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How to mod an ATX PSU for 10 Pin Macintosh (for example IIsi, IIci, Quadra 700 and others)


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Being that there were no instructions in the SeaSonic box, I was careful when approaching the heatsink.  I was pretty sure I'd be OK as the heatsinks all come in contact with the top of the SeaSonic chassis. 

 

As to what is missing...

 

1625592526_2018-08-2214_42_45.thumb.jpg.db1f5b2d0d6d9b0219996574ab249511.jpg

 

Above is the back of the stock IIsi PS. When I put the SeaSonic in the IIsi chassis, the power plug from the wall goes in the male connector on the left. The fitting on the right is not used and that is where the fan blows out. I believe it is for the monitor so that it will turn on with the IIsi soft power. I never had that power cord for my IIsi.  I don't feel this is a big loss as that fan needs somewhere to vent the heat and that opening will work nicely.

 

This is what it looks like from the back of the IIsi case outside looking in...

 

175871838_2018-08-2214_53_09.thumb.jpg.18b4793e5565143d60ad5fd1b821b2a3.jpg

 

 

Edited by Von
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Nice work!

 

If I were doing this (and I might!), I'd probably take the connectors from the old PSU and wire them up to the new one because I'm very particular about aesthetics, and I like mods like this to look as close to stock as possible. It's extra work, but it looks much better in the long run.

 

Here's a little side story to illustrate my point: I recently did this to an HP Pavilion 5040 I've had for about 12 years. Well, I did it about 11 years ago when the stock power supply died, but I redid it recently so that I could make it safe and proper (it finally has an on/off switch again!). When I did it he first time, I simply unscrewed the monitor port and chipped away the mounting ears, so I could push it into the PSU enclosure far enough to let the thing fit properly. Obviously this isn't safe, but it worked. I could've modded the computer by cutting a hole for the extraneous port (it would be a useful feature, in this context), but I didn't want to damage it, plus there's a plastic trim piece that covers it up, and I'd have to cut a hole in that as well, and since this is not a replaceable part, I didn't want to risk ruining it.

 

Fast forward to this year, and I decided that I should finally fix this properly, so I ended up actually removing the plug altogether, now that my soldering skills are 1000% better than they were.

 

So, anyway, this is an example of the opposite situation, which is a case of modding the PSU to fit the computer, rather than modding the computer to fit the PSU. The end result, however, is the same: it looks 100% stock from the outside, thereby maintaining the aesthetics of the computer.

 

c

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4 minutes ago, CC_333 said:

...I'd probably take the connectors from the old PSU and wire them up to the new one because...

I thought about that too. While certainly doable,  I think there'd be a bit of work to get it functioning like the stock PS. I suspect that the power socket for the monitor is not hot until soft power is enabled.  I don't know how to wire that up. As to the fan...that probably could go at the other end of the PS chassis and blow on to the innards.  This is still a work in progress...

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Hmm. I'd probably wire it in series with the main power in socket, so it's always hot. It probably diminishes it's usefulness a bit, but it wouldn't be a load on the PSU itself, then. EDIT: You could wire a relay in, which will engage and supply power to the monitor socket when the PSU is powered on. Perhaps one of those relays that switch AC, but whose contacts are energized via a 12VDC current? Probably more work thatn it's worth, especially if you'll never use it (there does exist an adapter that basically takes that monitor socket and turns it into a regular mains plug (I actually have one, somewhere...), allowing one to plug anything into it without needing a special cable, so that might be worth considering?)

 

Works in progress are fun to tinker with! My Sandy Bridge PC is such a project. I'm always tweaking it (my latest bit of work on it involved dremelling out the fan grille on the back (it's designed as a late-model AT/early ATX case (it's beige :) )*.

 

The fan works much better now. Next step is to do the same for the front grille (behind the front panel) so air can come in as easily as it goes out.

 

c

 

*Why not get a more modern case with better cooling? Well, I could, but I really like the aesthetics of this case (it's mid-90s NOS, so it hasn't yellowed like so many used ones have (alas, it will yellow eventually now that I'm actively using it, but there are ways of preventing slowing down the yellowing process nowadays, so I'm not *too* concerned about it).

Edited by CC_333
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I started the process of retrofitting a Seasonic into a IIci/IIcx PSU and built and tested the soft power on circuit.  I ended up just using a transistor and two resistors to create the inverter switch (When input is +5v, the output is low and vice-versa.  As the Mac sends +5V when the keyboard power on button is pressed, the inverter makes the output low which triggers the ATX power supply.)

 

The circuit I used is from https://electronicsclub.info/transistorcircuits.htm (Search for inverter).  I used a PN2222 transistor that I had from an old Sparkfun kit I had laying around.  I used the resistor values from the electronicsclub in the circuit.

trinvert.gif

 

I first laid everything out on a breadboard to make sure it worked fine with the ATX supply.  The red wire was connected to the power supply +5V standby.  The black wire connected to ground.  The yellow wire connected to the ATX power supply green wire (PS_ON).   The blue wire is the trigger wire that turns on the ATX supply when connected to +5V.  When the blue wire was connected to the +5V standby the power supply turned on as expected.

IMG_3961.thumb.jpeg.71dce83925a7495e0069fec5a303fe3d.jpeg

 

I then re-laid the components out on a small cut-out PCB as follows.

IMG_3968.thumb.jpeg.00fa46b6d2083159f0922c1c65e6ca4c.jpeg

The side with three wires connects to the Seasonic power supply output.  (Black = Ground (Black on Seasonic), Purple = +5V Standby (Purple on Seasonic), Orange = ATX PWR_ON (Green on Seasonic).

 

The side with the two wires connects to the 10 pin connector that plugs into the Mac motherboard.  (Purple to pin 10 of Iici Mother board connector, Yellow to Pin 9 of Motherboard connector).

 

IMG_3970.thumb.jpeg.2a951a93f1666d0aba6882ab3296203e.jpeg

 

I then used shrink-wrap tubing to cover up the circuit board and then added it to my connector (between the Seasonic and test 10-pin Iici plug)

IMG_3971.thumb.jpeg.8b511f1a0f19ef0a6a1b47f4aa076e4b.jpeg

 

IMG_3983.thumb.jpg.ddbbbd288a97cc9c89cba8c04c181b03.jpg

 

I tested it on my IIcx and it powered up from the keyboard perfectly.  Next step is to mount the Seasonic inside the PSU case.  The only issue I just realized is that the Antec supply in my Iici provides 1.0A on -12V whereas the Seasonic is only 0.8A.  I don't expect I'll have any issues I've seen a number of posts indicating the IIvi supply is compatible and that only puts out 0.6A.

 

IMG_3978.thumb.jpeg.fef2218908425536b2407034d1f6cdf6.jpeg

Edited by superjer2000
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@superjer2000 exceptional work and exceptional timing. I will follow your lead when time allows.

 

Here is the progress I made today on getting this running in my IIsi.  I had mocked up the fit with a piece of ABS plastic however I was concerned that the board was not grounded to the chassis.  This is the bottom of the SeaSonic:

2018-08-25_14_01_46.thumb.jpg.5ec148a18eeeab4e380bb6ca7346f94c.jpg

3 of the 4 mounting points look like they were grounded to the chassis so I created a harness to do this so that I didn't need to drill any holes into the IIsi PS chassis.  

 

This is the grounding harness next to the ABS:

1874711425_2018-08-2515_25_09.thumb.jpg.4df45444175c853aa41364014575fc20.jpg

 

The harness goes under the ABS next to the bottom of the chassis:

2018-08-25_15_27_15.thumb.jpg.448565cf76c64b4148f27784ff7b264b.jpg

 

Above is a pop rivet about to be set in one of the existing IIsi PS chassis standoff/risers.

 

Here is the harness with crimp-ons bent to 90 degrees so everything will fit:

1723493221_2018-08-2515_39_02.thumb.jpg.dab9ccad3cc289598b0c8f55e882c3b3.jpg

 

I hot glued some washers to the ABS to ensure crimp-on O would have good contact to the bottom of the SeaSonic:

 

2018-08-25_16_00_05.thumb.jpg.fccc30951ce152cb7f223681e033f618.jpg

 

In above photo, bottom right corner of the SeaSonic does not have ABS underneath it so it just has a screw screwed into a riser with its male thread post filed off.

 

This is where power enters and it is surrounded by the metal that is secured to the floor of the SeaSonic chassis. In the IIsi chassis, the plug is rotated 90 degrees and I riveted a male tab through the mounting hole and covered the bottom with hot glue for a bit of extra protection from it shorting something:

2018-08-25_17_57_41.thumb.jpg.c96bcb8c5f472524b34b8bef89f7be49.jpg

 

And here is the plug installed in the IIsi chassis with a female crimp-on as the last connection on the grounding harness:

 

2018-08-25_18_20_14.thumb.jpg.bd523380d120c666610d21eabe7cc5b8.jpg

 

THe fan is now installed with automotive trim double-stick tape and it is not going anywhere.

 

Here is the unit installed showing the 4-pin molex exiting the chassis cover and powering my IDE SSD:

2018-08-25_18_38_28.thumb.jpg.998bee7e2cdd35e4e4865ef7183538f4.jpg

 

I let it run for about 3 hour and I put a bit of a streamer on the back side of the case to see fan activity.  It came on after about 15 minutes and appeared to run the entire 3 hours.  I left several times and it was always blowing when I returned. When I touched the top of the case it was barely warm.

 

Next step is to build that circuit!

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I finished retrofitting a Seasonic into a IIci/IIcx power supply (Antec) case.  Compared to the SE/30 retrofit, this was a lot more work as:

1) The wires from the power plug to the power supply board aren't nearly long enough for the IIci PSU case so I needed to splice in extensions.

2) The power plug hole in the PSU sheet metal case was about 1mm to small so I needed to Dremel it out a bit so I could push the plug into the case.

 

@Von Like I did for the SE/30, I used standoffs to mount the PSU in the IIci PSU case, but when I was doing my final tests, I realized that only 1 of the four mounting points on the Seasonic are tied into the PSU's ground.  You built a grounding harness that covers all four points, but something to keep in mind for future projects as I only used three standoffs to mount my PSU board so it could clear the 10 pin power connector that exits at the bottom and I needed to reorient my board so the one mounting point was making contact with the chassis.  (Three mounting points are ringed with metal oddly enough though).

 

I took this opportunity to replace the stock fan with a Noctua 80mm fan.  Although I haven't had much success with Noctua before, for this purpose it puts out way more than enough air and is really quiet.  I plugged the Noctua directly into the Seasonic power plug so it is always on.  It's quiet enough you wouldn't notice it.

 

The power on transistor circuit works perfect.  Overall, I'm still very pleased with this mod even though it was more work that I though it was going to be.  It's neat how much smaller this PSU is than the unit that was in the case before.  A few pics are attached.IMG_4019.thumb.jpg.d6577377d81dcf1841773b91bae90d2a.jpgIMG_4020.thumb.jpg.45f5997ecb086d39b346b11b55ebb0f7.jpgIMG_4022.thumb.jpg.eda678400d2457b48c042f85e5a450e3.jpgIMG_4023.thumb.jpg.7c986507fca27385e73a4cb7fb5a4ff9.jpg

 

 

IMG_4021.jpg

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On 8/29/2018 at 8:12 AM, MrGasS27 said:

How do you attached the IDE drive to the SCSI controller? Is that board an IDE to SCSI?

Acard AEC 7720U card is what is shown.  Here is what is available on Ebay

 

At some point I'd like to do a bake-off between that card and my SCSI SSDs when time allows...

 

18 hours ago, superjer2000 said:

@Von Like I did for the SE/30, I used standoffs to mount the PSU in the IIci PSU case, but when I was doing my final tests, I realized that only 1 of the four mounting points on the Seasonic are tied into the PSU's ground.  You built a grounding harness that covers all four points, but something to keep in mind for future projects as I only used three standoffs to mount my PSU board so it could clear the 10 pin power connector that exits at the bottom and I needed to reorient my board so the one mounting point was making contact with the chassis.  (Three mounting points are ringed with metal oddly enough though).

 

Great progress on conversion and thx again for the how-to on the circuit.

 

I am trying to follow along with your comment about grounding.  The stock SeaSonic has ground enter the chassis from the power plug which has the ground wire grounded to the chassis with that metal bracket that surrounds the power plug on 3 sides and is screwed to the chassis with one of the 5 screws in the bottom. The other 4 points where the SeaSonic board mounts to the chassis are the remaining 4 screws that go into the stock standoffs.  Of those 4 mounting points, 3 appear like they should be ground as there is metal, that would be top left and both on the bottom of this photo:

On 8/25/2018 at 10:52 PM, Von said:

This is the bottom of the SeaSonic:

2018-08-25_14_01_46.thumb.jpg.5ec148a18eeeab4e380bb6ca7346f94c.jpg

 

What my harness did was ground those 3 points along with the power plug.  Are you saying that only one of the 3 with metal is actually needed to ground the board?  I did not test this, I just mimicked the stock setup which may have been overkill.

 

 

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@Von Your last comment is correct - as far as I can tell, only one of those 3 metal ringed mounting holes seemed to tie into the PSU ground.  After I had my PSU mounted in my case, I was checking for continuity between the ATX connector ground pins and the metal power supply chassis and I didn't have any.  I pulled the PSU out and tested the ground pins against those three metal ringed mounting holes, and only one had continuity.  I think it was the one in the top left of your picture.  The bottom right hole seems to also have something connected to it (the two through hole pins), it looks like it might be the two little blue caps.  I then turned my PSU mounting 180-degrees and I then had continuity between the ATX connector ground pins and the metal chassis.

 

Looking at my pics again, it looks like that fourth hole I didn't mount to the chassis is that hole that is on the bottom right of your picture, so I might need to go back and hook up a ground wire from there to the power supply chassis.

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  • 1 month later...
On 8/25/2018 at 7:15 PM, superjer2000 said:

I started the process of retrofitting a Seasonic into a IIci/IIcx PSU and built and tested the soft power on circuit.  I ended up just using a transistor and two resistors to create the inverter switch (When input is +5v, the output is low and vice-versa.  As the Mac sends +5V when the keyboard power on button is pressed, the inverter makes the output low which triggers the ATX power supply.)

 

The circuit I used is from https://electronicsclub.info/transistorcircuits.htm (Search for inverter).  I used a PN2222 transistor that I had from an old Sparkfun kit I had laying around.  I used the resistor values from the electronicsclub in the circuit.

trinvert.gif

 

I first laid everything out on a breadboard to make sure it worked fine with the ATX supply.  The red wire was connected to the power supply +5V standby.  The black wire connected to ground.  The yellow wire connected to the ATX power supply green wire (PS_ON).   The blue wire is the trigger wire that turns on the ATX supply when connected to +5V.  When the blue wire was connected to the +5V standby the power supply turned on as expected.

IMG_3961.thumb.jpeg.71dce83925a7495e0069fec5a303fe3d.jpeg

 

I then re-laid the components out on a small cut-out PCB as follows.

IMG_3968.thumb.jpeg.00fa46b6d2083159f0922c1c65e6ca4c.jpeg

The side with three wires connects to the Seasonic power supply output.  (Black = Ground (Black on Seasonic), Purple = +5V Standby (Purple on Seasonic), Orange = ATX PWR_ON (Green on Seasonic).

 

The side with the two wires connects to the 10 pin connector that plugs into the Mac motherboard.  (Purple to pin 10 of Iici Mother board connector, Yellow to Pin 9 of Motherboard connector).

 

IMG_3970.thumb.jpeg.2a951a93f1666d0aba6882ab3296203e.jpeg

 

I then used shrink-wrap tubing to cover up the circuit board and then added it to my connector (between the Seasonic and test 10-pin Iici plug)

IMG_3971.thumb.jpeg.8b511f1a0f19ef0a6a1b47f4aa076e4b.jpeg

 

IMG_3983.thumb.jpg.ddbbbd288a97cc9c89cba8c04c181b03.jpg

 

I tested it on my IIcx and it powered up from the keyboard perfectly.  Next step is to mount the Seasonic inside the PSU case.  The only issue I just realized is that the Antec supply in my Iici provides 1.0A on -12V whereas the Seasonic is only 0.8A.  I don't expect I'll have any issues I've seen a number of posts indicating the IIvi supply is compatible and that only puts out 0.6A.

 

 

Hey @superjer2000 I am about to go shopping and make a couple of these and I tried to stitch everything together and I have a question for you on your final assembly.

 

Inverter_1.thumb.png.709f729ce163d64847b4dfac650a9dab.png

 

Could you take a look at what this and LMK if I interpreted your connections correctly and LMK what that center connection is?

 

THx!

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Hi @superjer2000, I looked at pin diagrams after posting this. I had assumed PN2222 only had 2 pins and it was the 74LS04.  I think I get how this goes together with the 3 pins on the PN2222 and I will update that diagram after some sleep.  

 

You mentioned that this powers the IIci from the keyboard. Does it also shut the system down when you do Shut Down from the OS?  

 

THx!

Edited by Von
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6 hours ago, Von said:

 

 

Hi @superjer2000, I looked at pin diagrams after posting this. I had assumed PN2222 only had 2 pins and it was the 74LS04.  I think I get how this goes together with the 3 pins on the PN2222 and I will update that diagram after some sleep.  

 

You mentioned that this powers the IIci from the keyboard. Does it also shut the system down when you do Shut Down from the OS?  

 

THx!

@Von  Yup... IIci soft power works perfectly. Power on and off. Above the breadboard picture is a summary of what Color wires are what.  

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Yay, the site is back.

 

@superjer2000 I went shopping and have 2 of the PN2222's and when it came time for the 1K resistors, the guy behind the counter asked what wattage...

 

What wattage did you use for this?  The guy thought they looked like 1/2 watt so I left with 4 of those.  The shop didn't have protoboard so I have some on order that should arrive before the weekend.

 

THx!

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For both resistors, worst case, you're connecting 5V to 0V, although the Base should be considerably more limited than that.

 

Power through a resistor is V^2/R, where V is the voltage drop across the resistor and R is the value of the resistor.     So the maximum powers in the resistors are 5^2/1000 and 5^2/10000   =>   25/1000 and 25/10000   =>  .025 watts and .0025 watts.    So anything from 1/8 watt on up should be fine.   It won't hurt anything to use a 1/2 watt resistor, although it might be slightly more expensive.

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2 hours ago, trag said:

For both resistors, worst case, you're connecting 5V to 0V, although the Base should be considerably more limited than that.

 

Power through a resistor is V^2/R, where V is the voltage drop across the resistor and R is the value of the resistor.     So the maximum powers in the resistors are 5^2/1000 and 5^2/10000   =>   25/1000 and 25/10000   =>  .025 watts and .0025 watts.    So anything from 1/8 watt on up should be fine.   It won't hurt anything to use a 1/2 watt resistor, although it might be slightly more expensive.

Exactly - I just used 1/4 watt resistors as I had those lying around.

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10 hours ago, trag said:

For both resistors, worst case, you're connecting 5V to 0V, although the Base should be considerably more limited than that.

 

Power through a resistor is V^2/R, where V is the voltage drop across the resistor and R is the value of the resistor.     So the maximum powers in the resistors are 5^2/1000 and 5^2/10000   =>   25/1000 and 25/10000   =>  .025 watts and .0025 watts.    So anything from 1/8 watt on up should be fine.   It won't hurt anything to use a 1/2 watt resistor, although it might be slightly more expensive.

 

7 hours ago, superjer2000 said:

Exactly - I just used 1/4 watt resistors as I had those lying around.

 

Thanks for this guys. Vetco is between work and home so I will swing by and replace the 1/2 with 1/4.  I think all of their 1K resistors were $0.29/each. Hopefully the protoboard will be waiting for me when I get home.

 

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Some good progress made today and I am now paused with a question.

 

Here is my PN2222 (generic version)

 

831985185_2018-11-1113_59_21.thumb.jpg.d04d4ba2c916873390c1d677048a5d23.jpg

 

I don't have a breadboard so here is how the PN2222 is connected to my SeaSonic PS:

  • Leftmost leg...Purple +5v is connected to the PS and the motherboard (2 complete wires from 2 different SeaSonics), in the middle I have a jumper connecting the PS to the MB and one end of a 1K resistor. The other end of the 1K resistor then feeds through the Green PS_ON connected to the PS; that end is then alligator clipped to the leftmost leg.
  • Center leg has the red alligator clip. In the clip is a 1 K resistor and at the opposite end of the resistor is a grey wire that goes to the MB connector #9.
  • Rightmost leg is connected to the black alligator clip that clips to a black ground coming from the PS.

The above describes the hairball below:

541865409_2018-11-1112_03_03.thumb.jpg.7de3badb4c9c1b97bec1ddffa039d5a4.jpg

 

I had this setup first attached to my IIci and this did not work. Note that the IIci is fairly new to me and when it arrived its stock PS never fired it up. I added the SeaSonic and that worked fine but it needed to be manually switched. The board has never emitted sound so a recap is in order. I don't know if the caps situation could affect the power on so I decided to move to my IIsi that also needs soft power for its SeaSonic PS.

 

The IIsi also failed to start in this configuration but it did make a sound and the monitor did briefly light up so some progress.  I then tried removing the 1K resistor between the center leg and the the grey wire connected to the MB at position 9. You can see the grey wire in the red alligator clip with the 1K resistor connected to nothing (apology for the blur on that side of the photo):

2018-11-11_13_54_14.thumb.jpg.225447355c1399e062bbe5683eba311e.jpg

 

This setup worked as expected where both the power button on the keyboard and the power button on the PS fired the IIsi up. The OS also shut the machine down as expected so that is great progress.  I then wondered what purpose the other 1k resistor was offering on the leftmost leg so I tried this:

  • Removed the other 1K resistor
  • Kept the purple +5v connected to the PS and MB but not attached at all to the PN2222
  • Attached the green PS_ON from the PS to the leftmost leg of the PN2222
  • Attached the grey wire in MB position 9 to the center leg of pf the PN2222 (photo above)
  • Rightmost list of PN2222 is still connected to PS ground

Here is what that looked like:

2018-11-11_14_52_37.thumb.jpg.3a90872461eb018cc9832085f5e34934.jpg

 

This setup with no resistors worked as expected turning the IIsi on from the PS & KB and shutting down completely from the OS.

 

Can anyone tell me where I strayed from @superjer2000's directions  or why the no capacitors path I found works? 

 

THx!

 

 

 

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Hi Von you definitely need the resistors or else you'll burn up the transistor or create a short.  

 

I wonder if your connections aren't that solid given the use of clips etc...

 

To confirm. Left leg of transistor is connected to the 1k resistor and the green power on wire on the PSU. The other side of the transistor is connected to the purple PSU 5vsb line and pin 10 of motherboard connector. 

 

The centre pin pin goes through the 10k resistor and then to pin 9 of the motherboard connector. 

 

The right leg goes to psu ground.  

 

You our should be able to test it by seeing the input voltage going to the middle pin. It should be zero and the output line  output voltage on the wire coming from pin going to PSU green should be 5v. If you touch 5v from the standby line to the resistor connected to the middle pin the output line should go low and the supply should turn on. 

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2 hours ago, superjer2000 said:

I wonder if your connections aren't that solid given the use of clips etc...

I am thinking this may be the case as I had the connections as you described.  I will try to solder it up tomorrow and see how that goes.  THx

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