Apple IIe Astec AA 11040B Power Supplies

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Apple IIe Astec AA 11040B Power Supplies

I have a pile of Apple IIe's I'm refurbishing, and I just ordered a bunch of cap kits from Console5 to recap the power supplies, most of which are the Astec AA11040B style.  Iniitally, I discovered all but one worked properly, so I was a bit surprised to see varying behavior when I started the recap process.  Specifically, several would provide the +/-5V and +/-12V outputs when powered on.  Others simply made a repeated ticking sound, a symptom I've come to understand is often a capacitor issue - such was the case when I worked through a few IBM power supplies.

 

Then I duscovered that the ones that tick apparently need to be loaded to provide output.

 

My confusion is, I see no significant difference between one that ticks and one that does not - there's no obvious model / revision numbers anywhere to indicate a difference, the boards are often identical.

Is there a telltale way to determine if one of these power supplies needs to be loaded, or if the ticking is an indication of failure (apart from plugging it in to a motherboard, of course)?

 

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Chris's Video

Watch Chris's video and see if any of his tips help. Guy is an Apple genius.

 

https://m.youtube.com/watch?v=tNIjMOF5sx4

 

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My confusion is, I see no
My confusion is, I see no significant difference between one that ticks and one that does not - there's no obvious model / revision numbers anywhere to indicate a difference, the boards are often identical.

Is there a telltale way to determine if one of these power supplies needs to be loaded, or if the ticking is an indication of failure (apart from plugging it in to a motherboard, of course)?

 

A ticking power supply is indicative of some sort of short or voltage sag, triggering protective circuitry.

 

Check for a shorted capacitor or other issue, starting at the output voltage leads.Generally the output caps don't fail on that power supply.  They are quite good quality.

As I've said before, the only one that I've seen fail occasionally apart from the RIFA noise suppression capacitor at the mains input, is the small 220 uF one at C12.

 

But if that one blows the power supply will not start up at all.

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ASTEC PSU update

Since I've completely recapped "ticking" boards and they continue to tick, I must assume that's part of the design for some of the ASTEC PSUs when unloaded.  Every one that's "ticked" unloaded provides stable voltages when plugged into a motherboard.  No other PSU that I've encountered does this unloaded.

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joel_graff wrote:Since I've
joel_graff wrote:

Since I've completely recapped "ticking" boards and they continue to tick, I must assume that's part of the design for some of the ASTEC PSUs when unloaded.  Every one that's "ticked" unloaded provides stable voltages when plugged into a motherboard.  No other PSU that I've encountered does this unloaded.

It's not part of the design.

Astec power supplies do not tick when they're unloaded.  Neither do the DynaComp ones for that matter.

Something is goin on there...

 

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Some PSUs ae switched and

Some PSUs ae switched and some are unswitched. I went through this all about 6 months ago. I had a Dynacomp I fully recapped and just ticked when powered up unloaded. Connected it to a motherboard and no ticking and gave great readings. I have Astecs that don’t tick when not connected. Connect it and the ticking will go away, it needs to be under a load. 

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They are all switched mode

They are all switched mode supplies I believe ?

 

And some have enough leakage through various bits to allow the regulator to see a voltage and to stabilise it. 

 

Its very likley that recapping with modern healthy caps may cause some suppiles to trip out on the SCR as the regulator wont wind back enough to control the voltage, the SCR fires, pulls it down to 0V, resets, voltage ramps up, over volts and fires the SCR again, hence tick tick tick.

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Gary C wrote: Its very likley
Gary C wrote:

 

Its very likley that recapping with modern healthy caps may cause some suppiles to trip out on the SCR as the regulator wont wind back enough to control the voltage, the SCR fires, pulls it down to 0V, resets, voltage ramps up, over volts and fires the SCR again, hence tick tick tick.

 

As I always say, recapping for the same of it has a fair probability to make the device perform worse.

Just repair the bad components.  The capacitors in Astec power supplies are high quality and are not in danger of failing any time soon, especially if they are in semi-regular use.

 

 

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