Thanks Exxos.
I just checked my Mega STe PSU and the colours are correct according to previous discussions. The output seems to be within spec as well, which is good, although I will recap. Here are my measurements (before recapping) which I got from the PSU power connector, attached to the computer:
+12V (yellow):
12.040V
-12V (blue):
-12.619V
+5V (red):
5.040V
-5V (white):
-5.040V
GND (black)
PG (orange):
4.904V
Actually, I think I might just order that recapping kit of yours for the STe as well (SR98). I'll eventually replace it with something better when I recase the computer, but it's probably a good idea to feed it with "clean" power while I'm working on it, so as not risk damage the computer.
Exploding PSUs! I don't want to risk that, so let me summarize to make absolutely sure I've understood what you're saying:
In order to test the MSTE PSU (while disconnected from the MSTE) I need to:
a) connect a resistor between PG and GND.
and ....
b) connect a resistor between +5V and GND.
This will allow me to power up the PSU safely and let me check the PG and +5V output voltages. Its absolutely essential to have these two resistors in place when powering up the PSU (or it'll explode/get damaged?).
in
addition to the above:
c) for checking the +12V line I need to (in addition to steps A and B) put a resistor between +12V and GND
d) for checking the -5V line I need to (in addition to steps A and B) put a resistor between -5V and GND
I only need to put a resistor across one of the lines at a time (the line I'm measuring), so after checking one line and powering off I can move the resistor over to the other line, power on again and check that line.
Did I get it all right?
I think you may be confusing -12 with +12V. The resistors kit I sell is for +5 and +12V, for the STF PSU's etc.
+12V 10R = 1.2amps. ~15watts.
+5V 2.2R = 2.27amps. ~12 watts
-12 330R = 36mA. ~ 0.5 watts.
-5 100R = 50mA. ~ 0.25watts.
Total load ~28watts.
The first two (10 Ohms and 2.2 Ohms) are the same as in your SR98 dummy load kit -
is the Watt rating suitable for using them with the MSTE PSU as well (for testing +12V and +5V)?
Yes, I'm a little confused about + and -12V, and I see why:
Looking at the SR98 (for my STe) schematic I see that its PSU only outputs +5V (red) and -12V (blue).
But the MSTE PSU outputs the following in addition to those: -5V (white), +5V (orange -for "Power good") and +12V (yellow).
I assumed the dummy load kit was for any Atari PSU, so when I read:
5V uses 2.2R (loads 5V rail with 2.2amps) and 12V uses 10R (loads 12V rail with 1.2amps)
.....I assumed you were talking about
+12V since there was no mention of a negative voltage. But that's cleared up now,
so if I've understood it right I just need to buy the following resistors in addition to your ST PSU dummy load kit so I can test both PSUs?:
330 Ohms/0.5W or more (for testing -12V from the MSTE PSU)
100 Ohms/0.25W or more (for testing -5V from the MSTE PSU)
How about the PG (+5V) line? Do I need another 100 Ohm/0.25W resistor there, or another 2.2 Ohm/12W resistor?
Judging by the choice of the MSTE -12V dummy load resistor above (330 Ohms/0.5W) being different from the -12V dummy load resistor for use the with ST PSU (10 Ohms/?? W)
I suppose you need different resistors for each switched mode PSU you're testing?
Hopefully all my questions will help others with the details as well so they don't need to ask as much
