500 series Sontec / GML type eq

My case is not very representative but for a dual channel with PSU (JLM Audio), the 2U rack case and front and rear panel by Schaeffer it will cost about 1200€.

Hi guys,

Problem here!!! I’ve just finished soldering all the parts and made primary tests. While there’s no short between rails when the unit is off, when I turn it on there’s continuity between V+ and V- and I read +16V at 0V!
Any idea?
FYI I have not filled Ccomp4 and Ccomp5.
Thanks for your help

Ben

evilcat said:

Hi guys,

Problem here!!! I’ve just finished soldering all the parts and made primary tests. While there’s no short between rails when the unit is off, when I turn it on there’s continuity between V+ and V- and I read +16V at 0V!
Any idea?
FYI I have not filled Ccomp4 and Ccomp5.
Thanks for your help

Ben

Click to expand...

Hi Ben,


do you mean full continuity meaning zero ohms between the rails?If so then you will have a short somewhere,could be a solder blob,a residual ultra small piece of wire somewhere etc. Hard to tell.
Also why do you want to measure continuity while the unit is powered up?The resistance between the rails will of course change due to caps charging,stuff like that.
How did you read +16v at 0v when 0v should be the reference for measuring voltages?
I can only guess,but looks like you measured something wrong.Are ics in already,did something get very hot or even burning?
In any case you must have your black probe attached to a 0vdc point,dmm set to read dc.Then check the corresponding pins for propper positive and negative voltages on the ic sockets and the millmax points(for the doas).
Maybe some closeup pictures might help.
Also,how did you set up the rails for main and filters?Maybe something went wrong with your ptc and/or zener diode placement?
Just thinking,

Best,


Udo.

Hi Udo,

First, thanks for helping! I had tested continuity because I've measured 0V between V+ and 0V and +32V between V- and 0V. So I suspected a short.
I attache my black probe to the chassis, which is connected to my PSU 0V, which is connected to the ground gold finger of the PCB. One weird thing is that I don't have continuity between the gold finger and the 0V test point!
I have set up PCB for +/-16V operating.
Unfortunatly I will not have the time to work on it before monday for further tests. As soon as I'll do I keep you inform. First I will look for a short...
Anyway, thanks again.

Ben

Ben, your chassis is somehow running on +16V ...

Has anyone used jh990c in 24v?  Thoughts?

evilcat said:

Hi Udo,

First, thanks for helping! I had tested continuity because I've measured 0V between V+ and 0V and +32V between V- and 0V. So I suspected a short.
I attache my black probe to the chassis, which is connected to my PSU 0V, which is connected to the ground gold finger of the PCB. One weird thing is that I don't have continuity between the gold finger and the 0V test point!
I have set up PCB for +/-16V operating.
Unfortunatly I will not have the time to work on it before monday for further tests. As soon as I'll do I keep you inform. First I will look for a short...
Anyway, thanks again.

Ben

Click to expand...

Ben,


I've digged in your posts in this thread.
I wasn't aware that you are doing your own housing and psu,so not 51x or 500 series.Is that correct?
If so then I'd definetely start to look at the psu first!
I have a vague feeling that the culprit is not the eq modules but happening before them!
This would proof Volker's statement.
Looks like your psu makes an unwanted contact to your chassis.
To check this simply lift the connections to the eqs,if you used an edac style or card edge connector  unplug it.
Then,from what I remember from Joe's psus,measure the resistance from 0v directly on the psu board to the chassis.There should be something like 10 Ohms.Power to off during this procedure.If this resistance is zero then I think we found it,might be an easy fix.g
Where are the psu regulators seated,are they screwed to the chassis?
Also you can do the dc measurements again but with the eqs still lifted/unplugged.E.g. measure dc from the 0v on the psu to chassis etc. with power on.It might be you'll get the voltage readings a little higher because it is now unloaded.
This way you can sort out if it is eq or psu related.
I would bet it's the psu.......is it an ac/dc,a powerstation or kraftwerk?
Can you show us a picture of the psu and how it is mounted to the chassis?


Udo.

qmp audio said:

Has anyone used jh990c in 24v?  Thoughts?

Click to expand...

Hi,


no,I didn't,but I'm about to try APP992 when I find some time.


Best,


Udo.

Hi Udo,

Thanks a lot for you help, it's very kind of you. Yes the unit is in a rack with JLM PSU, regulators screwed to the chassis. I'll check what you suggest.
Unfortunatly I'll have very busy days today and toomorow so I'll won't be able to work on it before monday. As soon as I can I'll take pics and post them.
Thanks again for all your help.
Best,

Ben

evilcat said:

Hi Udo,

Thanks a lot for you help, it's very kind of you. Yes the unit is in a rack with JLM PSU, regulators screwed to the chassis. I'll check what you suggest.
Unfortunatly I'll have very busy days today and toomorow so I'll won't be able to work on it before monday. As soon as I can I'll take pics and post them.
Thanks again for all your help.
Best,

Ben

Click to expand...

Just take your time,patience is the key.


Good luck,have a not-too-busy weekend,


Udo.

evilcat said:

Hi Udo,

Thanks a lot for you help, it's very kind of you. Yes the unit is in a rack with JLM PSU, regulators screwed to the chassis. I'll check what you suggest.
Unfortunatly I'll have very busy days today and toomorow so I'll won't be able to work on it before monday. As soon as I can I'll take pics and post them.
Thanks again for all your help.
Best,

Ben

Click to expand...

Some regulators cannot use ground/chassis as a heat sink. You might need to electrically insulate them.

john12ax7 said:

Some regulators cannot use ground/chassis as a heat sink. You might need to electrically insulate them.

Click to expand...

Yes,that's why I asked Ben to measure dcr between ov and chassis connection.On JLM psus there is a 10 ohms resistor.If you measure 0 ohms it indicates a connection beetween one or more regulator backs to chassis.Normally caused by missing silicone insulators or overtightening the screws while mounting,the little plastic washers leading the screws isolated through the mounting hole are easy too break.


Udo.

Hi Udo,

I still have lots of work, I only had 5 min to work on it!
Things I have checked and noticed:
- I have 12 ohms between PSU and chassis, and there's no shorts between regulators and case.
- voltages at the PCBs gold fingers are ok: +/-16V and 0V (ground) connected to chassis (connectors 12, 13 and 14 according to 500 series spec)
- I doesn't have continuity between gold finger 13 (GND) and the 0V tests points. Is it normal?
- I have DC voltages at the inputs and output of Op Amps (about 14,75 V)

As soon as I can I'll take some pics and look for shorts.

evilcat said:

Hi Udo,

I still have lots of work, I only had 5 min to work on it!
Things I have checked and noticed:
- I have 12 ohms between PSU and chassis, and there's no shorts between regulators and case.
- voltages at the PCBs gold fingers are ok: +/-16V and 0V (ground) connected to chassis (connectors 12, 13 and 14 according to 500 series spec)
- I doesn't have continuity between gold finger 13 (GND) and the 0V tests points. Is it normal?
- I have DC voltages at the inputs and output of Op Amps (about 14,75 V)

As soon as I can I'll take some pics and look for shorts.

Click to expand...

Hi,
measure pin 5 on the card pcb goldfinger to the test point please.This is another ground point.Just ohm it out.
The 12 ohms between chassis and psu 0v are correct.
How did you measure the opamps' dc,to be more specific:Where was the black probe at that time?


Udo.

@Ben,


I think I found the culprit,at least a major one.
Looks I´m right with thinking of a wiring mistake.
I have even pulled out one of my modules out of a rack to proof what I thought.

Please look at goldfinger number 13 on the pcb,hold it against a light if you want.
There´s absolutely no connection to anything!So you run the card without 0v reference!
Use goldfinger number 5 instead,this also connects to the test point.Simply rewire your 0v to pin 5 on the card edge connector.
Then-without ics inserted-carry out the initial voltage tests again and please use the test point for 0v reference.
Tell us what you´ve come up with then.


Fingers crossed,


Udo.

Wow, that would be awesome. I think I'll have some time to try this toomorow morning 1st hour!!! Damn Christmas, lots of work in commercial advertising I record in the studio. This is not a good time for hobby right now
Again, thank you very, very much for all your support Udo, you deserve a medal, man!

Ben

evilcat said:

Wow, that would be awesome. I think I'll have some time to try this toomorow morning 1st hour!!! Damn Christmas, lots of work in commercial advertising I record in the studio. This is not a good time for hobby right now
Again, thank you very, very much for all your support Udo, you deserve a medal, man!

Ben

Click to expand...

Not yet,make it work first  ;D


Best,


Udo.

I was too impatient and took a break to test your idea. Guess what? IT WORKS!!!
The test points are good, pins for ICs are good. Except for those on the filters sections with some mV (30-ish) on some pins, but I guess it's ok, isn't it?
Next step, put the ICs and proceed calibration... as soon as I'll have some break in my work!

evilcat said:

I was too impatient and took a break to test your idea. Guess what? IT WORKS!!!
The test points are good, pins for ICs are good. Except for those on the filters sections with some mV (30-ish) on some pins, but I guess it's ok, isn't it?
Next step, put the ICs and proceed calibration... as soon as I'll have some break in my work!

Click to expand...

Great stuff Ben!
The dc offset at some points should improve after calibration,that's the fun part.
Keep us posted when you're done,maybe some nice pics?


Have fun,


Udo.

Hi there!

Little report. Calibration went flawlessly now that my grounding is ok

I have tested the unit with some audio... OMG!!! That eq is awesome.

IT IS THE DEFINITION OF SWEETNESS !

What a powerful eq. I hadn't heard an eq that sweet and that transparent! Maybe my Millenia STT1 but it's less flexible as the Hi and Lo band have stepped freq and it "only" have 4 bands...
Gorgeous hi-end unit. I only had a quick test with a rough mix but it was awesome.
I don't have any front panel yet so no pics for the moment, that will be for 2016

Thanks again to David for making this wonderful project and his help, and to Udo for his big support. You rock guys! If you're coming to Paris, let me know, I'd buy you a drink!!! ;D

Best

Ben