Metcal MX-5200 - "Power" But No Heat

[Stephen]

Hello,

My Metcal MX-5200 powers on and appears to respond normally. However, the cartridge doesn't heat and the "power" reading does not exceed "00", except for briefly up to "05" when I first power on. I'm at an impasse, any suggestions would be greatly appreciated!

Debugging Steps Taken

• I've tested my handle and cartridge on an MX-500 without issues.
• I've upgrade the firmware from 1.33 (original) to 1.36, copied from this EEVblog forum post.
• I've also checked the "cal" (calibration) option under the settings menu, which shows a maximum power of "15" and the message "Pres&Hold:Bad" [sic]. I repeated this process for 4 cartridges with the same result.
• I've inspected the diodes to the two channel outputs (Left: D15 / D16, Right: D11, D10)
• I've swapped the relays between Left / Right to no effect, including testing each channel setting separately.

imgur gallery

[thm_w]

The calibration is just the power meter bar, so shouldn't matter for normal operation from what I've read.

When you power up with the handle plugged in, do you get any voltage on the connector or input to the relays when seen with scope?
When you press the button to switch between channels, the behavior is the same right. Just says power 0 and does nothing.

Kind of odd it doesn't detect an issue with RF, maybe the RF is not being generated?

https://www.eevblog.com/forum/repair/metcal-mx-5200-how-does-a-good-unit-behave-(my-left-channel-is-bad)/
https://www.eevblog.com/forum/repair/metcal-mx500p-11-power-comes-on-but-no-heat/ (not the same product but troubleshooting is similar)