Doepfer LC9 PSU3 problem

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synth.void
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Doepfer LC9 PSU3 problem

Post by synth.void » Sun May 10, 2020 12:13 pm

I've bought a second hand LC9 PSU3, and the first time I've launched it, some modules started to behave weirdly.

Plaits changes its models and pitch, and Zadar switches envelope shapes back and forth. The changes are very slow, i.e. the pitch of Plaits slowly grows higher. It also changes in reaction to Disting EX changing algorithms and mode (single vs dual). Nothing is patched, the plaits doesn't use the CV/Gate bus.

There might be more symptoms, but I removed everything else from the system, keeping only the Plaits and the Disting as the easiest combination to test against.

Everything works smoothly if I move the modules to the uZeus case. The previous owner has reassured me they've never had any problems.

I've briefly looked through the existing topics re PSU3, but couldn't find anything that seemed related. What should I check next?

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synth.void
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Re: Doepfer LC9 PSU3 problem

Post by synth.void » Sun May 10, 2020 12:57 pm

Recorded a demo


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foliephonics
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Re: Doepfer LC9 PSU3 problem

Post by foliephonics » Sun May 10, 2020 1:11 pm

It may actually not be the PSU but a power connector.
I have a A-100P6 which has a faulty connector. If I plug a module in the second connector from the right on the top row, I have no power anywhere.
Soooo you might want to switch connectors and check ?
Good luck on your trouble-shooting !

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Re: Doepfer LC9 PSU3 problem

Post by synth.void » Sun May 10, 2020 1:17 pm

foliephonics wrote:
Sun May 10, 2020 1:11 pm
It may actually not be the PSU but a power connector.
I have a A-100P6 which has a faulty connector. If I plug a module in the second connector from the right on the top row, I have no power anywhere.
Soooo you might want to switch connectors and check ?
Good luck on your trouble-shooting !
Thanks, but I've tried many of them actually, on all of the rows, both left and right sides. Seems the same everywhere, although at first changing the connector helped to "fix" Zadar. It glitched a couple times even after that.

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Re: Doepfer LC9 PSU3 problem

Post by Keltie » Sun May 10, 2020 2:12 pm

It sounds like you’ve had a good look around, but have you checked each and every power header to check no shorts on the pins? One of my doepfer cases, bought new, arrived with two pins bent and in contact on one of the headers. I don’t know if this would cause your problem, but might be worth checking?

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Re: Doepfer LC9 PSU3 problem

Post by synth.void » Sun May 10, 2020 4:04 pm

Keltie wrote:
Sun May 10, 2020 2:12 pm
It sounds like you’ve had a good look around, but have you checked each and every power header to check no shorts on the pins? One of my doepfer cases, bought new, arrived with two pins bent and in contact on one of the headers. I don’t know if this would cause your problem, but might be worth checking?
Yea, sounds good, will do.

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Re: Doepfer LC9 PSU3 problem

Post by synth.void » Sun May 10, 2020 4:58 pm

Keltie wrote:
Sun May 10, 2020 2:12 pm
It sounds like you’ve had a good look around, but have you checked each and every power header to check no shorts on the pins? One of my doepfer cases, bought new, arrived with two pins bent and in contact on one of the headers. I don’t know if this would cause your problem, but might be worth checking?
Ok, checked all the headers to the best of my knowledge. Nothing beeps where it shouldn't.

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Re: Doepfer LC9 PSU3 problem

Post by Keltie » Sun May 10, 2020 6:57 pm

synth.void wrote:
Sun May 10, 2020 4:58 pm
Keltie wrote:
Sun May 10, 2020 2:12 pm
It sounds like you’ve had a good look around, but have you checked each and every power header to check no shorts on the pins? One of my doepfer cases, bought new, arrived with two pins bent and in contact on one of the headers. I don’t know if this would cause your problem, but might be worth checking?
Ok, checked all the headers to the best of my knowledge. Nothing beeps where it shouldn't.
I’ve just read your OP again, and it’s really odd.... disting mode changing plaits, model shifting, etc etc. I’ve never heard of anything like this. I think you need to go back to the seller, and if it’s Ebay, PP, or something with protection, open a case, because it sounds to me like you’ve been sold a pup. Any sign of postal/ shipping damage?

Just to check, what is cv/ gate buss doing? IIRC, it’s sold with a cap/ jumper... is that in place? Nothing connecting those pins to anything else? the cables for the psu in place? Voltage lights on normally? Lastly, not knowing how experienced you are, I take it it’s not user error... power headers are on right? Sorry to ask that, but it’s easily done.....

If all of that checks out, it needs to go back imo.

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Re: Doepfer LC9 PSU3 problem

Post by synth.void » Mon May 11, 2020 3:48 am

Keltie wrote:
Sun May 10, 2020 6:57 pm
I’ve just read your OP again, and it’s really odd.... disting mode changing plaits, model shifting, etc etc. I’ve never heard of anything like this. I think you need to go back to the seller, and if it’s Ebay, PP, or something with protection, open a case, because it sounds to me like you’ve been sold a pup. Any sign of postal/ shipping damage?
It looks like it's been used carefully, and I've picked it up myself - it's a couple stops away from my place.
Keltie wrote:
Sun May 10, 2020 6:57 pm
Just to check, what is cv/ gate buss doing? IIRC, it’s sold with a cap/ jumper... is that in place? Nothing connecting those pins to anything else? the cables for the psu in place? Voltage lights on normally? Lastly, not knowing how experienced you are, I take it it’s not user error... power headers are on right? Sorry to ask that, but it’s easily done.....
Honestly, I'm on a hunt for a user error here, so every advice is useful! I've been plugging in modules one by one and checking the red stripe orientation carefully. Now, I _could_ make a mistake with some of the doepfer modules (A-160-1 and A-160 in particular) but in the end every module worked as expected.

The PSU cables around the case are in place, but I haven't opened the PSU cover, and I haven't checked the ribbon cables yet.

Now, as for the voltage lights. The +5V LED is on for 4-5 seconds longer than the other LEDs when I turn off the case. Apart from that everything looks good.
Keltie wrote:
Sun May 10, 2020 6:57 pm
If all of that checks out, it needs to go back imo.
That would be my last resort. Not sure if that's possible tho.

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Re: Doepfer LC9 PSU3 problem

Post by foliephonics » Mon May 11, 2020 4:20 am

Just a thought... would the modules be trying to communicate through the bus ? In which case there a jumper or something somewhere to make them stop.

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Re: Doepfer LC9 PSU3 problem

Post by Keltie » Mon May 11, 2020 4:21 am

FWIW, my 5 volt also stays on for a bit, on all 3 of my doepfers. I believe that’s normal. I’m not an EE, but to my limited understanding, it’s due to the capacitors on the 5v rail discharging at power off.

You might try to email Dieter Doepfer directly. Contact details via the website IIRC. It’s a weird one alright, and I’m out of ideas. Good luck with it!

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Re: Doepfer LC9 PSU3 problem

Post by EATyourGUITAR » Mon May 11, 2020 4:46 am

if there is nothing loading the 5v rail it could take up to 60 seconds to fade out on the 5v LED. basically the LED is the only thing using 5v power so it takes longer. the capacitor on 5v acts like a battery.
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Re: Doepfer LC9 PSU3 problem

Post by synth.void » Mon May 11, 2020 5:10 am

Keltie wrote:
Mon May 11, 2020 4:21 am
FWIW, my 5 volt also stays on for a bit, on all 3 of my doepfers. I believe that’s normal. I’m not an EE, but to my limited understanding, it’s due to the capacitors on the 5v rail discharging at power off.

You might try to email Dieter Doepfer directly. Contact details via the website IIRC. It’s a weird one alright, and I’m out of ideas. Good luck with it!
Thanks, Dieter responded earlier today. His suggestion was to check the supply voltages and if it is ok, contact the module manufacturers. Will do both later today.
EATyourGUITAR wrote:
Mon May 11, 2020 4:46 am
if there is nothing loading the 5v rail it could take up to 60 seconds to fade out on the 5v LED. basically the LED is the only thing using 5v power so it takes longer. the capacitor on 5v acts like a battery.
Thanks, that's what I thought.
foliephonics wrote:
Mon May 11, 2020 4:20 am
Just a thought... would the modules be trying to communicate through the bus ? In which case there a jumper or something somewhere to make them stop.
I shuffled around the jumpers on the bus board with no luck. I haven't figured out the jumper situation on the disting as it clearly uses the CV/Gate bus. Will do :tu:

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Re: Doepfer LC9 PSU3 problem

Post by synth.void » Mon May 11, 2020 3:25 pm

synth.void wrote:
Mon May 11, 2020 5:10 am
shuffled around the jumpers on the bus board with no luck. I haven't figured out the jumper situation on the disting as it clearly uses the CV/Gate bus
Asked os about the CV/gate bus, seems the problem is somewhere else.

I'm almost out of options here. Next thing I'll try is to measure the voltage on the rails, which I'm skeptical about unless it's so obvious that a multimeter would be able to spot it.

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Re: Doepfer LC9 PSU3 problem

Post by synth.void » Mon May 11, 2020 4:10 pm

The multimeter readings are: 12.05V on +12, 5.05V on +5 and 11.93 on the -12V.

I guess that's a sign of a problem? Bad math, seems the PSU is ok.
They have to be exactly +12V (+/-1%), -12V(+/-1%) and +5V (+/-5%). And the voltages have to be clean without ripple or noise.

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Re: Doepfer LC9 PSU3 problem

Post by synth.void » Fri May 22, 2020 7:36 am

To follow up on the story, I replaced the PSU3 with a new one, and the problems are gone (what a surprise).

With the old unit all the other digital modules in the case were affected too, the case effectively became a 9U noise machine. I just had to wait a couple more minutes before it gets to this state.

Huge thanks to the responsive and patient people who I contacted (XAOC, MI, Doepfer, ES) while debugging this :sb: I've learned a ton already, and I'm getting a scope to troubleshoot and fix the faulty PSU.

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