merging two cases into one issue

[Pav]

Hi Tony,
Hi Oakley aficionados,

Im wondering if anyone has taken the trouble to spreadsheet the Oakley module set in terms of mAmps ?
so i can see if i have pushed the limit of PA30.

You see I am experiencing strange pitch modulation in my ASV output and it appears to come from a Dual LFO
- and is exaggerated if the Drive knob of a Flanger is turned full Clockwise. Neither are patched to the ASV
All modules appear to be working as expected otherwise.

I had two 6u high cases each with a rev3/rev4 psu and a single dixie each.
I checked that they had R2 &R3 with 0.82R wire wound resistors. (thanks to reminder from eljay)
Yamaha PA30 is used.

I suspect current exhaustion as a result of combining the two case of modules into one.
A possible red herring is the red AC led comes on then goes out, though testing suggests may also be a dodgy connection.
Amber and Green are steady lit.
Wondering Is the AC lamp going out a sign of current starvation too?

I have done some measurements of the voltage across +15 and -15 rail (Note tests wIth all modules connected to Dizzies however)
and it only shows 24V. 0 and +15 rail test shows around 12v and negative rail similar.
Adjusting the psu trimmer has no effect.

I have stopped short pulling all the power leads to test without the load yet for fear i do more harm than good.

5U row 1: Overdrive | EFG Deluxe | Discontinuity | Quad VCA | DUal LFO | Deep Equinox | Flanger
5U row 2: ASV | TSL | HVM | 904A VCF | DSL | Multimix
1U row 3: MidiDAC
1U row 4: MFOS Quantizer and YuSynth Clock Divider //Temporarily disconnected to see if the problem goes away.

I can remove modules until problem resolves or going back to dual psu s .. but i have a similar 12U case of 19 modules without
this problem but with regular VCO and VCO-Bs instead of ASV.

Cheers,
Pav.

[eljay]

File attached, has a few non -oakley modules, that you can ignore. The HVM and SE330 lines are for the older rack mount versions not the later HVM module or SRE330.

[Pav]

thanks v much!
this confirms i am close to 780mA guide limit .. my case is 757 mAmp positive rail, 652 mAmp negative rail.
with the yusynth and mfos additions im over - which is why i disconnected them.

the other case i mentioned comes in at +668mA and -566mA respectively.
Ill try tomorrow removing modules to get lower to see if problem resolves.
Still a puzzle the voltage drop with all modules connected... would still like advice on this.

[Schlumpfhut]

The voltage drops occurs when you draw more power from the regulators than they can provide. I had the same problem in the past and therefore put everything into storage until i can install my new cases with a much more beefy PSU later this year

[Synthbuilder]

Still a puzzle the voltage drop with all modules connected... would still like advice on this.

As Schumpfhut says if you take more current than the power supply is built for the output voltage will drop. What you've got with the older PSU is a current limit circuit. The limit cannot be exceeded and to keep the current at that limit with a too great a load the output voltage will fall.

It's worth noting that the current limit is not exact. It will change with temperature and be affected by the real resistance of the big resistors on the PSU (which isn't exactly what it says on the resistor). Also the current draw for each module given in the User Manual or webpage is not precise either - it's simply what my meter read on the day I measured it. And the moment you start putting signals through any module the current taken will rise.

Personally I'd not go any closer than 85% of the limit.

[Pav]

Ha...just as I thought, ohms law at work. Maybe a transformer bases Psu might give me headroom. That or feed the synth building addiction with a third case.

[Pav]

So i disconnected the power to an EFG giving me an approximate 701mA +V rail ie 89%
This solved the modulation issue. The AC LED in the psu lights on power on.
But After 5 minute or so LED goes out.
I power off the DC leaving PA30 connected.
After a couple of minutes the AC LED comes on again
Suggests maybe a warming up issue but panel heat sinking isnt warm.
I repeated this sequence and got the same results.
Wondering if I have a regulator issue, or caps, or still current starvation.
Unplugged Discon. 82% of 780 now and LED goes out 5 minutes in.
Unlikely starvation now.

[Synthbuilder]

After a couple of minutes the AC LED comes on again...

The AC input LED is not connected to the regulator output. It only monitors the voltage coming from the PA-30. Assuming that there still is a steady DC output from the PSU when the AC LED is not lit, there is either a connection problem with the circuitry that supplies the LED (ie. D8, R12, C12), or the LED itself has an intermittent fault. Whichever it is, it's very unusual.

[Pav]

Oops - not regulator then. Thanks Tony, ill work backwards try change the LED , then components.

[Pav]

Took the Psu board off panel and Found the bad joint on molex header pin used by ac led. Tested Psu voltages without modules and have my +\-15v back. Sorted thanks