QPS6+ Power Issue Help

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QPS6+ Power Issue Help

Post by Synths and Stuff » Mon Jun 07, 2021 1:12 pm

Hello!

Edit: Shortened for readability.

I've got a situation I need some insight on. I just got a bulk of modules for my QCF22 Dotcom Folding cabinet I'm powering it with the QSP6+, which has the specs: +15V@1200ma, -15V@1200ma, +5V@1000ma.

Here is the current setup in the case: https://www.modulargrid.net/d/racks/view/1599564

I got the specs for the FSFX Supra Resonator from FSFX, which is +15V@10ma, -15V@10ma, +5V@120ma. The triple waveshaper was built by LWSS, and last I asked, he was unsure of the specs for the CGS85, but there's no way it needs as much current as the headroom I have left.

This leaves me somewhere around: +15V@518ma, -15V@333ma, +5V@433ma

I thought I had done everything correctly with the current draw on the different rails way under the QPS6+'s specification. However, after about 30 or so minutes of playing, the lights on the top row digital modules start blinking and fading. The noise engineering eventually start alternating on and off. The Supra Resonators stay on, but the lights on them are blinking, and the parameters start drifting. Feeling the QPS6+, it does feel hot, but I've also never felt it's temperature after a session with nothing wrong, so I have nothing to compare that to.

Any insight would be greatly appreciated. Thank you!
Last edited by Synths and Stuff on Mon Jun 07, 2021 4:24 pm, edited 1 time in total.

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Re: QPS6+ Power Issue Help

Post by Synths and Stuff » Mon Jun 07, 2021 4:23 pm

After removing the two Supra Resonators, the strange behavior goes away, and the noise engineering modules act fine, so I believe it is a power issue.

How does something like this occur when I have plenty of headroom with respect to the power supply (at least on paper)?

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Re: QPS6+ Power Issue Help

Post by daveholiday » Wed Jun 09, 2021 6:03 am

My gut feeling is that you are drawing a bit more from the 5v rail than Modular grid indicates. I would suggest removing one of the "Rings" and try it that way. If everything works as expected, you may need to look into a different power supply option.
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Re: QPS6+ Power Issue Help

Post by Rex Coil 7 » Wed Jun 09, 2021 9:28 am

daveholiday wrote:
Wed Jun 09, 2021 6:03 am
My gut feeling is that you are drawing a bit more from the 5v rail than Modular grid indicates. I would suggest removing one of the "Rings" and try it that way. If everything works as expected, you may need to look into a different power supply option.
^^ what he said ^^
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Re: QPS6+ Power Issue Help

Post by KSS » Wed Jun 09, 2021 12:32 pm

Synths and Stuff wrote:
Mon Jun 07, 2021 4:23 pm
After removing the two Supra Resonators, the strange behavior goes away, and the noise engineering modules act fine, so I believe it is a power issue.

How does something like this occur when I have plenty of headroom with respect to the power supply (at least on paper)?
While in agreement with Dave and Rex, I would point out that remving the resonators doesn't remove them as the potential cause. Power may be fine and the Supra's -or other modules- are the problem. If you suspect power, then you need to remove different modules singlly and in sets, checking on results each time- to discern between one or more of them being the bad actors upon the powerr supply.
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Re: QPS6+ Power Issue Help

Post by Rex Coil 7 » Wed Jun 09, 2021 3:26 pm

KSS wrote:
Wed Jun 09, 2021 12:32 pm
Synths and Stuff wrote:
Mon Jun 07, 2021 4:23 pm
After removing the two Supra Resonators, the strange behavior goes away, and the noise engineering modules act fine, so I believe it is a power issue.

How does something like this occur when I have plenty of headroom with respect to the power supply (at least on paper)?
While in agreement with Dave and Rex, I would point out that remving the resonators doesn't remove them as the potential cause. Power may be fine and the Supra's -or other modules- are the problem. If you suspect power, then you need to remove different modules singlly and in sets, checking on results each time- to discern between one or more of them being the bad actors upon the powerr supply.
... but it sure narrows down the actual culprit, which seems to be an overloaded power system., which is what I was getting from that.
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Re: QPS6+ Power Issue Help

Post by Synths and Stuff » Thu Jun 10, 2021 2:19 pm

Thanks for all the input everyone!

I haven't had time to fully diagnose the issue, but I've had play sessions that worked fine when removing the Supra's, or one of the Noise Engineering modules. Based on what everyone is saying, it sounds like it's not am individual module, but their total impact on the power draw?

The next level up for the Dotcom power supplies, the QPS5, seemed way overkill for me on paper. However, the QPS6+ seemed plenty sufficient on paper, too. Should I invest in the QPS5 or are there other power supplies I should look into?

Thanks again!

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Re: QPS6+ Power Issue Help

Post by burdij » Thu Jun 10, 2021 2:42 pm

Do you have a digital voltmeter to measure voltages under operating conditions? Retailers like Harbor Freight have suitable units for around $25.

I think you need to determine if there is a fault with your power supply. As you have pointed out, this unit should be adequate for your needs. There may be a problem or it may have internal adjustments that can be set.
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Re: QPS6+ Power Issue Help

Post by Synths and Stuff » Thu Jun 10, 2021 3:29 pm

I have been advised before to get a DMM. My technical skills are not the most up to date in this respect, unfortunately. Probably have some reading to do.

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Re: QPS6+ Power Issue Help

Post by EATyourGUITAR » Thu Jun 10, 2021 5:31 pm

If the QPS6+ can't survive being loaded at %50 I would send it back! It is either broken or the manufacturers claims were overstated or modular grid is underestimating your total current draw per rail. Is it under warranty? I am assuming you don't have all the specialized tools to test each module's current draw. It is more than a multimeter. It requires custom tooling. Same for testing the power supply. It requires specialized digital loads. There is also the proprietary power connector that needs an adapter if you want to test it with the power supply not opened up. There might be an easier way to test the power supply with the cover off but for safety reasons and for a proper thermals test that cover should never be off during testing.

For example you would need 3 of these
https://www.amazon.com/gp/aw/d/B091FFSHD5/

But that is not your job. I would contact synthesizers.com for tech support, testing, and warranty claim.
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Re: QPS6+ Power Issue Help

Post by KSS » Thu Jun 10, 2021 6:50 pm

Jeebus, EYG. Custom tooling to test a module's current draw? :despair:

All he needs is a series connection to a DMM with its knob set correctly. Any number of ways to do this depending on the actual module but none I would consider custom tooling.

I do agree that if 50% load is over-taxing the supply it's time to contact Dotcom and see what's up. But i generally make that my first move instead of a forum post anyways.
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Re: QPS6+ Power Issue Help

Post by EATyourGUITAR » Thu Jun 10, 2021 7:22 pm

KSS wrote:
Thu Jun 10, 2021 6:50 pm
Jeebus, EYG. Custom tooling to test a module's current draw? :despair:

All he needs is a series connection to a DMM with its knob set correctly. Any number of ways to do this depending on the actual module but none I would consider custom tooling.

I do agree that if 50% load is over-taxing the supply it's time to contact Dotcom and see what's up. But i generally make that my first move instead of a forum post anyways.
Yes this kind of connection can not be made with a multimeter. You need something to insert into the holes of your dotcom harness that will also connect to the probes of the meter which may be hardwired to the meter if the meter has no removable probes. Then you need something to connect to the other probe that will also connect the module header. You need some male female DuPont wires to pass through the other power rails from the harness to the module. Assume the meter does not have grab hooks. How are you going to hold the probes on a male DuPont 0.1 header flying wires with two probes in one hand, then reach over to turn the synth on. Then patch your synth without ever lifting the hand with two probes in it? You need some very specific off the shelf wires, you need grab hooks on your multi meter which is sometimes not even possible at all on some pocket multimeters.

OP is not some experienced electrical engineer. I wouldn't expect OP to know all of the stuff about ordering DuPont wires and grab hook meter probes. If those items were purchased simply to test dotcom modules then there is only one reason and one application for it. Specifically to test dotcom. That is why I say custom. It is beyond buying a multimeter.

I'm not concerned with testing modules anyway. That is a waste of time in my opinion. I would much rather test the power supply at %50 %80 %100 load so I know I am sending it back. I don't think any of these modules have faults in them since they have been tested working individually on that same power supply.

I looked at the DIN connector on the QPS6+. The female socket for that does not come with the multimeter. You can't short the supply through the meter because the meter is not a dummy load and we don't know the value of the resistor in the meter. So you need a female DIN socket, some current sense resistors, a male din socket. Solder that together. Now you have a way to measure total current draw from all modules with a meter.
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Re: QPS6+ Power Issue Help

Post by KSS » Thu Jun 10, 2021 9:07 pm

C'mon. Anyone can cut one of the wires in the power distro leading to one module. strip a little off the ends with knife. Wrap it around the meter tips. Get the measurement, and twist the ends together and cover with electrical tape. Repeat for the 2nd rail. It's now fully ready to repeat this for any other module whose power draw is in question.
Most can do far more than this super simple method, and it's a pretty low bar of what is actually required. None of the rest you mentioned is needed.

I've seen you defend yourself in other threads saying we're taking to much of a pro approach for newbies. I'll suggest you're doing that now.

We're still in agreement that Dotcom is in the best position to give real answers about their power supply if no personal testing can be done.
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Re: QPS6+ Power Issue Help

Post by Synths and Stuff » Thu Jun 10, 2021 9:54 pm

Thank you all for the advice. I have contacted Synthesizers.com about the matter. Under 50% load does seems strange.

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Re: QPS6+ Power Issue Help

Post by burdij » Thu Jun 10, 2021 11:00 pm

Initial troubleshooting, in this case, does not require current measurement. If the power supply regulators are not working (i.e. can't supply enough current at the expected voltage) the voltage will droop. A simple test of the voltage will reveal if one of the three supplies is not compliant with the current draw.

A more crude way of testing the voltages is by using the power monitoring LEDs on the chassis or power supply. Do you see any flickering or dimming of these indicators when the unusual module behavior is occurring? This is not a very good test because LEDs will light to almost full brightness when driven at a fraction of the voltage but there should be no overall brightness changes if the supplies are working correctly.

Does this system have Box 11 style cases? The earlier version of these cases (where the power input connector is roughly centered in the back of the case) have internal power harnesses that where made with 11 separate cables with the three power wires and one ground were joined using wire nuts. The later versions, using a PC board to join the 11 cables together has the input connector in the lower left corner, viewed from the back. I had one of the earlier style and had a couple of the cables go bad because of faulty wire nut connections. I dumped the wire nuts, bundled the wires together, soldered them, and covered the connections with heat shrink tubing.
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Re: QPS6+ Power Issue Help

Post by Synths and Stuff » Fri Jun 11, 2021 12:45 am

The LED's stayed bright, though I probably could have looked closer at the +5V light since that is most likely the culprit. I haven't put back in the Manis, because it works that way. How bad would it be to put it back the way it was to recreate the bad behavior and check? Again, new to the power thing.

The case are Box11's, bought pretty recently. There is a PCB in the lower left viewed from the back, which has the power LED's mounted on it. Is this what you are talking about?

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Re: QPS6+ Power Issue Help

Post by Henfield » Fri Jun 11, 2021 7:59 am

I have a system that is using two Box 11's, configured as the QCF22, and I am using this power supply from the Analog Craftsman to power it.

http://analogcraftsman.com/?product=acp ... escription

I do not have any digital modules, and I have not had any power issues. I currently have 18 modules that it is powering.
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Re: QPS6+ Power Issue Help

Post by EATyourGUITAR » Fri Jun 11, 2021 12:54 pm

KSS wrote:
Thu Jun 10, 2021 9:07 pm
C'mon. Anyone can cut one of the wires in the power distro leading to one module. strip a little off the ends with knife. Wrap it around the meter tips. Get the measurement, and twist the ends together and cover with electrical tape. Repeat for the 2nd rail. It's now fully ready to repeat this for any other module whose power draw is in question.
Most can do far more than this super simple method, and it's a pretty low bar of what is actually required. None of the rest you mentioned is needed.

I've seen you defend yourself in other threads saying we're taking to much of a pro approach for newbies. I'll suggest you're doing that now.

We're still in agreement that Dotcom is in the best position to give real answers about their power supply if no personal testing can be done.
You are suggesting that someone cut the harness before sending it back under warranty???
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Re: QPS6+ Power Issue Help

Post by KSS » Fri Jun 11, 2021 1:59 pm

EATyourGUITAR wrote:
Fri Jun 11, 2021 12:54 pm
KSS wrote: We're still in agreement that Dotcom is in the best position to give real answers about their power supply if no personal testing can be done.
You are suggesting that someone cut the harness before sending it back under warranty???
Underlined above is my position. Here is what I suggested from the start.
KSS wrote: If you suspect power, then you need to remove different modules singly and in sets, checking on results each time- to discern between one or more of them being the bad actors upon the power supply.
The rest has been a response to your sillyness in trying to make this pretty basic thing into some kind of epic event that requires tons of experience, tools and new purchases.
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Re: QPS6+ Power Issue Help

Post by Synths and Stuff » Fri Jun 11, 2021 2:33 pm

Henfield, thank you for the alternative. It looks similar specs to the QPS6+.

EATyourGUITAR and KSS, I appreciate each of your opinions, and I will be able to understand them more when I start DIYing (someday), but can you please not derail this thread with an argument and personal attacks. It is no longer helpful. Thank you.

At the end of the day, even if something is easy, it still must be learned, especially safety precautions. I took some basic circuit classes long ago and really only did simple breadboard stuff. I've forgotten mostly everything, but it's not hard to remember not to stick metal prongs into electrical sockets I no longer understand.

I've contacted Synthesizers.com and am waiting for a reply.

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