I also wonder with 44 modules you must have one hellova power supply torun them. You might want to do the math on your module load vs.your power supply. It might be time for another.
Eric (whojust received his 950 power supply just minutes ago!)
At 10:59 AM 12/27/2003 -0600, J. Larry Hendry wrote:
I've often wondered if we weretaxing the short circuit power-p current of
these power supplies with the all the caps we put on these modules. Every
module has at least a 10 uF to 22uF cap on each power leg. Thatcould
easily reach ~ 500uF on top of the caps in the supply. A cap doesindeed
look like a short circuit when power is first applied. Some moduleshave
lots more. And, some modules, like the Blacet Time Machine andothers draw
a lot more normal current. 38 of those would way overload a supplylike.
But, who would have 38 Time Machines. :) Perhaps someone trying toimpress
list-lurker Harry with his collection of BDDs. :)
Larry H
----- Original Message -----
From: charlesosthelder <osthelder@...>
To: <motm@yahoogroups.com>
Sent: Saturday, December 27, 2003 8:40 AM
Subject: [motm] power anomoly
Hey all!
Here's one for the troubleshooting crowd - my power supply is doinga
∗funny∗ thing. Back when module #38 was installed, I switched onthe
power and only the red LED's lit and stayed on solid-no modulation
from the LFO's, etc. Naturally, I switched the supply off! When I
got the courage to power it up again, all was well. Or so I
thought...
Yesterday I installed module #44. A new distribution board wasadded
and the wiring was rearanged to tidy up. I powered up and thistime
the green LED's lit solid. I turned it off and then back on. Now
the red LED's lit solid! I left it like this to confirm what I
thought was happening. Checking the voltages at my DC terminalson
the supply, I found a solid -15vdc and only +.71vdc. When thegreen
LED's lit solid, the opposite was true- solid positive voltage and
only -.71vdc from the supply.
When the supply powers up normally, all works well. The voltagesat
any module show no sign of brownout. With no load, the supplyalways
powers up correctly. I haven't pulled one supply at a time tofind
an offending module, because the odds are against any one module
shorting one-or-the-other half of the supply. That is next onthe
agenda, however. The supply is a Power One HBB-15 which accordingto
many, ∗should∗ handle 45-50 modules. A star wiring pattern hasbeen
maintained, and the three distribution boards are MOTM-960's. The DC
wiring is 12-guage stranded from the supply to the first terminaland
12-guage to each distribution board.
What do you think? My guess is the power supply goes intoshort
protection during inrush. The .71 vdc would be a normalforward
voltage drop from the pass transistor, showing up in parallel at the
shut-down side of the supply. Anyone else, have something likethis
happen as they neared the limits of power? Am I just going topop
for the next bigger (or greater!) supply?
I summon the vast power of knowledge that is the MOTM Group!
Chub - half-powered!
ps-Paul should really go into cartooning!
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