Zhongdi ZD-987 help wanted to repair

[mitsos]

hi

I use the last years this cheap station and suddenly the desoldering part is no more working.
After power on, every second, all segments of LCD are tuning on and a beep is sounding for a moment.
The desoldering gun is no heating.

I reverse engineering the microcontoller pcb, ZD-LTY-2, it uses the C8051F310.

The soldering part is working OK. Is there a way to read the contents of C8051F310?

regards
mitsos

[h0nk]

Hello mitsos,

there is a C2 interface for 51er Silicon Labs Controller.
Look for Silicon Labs Applikation Note AN127.

I bought a cheap clone of the JTAG/ISP-Adapter on Ebay.
It works well.

But i am afraid that the security options are set and
Flash Read-Out is prohibited.


Good Luck, and

Best Regards

[fpgaguy]

there's a couple teardowns of this device with suggestions to improve
usually this is a heating element or pump problem and not the micro

[pickit2]

This maybe a starting point.
https://www.eevblog.com/forum/chat/firmware-for-zd915-solder-station-converter-in-hex/msg1221804/#msg1221804

[bigtoy]

I had problems with my cheap Chinese hot-air desoldering system. I took the handle apart. Turned out there was a thermal fuse up close to the heating element in the handle. And it had done what thermal fuses often do - it went open-circuit. I just bypassed it and the unit started working again.

[mitsos]

hi

I upload a small video to see the fault here:
https://we.tl/t-D10ME6I8s1

you'll see after power-on that in every flashing displays for a moment the working temperature 440°C and then go to faulty operation forever, either the gun is connected or not.

I attach the power PCB. When I force 3V through a 300ohm resistor to optocoupler pin 1, the gun is starting to heat.
I ask also the Zhongdi for this fault.

regards
mitsos

[pickit2]

Both controller pcbs are the same. only the code is different.
the unsoldering gun has an extra pin for the trigger, your heater seams to work.
how about the thermistor.

I looked if the workshop stores to see if they had any scraped zd915's
but they have been moved, the store keeper is away on holiday for another two weeks.

[mitsos]

hi

I forget to write some notes:

the resistor of 120k, at the feedback of 358, is present only on the desoldering control PCB

the value of VRA1 comes from measurement

I take measurements on thermocouple from the soldering part, I find about 74microvolt/°C and the gain of 358 is about 65. With Vref=2.5V you get a maximum temperature 520°C.

The gun has a smart sensor of "busy" station,the SW-18010P from SUR (on net you find the same from SOYO), it is a spring that has at its centre a piece of wire. The spring action is like an inverted pendulum and as it vibrates, during working with the gun, it touches the wire. It is a simple switch that put the pin P1.4, through a resistor RA1 with value 1kohm (not appeared in my schematics), to earth. If for 15 minutes the spring is not touch the wire, the C8051 set the temperature to 200°C.

The small fan (not appeared in my schematics) gets its supply with half rectification like D2 and E1 in the control PCB schematic.

regards
mitsos