Author Topic: Repair Keysight E3616A  (Read 1118 times)

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Offline sosokruashviliTopic starter

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  • Country: ge
Repair Keysight E3616A
« on: November 21, 2016, 12:54:06 am »
Hi all,
I purchased HP Keysight E3616A bench PSU 5 days ago from ebay. It was in not working condition and I decided I could fix it. :D But it became my nightmare. The problem is that it turns on, outputs voltage but very unstable, voltage is floating and has extremely high noise and peaks. Almost 3 vpp and 400mv floating with random waveform. I've got oscilloscope and good measurement staff so I can check almost anything. I have schematic and repair manuals.
 I have checked reference voltages and they have identical noise as the output, but when I drop output voltage to 0 noise is gone in reference voltages. I checked every part in reference circuits and they are ok. Also checked Constant Voltage circuit parts, main mosfets input voltages, diodes caps they are all ok. +5 volts, -12 volts, +10volts they are all ok. I also disconnected other circuits like SCR controls and OVP circuits and Constant Current circuit but noise is still there.
In repair manual there is some check points and there I have huge problem. There is Reference and Bias Circuit Troubleshooting chapter and I cannot pass the check voltage between TP6 and point3 and voltage between TP6 (common of reference voltages) and point5. I am getting -2.5 (should be -5.1) volts with noise and 0.8 volts (should be +5v) also noise. When I disconnect the panel meter from mainboard the voltages are -12 and +8 :D. But I think panel is making some common connections to make circuits.

So, I found that when I disconnect the panel meter from mainboard, PSU is more stable and there is no noise in the output. Then I checked pannel meter inputs and there is constant 100 ohm resistance between +5v and 0.  Panel schematic is draining 300ma current and making about 70mvpp noise.

I need help and some advises. Do you think that panel is causing this problem? And If anyone has the same PSU I will be happiest man in world if will tell me what is the resistance between panel  pin 1 and 2 (+5v and 0). These are the panel power pins. Also I forgot to mention, panel is lighting up and showing some +-3 volts difference from output voltage, and current meter displays 1.999, sometimes 1.000 it does not correspond the load.

I will provide schematic and measurement data if anyone is interested. Also if anyone has schematic of panel itself please provide, I could not find anywhere :(

NOT Noise OSCILLATION :D
« Last Edit: November 21, 2016, 01:00:34 am by sosokruashvili »
 


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