From:	KIM::DOWNEND      13-MAY-1986 14:56
To:	RAINS,VANELDREN,MOORE,MCCARTHY,STEMPLER,ERNIE::MEYETTE,HOFF,SHERMAN,SANDY::DAVE,LY,DOWNEND
Subj:	Power Supplies: Opinions Solicited


13 MAY 86

In our never-ending search for a more cost-effective power supply, it
has been suggested that we look into using the same power supply found
in the IBM PC/XT. They have beefy outputs and due to volume, they
have become very cost-effective. A quick scan of PC magazines shows
XT-style 135 watt supplies selling for $88.00 quantity one ($.65/watt).
This is the retail price and includes a chrome/nickel plated enclosure,
fan, and sexy-looking on/off switch. The assumption is that we should be
able to to buy them at substanially less than $.50/watt in volume (5000)
and without enclosure/fan/switch.




QUESTION: Assuming the economics make sense, do the technical specifications
make sense?  Here is data gleaned from the label on an actual XT power supply:
-----------------------------------------------------------------------------
CON. P8 (GOES TO MAIN LOGIC PCB): +12V @.20A
				 	    -12V @.25A	
CON. P9 (GOES TO MAIN LOGIC PCB):		      -5V @.30A
								+5V @ 12.00 A
CON. P10 (GOES TO FLOPPY DRIVE):  [email protected]
							        +5V @  1.50 A
CON. P11 (GOES TO HARD DISK):	  [email protected]		
							        +5V @  1.50 A
				      -----      -----    -----       -----
				       4.2        .25      .30        15.0
MFG: ASTEC MODEL #AA12152
     INPUT 110V,3A, 50/60 HZ
     MADE IN HONG KONG

REMOTE SENSE: ??? There is a line labeled "power good"; maybe its remote sense.


Please send comments to kim::downend, or speak up the next time our paths cross.

RE. XT power supplies.

The ASTEC spec that Chris published breaks down to :
 75 watts @ 5 volts, 50 watts @ 12v, 3 watts @ -12v & 1.5 watts @ -5v.

This sounds like a big brother to the ASTEC supply we used on Gauntlet when 
we were stuck for one week with no supplies for production. We had to put a 
dummy 1 amp load on the 12 Volt output to maintain regulation.

The 'Power OK' signal is probably a Power On Reset, not remote sense.

The 12 Volt output is reasonably useless to us. Future designs could make 
use of it if it came for free. We would still need a seperate power supply 
for our audio amplifiers (unless we went to use 2 ohm speakers).

My conclusion.
This particular supply has to compete in price with our 50-70 watt
supplies. 
We should see if ASTEC (or any other third party supplier in the Personal 
computer industry) is interested in working with us. 


P.S.
You can use the [MCCARTHY]PSUP distribution list to reply on this topic to 
the people addressed in Chris's original message.

Are the specifications with all outputs fully loaded?

The audio could be done with Bridge amplifiers (at additional
cost).

If it doesn't have remote voltage sense, we shouldn't use it.

How do the cost figures really compare for this supply verses one
built to our spec, assuming we buy 25,000 ?

A few days ago I solicited comments on the technical aspects
of using an IBM PC style Power supply in our games - mainly for
cost savings.

Overall, I recommend a two-prong approach from here:
	1) Leave existing designs as-is since there are too many conversion
	   problems to change now.
	2) Seriously consider this type of supply on new designs with
	   new cabinets and new electronics which could take advantage
	   of the large 12 volt supply, the built-in fan and the built-in
	   on/off switch. There is NO REMOTE SENSE which is still a problem.

I found more technical specifications in the IBM Technical Reference:
	1) output voltage	current,min.	current max
		+5	   	2.3		   15.0
		-5	     	  0		     .3
		+12         	 .4                 4.2
		-12          	  0                  .25
	2) The "power good" signal is the logical AND of the DC output-voltage
	   sense signal and the AC input voltage fail. It is TTL compatible 
	   up-level for normal operation or down-level for fault conditions.
	3) There was no information about temperature de-rating.
	4) Provides a filtered AC output (switched by on/off), 120VAC @ 1.0 A -
	   this is a non-standard connector designed for use by the IBM 
           monochrome monitor. 

Here is a summary of the feedback received:
	1) McCarthy:...sounds like big brother to ASTEC we used in Gauntlet
                       for awhile - had to put a 1AMP load on 12 volt output
		       to maintain regulation.
		    ...12 volt output is relatively useless to us; would still
		       need separate supply for audio amp. [ I believe this 
		       is meant in the context of EXISTING system designs]
		    ...we should see if ASTEC or other 3rd party in PC industry
		       is interested in working with us.

	2)Hoff:     ... sounds like some level of investigation is warranted.
		    ...Is audio voltage/current correct?
		    ...how much would the supply save in $'s?

	3)Margolin: ...Are specs with all outputs fully loaded?
		    ...The audio could be done with a bridge amp (at extra cost)
		    ...If it does'nt have remote sense, we should'nt use it.
		    ...How do the cost figures really compare for this supply
			versus one built to our spec, assuming we buy 25000?
 
...............................................................................

For future reference, here is our current power supply cost:
	output: 5 VDC @10 Amps 0-55 degrees cent. remote sense optional;
	       12 VDC unreg @ 2amps from transformer; 12VDC reg @ .5 A added
	          to Audio Aux PCB in later revisions to support System I. 

SL POWER SUPPLY
        A043363-01 (10 AMP SWITCHER):	A043625-01 (15 amp switcher)
	CHASSIS: 	3.21		no data in ASK system, but I
	5V SWITCHER:   30.92		have a cost from Cost Accting.
	LINE FILTER:    3.65		as of 5/5/86 for materials of:
	TRANSFORMER:   11.45
	MISC:		3.54
		------------
	MATERIAL:      52.77					65.56
	LABOR:		 .84					  .84
	FIXED OVRHD.:	6.07					 6.07
	VAR. OVRHD.:    2.25					 2.25
		------------				-------------
	FULLY ABSORBED:61.93					74.72

AUDIO AUX PC BOARD, A043354-01 (ORIG. STYLE W/O EXTRA REGULATORS):
	MATERIAL:      13.36
	LABOR:	        2.12
	FIXED OVRHD.:  10.52
	VAR. OVRHD.:    3.89
		------------ 
		       29.89
(I find it amazing that we DOUBLE the cost of a PCB with labor and overhead...
 probably due to the high-labor content of this hand-stuffed board and a 
 overhead rate that is 6.8 times the labor content; the overhead is 9.9 times
 the labor content on the power base!?)

These numbers are "standard costs" pulled from the ASK system on mike via
MANMAN using the LI,1215 command. 
	
Final Note: I just opened the latest issue of PC Week Magazine and found 
an advertisement from 47st. Computer (Mailorder discounter) for a 135W supply 
for...$64.95 (qty. 10+)...wow, that's $.50 a watt including a fan, a case and an
on/off switch and connectors. That compares favorably with $74.72 for the
existing 15-amp power base.