Metcal MX-5200: how does a good unit behave? (resolved)

[benj38]

I have a Metcal MX-PS5200, in which the left channel gives "open error" even when a hand-piece with tip is connected to it.

It would be of great help to me if someone with a working unit can listen to the clicking sounds of the output relay in a few scenarios.
Note that since the relay latches on to the last position used, even when power is removed, the behavior may differ depending on the channel used before the unit was last turned off.  Here are the scenarios:

1. Connect a hand-piece only to the left channel; turn unit on and wait for it to start heating; turn unit off; disconnect hand-piece;
  now turn unit on and count the clicks!

2. Do the whole sequence again but now using the right channel.

3. If you have them, connect two hand-pieces with tips and count the number of clicks on turn on (also see if you can tell whether the left or right channel is detected first).

The circuit has a latching relay that switches the output between the two channels (a second relay is apparently used to turn both channels on for simultaneous use). It looks like the channel that is not latched on is completely disconnected from the circuit, and thus in order to detect which channel has a hand-piece connected to it the relay has to be switched between the channels. However, the PCB is multi-layer, so there may be some connection that I cannot see. 

The number of clicks can tell if the unit indeed needs to switch the relay to detect the hand-piece, and also may hint on the order the channels are checked and if the unit remembers the last used channel. All of this would greatly assist me. Unfortunately, when the unit worked I had never really payed attention to the clicking sounds...

Thanks in advance to whomever is willing to help!

[ivaylo]

Bummer, I thought I’d help, but turns out mine’s a PS5000. The two output model, but before yours. Behavior is completely different. No clicks at turning on, just a single click when I switch channels. It does remember the last channel used. Also both channels can’t be used at the same time by design.

[Zucca]

Give me some weeks, I could help you. Unfortunately I am very busy at the moment.

[benj38]

@zucca Thanks a lot, that would be great!

If anybody else is willing to pick up the glove I would be delighted.

[Zucca]

https://www.dropbox.com/s/rpf7wxxzn7zrcl5/00007.MTS?dl=0

Hope it helps

[benj38]

@zucca Thanks a lot!

It does look like it works differently than I thought.
I have always had only one hand-piece connected to the left connector, so I never noticed how it handles the two channels.

It seems from your video that it does not look for both hand-pieces on boot, and simply uses the fact that the relays are latching, and gives an "open error" if the side that last had a hand-piece connected to it no longer has one (even if the other channel now has something on it -- see time 1:14 in the clip)

In fact, it seems like in no scenario was there any clicking of a relay on turn on! The relays click only as a result of the button presses. Is that correct, or did I miss something?

Also, I would very much like to know, when nothing is connected to both sides, do the relays click as one presses the button? (in my unit nothing clicks in this scenario)

BTW, the two relays are controlled by the MCU using MOSFETs. The relays, MOSFETs, protection diodes, and the gate resistors all check out 100% fine. I have also replaced the MCU to no avail 

[Zucca]

In fact, it seems like in no scenario was there any clicking of a relay on turn on! The relays click only as a result of the button presses. Is that correct, or did I miss something?

To be honest I hear a very weak "click" at power on. About 10 times less powerful than the one when I press the button.

Also, I would very much like to know, when nothing is connected to both sides, do the relays click as one presses the button? (in my unit nothing clicks in this scenario)

Yes they click and the little position indicator on the display switch position.

Do you have the same FW as mine? 

[benj38]

@zucca thanks again.

I believe the very faint click is not the relays if it is 10 times more faint.
I think I hear the relays in the clip. There seems to be a clicking sound not originating from the button itself (easy to tell I guess, by comparing to a button press when the unit is off)

The fact that you hear the relays as you press the button even when nothing is connected is very different than my unit's behavior. I hear no relays (the button itself is OK, since a long press enters the "sleep timeout" menu).

I hope these are not firmware differences, and are indicative of the fault.
My firmware is 1.36, thus, slightly different than yours.

[Zucca]

Since you have the device open, any idea how to upgrade/flash the FW?

it looks like we need somebody with more knowledge on Metcal puppy to solve your problem.

[cs.dk]

Mine does not click at all on power up. I can only hear the switch, even if i turn it on as gentle as i can.
It does have a faint click when switching channel though.

Video: https://photos.app.goo.gl/ZRQRNK4jfhHirt7g7

[Gerhard_dk4xp]

Mine clicks loud on Power-on, when it has been off for a long time and that takes 300msec delay..
When I switch it on, off and on again after a second, it does not click.
Probably a capacitor that keeps charge for some time.

I remember that I was thinking that the left channel was broken, but it was only the
black-on-black switch left to the display that I had never ever used and that was
touched by accident.

regards, Gerhard

[ChuckDarwin]

Way late in reply.  I hear no clicks after selecting a mode, powering the unit off, pulling and handpiece and then powering it back on, except in simultaneous mode as noted below.  If either handpiece is open, there is one click and the 5200 reverts to the left channel, with an OPEN error if the left channel is open.

Test unit is an MX-5200 (factory repaired main board), firmware 1.33.  Board isn’t particularly clean from the rework.

I think the matrix is a correct pinout, but I would welcome corrections.  I will get a visual trace and photo of the other side of the PCB with the relays out and the goo cleared when I get to replacing one of the relays, and check again.  Diagram is looking at the front of the MX-5200 with the face off, which presents the under/back side of the PCB.  If you are pinning out while the handpieces with tips are connected, you will get >= 1 ohm on pins where the handpiece has a relation.  Without the handpieces everything should be < 1 ohm.  My two relays are ~0.22 ohms on left and ~0.05 on right.   Pin pair 4,13 in each relay pass through what look like current sense ckts.  Pin 11 on the left relay has almost no resistance with pins 4,13 on the right relay but looks like it comes off the feed (well) before the sense ckt.   

The power supply in the 5000 and the 5200 appear to be the same layout, and the 5200 main board is a slight respin of the 5000 and an additional sense board glued in.  Chassis disassembly is four security Torx 15 in the back and removing the nuts from the F connectors in the front.  A 13mm or ½ SAE socket work well for the nut removal.  The chassis separates into three sections: blank front, center with main logic/RF board screwed in, and rear with the power supply PCB. 

My observation of the relay switching so far is: If only the left or right channel is selected, the left relay is effectively switched out of service to the not-connected pins 8,9.  The right relay can switch in either of the channels.  In simultaneous mode, the right relay will eventually switch to the right channel, pin 8, and the left relay will connect pins 6,11 which feed pins 6,11 on the right relay, which feed the right channel.   While in simultaneous mode, if either handpiece or tip is removed, the left relay switches out to pins 8,9 (n/c) and you are presented with a LOAD ERROR A or LOAD ERROR B message.  I need to power cycle the clear the error.  If just the left or right channel is selected, then an OPEN error message is displayed and cleared when the error is corrected.

When switching to simultaneous use of left and right, there is one click when the select button is pressed (step 1), about 8 seconds later a second click is heard (step 2), and about 8 seconds later a third click is heard (step 3).  The third click is an actuation by both relays. 

I cannot switch from right channel to simultaneous if the left handpiece is disconnected.  This makes sense.  If the right handpiece is disconnected, there is one click and an OPEN error for the right is displayed.

I have noticed some randomness in what channel mode the 5200 selects on powerup after being in simultaneous mode and having used both handpieces.  It resumes in left channel mode more than 50% of the time, simultaneous mode a little less then 50%, and on very little occasion, the right channel. If one or both pieces are not used, but remain in the sleeper stands, the 5200 will power up in left channel mode almost all the time on following power-ups.  I would think it would come up in the same mode it was last used in if the handpieces are still present.  It might be an issue specific to my unit.

[benj38]

Thanks everybody for the data!
It allowed me to trace the problem in my unit to the MCU.

I would summarize the findings in this thread as follows:

1. The 5200 remembers which channel(s) were used just before the unit was last turned off.

2. On subsequent power-on it does not scan the channels for connected hand-pieces, but simply assumes the remembered state, issuing an "open error" if the actual state does not match the remembered one.

3. When only one channel is selected, the other hand-piece is completely disconnected from the circuit by the relay (thus, no sensing is possible for this unselected channel).

[Zucca]

Follow up:

https://www.eevblog.com/forum/reviews/metcal-mx-5200-and-mx-5000-firmware-and-data-eeprom-information/