Model 90 Power Supply
Check the voltages with connectors P1 and P2 plugged into the system board.
Power Supply Models
There are at least two different PS for the 90- I have heard rumors of a 150W PS.
Rich Wolos said
64F4114 194 watts (from Jan 92 HMM) (Thanks for the +5v Amps, Rich!)
A post from Don Peter on the Model 90 Power Supply-
The most important point is that the "testing the power-supply" topic extends only on testing the thing as "one box" and *not* open it. You should leave that to trained experts, because it bears some risks - from which sudden death is the most evil (can spoil the whole day - and more). This sort of "shocking experience" should be left out.
The easiest way to test the power-supply if it is still working at all is to open the case, look at the right side under the power-supply, locate the 2 plugs from the power supply to the systemboard and carefully unplug them by simply pulling them out. It might be a bit difficult to get them back this way - but if the power-supply is broken you will have to remove it nyways when you get another one, so we can leave that at the moment.
Now: once you got the two plugs pulled out - look at them.
The one "P1" marked connector has 2 blue, 6 red and 1 black cables ...
that's the lesser important one at that point. The second "P2" marked is
the one we need to look at closer. Do the following: re-attach the machine
to the AC, then use a piece of wire or a bended paperclip and connect the
white wire with one of the neighboring black ones.
In case the connection is good and the power-supply itself is functional
the power-supply fan should come up - and most likely the machines' harddisks
as well, which are directly attached to the power-supply with 4-wire DC-cables.
If the power-supply comes up the problem sits somewhere else:
In case nothing happens apart from a faint "click" inside the power-supply ... now ... get familiar with the idea of getting a spare from somewhere. It often pays trying to get an entire working machine rather than only a power-supply.
Mod. 8590 without harddisks and memory often sold for some 30 - 40 bucks ... some ask 40$ for the power-supply alone. The 9590s may cost some more - the power-supplies however are identical as far as I know. The main difference between an 8590 and a 9590 is the 1.44MB FDD on the 8590 and that some versions come with only a 512K XGA-1 on the planar. Everything else (processorboard, memory, power-supply, harddisks) can be interchanged among the models.
Since you notified this "high pitch whistle" in your first mail I think it will not pass this test and is broken. Usually these power-supplies are pretty reliable - some of them suffer on "long term problems" with dust contamination and related overheating. In case there were an over-current condition (overload on +5V / +12V lines) it should come up in the above-mentioned test - if that malfunction is not caused by the harddisks. Try detaching the 4-pin power-plugs from the harddisk(s) and retry ... if the malfunction persists even with nothing attached to the power-supply it is definitely broken.
To fix these kind of "switching power supplies" you need some more equipment than only a multimeter, a pair of scissors and a roll of duct-tape. Parts inside these supplied are directly connected to mains AC and converted into DC impulses of hazardous voltages and frequencies ... so I would not even recommend trying to open the box if you do not exactly know what you are doing. In case of doubt: leave it as it is. There are a few "power-supply gurus" out which may be able to repair the unit - but they are hard to find.
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