Have you dealt with Yokogawa Power Analyzers generally before?
It is weird that this only has a three-bay back cover installed. I wonder if expanding to six bays was just a matter of a back panel or if some electronic tweaks are also required.
This has been the first Yokogawa Power Analyzer on my bench, I've seen various others before. Some 20 years ago, my job was developing "Power Quality Analyzers" which include most of the power analyzing functions the WT1600 has and a lot more PQ specific stuff, but specialized on power line frequency usage. So they had lower bandwidth (in the 5 ... 50 kHz ballpark).
I can't remember, the unit is already packed and I couldn't find photos that showed the backplane. So I can't tell whether the connectors for ch 4..6 were fitted or not. In general, I would expect the chassis to be able to work with up to 6 channels, and this particular unit might have been a 3ch unit somewhen in the past - but that's just guessing. As you most probably already know, one can easily swap the input modules, the software maybe complains once because of the modified configuration and forces a factory reset, but otherwise this just works with any number and any combination of modules.
Edit: Looking at the photos within this thread, I'd say the back panel can take up to 4 modules, and the backplane should have all connectors for up to 6 channels fitted.
Also, the general mode of failure of these 5A elements is people passing too much current thru the elements and frying shunt resistor. Do you have experience repairing shunt resistors on these modules?
The shunt is a 100mOhm one, that of course can be easily fried by overcurrent. The input amplifier circuitry apparently is protected against overvoltages due to overload or shunt failing open, if there's enough overvoltage due to a failed open shunt, I'd suggest to check the protection circuitry, especially the 51R series resistor - as shown in one of my schematic sketches before. I've seen some components fitted at the sense side of the shunt, most probably for frequency compensation purposes. One would have to check if these are specific to the particular shunt and must be "re-adjusted" if the shunt is replaced. Otherwise, I'd expect some issues sourcing a replacement and actual replacement since they've used some small PCBs at both sides of the shunt that would have to be removed from the old and fitted to the new one, or some bodging involved in case you cannot source a mechanically identical shunt.
No, haven't done this before, as I prefer not to fry my instruments
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/wink.gif)