out. It I forgot to mention that I have used car/motorcycle bulbs before, but I find them a bit awkward to work with. Regards Rob

On 08/24/2014 3:01 PM, Fred Cisin wrote: I dunno, a 5 ohm 5W resistor takes up a lot less bench space...heck even a two watt would be OK for short periods of time - lets see 5 volts across 5 ohms = 1A at 5Watts. John :-#)#

Anyone know what the original IBM PC AT Load was made of/from? This was for the models w/out a HDD which I believe were far and in between so there aren't too many of them around.... -----Original Message----- From: Dave G4UGM [mailto:dave.g4ugm at gmail.com] Sent: Sunday, August 24, 2014 3:18 PM To: 'General Discussion: On-Topic and Off-Topic Posts' Subject: RE: Test Loads for Power Supplies I only test PC style supplies and keep some wire-wound resistors like these http://www.ebay.co.uk/itm/351150912079 for dummy load..... ... not sure if they draw enough current to test yours. http://jumperone.com/2011/06/atx-power-supply-tutorial/ Dave G4UGM -----Original Message----- From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Robert Jarratt Sent: 24 August 2014 22:24 To: 'General Discussion: On-Topic and Off-Topic Posts' Subject: RE: Test Loads for Power Supplies out. It I forgot to mention that I have used car/motorcycle bulbs before, but I find them a bit awkward to work with. Regards Rob

That has been my experience as well. I know it was something simple mounted in a bracket that could be installed in place of the HDD. It would be nice to know what they used just for the historical aspect of it if nothing else. I would assume it was designed to operate for prolonged periods (i.e. as long as the computer was on) so it must have had some sort of (passive) cooling as well. -----Original Message----- From: Tony Duell [mailto:ard at p850ug1.demon.co.uk] Sent: Monday, August 25, 2014 1:17 PM To: cctalk at classiccmp.org Subject: Re: Test Loads for Power Supplies It gets a beif mention (with no description) in the HMS manual, but nothign i nthe TechRef :-( line. That is a resistor wired to a 4 pin disk drive power plug (to conenct to the hard drive power cable) between the +12V pin and one of the ground pins. I do not know the value of the resistor, that is not in any of the manuals I've seen. -tony

Me too. I have a little board with two SBC lampholders on it, wired to one of those 4-pin connectors that used to be used for disk drive power. In one lampholder goes a 12V car side lamp bulb (5W - a bit under 0.5A) aand in the other a 6V car headlamp bulb (36W - around 6A assuming the bulb approximates a constant current load. It's not a constant power load as someone suggested, but I take it constant current was what was meant.) Before you ask, my truck (which has 6V electrics) used to take the old double dippers with two identical filaments one above the other. Switching filaments switched between a source above the axis of the reflector and one below, so careful positioning of the bulb and reflector gave you the dip effect. The bulb had a symmetrical bayonet because it didn't matter which way round you put it in - reversing it merely swapped the roles of the filaments. I can't remember now whether I added a switch to give both filaments in parallel if a larger load was required. I wouldn't recommend under-rated resistors. If you're going to have the load on for long enough to check voltages accurately, measure ripple, and (could be important) make sure the PSU behaves itself as it warms up, a resistor could easily catch fire. Philip.