My //c is back and I want to keep it that way!!!!

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Last seen: 1 week 7 hours ago
Joined: Jul 14 2018 - 12:54
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My //c is back and I want to keep it that way!!!!

To recap:  The voltage regulator on my //c died and fried the fuses in both the PSU and the motherboard.   I spent about a month or so trying to trace the faults, found several, but not all.  So I replaced the regulator!  So now my //c is back and running!!! :-D  

 

So far, I've replaced the DUV26 Transistor at Q2, the HA17339 IC, all of the electrolytic compactors, and the regulator abled IC2 (not sure why it was abled that way).  I've also checked all of the diodes in and out of circuit.  Basically, I've been poking blindly as there are no schematics online for my particular regulator (Astec AA 7343A).  Hopefully, the working one will point me in the right direction.  

 

So far, all is good.  However,  I noticed that the text has a noticeable rainbow-bleed on the screen.  Admittedly I'm using an old SAHRP CRT TV from the '90s, but it's still a bit more severe than it should be.  I remember a similar issue just before the old regulator died.  It took several years. And at first, I thought it was just the natural result of having been in storage for more than a decade.  But then it got really bad the day it died.  Then the video started to cut out, and it just shut off and wouldn't power on again.  So I'm a little concerned about this.  As such, any suggestions on how to keep my beloved //c healthy would be appreciated.

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Last seen: 6 hours 19 min ago
Joined: Aug 4 2015 - 14:30
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I have the same concerns with my Apple II europlus.

6 years ago the power supply died, but with help from this site I got it up and running. One thing I did was replacing all electrolytic capacitors.

Now just recently the mainboard began acting strange. Long story short: I replaced 2 electrolytic capacitors on the mainboard and then it was up and running again.

Now these capacitors are 40 years old, so it's not strange I think that they are dying.

So my thoughts are that all old electrolytic capacitors should be changed. And that includes all expansion cards, and inside the disk drive, and also my Apple /// monitor.

I took a look inside my monitor, there are a lot of electrolytic capacitors, and I worry that they will die in a short time. They are after all 40 years old.

I haven't changed these (yet), but would like to hear people's thought about this issue.

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Joined: Jun 6 2020 - 10:50
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Ask 10 people their opinions

Ask 10 people their opinions on if caps should be replaced, you'll get 10 different answers. Those 10 people will generally fall somewhere into 1 of 3 or 4 categories though.

 

Some people believe there is no reason to recap unless you suspect a cap is bad, either through testing or it's visibly bulging or leaking.

 

While others believe caps that are stressed out (typically power supply caps) should be replaced, but caps on the logic board that are not stressed out can be left (assuming there is no evidence of failure).

 

Sometimes people in the above group also look at the quality of the original caps to decide if they should be replaced. If they see good name brands like Nichicon or United Chemi-Con, they are more apt to leave them. But if they see some no name brand caps, they may decide to replace them regardless.

 

Then there are those that believe after 30-40 years it's not a matter of if a cap will fail, but rather when. And to avoid that they automatically recap all the electrolytics, which should last another 30-40 years. 

 

I personally tend to fall into the last category. Mainly because I know these caps will fail at some point. And I'd rather not gamble on it. Plus I'd rather do the work now while my hands are still steady and eye sight still good. 20 years from now if these caps start failing and I need to replace them, that may not be the case. And if these new caps all last 30-40+ years, chances are they will out last me. And then it will be the next guys problem. 

 

 

 

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Last seen: 4 days 12 hours ago
Joined: Apr 26 2016 - 08:36
Posts: 187
High quality capacitors that

High quality capacitors that are operated well within their design limits for voltage and temperature will last many decades.

(low quality ones won't last...the surface mount electrolytics in the Mac SE/30 are a case-in point - they all fail)

 

Now, if you put a 16V capacitor on a 15 volt circuit (something I see all the time, especially on Chinese made LCD monitors) they WILL fail eventually.

The product developers do this deliberately to save a few pennies per component (and to make sure that you buy replacement monitors from time to time).

Put a 20V or a 24V capatcitor in its place and it will last longer than the device it's installed in.

 

If you put an 85°C capacitor into a circuit with an ambient temperature that approaches 80°C or even 70°C then it WILL fail.  Especially when the temperature cycles up and down all the time (like in a power supply metal can)

Put a 105°C capacitor in its place and it will last as long as the device lasts, provided the voltage is in range of the circuit.

Voltage spikes also damage capacitors.

 

As an extreme counter example vintage audio enthusiats DO NOT like to recap.  (Especially on vintage electolytics that have a particular pleasing "sound" and antique paper-in-oil or wax small value capacitors that also have characteristic "sound" to them.)

What they generally do is RE-FORM the capacitors by applying low voltages and increasing them slowly over a period of time.  The vintage electrolytics quite reliably re-form their electrolytes and self-heal their insulators.  I'm not BSing you.

 

So what camp am I in?  Well, there is one capacitor in the Astec II+ and IIe  power supply that is marginally specced.  I have had to replace that one (a 22o uF cap).  But in testing all the others they all test in spec, so I leave them in place.  Most of the Apple IIs in my collection are regularly used including one that runs 24-7 hosting a BBS.

I can't comment on IIc power supplies other than to say that the sealed power brick power supply is a great place to cook components if it is allowed to run hot.

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