Recapping Falcon PSU - My rectifier is different

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derkom
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Recapping Falcon PSU - My rectifier is different

Post by derkom » Wed Sep 19, 2018 10:39 am

I'm in the process of recapping a Falcon PSU with exxos' kit (hoping to tame a ~300 mV ripple on the +12V rail) and after replacing all the caps, I've noticed that my rectifier doesn't look anything like the one in the photo on exxos' PSU page, and also there's a resistor missing from right next to it (R4). (I imagine it's simply not supposed to be there, and this is just a slightly different revision of the PSU. I am also missing R18 in the upper right.)
IMG_20180919_122549.jpg
IMG_20180919_122549.jpg (412.05 KiB) Viewed 201 times
I am reasonably comfortable with electronics, but not nearly the level of a lot of you guys, so I figured I'd better ask here before continuing. Does anyone recognise this revision of the Falcon PSU, and am I good to continue here and replace the rectifier with the new one from exxos' kit?

Thanks!

kodak80
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Re: Recapping Falcon PSU - My rectifier is different

Post by kodak80 » Wed Sep 19, 2018 11:39 am

The bridge rectifier is the original square one and is correct. The one Exxos supplies is slightly different but has 4 legs so you need to make sure you align the positive and negative legs:

Image

R4 and R18 was missing from my Falcon PSU and they look the same. Recap worked fine.
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derkom
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Re: Recapping Falcon PSU - My rectifier is different

Post by derkom » Wed Sep 19, 2018 12:08 pm

kodak80 wrote:
Wed Sep 19, 2018 11:39 am
The bridge rectifier is the original square one and is correct. The one Exxos supplies is slightly different but has 4 legs so you need to make sure you align the positive and negative legs:

R4 and R18 was missing from my Falcon PSU and they look the same. Recap worked fine.
Yep, no worries on the legs. Thanks for filling me on the other details. I shall continue the project. :)

derkom
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Re: Recapping Falcon PSU - My rectifier is different

Post by derkom » Wed Sep 19, 2018 12:13 pm

Oh silly me. If I'd just looked at the beginning of the Falcon section on the PSU page, I would have seen a picture that matches mine. Good job, me. :oops:

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Re: Recapping Falcon PSU - My rectifier is different

Post by exxos » Wed Sep 19, 2018 12:20 pm

The differences on the resistor are 110V vs 240V configs.. some better images in this section.

viewforum.php?f=59
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derkom
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Re: Recapping Falcon PSU - My rectifier is different

Post by derkom » Wed Sep 19, 2018 12:54 pm

...and it's done.

+12V ripple before...
MZK8UfN.jpg
MZK8UfN.jpg (37.97 KiB) Viewed 180 times
...and after...
IMG_20180919_145713.jpg
IMG_20180919_145713.jpg (37.37 KiB) Viewed 179 times
50 mV/div in both cases.

:dualthumbup:

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Re: Recapping Falcon PSU - My rectifier is different

Post by exxos » Wed Sep 19, 2018 1:20 pm

:bravo: :goodpost:
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

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Re: Recapping Falcon PSU - My rectifier is different

Post by Atarian Computing » Wed Sep 19, 2018 2:45 pm

derkom wrote:
Wed Sep 19, 2018 12:54 pm
...and it's done.

50 mV/div in both cases.

:dualthumbup:
Cool, so from 250mVpp to 100mVpp? What kind of load are you running here?

derkom
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Re: Recapping Falcon PSU - My rectifier is different

Post by derkom » Wed Sep 19, 2018 5:24 pm

Atarian Computing wrote:
Wed Sep 19, 2018 2:45 pm
Cool, so from 250mVpp to 100mVpp? What kind of load are you running here?
Both times just using the load resistors supplied by exxos. :) "5V uses 2.2R (loads 5V rail with 2.2amps) and 12V uses 10R (loads 12V rail with 1.2amps)"

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