evilcat
Well-known member
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 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
Ben,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
Hi,qmp audio said:Has anyone used jh990c in 24v? Thoughts?
Just take your time,patience is the key.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
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
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.john12ax7 said:Some regulators cannot use ground/chassis as a heat sink. You might need to electrically insulate them.
Hi,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.
Not yet,make it work first ;Devilcat 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
Great stuff Ben!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!
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