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Power Supply dead

PSU check

PSU check

scommstech said...Really you should be checking your Power supply properly.
Click to expand...

I think Vifa's already done that:
Vifa said...
Pin 1: (-5,7) - (-6,3)
Pin 8: 11,8 - 12
Pin 9: 4,95
Click to expand...

There's some more measurements in the thread if you dig for them.

The clicking/shutdown of the switcher was due to Vifa attempting to measure the voltage legs with the multimeter set to current, thus causing a short.

patscc
 
Power supply

Power supply

I was in a hurry, didn't read all the threads.
As the volts are reasonable it does look as though the prob
is with the motherboard.
I repaired about a dozen apples last year but I did need my scope.
Regards
Scommstech.
 
Voltages

Voltages

scommstech said...volts are reasonable
Click to expand...
The only one that was a bit of a concern was the -5V leg. The max spec for the 4116's -5 leg is -5.5 V, and Vifa's power supply seems to be slightly out of that range.
It seems there's no clock, so I think right now we're all waiting to see if Vifa can get his hands on a scope or probe or logic analyzer, or take the Apple to a location that does.
patscc
 
Apple II Probs.

Apple II Probs.

No mention of the +12v

However here are some scope results of the clock generation cctry
taken last year on a motherboard.

IC B2 pin8 (14M clock) 1.5v peak to peak sign wave 1:1 ratio .075us
B1 pin3 (col ref) 4V p-p square wave 1:1 .3us
B1 pin15 (7m) 5V p-p sign wave 1:1 .5us
B1 pin14 (-7m) 5V p-p sign wave 1:1 .15us
C2 pin15 -ras 5V p-p squarish 1-3 app .5us
C2 pin14 AX 5V p-p square 1:1 .5us
C2 pin13 -cas 5V p-p square 1:1 .5us
C2 pin12 03 5v P-P square 1:1 .5us
B1 pin7 00 5V P-P square 1:1 1us
B1 pin6 01 5V P-P square 1:1 1us
B12 pin8 LD194 5V P-P +ve pulse 1 or .1us
A2 pin3 -LDPS 5V P-P -ve pulse 1 or .1us
B6 pin15 -RAMSEL 5V P-P 1:1 1 or .1us

Last 3 measurements, I changed the decimal point on my notes and can't
remember which is right.
Hope these help
regards
scommstech
 
pin 8

pin 8

scommstech mentioned...No mention of the +12v
Click to expand...
That's the voltage on pin 8 of the 4116's, it was measured (see a couple of posts back).
What I can't remember is if the -12V supply ever got mentioned.

Vifa, have you managed to gain access to an oscilloscope yet ?

patscc
 
patscc said:
That's the voltage on pin 8 of the 4116's, it was measured (see a couple of posts back).
What I can't remember is if the -12V supply ever got mentioned.

Vifa, have you managed to gain access to an oscilloscope yet ?

patscc
Click to expand...

I knew only 3 levels had been mentioned. miss read the - sign as -ve
The -12v winding sits on the -5v. If the -5v is out the -12 probably is also.
Don't think -12V is used on the motherboard though.
Scommstech
 
Even if all the RAM is fried (which I doubt... the -5 was used for the charge pump), there still should be some glimmer of partial life showing up on the monitor.

I've replaced the 14.318MHz crystal in a number of II+/IIe machines back in the day. If you can't find the test gear, just try to replace that crystal and see what you get.
 
clock

clock

channelmaniac said...just try to replace that crystal and see what you get
Click to expand...
The fact that when Vifa tried to get an AC signal off a couple of pins to see if there was activity and drew a blank makes channelmaniac's suggestion a real good one.
patscc
 
I wouldn't recommend swapping out soldered in parts without some more concrete reason. Something IS possibly wrong with timing here. However the crystal is the last place I would look. Could be system timing, which includes the following ICs: B1, C1, C2, B12, A2, D2, B2, B12 or sync counter D11-D14. Just as likely to be a bad connection to a socket as a bad component. There could also be something wrong with the last stage of the video generation, which involves a bunch more chips and some discrete components. You might try swapping some of the chips around, before getting out a soldering iron. If you don't have a donor board to use for a source of ICs. many of the chips in the Apple II are used in multiple places and like chips can be swapped with each other to see if the behavior of the board changes. Your best bet is to debug with a logic probe or oscilloscope, rather than by trial and error.

PS I believe that video generation should only require +5 and +12 volts. +12 volts is only needed for oscillator circuit. Note that the screen will not have a useful display of text or graphics without DRAM and associated voltages also working.
 
Last edited:
scope

scope

mwillegal said... logic probe or oscilloscope, rather than by trial and error
Click to expand...
I think we all agree on that, unfortunatly it seems Vifa doesn't have one, and thus far hasn't managed to get his hands on one. I wouldn't suggest randomly swapping out IC's, but replacing a crystal is pretty straightforward, and following channelmaniac's suggestion certainly would be something quick to do, and wouldn't do any harm, or would it ?
patscc
 
Ah, the joy of Monday Morning Quarterbacking. :rolleyes:

I've replaced way more than one bad crystal on Apple II series machines back in the day.

(Back in the day = working for Contemporary Concepts in Paris, TX back in the mid 90s. We did grey market component level Apple II and Mac repairs)

It's the quickest and easiest thing to replace when you have power but absolutely NO signs of life on the monitor. And, it's cheap. You can find those (14.318 ) crystals in many different pieces of gear if you want to rob one to try.

RJ
 
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