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MA5000VZ strange fault

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Hi, got an MA5000VZ (internally same as 5002 late model) with a fault. It shows IOC (bright led) on Ch1 on switch on. The ODEP light comes on fine at the same time as the good channel. The output is muted. I've swapped the output modules over, fault is still on Ch1.

Voltage checks show normal ODEP voltages and temperature. There's no DC offset at power up, bias is all zeroes suggesting the drive has been removed. The mains relay is in, there's power on the DC caps +/- balanced. If VZ-Auto is switched in, the VZ goes straight into high voltage mode. In lock low, it locks into low fine.

Volt checks around the IOC warnings show the LED is being brought on by the 'ES1' line. Checks on the error amp show it is driving hard to +14V. I've swapped the error amp.

I'm wondering where to probe next?

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joust    0

This is a long shot: A few weeks ago I had a strange issue with one channel, that had to do with IOC. I discovered a bad op-amp on the output terminator board! the signal to the IC appeared to be normal but the output was completely wrong (compared to the other side). Replaced the IC and the fault disappeared! Also, some weird issue can happen if the flat output cable (output flex bar) going to the output terminator board is sheared off at the solder pad.

Alain

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Well, it was the flat cable sheared on the terminator end. But no cigar for you...I found out this morning after more or less eliminating everything else! The amp had been repaired elsewhere some time ago and I guess they were none too careful with the strips.

B)

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