Ticking sounds from PSU

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Ticking sounds from PSU

OK, my friends... next day, next problem :( - It seems as I should not get my II europlus to work :(

 

After recapping the PSU I get a ticking sound (about twice a second) from it.

At every tick all voltages break down an build up again. It seems as a cap charges and then discharges in an electric arc... but I cannot see any arc.

I also was not able to localize the tick exactly.

 

Any clues on that?

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A capacitor with the polarity

A capacitor with the polarity inverted? A small solder ball shorting traces?

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Hang in there

My europlus is STILL not working fully after months, but it's a lot closer.

Have you got access to a multimeter? First, check the voltages you're getting out of the PSU. One might become obvious. Remember they're going to be a little "overvoltage" when they don't have a load.

Measure the resistance between ground and the various voltage rails. I'll do the same. This will help you work out what rail to look for the fault could lie on.

Visually inspect the underside of the PSU carefully  (Remember those BIG capacitors will hold a charge potenitally for days) to look for carbonization.

Also I tend to do the "smell" test. Failing components will often smell like burning bakelite. Don't do this while it's on. No-one wants to be electrocuted via their nose.

 

Let me know if you want me to check anything else on my europlus.

 

Cheers!

 

 

 

 

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PSU resistances

Between GND and the RED wire I see quite a varying resistance. (Obviously some capacitors involved). It seems to stabilise down around 20KΩ after a while. 

GREEN was pretty stable at 220Ω.

BLUE was a clean 80Ω

YELLOW had another cap. Stabilised at around 330KΩ

 

Hope it helps you diagnose your europlus.

 

Chesh

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tony359 wrote:A capacitor
tony359 wrote:

A capacitor with the polarity inverted? A small solder ball shorting traces?

I have double checked the polarity before soldering them in. I also checked the traces for shorts... couldn't find anything.

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CheshireNoir wrote:Have you
CheshireNoir wrote:

Have you got access to a multimeter? First, check the voltages you're getting out of the PSU.

As I wrote: the voltages break down to zero with each tick, then go up again to their nominal values.

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Was the PSU working before? I

Was the PSU working before? I mean, did you test it before recapping? I am not sure whether your PSU is similar to my Apple //e one: any chance the PSU needs a load to work? Are you testing it disconnected? I am not really suggesting that you plug into your Apple but maybe you plug a load to it to see if it works.

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Apple II PSUs will fire up

Apple II PSUs will fire up without a load.

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As tony said, a ticking sound

As tony said, a ticking sound is usually caused by a short.

To go further, we need to know if the PSU is connected to the motherboard when the ticking is present. If it's the case, can you make a test without any load and report back the result ?

 

 

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