Kikusui PLZ-300W Part ID for Repair

[rubidium]

I recently acquired a used Kikusui PLZ-300W electronic load in great cosmetic and working condition - except for 1 thing. There are 2 ganged latching push-button switches that are used to select the range for constant current operation (0-6A or 0-60A). One of those push-buttons, for the 0-60A range selection, latches properly and is released upon pushing its partner (for the 0-6A range) - as it should. Unfortunately, the reverse is not true. Upon depressing the 0.6A push-button, it does not latch down and hold. Rather, it just springs back and the functionality only persists when it's continuously held down with a finger. I wrote to Kikusui to inquire the part number and, of course, they responded by noting that the unit has been out of production for some time and they no longer support repairs or maintain spare parts for it. (And, of course, they followed up by suggesting the purchase of a new contemporary product in having a similar performance range - which I'm certainly not going to do.)

This looks to be easily repairable, if I only had a replacement switch. So, does anyone have one of these units and can identify a replacement switch from one of the standard U.S. distributors? Or are these latching switches repairable, given that it functions properly electrically, but just isn't latching mechanically? Also, if anyone has schematics for the PLZ-300W, that would be helpful as well.
Thanks,
Jim

[bob91343]

I have experienced similar problems.  If you study the switch you will see where the latching function is supposed to work and, if it's only bent or sticky, repair it.  If something is broken it may or may not be repairable.  Check any springs or keeper blades.

Some of the plastic units won't be repairable but metal latches usually just get bent and don't hold, or they get dirty and need cleaning and/or lubrication.

If it's not repairable you are probably out of luck.  I am also familiar with the boiler plate response to a need for parts or information on old gear.  There is a large number of hobbyists who own this obsolete stuff and that's why we have the storehouses of manuals.  But parts are a different story; if you even find the same model on ebay you won't want to pay what the seller hopes to get.  Even for stuff that doesn't work.  And you may end up with two units that have bad switches.

[edpalmer42]

If the switch is unrepairable, it would be quite a project, but you might be able to replace it with an electronic module.  Lots of reverse-engineering, but theoretically possible.

Ed

P.S.  How did things work out with your CS-4000?  Did you bring it back to life?

[dacman]

Try lubricating the switch with a switch lubricator.  Also, if it is the type of switch with a pin that catches to hold it in place, then one thing to try is to take the switch apart and flip the pin over (if the pin is worn on one end). 

[rubidium]

Turns out the 2 ganged 6A/60A push-button switches appear to suffer from a weak spring on a common slider bar. If I extend the bar with the tip of a pair of tweezers (in the intended direction that the spring action would take it) then the complementary relationship between the 2 buttons works perfectly. In my attempt to remove the spring, possibly extend it a bit, and replace it, the very tiny spring broke into 2 pieces. I hate to admit this "Rube Goldberg" practice but, rather than be SOL, I managed to tie a fine strand of nylon dental floss to the slider bar, and then tied the other end to a thin O-ring which I anchored to a nearby bracket. This re-creates the action that the original spring was intended to provide, and the unit functions perfectly now.  This load is a fine working unit for my needs and, I suppose, one needs to do whatever "dirty deed" necessary to help it along in its elder years. If I can find the proper replacement switch down the road, then I'd be happy to replace it. But in the meantime, this kluge gets the job done.
Jim

[rubidium]

@edpalmer42, the CS-4000 eventually made it, piecemeal, to the parts bin - sans the worn out tube. It never achieved lock and all of the parameters were indicative of the cesium supply being exhausted. When you take a gamble with such things you have to be prepared to occasionally draw the short straw ...

[edpalmer42]

@edpalmer42, the CS-4000 eventually made it, piecemeal, to the parts bin - sans the worn out tube. It never achieved lock and all of the parameters were indicative of the cesium supply being exhausted. When you take a gamble with such things you have to be prepared to occasionally draw the short straw ...

Sorry to hear that.  A worn out tube is the most likely result with an untested Cs standard, but there's always hope.  If it wasn't such a pain in the wallet .......

Ed

[Ordinaryman1971]

I wonder if you could post the picture of the switch assembly.... somebody may have one as unlikely as it may sound.