LC, LC III, Quadra 605 TDK Power Supply Re-cap

[Fizzbinn]

*** Originally posted 4/11/2021, reposting due to outage. Thankfully the text was in Google Cache. ***

I finally got around to re-capping the TDK power supplies in my two original LC's, LC III and Quadra 605. There is a bunch of info in different threads and on other sites but thought others might find this summary useful.

My two original LC's had non-working TDK power supplies labeled:

TDK Model Number: 699-0153
Apple Part Number: 699-0153
+5V 3.25A
-5V 0.075A
+12V 0.75A

My LC III and Quadra 605 had working TDK power supplies labeled:

TDK Model Number: 614-0003
Apple Part Number: 614-0003
+5V 3.75A
-5V 0.075A
+12V 0.78A

I had expected it was likely there might be noticeable differences in general and/or with the capacitors I'd find inside but turns out they are identical from a capacitor prospective and while I didn't go over/compare every component I didn't observe any obvious, noticeable differences.

699-0153 (LC):







614-0003 (LC III & Quadra 605):





Capacitor List:
C3 - 180µf | 385WV d:30mm h:25mm
C8 - 8.2µf | 50V d:5mm h:8mm
C51, C52, C55 - 1000µf | 10V d:10mm h:20mm
C53, C54 - 270µf | 25V d:8mm h:20mm
C56 - 56µf | 25V d:6mm h:12mm
C60 - 47µf | 25V d:6mm h:12mm
C64 - 270µf | 10V d:6mm h:15mm

Capacitor Diagram:

Notes:​

Other sites have noted that on the AC side of the board C5 and C8 likely don't need to be replaced. I generally like to replace them all just to be sure but couldn't find Nichicon caps to match on Mouser and decided to leave the originals for now.​

I ordered the following replacement electrolytic capacitors from Mouser:

C51, C52, C55 - 1000µf | 10V d:10mm h:20mm
647-UPW1A102MPD

C53, C54 - 270µf | 25V d:8mm h:20mm
647-UPJ1E271MPD

C56 - 56µf | 25V d:6mm h:12mm
647-UPM1E560MED

C60 - 47µf | 25V d:6mm h:12mm
647-UPV1E470MGD

C64 - 270µf | 10V d:6mm h:15mm
647-UPJ1A271MED


...And the results:

LC PS #1: 5V works now, however 12V is reading only 2V...
LC PS #2: Now Works!
LCIII PS: Still Works!
Quadra 605 PS: Still Works!

Overall I'm pretty happy, the 699-0153 (LC) PS's had clear leakage, especially bad on the C53, C54 -270µf 25V capacitors. Even though they both worked before, the 614-0003 (LC III & Quadra 605) power supplies' C56 - 56µf 25V and C60 - 47µf 25V capacitors had some leakage. Hopefully these will last a good while longer now!

I need to dig into LC PS #1, anyone have any thoughts on what might cause 12V to only measure 2V?

 

[Juror22]

Thanks for the repost, I have a spare Power supply for my LCIII that I was planning to re-cap after a few more items are out of the way.

 

[reallyrandy]

I just fired up 2 of my LCII's to discover both power supplies are being wonky. One of them does nothing and the other one makes the speaker hum and lights up the screen but won't chime or spin the HD.

 

[SuperSVGA]

One of them does nothing and the other one makes the speaker hum and lights up the screen but won't chime or spin the HD.

Have you measured the voltages yet?

LC PS #1: 5V works now, however 12V is reading only 2V...

I'm still learning what does what in the circuit, but a good place to start would be to check:
CR52
L52
L53
IC55
R59
R63
R66

Here's part of the 12V circuit highlighted on my sad incomplete schematic (ignore the label on CR54 it's a place holder):



Also, if you get a chance can you measure the inductor at L53 on some of your units? Preferably with something that can measure inductance like an LCR meter, but if you don't have one then try resistance at the very least so I can get a better idea of what's nominal.

 

[Fizzbinn]

I'm still learning what does what in the circuit, but a good place to start would be to check:
CR52
L52
L53
IC55
R59
R63
R66

Thanks for the advice! I desoldered and measured the resistance of the "R" (resistors) and "L" (inductors) components, I only have a pretty basic multimeter:

L52: 0 ohms - ?
L53: 0 ohms - ?
R59: 6.8 ohms - Within Spec!
R63: 219K ohms - Within Spec!
R66: 2.19K ohms - Within Spec!

I'm not sure how to test CR52 or IC55...

Also, if you get a chance can you measure the inductor at L53 on some of your units? Preferably with something that can measure inductance like an LCR meter, but if you don't have one then try resistance at the very least so I can get a better idea of what's nominal.

I can pull L53 from one of my working units to compare resistance but I'm thinking it might be time to invest in a better multimeter, one that can measure inductance and capacitance...

 

[SuperSVGA]

I bought some inductors to test and an LCR meter (which for some reason is sized for giants) and did some testing. It seems the low resistance reading (~0.1Ω) I was getting from the inductors is fine, unlike most things I saw online that said that meant they were shorted.

I tested the inductors on my units:
L51: 2.6uH (should be 2.2uH)
L52: 5.2uH (should be 4.7uH)
L53: 2.8~3.0uH
L1: ~27uH (should be 29uH?)

L51 and L52 are a bit higher than their base rating, but I think those parts may have a ±20% tolerance. I also tested against a 4.7uH inductor I bought and it was nearly a perfect 4.7.

I now also have a closer idea of what specs of L53 should be, but I'm still uncertain because there's the chance that both of mine are bad.

Out of curiosity, I got out my old Fluke 8050A (although I have an even older 8000A, probably made in the late 70s) and measured resistance on the inductors. They measured at about 0.16-0.20Ω, which seems to match the spec of the newer Bourns parts at least. So I guess part of the problem was just the "cheap" multimeters.

I'm not sure how to test CR52 or IC55...

CR52 is essentially two diodes, anodes on pins 1 and 3 and cathode on pin 2. Put a multimeter in diode test mode, connect negative to pin 2 and positive to either pin 1 or 3, and you should get a reading. You can also reverse cathode and anode or test from anode to anode and get no reading.

IC55 is a thyristor/SCR which is a bit trickier.


Theoretically you should be able to connect negative to the cathode, positive to the anode, and measure that the circuit is open. If you short anode to gate, the circuit should now be closed and stay closed even when the short is removed as long as the multimeter remains connected.
I haven't been able to make this work. I'm not sure if it just doesn't work with any of the multimeters I've tried or both of my parts are bad.

 

[llq1999]

now my IC55 was very hot ,can not view 5v and 12 v ,only -5v is normal ... may i replace it? or some other compoents made it ?