I recently found a cheap (~$200) Metcal MX-5200 on eBay listed as powering on but otherwise untested. When powered up with good hand pieces connected it would display "Open Error" on the left channel. Opening it up revealed loose screws and nuts from the LCD panel, likely because someone tried and failed to take it apart to fix it previously.

There was nothing obviously burnt, so I thought swapping components near the channels might help reveal a culprit. I started with the relays (p/n DS2E-SL2-DC24V). Swapping them with each other ended up fixing the issue. Perhaps one was stuck and heating it up and moving it around unstuck it. The relays are obsolete, but I found and ordered a couple from eBay to have as backups in case the originals fail again.

One other issue is that the power switch was physically broken and only making intermittent contact. It's a Cherry RR812C1000-116 DPST 16A 125V switch. Fortunately this is still a part available at places like Digikey.

Hopefully these notes are helpful to someone else with the same issues in the future.

This will be a nice upgrade from the MX-500 I've been using the past several years. It outputs 80W per channel and can do so simultaneously compared to the MX-500's 40W for a single channel at a time. Having nice tools has made repairing things so much more enjoyable. And hunting for great deals on used tools and repairing them is turning into a hobby itself.

As a little follow up, the Cherry RR812C1000-116 DPST 16A 125V switch worked great. To get to the switch, remove 4x T15 security screws on the four corners of the rear housing. There should be just enough room to place it parallel to the rest of the enclosure. Note the placement of the switch wires. Blue is on the left side of the ROM, brown on the right. I used tape to keep track of which wires were top and bottom. The switch contacts that are wider apart should face up. Pull back the plastic sleeves. You might need to use something poky to get the terminals to release. Once the wires are removed, push the two tabs on the switch and rock it out of the enclosure. There's a little nubbin of plastic to help key the new one into place. It still might take some force to get the new one to pop in.

Instead of starting a new thread, I figured it'd be more effective to post here, as I'm also working on a 5200 power supply. My unit works well with the right port, but the left is hit-or-miss. If I connect the hand-piece to the left port and leave it in the auto sleep work stand before power up, it will display power levels on the LCD as it's supposed to when I turn on the PSU. When I remove the hand-piece from the work stand, I see the power meter climb as the tip heats up, then within a second or two, the relay clicks off and I get "open error". I've previously replaced the relay on the left side. Nice strong click on and off. I am not sure where to look from here. Any ideas are appreciated!

Does it do that with any cartridge installed? I had a cart go bad and it would similarly ramp power then say something like "incompatible cartridge".

>> Elemenoh said:

Does it do that with any cartridge installed? I had a cart go bad and it would similarly ramp power then say something like "incompatible cartridge". Click to expand...

The exact same handpiece and cart are working fine on the right port, so I think it's safe to eliminate it as a suspect here. Good train of thought though!

I'd keep testing components downstream from that port. Maybe a leaky diode or bad transistor? Also it'd be good to make a post about this on EEVblog forums as well since there are some folks there familiar with repairing Metcal stuff.

>> Garrett said:

Instead of starting a new thread, I figured it'd be more effective to post here, as I'm also working on a 5200 power supply. My unit works well with the right port, but the left is hit-or-miss. If I connect the hand-piece to the left port and leave it in the auto sleep work stand before power up, it will display power levels on the LCD as it's supposed to when I turn on the PSU. When I remove the hand-piece from the work stand, I see the power meter climb as the tip heats up, then within a second or two, the relay clicks off and I get "open error". I've previously replaced the relay on the left side. Nice strong click on and off. I am not sure where to look from here. Any ideas are appreciated! Click to expand...

Hello Garrett,
Have you managed to solve this issue? I have the same problem, however I haven't touched left relay yet (as right side still working). Hence, I am preparing for the worst case and maybe at some point of time relay change will not solve the issue. Many thanks.

This sounds a little different from your issues, but maybe worth checking D12 just in case.
https://www.eevblog.com/forum/repai...red-for-not-heating-up/msg1343323/#msg1343323

Also this thread mentions there's a hidden factory reset you could try. Sounds like you need to hold down the menu button then switch on the power.
https://www.eevblog.com/forum/revie...5000-firmware-and-data-eeprom-information/25/

>> Maxxutk0 said:

Hello Garrett, Have you managed to solve this issue? I have the same problem, however I haven't touched left relay yet (as right side still working). Hence, I am preparing for the worst case and maybe at some point of time relay change will not solve the issue. Many thanks. Click to expand...

I haven't fixed the issue yet, although I did check and verify that D12 was not shorted.

>> Elemenoh said:

This sounds a little different from your issues, but maybe worth checking D12 just in case. https://www.eevblog.com/forum/repai...red-for-not-heating-up/msg1343323/#msg1343323 Also this thread mentions there's a hidden factory reset you could try. Sounds like you need to hold down the menu button then switch on the power. https://www.eevblog.com/forum/revie...5000-firmware-and-data-eeprom-information/25/ Click to expand...

Good call on the factory reset. Maybe the ROM got corrupted somehow. I have a programmer, I suppose I could check that as well to see if it's software related.

Hi everyone,


I'm experiencing the same issue with the left channel on my Metcal MX‑5200 station. Has anyone here managed to fix this problem?


What I've done so far

• D12 diode tested OK.
• Continuity checks on every discrete component (except ICs) show no opens or shorts.
• All transistors read normally on a multimeter.
• Electrolytic capacitors look in‑spec (as far as you can tell in‑circuit).

Parts already replaced




After these swaps the fault is still present.


I've also tried a factory reset--no luck.


I'm a bit stuck at this point and would really appreciate any pointers or success stories. Thanks in advance!