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

[Tarantulas]

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.

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]

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]

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!

 

[Tarantulas]

Correction on C9...  UHE1V330MDD

 

[joshc]

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]

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]

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]

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]

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]

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]

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]

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?

 

[dougg3]

I also wanted to say thank you @Tarantulas for coming up with a list of capacitors for this power supply. I finally got around to recapping a dead one yesterday, and the new caps worked perfectly and revived it. Here's the list of parts I used, along with Digi-Key links. I had to find a new part for C26 because the linked one was obsolete and unavailable. No idea if it's appropriate...but it works.

• 1 x 2200 uF, 10V: C18 - UPM1A222MHD
• 2 x 1000 uF, 10V: C19, C20 - UPM1A102MPD
• 1 x 330 uF, 35V: C15 - UPM1V331MPD1TD
• 3 x 82 uF, 35V: C16, C21, C22 - UPW1V820MED
• 1 x 33 uF, 35V: C9 - UHE1V330MDD
  • On some units apparently it's 22 uF, for that I would have used something like UHE1H220MDD instead.
• 1 x 10 uF, 35V: C26 - UFW1H100MDD1TD

On a side note, I really didn't enjoy working on this power supply. I found the TDK unit much easier to deal with.

I ended up needing to temporarily remove a few other random parts to clean them because of corrosion and thought I'd mention them here just in case it's useful for someone out there in the future. I'm unsure of the exact resistor wattages, some are bigger than others so they definitely vary.

• CR3: 1N4935
• CR5: 1N4003 (I think, marking was hard to read)
• CR9: 1N4003 (I think, marking was hard to read)
• CR10: 1N5231B
• CR11: 1N4448
• CR13: 1N5250B
• R15: 10 ohm 5%
• R20: 4.7k 1% metal film
• R21: 470 ohm 5%
• R22: 2k 1% metal film
• R33: 1.2k 5%
• U4: MC7905C, this is the -5V regulator

Also, the screw that holds down the PCB to the case was somehow corroded so badly that it was stuck onto the nut and I broke it while trying to unscrew it. In case that happens to someone else, it's a #4-40 pan head Phillips screw, 5/16" length. The nut is a standard #4-40 hex nut: 1/4" width, 3/32" thickness.

Oh, I should add that croissantking already figured out C1 and C2 as mentioned above in a different thread, but I'll repeat here: they are both X2 0.22uF +/- 10%.

 

[croissantking]

Nice to have this extra info @dougg3 - it will help others down the line (and glad I picked the right RIFAs). This PSU is kind of special in that recapping it does seems to bring dead ones back to life. I’ve usually found that if a PSU is already dead or malfunctioning, that it’s not much to do with caps.

 

[Paskuale]

I’m searching the schematic of the DynaComp power supply, someone can help me?

 

[MBehr]

Cannot help with the schematic but can report that on my Dyna Comp in LC 475, the C9 was the (only) problem. It was completely dead, no voltage on any pins, but now is completely stable with a new C9.

 

[Paskuale]

Cannot help with the schematic but can report that on my Dyna Comp in LC 475, the C9 was the (only) problem. It was completely dead, no voltage on any pins, but now is completely stable with a new C9.

Thank you