Kikusui PLZ603W Troubleshooting Identity Crisis - Page 1
Forum section: electronics / repair

author: Johnny10
author_rank: Frequent Contributor
timestamp: October 24, 2020, 11:28:01 am
content: I thought I might post a curious problem on a Kikusui PLZ603W I have on the bench.It is a 603W unit that thinks it is a PLZ153W model.The load presented at the terminals is about 4X what is on the display.Tried recalibrating unit but I cannot select the 603W in the calibration mode only the 153W.The Calibration data table from Operations Manual can match differences exactly as per 153 to 603.My assessment would be the firmware eprom.This is a unit with unknown history.As I said, everything works it is simply presenting 603 loads while showing 153 display. i.e. when set for .34A the actual load is 1.26A.While proceeding to order an eprom programmer and asking around for a download of 603 Firmware (Firmware not available from Company), I thought I would post the problem.The Kikusui PLZ-3W Models look to all have the same CPU board.The difference being the number of add on load modules.How the CPU determines which Model number baffles me at the moment.Talked to a company Rep but they say not much data available for older units.

author: perieanuo
author_rank: Frequent Contributor
timestamp: October 24, 2020, 12:40:32 pm
content: hi,try to read the epromusually things like model/fw are not encrypted, you will see them in clear in asciiregards, pierre

author: DaJMasta
author_rank: Super Contributor
timestamp: October 24, 2020, 05:17:24 pm
content: Not that familiar with the unit, but do you think debug/boot information from the rs232/remote control port could be valuable in figuring things out? Also is there any evidence of configuration jumpers of some sort on the board? It could be that a dip switch/jumper/resistor configuration sets the model configuration.Perhaps less likely, these units probably use the same front panel controller and then modules for the various configurations - maybe the module connected to the front panel controller is somehow reporting itself incorrectly, so maybe troubleshooting any digital links between them could shed some light on the issue.

author: Johnny10
author_rank: Frequent Contributor
timestamp: October 28, 2020, 03:29:50 pm
content: Has GPIB PortI have just ordered TL866ii+ from China, guess this project will be on hold till delivery.If anyone has downloaded firmware for the PLZ603W I might need a copy.EPROM chip is easy to get by removing top cover and it is socketed.Have not found a jumper to identify model to the CPU.

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 13, 2020, 08:25:10 pm
content: Programmer came today and to test it out I put the AM27C020 in the device and read the contents.Seems to me this eprom is for all PLZ3W versions. 153W, 303W, 603W, 1003WHmmmmmmmGuess there is a circuit somewhere that identifies the unit to the processor.

author: coromonadalix
author_rank: Super Contributor
timestamp: November 14, 2020, 04:30:33 am
content: please save the content as an hex file, and share it here ...

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 14, 2020, 04:08:09 pm
content: Kikusui PLZ603W EPROM hex file

author: Johnny10
author_rank: Frequent Contributor
timestamp: December 19, 2020, 02:10:49 pm
content: I am definitely not good with software.Did anyone notice in the downloaded file where the program looks for Model Type.I see the request but not the location.

author: hp3310a
author_rank: Regular Contributor
timestamp: September 14, 2025, 07:08:47 pm
content: I'm curious, did you ever manage to solve this problem?

author: fenugrec
author_rank: Frequent Contributor
timestamp: September 15, 2025, 06:39:57 pm
content: Quote from: Johnny10 on October 28, 2020, 03:29:50 pmIf as I suspect the "power" PCBs are different from one variant to the other, sometimes they will identify their type with one or a few pins on the backplane (or in your case, the ribbon cable) by combinations of open/gnd/vcc. Then that is somehow read by the CPU, many ways of doing that, could be via a latch, or IO expander, etc.Without schematics it's a bit harder to guess. I've only ever seen schems for the earlier analog PLZ153/300W units. Second best would be to compare boards to other models in the series. The worst is by looking at the firmware, which at a first glance I can only say is x86 code. Did you notice what CPU they are using when you had it apart ?Lucikly x86 is very well supported by reverse engineering tools, but you would still have to spend time figuring out the memory map, peripherals, and looking at disassembly.Oops, just noticed this is thread was just necro'd, but there is very little servicing info on these PLZ units, so I think it's fair

author: Johnny10
author_rank: Frequent Contributor
timestamp: September 23, 2025, 03:44:52 pm
content: No :-(I still have the Unit in storage. I thought could see in the software subroutines for all models but I can't find the pin which the software uses to identify unit versions.I can get it to output and read various voltages but they are at different multipliers depending on unit version, ie.. 300 603 or 1003 watts. It's been a while but if I remember correctly if I figure 4X or /4 it outputs the voltage I am looking for.