Electronics > Repair

Fluke 5500a repair attempt

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Dear ddrl46,

                Thanks for the help, I reprogrammed the all the ICs via TL48 programmer calibrator is up now.

After some time after opening up this thread, and more time since i got this calibrator, it finally has come back to life

The idea of modding the Fluke 5820's A9 to use it as a Fluke 5500a's A9 board, although possible requires a lot of work and modding that involves cutting traces. So i dropped that idea

But thanks to ddrl46's amazing work the Fluke 5500a has now a working A9 board. He took the time and effort to have develop a working A9 board

The board came and was installed without much trouble.

But after powering up the calibrator the first time with the new board I realized that calibrator had other issues, and that probably was the reason that it got his a9 board removed.

I was getting the Error 104, and if I executed the diagnostics I also got Error 399

Also thanks to ddrl46's help, i was pointed in the right direction, and started to look for the problem

The problem was located in the A8 board, the voltage generation board. Initially found a missing component, Q19.

After some troubleshooting, realized that the Error 104 is always triggered by the _Fault line that it's shared between boards. Leaving connected just the A8 and the A6 board narrowed the problem

And after some time i noticed that under some circumstances the 65v supplies were faulty. +65 were quite high (72v) and -65v supply was down (-15v)

The transformer it's good, and also the capacitors, diodes and transistors. But i found 2 of 4 1ohm resistors that connect the 65COM to SCOM open, so the 65v secondaries from the transformer were floating in relation to the SCOM 

I replaced the four resistors in the A8 board (R55, R56, R63 and R65). The supplies were good again and I tested the calibrator. That showed no more errors.

The calibrator it's being tested right now, but it doesn't seem to have any other error.

The zero function it's executed without problems. I could also adjust and store calibration coeffients.

So now this Fluke 5500A seems to be fully working, and it also have the SC300 scope option.

There are two details that are missing to me. The encoder knob and the fan filter are missing.

If any one knows where i could purchase them please let me know.

In the mean time i'm going to order a chinese replacement button membrane for the calibrator   


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