Identifying replacement diode

Hyper_Eye · August 7, 2022

I have a Panasonic FZ1 3DO which has power issues. I've had this unit for years and it used to work fine. Over time it developed an issue where once plugged in it would power on and run fine but once it was turned off it wouldn't boot again. The power LED flashes and the fan spins up and down continuously. If I unplugged it for a while and then plugged it back in it would boot again. It worsened over time to where it had to remain unplugged for longer and even then it wasn't guaranteed to boot. Now it doesn't boot at all. The power LED still flashes on and off and I can hear the fan whirring up and down. I have another unit that had a similar issue and after a recap it is working perfectly. Unfortunately I completely recapped this unit and it still isn't working. I used a board diagram to go around and test continuity on every cap and everything seems good there. I haven't identified any shorts.

I believe I have identified a bad diode in the area of the power supply. The diode in question is D3. I checked continuity on the diodes in this area and all looks good. Testing the diodes themselves D33 and D12 test as expected where I get a reading of 0 in one direction and roughly 0.75 in the other direction. When I test D3 I get around 0.75 in one direction but when I test in the other direction the value is not 0. Instead it continuously climbs until I remove the probes. I removed the diode from the board, which is slightly bigger than a spec of dirt, and tested it out of circuit. It wasn't easy to test this little thing out of circuit. At one point I thought it was measuring 0 but I also had instances where it seemed to be exhibiting the same behavior as when it's in circuit. I cleaned up and retinned the pads and soldered the diode back in place. The behavior is unchanged. I suspect this diode is the problem.

I don't know enough about this stuff to identify the diode and source a replacement. Can someone help me out? In this image you can see D3 which is below D2 and above D12. On the diode it is labeled E6. (higher resolution version is here: https://i.imgur.com/GcB8pwM.png)

Here is a section of the board schematic. Based on the symbol for D3 it appears this is a Zener diode. Is it even possible to properly test a Zener diode in circuit?

Any help is appreciated!

Edited August 7, 2022 by Hyper_Eye

Hyper_Eye · August 7, 2022

The service manual I was looking at does not include the part numbers for any diodes. A friend of mine found a version of the service manual that does have them. That Zener diode part is DEDDTZ033CTT. So now I need to find an acceptable replacement.