Iicx Power Supply Clicks, no go

[techknight]

That would be a rectifier bridge.

In this case, the SMPS uses shottkey secondaries, which is only a single diode per rail.

If there was a short in one of them, you would get 0 ohms from that rail to ground. Which would cause it to tick.

 

[unity]

Okay, if I am understanding you right I did the following based on pinouts above:

Grounds to grounds, 0 ohm as expected:

Each 5v to 5v ground, 45ohm give or take 2

12v+ (pin 1) to pins 6 or 7, 165 ohm.

Pin 1 to 8, 492 ohm

Pin 10 to 6 or 7, nothing with negative at ground. If I put positive to ground, 566 ohm

So from that, if I am reading things right, seems okay?

 

[techknight]

165 ohm seems VERY low for 12v....

50 ohms for 5V is eh... well give or take.

Something is wrong in there somewhere.

 

[unity]

165 ohm seems VERY low for 12v....
50 ohms for 5V is eh... well give or take.

Something is wrong in there somewhere.

What about pins 1 to 8? Should +12v on pins 6 & 7 match in ohm?

 

[techknight]

6 and 7 are tied together, to ground.

Now, since you got a different result between 1 and 8, that means the +12V is split into 2 separate rails.

Now, are you doing this in ohms? or are you doing this in diode check? Ohms isnt a valid measurement in diode check, and the results mean something totally different. if you are measuring in DIODE CHECK, then 165 isnt bad. thats actually ok. .045 in diode check is bad.

 

[unity]

6 and 7 are tied together, to ground.
Now, since you got a different result between 1 and 8, that means the +12V is split into 2 separate rails.

Now, are you doing this in ohms? or are you doing this in diode check? Ohms isnt a valid measurement in diode check, and the results mean something totally different. if you are measuring in DIODE CHECK, then 165 isnt bad. thats actually ok. .045 in diode check is bad.

Diode, cause that is why you said to use before to look for 000 across rails. I will recheck with actual ohm setting:

Pin 5 to 4,3,2 = 47.3 ohm

Pin 1 to 6 or 7 = 166.5 ohm

Pin 1 to 8 = 487 ohm

Pin 8 to 6 or 7 = 323 ohm

 

[techknight]

the 47Ohm looks almost too exact for anything to be wrong with it.

Who knows, the resistance readings are low, but they are resistances. We are looking for anything close to 000 to 005. anything in that range is bad...

In your case, your secondaries might be ok. Your trouble is elsewhere. I am betting the feedback network.

 

[unity]

I wonder if one hard drive is just not enough to test with as a load. Maybe it needs more. I think I need to locate a second power supply to start eliminating things. I don't have enough on hand to properly bench test a power supply like this. Wonder if an SE power supply would work to at least test the motherboard. I may have to look into that, would not be hard to re-pin.

 

[volvo242gt]

Another idea... Pick up a power supply for a Quadra 650 or Power Macintosh 7100. Same basic unit, but much newer and more power. It's a drop-in upgrade for a IIcx, IIci, or Quadra 700.

-J

 

[unity]

Another idea... Pick up a power supply for a Quadra 650 or Power Macintosh 7100. Same basic unit, but much newer and more power. It's a drop-in upgrade for a IIcx, IIci, or Quadra 700.
-J

Except this is a prototype IIcx, sorta wanna try to keep it as original as possible.

 

[unity]

Well the SE power supply hack worked GREAT! The IIcx boots just fine less startup chime. So a re-cap is in order for the Mobo to fix sound, etc. I am really surprised how fast it boots with 128MB of RAM. But MODE 32 is needed, I think...

So the power supply is indeed an issue. I can not rule out that in some way the startup circuit is bad on the motherboard though and that the power supply needs a greater load to properly power up.

By the way, check out these. I love finding stuff like this on un-erased drives

 

[dougg3]

I honestly think a motherboard recap might help your IIcx power up correctly with its own power supply too. I've seen all kinds of weird behavior seemingly blamable on the power supply that was really caused by leaky caps on the motherboard screwing with the soft power circuit. I know on the IIci several of the electrolytics that leak are right over by the power button circuitry. I bet the IIcx is the same way. By hooking up an SE power supply you're probably bypassing that part of the motherboard's circuit...

Of course, on the other hand, maybe the power supply really is just bad. Who knows...

 

[unity]

I honestly think a motherboard recap might help your IIcx power up correctly with its own power supply too. I've seen all kinds of weird behavior seemingly blamable on the power supply that was really caused by leaky caps on the motherboard screwing with the soft power circuit. I know on the IIci several of the electrolytics that leak are right over by the power button circuitry. I bet the IIcx is the same way. By hooking up an SE power supply you're probably bypassing that part of the motherboard's circuit...
Of course, on the other hand, maybe the power supply really is just bad. Who knows...

Thats a thought too. I am going to talk to uni about a re-cap of the mobo. I will get that out of the way before I beat myself up on this power supply issue and find out it was indeed the mobo.

 

[CC_333]

If it's a prototype, you'd probably want it to be as stock as possible (including the caps).

So perhaps replace the caps with the same type?

Nonetheless, good find!!

c

 

[unity]

If it's a prototype, you'd probably want it to be as stock as possible (including the caps).
So perhaps replace the caps with the same type?

Nonetheless, good find!!

c

Ya, I am. Already talked to uni about them. In fact, already paid just need to ship it out. He said they new small aluminum cans are sealed better, etc. Once i get it working I will post a conquest thread.

 

[techknight]

Sealed better? umm nope I dont think so.

I have 2006 era DLP TVs that the caps all leaked/dried out. SMD Lytics are just plain bad.

 

[uniserver]

I was specifically referring to only the caps i use, panasonic.

i said these caps are going to be better then what is coming off.

Over all the composition of the seal and electrolyte is better.

Back in the late 80's early 90's SMT was cutting edge.

I'd say we've learned a few things over the years.

Unless your company is CAPXON. or any other company that is making caps with a stolen formula.

 

[techknight]

True... Not sure about panasonic SMD caps. I know their standard radial caps are ok.

But its hard to say these days, as I said before I had a Mits DLP fail from bad SMD caps, and it was made in 2006ish. Its possible they used junk ;-)

 

[uniserver]

oh yeah companies always trying to save a Penny or 2

by the way i was looking at this SE/30 you did..

pretty awesome job dude!!!

viewtopic.php?f=2&t=17885

I like how you were able to piece back together his audio circuit.

I've never seen that kind of damage, yet… lol.

 

[techknight]

Trust me, you dont want to see that kind of damage.

This is what I have to deal with daily at work:

[attachment=0]20131218_162706.jpg[/attachment]

Wouldnt be so bad if it was once in awhile. But its every single day, and just about every time. lol so it tends to get old after awhile. but I have mastered the technique. If its that bad, you have to dremel out ALL of that circuit board in the charred area, because the carbonized soot is conductive. Lay a new epoxy base, and re-route the damaged circuits with patch wires. Of course, that only works if you have some knowledge of the circuit.