We're here again for Power Supply Basics! This time, the Indigo (Indigo 1) is featured. The Indigo is the oldest machine I own, so I won't be covering any 68ks or IRIS 4Ds unless someone in the area brings one to examine.
The Indigo was a bit of a pain to figure out, only because I started with a dead supply! I spent a long time trying to figure out the secret to turning it on; but as it turns out, there isn't much of a secret to this at all. You just need to use a working PSU.
If referencing or duplicating this information, I ask that you maintain a prominent link to this original forum post for further updates, as well as a credit by name.
Just remember, the best SGI power supply information comes from the Silicon Graphics User Group
Like in the O2, the Indigo power supply fits into a recessed cubby hole in the chassis. Here is the power supply pinout from the Indigo backplane perspective:
Power is supplied over a 24 pin Molex Mini-Fit BMI connector. This is like the Mini-Fit Jr. commonly found on wire to board solutions, but has guide posts and no clip. A 24 pin Mini-Fit BMI "plug" (machine side) is pictured to the right, with the Mini-Fit Jr. to the left for pin number reference purposes.
The Indigo back plane (which connects the motherboard, power supply, graphics, and disks) has the male pinned connector, while the Indigo power supply has the female connector.
With a power supply disconnected from the motherboard / load, the main +5V rail is active by default. If you do not see +5V present on a powered but disconnected Indigo power supply, it is likely defective.
Wire colors are notated, however as you can see they are not distinct and do not follow any appreciable standard. Also as noted, the power supply contains a prominent internal speaker, like the Indy.
Pin numbers are as per the mechanical drawing. Wire colors are internal to the power supply, as only the connector is exposed when fully assembled.
Start-up and shutdown of the power supply is worth covering in a few bullet points:
One thing also worth noting is the power pass-thru on the back; the IEC outlet most commonly used to pass through power to a monitor. This outlet is actually switched, with a relay that turns on only when the power supply is in the active state, as opposed to standby or soft shutdown. In other words, the Indigo power supply is very considerate, and will turn off your monitor for you when the machine is off!
The unit under test is an ITT PowerSystems model PEC4044, part # 6064431, with the following specifications:
Test setup:
The dead Indigo power supply (disassembled) is pictured on top of the working Indigo power supply, which incidentally came from the famous "Browndigo" prototype Indigo 1, and has dark purple/brown Personal IRIS colored plastic on the speaker housing to match the main skins.
(C1 - Pin 12 / Active signal, C2 - +5V, C3 - +12V, C4 - -12V)
The above oscilloscope trace shows the power supply transitioning from standby to active, when load is enabled. The transition of C1 from low to high is the point at which the DC load was switched on. Notice that the Active signal does not provide a suitable "Power Good" signal. The +/- 12V rails continue to stabilize well after the Active line is asserted.
Unfortunately many Indigo power supplies seem to be dying or on their way out! At this point I would recommend pre-emptive replacement of capacitors, power diodes, and switching MOSFETs if possible.
The Indigo was a bit of a pain to figure out, only because I started with a dead supply! I spent a long time trying to figure out the secret to turning it on; but as it turns out, there isn't much of a secret to this at all. You just need to use a working PSU.
If referencing or duplicating this information, I ask that you maintain a prominent link to this original forum post for further updates, as well as a credit by name.
Just remember, the best SGI power supply information comes from the Silicon Graphics User Group
Like in the O2, the Indigo power supply fits into a recessed cubby hole in the chassis. Here is the power supply pinout from the Indigo backplane perspective:
The Indigo back plane (which connects the motherboard, power supply, graphics, and disks) has the male pinned connector, while the Indigo power supply has the female connector.
With a power supply disconnected from the motherboard / load, the main +5V rail is active by default. If you do not see +5V present on a powered but disconnected Indigo power supply, it is likely defective.
Wire colors are notated, however as you can see they are not distinct and do not follow any appreciable standard. Also as noted, the power supply contains a prominent internal speaker, like the Indy.
Pin # | Wire Color | Function |
---|---|---|
1 | Black | +12V |
2 | Black | -12V |
3 | Black | +5V |
4 | Black | +5V |
5 | Black | +5V |
6 | Black | +5V |
7 | Black | +5V |
8 | Black | +5V |
9 | Black | +5V |
10 | Black | +5V |
11 | Black | Soft start (ground to start) |
12 | Black | Active (+5V logic high when PSU started / 0V logic low when PSU in standby) |
13 | Black | 0V (return for +12V) |
14 | Black | 0V (return for -12V) |
15 | White | 0V |
16 | White | 0V |
17 | White | 0V |
18 | White | 0V |
19 | White | 0V |
20 | White | 0V |
21 | Yellow | Speaker 1 |
22 | White | 0V |
23 | Red | Speaker 2 |
24 | Black | Shutdown (+5V logic high pulse to standby) |
Start-up and shutdown of the power supply is worth covering in a few bullet points:
- The natural state of the power supply with no load attached is standby with the +5V rail active (the +/- 12V rails are disabled)
- The natural state of the power supply with a load attached is running, where all rails (and the fan) activate; in other words, the power supply senses load on the +5V rail to enter a running state
- A certain amount of load is required to enter a running state
- At 0.25A on the 5V rail things start to enable; the fan is spinning at a low speed, and regulation is not stable
- At 0.75A on the 5V rail, regulation stabilizes and the fan reaches its full speed
- In the running state Pin 12 (Active) is logic high at +5V; in the standby state the Active line is logic low at 0V
- The power supply can be soft shutdown by a brief +5V logic high pulse on Pin 24 (Shutdown)
- In a soft shutdown state, all rails are disabled including the +5V rail, unlike the initial standby state
- The power supply can be restarted from soft shutdown by a brief 0V logic low pulldown on Pin 11 (Soft start)
One thing also worth noting is the power pass-thru on the back; the IEC outlet most commonly used to pass through power to a monitor. This outlet is actually switched, with a relay that turns on only when the power supply is in the active state, as opposed to standby or soft shutdown. In other words, the Indigo power supply is very considerate, and will turn off your monitor for you when the machine is off!
The unit under test is an ITT PowerSystems model PEC4044, part # 6064431, with the following specifications:
Rail | Rating |
---|---|
+5V | 34A |
+12V | 4A |
-12V | 1A |
Test setup:
The dead Indigo power supply (disassembled) is pictured on top of the working Indigo power supply, which incidentally came from the famous "Browndigo" prototype Indigo 1, and has dark purple/brown Personal IRIS colored plastic on the speaker housing to match the main skins.
(C1 - Pin 12 / Active signal, C2 - +5V, C3 - +12V, C4 - -12V)
The above oscilloscope trace shows the power supply transitioning from standby to active, when load is enabled. The transition of C1 from low to high is the point at which the DC load was switched on. Notice that the Active signal does not provide a suitable "Power Good" signal. The +/- 12V rails continue to stabilize well after the Active line is asserted.
Unfortunately many Indigo power supplies seem to be dying or on their way out! At this point I would recommend pre-emptive replacement of capacitors, power diodes, and switching MOSFETs if possible.