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LC / LCII / LCIII / TDK Power Supply Ticking after Recap
Posted by: VeryVon on 2022-08-17 13:09:56
Hello, I just recapped a TDK Power Supply, but when I power it up I hear the clicking sound. 12V looks pretty good, but 5V and -5V are erratic. I found a thread here suggesting that either CR51 or CR52 are shorted, but that doesn't seem to be the case.

Does anyone have a schematic for this Power Supply? I'm still learning power-supply-fu so any suggestions / recommendations welcome. Thx.

p.s. don't mind CR56 missing, I took it out temporarily

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Posted by: Phipli on 2022-08-17 13:14:09
Can you get a photo of the other side of the PCB? There isn't as much to be seen from the top.
Posted by: joshc on 2022-08-17 13:25:06
Did you replace the small cap on the high voltage side?
Posted by: VeryVon on 2022-08-17 13:25:14
Can you get a photo of the other side of the PCB? There isn't as much to be seen from the top.
Sure!

p.s. As I said before, CR56 is missing, I took it out temporarily

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Posted by: VeryVon on 2022-08-17 13:26:53
Did you replace the small cap on the high voltage side?
No I didn't
Posted by: Phipli on 2022-08-17 13:32:43
Do you have some IPA / Rubbing alcohol? It looks like you've got some flux left on the board.
Posted by: Phipli on 2022-08-17 13:36:26
Oh, one thing, are you in the USA or elsewhere?

Edit - doesn't matter, I can see which PSU it is if I pay attention. 🙂
Posted by: joshc on 2022-08-17 13:41:14
No I didn't
Replace that first, mine didn't work until that was done.
Posted by: VeryVon on 2022-08-17 13:48:57
Do you have some IPA / Rubbing alcohol? It looks like you've got some flux left on the board.
Yes I do. Agree, I'll clean it up some more.
Posted by: VeryVon on 2022-08-17 13:49:40
Replace that first, mine didn't work until that was done.
Ok I'll see if I have that in stock. I just checked it with Blue ESR meter and it checks out OK. There doesn't seem to be any leakage on that side of the board.
Posted by: SpocksBeer on 2022-08-18 03:35:40
It likely needs a wash. I have one that I periodically does the same after a recap (went from totally dead). If it's still covered in cap goo, there's possibly a short somewhere and the ticking is the protection circuit kicking in. You might also need to test it under load. I think mine ticks when no load, and works (or fails to sometimes start) when plugged into the motherboard.

Or just do what I'm going to do and just replace it with a new unit, per this thread: https://68kmla.org/bb/index.php?threads/replacement-power-supply-in-quadra-605.41793/
Posted by: VeryVon on 2022-08-18 04:19:41
It likely needs a wash. I have one that I periodically does the same after a recap (went from totally dead). If it's still covered in cap goo, there's possibly a short somewhere and the ticking is the protection circuit kicking in. You might also need to test it under load. I think mine ticks when no load, and works (or fails to sometimes start) when plugged into the motherboard.

Or just do what I'm going to do and just replace it with a new unit, per this thread: https://68kmla.org/bb/index.php?threads/replacement-power-supply-in-quadra-605.41793/
Wow thanks for the tip! I feel a little bit silly for recapping now 🙂 and will definitely reconsider when attempting on a board with this much goo. I found a seller on AliExpress selling RPT-60A power supplies for about 30USD including shipping but didn't order yet.
www.aliexpress.com

24.01US $ |Mean Well Pcb Type Rpt-60 Series Triple Output Medical Grade Power Supply Rpt-60a Rpt-60b Rpt-60c Rpt-60d Rpt-6003 - Switching Power Supply - AliExpress

Smarter Shopping, Better Living! Aliexpress.com
www.aliexpress.com www.aliexpress.com
I'm going to spend a little more time on this original supply bc I'm already invested in it, but it's nice to have a backup plan!
Posted by: dankcomputing on 2022-08-23 09:48:38
Are you testing these with a load? Even working normally they’ll tick with nothing connected. Threw me off when I first started working on them.
Posted by: VeryVon on 2022-08-23 09:53:10
Are you testing these with a load? Even working normally they’ll tick with nothing connected. Threw me off when I first started working on them.
Yea good point, I'll put it back together and try with a load.
Posted by: techknight on 2022-08-23 13:23:55
Yea good point, I'll put it back together and try with a load.
they wont run without a load.
Posted by: Addicted on 2022-09-15 18:33:01
What would constitute a fair test load for the LC II TDK PSU? I want to test an LC II PSU without risking a logic board, or without risking frying a properly repaired PSU with some defective logic board.

I've come into a need to repair an LC II PSU (a TDK), but don't want to risk using the logic board as my lab rat when it's time to try the repairs out. And this logic board hasn't been tested either, so I don't want to confuse things with it until I know the PSU repair was good.

Any advice?

Thanks to all, as always, for reading my post..

PS: The PSU.. the heat sink with the two ICs on the narrow end opposite the power plug/switch.. IC55 and its neighbor.. get hot the moment it's turned on. I'm thinking this may be more than a recap. Ordered the caps, will try to identify those semi parts and get replacements for them as well.
Posted by: sergehi on 2022-09-16 04:15:00
Hello Addicted. I used two 12v bulbs (small ones from car turn signals)
Posted by: Addicted on 2022-09-17 09:54:53
Thanks! (I wasn't sure if I needed inductance and capacitance.)

Recapping the PSU went smoothly, and it now shows -4.97, 11.99, and 5.10V with the logic board attached. Close enough. Three caps had leaked badly, and one or two others had either leaked or had the leakage of other caps under them, so it needed to be done. It took a lot of swabbing and cleanup. One pad had corroded and required a little sanding to expose fresh metal nearby. Fortunately, it seems the ICs were unharmed.

FWIW I used a pre-packed, one-click component kit from console5.com . They had it in stock, it shipped same day, and included a little reference card about capacitor markings. Also included an Atomic Fireball (jawbreaker candy), just for fun. Recommend.

Now that I have power.. on to figure out my Chimes of Death 🙂 (Without a PSU, I hadn't discovered that the logic board also has issues.)
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