn't expect was the height of the Becker's board... The heatsinks are massive and are almost full height. The heatsinks on Geekdot's PSU seem to be only half height. That means I've had to rethink the PSU's placement. It's going to be right next to the OG fan. That way it won't overlap with the DC board. TBH, it probably would have been fine as there's going to be a 25mm gap between the top of the Becker and the DC board but better be safe than sorry!

The Becker's casing is going to be removed obviously. The real PSU bit is where the black plastic sheet is... And although it doesn't look like it's going to fit on the picture, trust me, I've buttoned it up with all the panels and it does fit.


More to follow...

PS: @GeekDot I've figured out (albeit too late) how you're supposed to remove the OG 20 pin connector and its cables... You just can't take it apart with the 20 pin plug installed, the only way is to separate each terminal from the plug individually and then slide them all the way out . What a stupid design. Thanks Delta. You've just lost a customer. I won't be calling you for my test rigs at work. 



Well-known member
So I made some progress on the PCB design. Keep in mind that it is my very first draft (and it also was my very first time using Kicad...).

A friend of mine (who BTW built his own 8 bit computer, yet he's not The 8-Bit Guy!) has agreed to check the boards for mistakes before I send them to manufacturing. We'll probably discuss what needs to be changed over the weekend.

As it stands now, it's far from perfect but hey it's there at least. 

Here's the AC Board schematic:

Bildschirmfoto 2020-04-03 um 12.33.12.png

- J1, J2 and J8 are the original connectors Delta used for the Q9x0's PSU. No need to change anything to the original wiring. J1 & J2 are spade connectors and J8 is a 3 pin (albeit with the middle one removed) Molex KK396.

- Since the Delta can pass up to 3A (@120V) to the monitor, I've selected a 3A cylindrical fuse and holder (J7). Don't worry, this won't be the only fuse. This one is there to protect the monitor. The remplacement ATX PSU has one as well. 

- K1 is a Panasonic DK2A-3V DPST relay. It'll "activate" the monitor plug once power is applied to its coil (ie when the Quadra is powered on). 

- J3 is a simple JST type 2 pin connector that brings DC from the DC board over to the AC board for the relay. 

- FL1 is a Schaffner FN405-10-2 EMI filter. The ATX PSU had one but it was soldered to the plug... So it'll have to be relocated to the AC Board. And to make things easier, I've decided to use an "all-in-one" unit. Theoretically, we needn't worry about electromagnetic emissions/interference as this isn't a consumer product (or massed produced) but might as well do things properly. 

- J5 is not a connector, it's just a plated hole that I'll use to connect the board to earth. The mounting screw (bottom left 'component side' picture below) will also serve that function. Maybe that'll be enough... Dunno. I need to think about that. 

- J4 and J6 are spade connectors that will be used to connect the AC Board to the ATX PSU. 

And here are some 3D renders of the board:

Bildschirmfoto 2020-04-03 um 12.19.54.pngBildschirmfoto 2020-04-03 um 12.20.39.png

The big T isolates AC from DC. It's 5mm wide. I may be a little too thick. Maybe 3mm is enough. 

There's one massive earth plane on the solder side. I've added a keep out area around the DC portion. Apparently that's the thing to do? 

More to follow...



Well-known member
Current revision: QuadrATX AC Board V0.2

Pcbnew view:

Bildschirmfoto 2020-04-03 um 17.46.20.png

3D Rendered View:

Bildschirmfoto 2020-04-03 um 17.34.11.pngBildschirmfoto 2020-04-03 um 17.34.24.png


- Deleted original J5 as screw will suffice for connecting the board to chassis ground.

- AC Neutral track re-routed

- Earth plane on both sides

- Screw hole now grounded (I had some issues with this as Kicad wouldn't understand that some pads were connected to earth even though they were clearly in the rectangle... weird)

- New slimmer T gap to isolate AC and DC. Now only 3mm wide.

- New connector for J3 (used to be a Molex Picoblade but was deemed too hard to solder due to its really small pitch. Now J3 is a KK396 like J8 but only has two pins.

- Added Silkscreen

- Mounting holes. Bottom left one of first picture (aka component side) is still a screw, the other two (top left and middle right of the same picture) will house the original PSU's plastic standoffs. Removal of said standoffs is of course non destructive.

Current questions/challenges:

- Are the thick AC tracks too big? They're 3mm wide.

- Is the right angle track (at J1) a problem?

- Damn logo/footprint won't load.

Apart from that, it's pretty much done. I'll start work on the DC board schematic tomorrow. 



Well-known member
FINALLY managed to make a logo that works!

Turns out that (for logos at least) you have to point Kicad towards a folder and not the actual file... Why is that so???

Bildschirmfoto 2020-04-04 um 15.01.48.png



Well-known member
This is starting to look like a monologue but no worries  :quadra:

As I started work on the DC board, something blew my mind. The Quadra 9x0s aren't using 22 pin logic board connectors, they have 24 pins!!

Which means I now have the opportunity to use ATX extension cables as the main logic board cable.

I'm trying to work out how to implement this. The good thing is that the wires could still be soldered in individually (ie the old way) for added authenticity. 

So the connector I'm thinking about using is this one: https://www.molex.com/molex/products/part-detail/pcb_receptacles/0460102411

Problem is, it doesn't have the lock parts on the side to secure it properly to the female end of the extension cable: https://i.ebayimg.com/images/g/6isAAOSw7ZpcpNRw/s-l1600.jpg

The black cable tie thing should be enough to hold the cable in place, right?

Bildschirmfoto 2020-04-05 um 15.17.07.png

I'd much rather use an extension cable if possible because buying and soldering all those cables individually will be a pain and really expensive! We'd need about 3m of red, 3m of black, and 30cm of orange, yellow, blue and white. 

The minimum length of wire you can buy on most websites is 5m, and they cost approx. 15€ per color. That would mean almost a hundred bucks for a LB cable... 



Well-known member
Thanks guys for your support! 

@cheesestraws I also have 220/230V where I live, but the 'worst case scenario' is with the US mains voltage. To get the same wattage, they need about twice the amperage, and more amperage means more heat and a bigger copper surface. For 230V operation, those requirements are basically halved. 

The AC tracks are 3mm wide. I calculated those using a PCB trace width calculator and got the following results (notice how voltage does not enter into the equation):

Bildschirmfoto 2020-04-05 um 16.16.43.png

The Becker draws 6A @120V (or 3A @240V). Because I chose a safety factor of 1.5, the maximum target current is about 10A. I decided to use a PCB with 2oz of copper (which translates into 70um of thickness for one copper layer) to cut the width down in two. The problem is, I'm not sure those calculators can be trusted.

Back to the DC side...

I think I found a solution to my problem...

Because of the black cable tie thing, the extension cable can't fit as is into the casing (the solution would be to get rid of said tie and that would reduce the structural integrity of the connection even more). 

One connector has to be removed to guide the cables inside the plastic cable tie. And here's the thing: What's the point of installing a connector if you can't remove the cable afterwards without modifying it some more...

So I think the following solution is the most practical: (it's not perfect so if anybody wants to chime in with a better solution, I'm all ears)

1/ Get an ATX extension cable. They're really cheap and plentiful.

2/ Cut the female side.

3/ Guide the cables into the cable tie thing. 

4/ Solder the cables directly to the DC board. 

If further modification has to be done, the male connector of the extension cable can still be removed. 

This solution is effectively what Delta thought was best for the original PSU...

I was all in for originality, but all black wires (I think) will look hella more professional.

Now, for the PSU 'rejuvenation' kits, I'll probably sell some boards (I'll have 4 extra 'DAY-1' boards since I have to order a minimum of 5) with everything pre-soldered. You guys would only have to put the 24 pin male connector (Quadra LB side) back in properly. The gerber files will still be provided free of charge but my boards may end up cheaper (especially if you're in Europe). 



Well-known member
I also have 220/230V where I live, but the 'worst case scenario' is with the US mains voltage. To get the same wattage, they need about twice the amperage, and more amperage means more heat and a bigger copper surface. For 230V operation, those requirements are basically halved.  
That's true.  Sorry, obviously a brain failure here.  And I'm not sure where I got the idea that you were in a 120V region, given that it plainly says where you are on your profile thing.

I'm doing well at the whole 'paying attention' thing today, aren't I...



Well-known member
Proposed DC board layout:

Bildschirmfoto 2020-04-07 um 17.10.34.png

Bildschirmfoto 2020-04-07 um 17.09.28.pngBildschirmfoto 2020-04-07 um 17.10.04.png


- As explained in my previous post, J1 "Quadra 9x0 Logic Board" is not a connector. The extension cable will be wired in permanently at this position.

- Added compatibility with 20 pin ATX PSUs. A 24 pin one is still preferred though. 

- Optional 3.3V and 12V dummy loads. 

- Added a SoftPower bypass for people who lost their keys or have a damaged motherboard (per @Compgeke's suggestion. Thanks again for sharing your first draft! It was really useful for a beginner like me.). External power switch required in any case to prevent arcing when connecting AC. People with original Quadra PSUs should also invest in one of these switch/cable assemblies anyway. 

- Ground plane on both sides but the screw holes on the top are not connected to earth this time. The other three holes are for the original standoffs. I may add another one...

- Couldn't find a smaller pot. This one will have to unless I find one of those low profile flat ones. BTW, you shouldn't mess with it when the power supply is on. ACHTUNG LEBENSGEFAHR!

And now, here's a nice picture showing how it'll look (NB DC board is an earlier revision, the AC board was changed a bit and the ATX PSU's casing will be removed of course...):


HD connectors are lining up really well!




Well-known member
I made a quite a mistake earlier and switched around -12V and +5Vsb on the Quadra Logicboard connector... I let you imagine what consequences it would have had if I hadn't corrected it... 

New board layout:

Bildschirmfoto 2020-04-08 um 16.59.45.png



Well-known member
Okay, the latest boards (v0.4) are in!

This time they should be pretty much finished. 

DC Board: 

Bildschirmfoto 2020-04-13 um 23.00.06.pngBildschirmfoto 2020-04-13 um 23.00.19.png

AC Board (not to scale, obviously):

Bildschirmfoto 2020-04-13 um 23.26.29.pngBildschirmfoto 2020-04-13 um 22.58.53.png

As promised, the Gerbers (fabrication files) will be available free of any charge... and here they are:

View attachment Gerbers QuadrATX DC.zip

View attachment Gerbers QuadrATX AC.zip

They'll be checked one last time but I'm pretty confident they're more than fine!

I plan on using JLCPCB. Stylurgys (not a member here, but he dedicated a lot of his time to my questions re: electrical engineering, board design etc) recommended them to me. Apparently they're cheaper than PCBWay. The next step is to get a quote from reputable manufacturers. 

I calculated the track widths based on 2oz copper layers. Use 2oz especially if you live in a 120V country. I've over dimensioned everything (the smallest track width used for the entire project is 1mm, more than necessary.) so 1oz is probably fine too. Expect to see price comparisons in the next days.

Final Bill of Materials (BOM) is also to come.



Well-known member
Back with some quotes. 2oz copper layers are way more expensive (20 bucks per card extra) than what I had in mind. Therefore, I'd had to recalculate every critical 'net' to accommodate for 1oz layers.

Bildschirmfoto 2020-04-14 um 15.57.43.png

I've used this site to calculate the temperature rise.

I'll be using FR-4 laminate (standard), so the MOT (Maximum Operating Temperature) is 130-140°C. The worst case scenario is with the Hard drive (aka Molex) connectors. I know a HD won't draw 10 Amps per rail continuously but that's the spec according to Molex. Even with a 3mm 1oz deep track, we should keep well clear of the 130°C limit (67°C in this case). Voltage drop is minimal (0.01V apparently). 

Both boards were revised. I can't seem to be able to delete previous attachments though...

Here are the new ones:

View attachment Gerbers QuadrATX AC new.zip

View attachment Gerbers QuadrATX DC new.zip

And now, the most interesting part... the cost (for 2x5boards):

PCBWay (+RoHS compliant boards): 84€ (custom duties included??? no idea)

JLCPCB (+RoHS compliant boards): 45.28€ (with S/H and custom duties).

Unless someone suggests another PCB manufacturing house, I'll go with JLCPCB. 

I'll keep 2 of the 5 boards produced. That means I'll offer 6 bare boards (3 AC & 3 DC) for 5 USD each. Anybody interested?

Last edited by a moderator:


Well-known member
I'm going to have to make yet another version. 

1/ I found some Molex spade connectors that have a slightly different footprint. I'll update the AC Board soon with the new dimensions. 

2/ The EMI filter is expensive (12 bucks). I'll investigate how much the raw components cost and perhaps make one myself. I don't think that deleting the filter is a good idea. 

3/ I FINALLY tracked down what the PC pin style connector on the original board was... It's a JST B1P-LV-TA. "Since the pitch between circuits is large, 8.0mm, this connector is ideally suited for the power supply circuits of TVs, stereo systems and VCRs." The "VCR" bit definitely dates it... It's not available anywhere but on alibaba: https://www.alibaba.com/product-detail/Original-New-JST-connector-spot-supply_60584095453.html?spm=a2700.galleryofferlist.0.0.75cb1e95wGhAtp

I've never bought anything on that site. Do you have any recommendations as to how to pay securely etc? 



Well-known member
Great work, BGE ! Keep it up :)
When you reach final design, I'd be interested in buying two of you boards (and I live in a country next to yours).



Well-known member
Sure thing @Renegade. I guess those will be for your 900 & 950? You want two sets (2xAC+2xDC) or only one set of the two (1xAC+1xDC)?

In other news, I've had to replace the relay. It now has a 12V coil. For one it was a bit on the expensive side and it was also out of stock at Digikey and Arrow. I could only find it on Mouser. 

I have decided (for now) to keep the EMI filter as is. Designing those things can be a little tricky and if I manage to make a poor one, while it may end up 5-6 bucks cheaper, I don't think it's worth it. That FN405 unit is a really high quality one. 

As ever, Arrow turned out to be the cheapest with a total of 33,79 USD for the parts. Mouser comes second at 43 USD, and Digikey third at 46,10 USD.

With S/H fees to Europe included, the price is:

- Arrow: $40,21 (about €37)

- Mouser: €59,25

- Digikey: $67,00 (custom duties NOT INCLUDED)

To US states:

- Arrow: $44,71

- Mouser: $51,61

- Digikey: $54,73

Again, Arrow won. The only issue is that I can't share my cart... Parts have to be added one by one if you plan on buying the parts through them. It only takes a couple of minutes so that's all right.

I'll upload an excel spreadsheet with links to parts and carts (for Digikey and Mouser) as soon as it's ready. 

Also, one last thing. Please let me know if like Renegade you'd be interested in getting some boards. If I order 10 of each, I'll be able to lower the price!



Well-known member
Ok, I'll order 10 sets then!

4 are still available (6 of the 10 are on hold, 2x for cheesestraws, 2x for Renegade and 2x for me). I'll probably post something on r/vintageapple, maybe someone there will be interested too. 

Now I can offer sets at $8 a pop (instead of $10, shipping still not included). 

I have solved the "PC pin connector" sourcing issue. I'll just buy a lot of these on eBay...


... and cut them in half. There won't be any downsides as the original connector used by Delta didn't have any plastic insulation to start with. I'll pre-solder and include them for free on my bare boards. I don't know if I'll have enough time on my hands (I have to go back to work next month) to offer fully assembled boards. Maybe though...

Which only leaves two relatively small issues:

1/ I'd like to find pre-crimped wires for the relay's DC connector. KK396 is now slightly obsolete and I don't know if L1NK terminals are 100% compatible with those connectors. I need to contact Molex about this. If they're not, I'll probably replace the KK396 connector by something newer.

2/ I would also have liked to find pre-crimped wires with spade connectors to connect the AC board to the new PSU. I think I'll just have to get some bare 16AWG wire and crimp those myself. 

More to follow.



Well-known member
Right, so awesome project, and I have two Q950s that will eventually need a power supply.

I don't really need one of these now, but I really have to say you should put this up on GitHub, with the KiCAD file, Gerbers, all the BOM, and maybe a few pictures and assembly instructions. Also link to the GitHub project in this thread. With that, anyone can make their own (and it would probably cost $70-80, if what I'm seeing is correct.) They'll also be able to make their own years from now.

In fact, I don't even care if you put it up on GitHub, just put it somewhere where people can find the KiCad, gerbers, BOM, and assembly instructions ten years from now. Just put it up somewhere.