MOTM

A really simple question:  Did you recheck all of your power 
connections?  I got one wrong once and while it didn't fry any modules, I 
did have some LEDs light solid (I think it was a 320 LFO that did 
that).  Anyway, it is always worthwhile to check your power connectors.  It 
is easy to get those off by one peg.

I also wonder with 44 modules you must have one hellova power supply to run 
them.  You might want to do the math on your module load vs. your power 
supply.  It might be time for another.

         Eric (who just 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 were taxing 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.  That could
>easily reach ~ 500uF on top of the caps in the supply.  A cap does indeed
>look like a short circuit when power is first applied.  Some modules have
>lots more.  And, some modules, like the Blacet Time Machine and others draw
>a lot more normal current.  38 of those would way overload a supply like.
>But, who would have 38 Time Machines. :)  Perhaps someone trying to impress
>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 doing a
>*funny* thing.  Back when module #38 was installed, I switched on the
>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 was added
>and the wiring was rearanged to tidy up.  I powered up and this time
>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 terminals on
>the supply, I found a solid -15vdc and only +.71vdc.  When the green
>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 voltages at
>any module show no sign of brownout.  With no load, the supply always
>powers up correctly.  I haven't pulled one supply at a time to find
>an offending module, because the odds are against any one module
>shorting one-or-the-other half of the supply.  That is next on the
>agenda, however.  The supply is a Power One HBB-15 which according to
>many, *should* handle 45-50 modules.  A star wiring pattern has been
>maintained, and the three distribution boards are MOTM-960's. The DC
>wiring is 12-guage stranded from the supply to the first terminal and
>12-guage to each distribution board.
>
>What do you think?  My guess is the power supply goes into short
>protection during inrush.  The .71 vdc would be a normal forward
>voltage drop from the pass transistor, showing up in parallel at the
>shut-down side of the supply.  Anyone else, have something like this
>happen as they neared the limits of power?  Am I just going to pop
>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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