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LC / LCII / LCIII / Q605 - Dyna Comp DCF 353 Power Supply Woes

Tarantulas

Well-known member
I recently picked up an Performa 410 (LCII education model) and have started down the road of recapping.  The motherboard is mostly under control, but I'm having trouble figuring out what's up with the power supply.

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Unlike most of the guides and videos I'm seeing online which are based around the seemingly more common TDK or ASTEC power supplies, my machine arrived with a "Dyna Comp model DCF 353" (Apple part number 614-0028).

Before disassembly, I checked the PSU with my multimeter and got some wonky readings.  +12V was OK... +5V was closer to +2.5V and erratic... and -5V was really really low and erratic. 

I went ahead and desoldered all the caps, and then tested each one with my multimeter.  Seemingly they all can make it up to infinity.... so I don't know if they're really bad or not.

So I guess what I'm asking is:

* Does anyone here have any words of wisdom in dealing with this power supply?

* Does anyone have a saved Digikey/Mouser/Arrow parts list that I could use for the replacement caps they'd be willing to share?

Thank you!

 

Tarantulas

Well-known member
Here's the list of the electrolytic caps and their locations.
(Note: All are rated 105c except for C7 and C28, which are rated 85c)

C7 400V 180μF

C9 35V 33μF

C15 35V 330μF

C18 10V 2200μF

C19 10V 1000μF

C20 10V 1000μF

C21 35V 82μF

C22 35V 82μF

C28 35V 10μF

 

Tarantulas

Well-known member
UPDATE:
 

Here's the list of the electrolytic caps and their locations.
(Note: All are rated 105c except for C7 and C28, which are rated 85c)

C7 - 400V 180μF - LGW2G181MELB25

C9 - 35V 33μF - UVR1V330MDD1TD

C15 - 35V 330μF - UPM1V331MPD1TD
C16 - 35V 82μF - UPW1V820MED

C18 - 10V 2200μF - UPM1A222MHD

C19 - 10V 1000μF - UPM1A102MPD

C20 - 10V 1000μF - UPM1A102MPD

C21 - 35V 82μF - UPW1V820MED

C22 - 35V 82μF - UPW1V820MED

C28 - 35V 10μF - UVR1V100MDD1TD

Would someone more learned than me be willing to take a second to verify that the linked caps would be worthy replacements?

Thank you!

 

joshc

Well-known member
C9 is a potential killer on these, at least from my experience of just fixing a completely dead one.

Symptoms before attempting repair was that it was completely dead, no power at all, nothing on any voltage rail. I recapped all the stuff on the low voltage side, no change. Checked diodes, resistors, replaced fuse, no change. Checked the big 400v cap, it looked fine.

But that tiny 33uf 35v cap on the high voltage side, C9, was the culprit - it had leaked quite badly and made a mess around some of the diodes/resistors around it. Cleaned all that up, replaced C9 with a new capacitor, and the power supply now has life again.

@Tarantulas thanks for this recap list/guide, it was handy.
 

joshc

Well-known member
C28 in the list above should be C26.

Also it seems C9 can sometimes be 22uf, perhaps depends on separate models of Dyna Comp?
 

djhaloeight

Well-known member
Out of my 5 pizzabox machines, the only two working power supplies are Dyna Comps. The other three that are dead are TDKs. I just bought 5 capacitor kits, one for each power supply, from Console5. I think my very basic soldering skills can handle thru-hole caps pretty easily…I hope…lol.
 

chiptripper

Well-known member
DynaComp LC units are pretty easy to take apart and work on, IMO, (easier disassembly than TDKs) but there's an incredible amount of solder on the underside to contend with. Worth it, though. Nice neat little supplies.
 

djhaloeight

Well-known member
Tried my hand at soldering them tonight. The first TDK didn’t work afterwards. Well, it sort of works. Fans spins at about half speed, HD doesn’t spin up. Either something else is broken or I goofed a solder joint. The second TDK works perfectly. They were both stone dead, and both had a buttload of cap goo all over. Gonna tackle the 3rd TDK tomorrow, see how that goes. Then onto the Dyna Comps.
 

Kubik

New member
I have a completely dead DynaComp one. The copper was corroded under one low side capacitor, so I have removed that one, cleaned up and I am waiting for the replacement, but when looking up for some more advices, I found this topic, checked the tiny cap on the high side - and yeah, it looked fine, but the bottom was all bubbly and wet. I was surprised as I measured good 12V on the power controller (pins 5 and 7) so I thought the high side is OK.
Anyway - I'll report back when I get the replacements. Thanks for the advices I found here!
 

Kubik

New member
So I have recapped some caps, especially the tiny one on the high side, and now I am getting ticking noises. Also, the voltage on the controller doesn't seem to be quite right, there's a 20V zener diode, but the voltage is some 13,5V only, so it looks like the controller isn't getting the necessary power. I am going to check the power supply to the controller. There's typically a high value resistor that feeds the input voltage to a diode as a rectifier, and that resistor is under a lot of stress.
 

croissantking

Well-known member
I am recapping one of these for @VMSZealot . It is indeed a cute little unit. I've put together a BOM here on Mouser, using the above list as a reference, and taking into account @joshc 's corrections. The only change I've made is to C9, which on my unit is a 22uf part.

The RIFA caps at C1 and C2 are missing on this unit, could anyone kindly tell me what values these should be?
 
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