2445B tick mode issue -- fixed (inverter and regulator board recap and repair)


post.marcel@...
 

Recently my 2445B didn't want to start up properly anymore. At power-on it was constantly resetting ('tick mode'). I replaced most of the caps as per the 2018 bill of materials that is saved in the Files section on this forum but had to update the list to 2021 equivalent parts as not everything was available. In the end the problem turned out to be diode CR1102 on the A3 regulator board that had gone dead short in both directions. I replaced it with an MUR160.

For those interested, I have documented my repairs in this video:
https://www.youtube.com/watch?v=vC9kd6zx5_M


Keith
 

Thanks Marcel!

I appreciate the video and the BOM file. I have a 2445b that is working fine, but I dread the day that the SMPS ever goes dead, as I know so little about them. Now, having your video and BOM provides me with a measure of peace of mind. Thanks again for your extra work to do these postings.

Keith
CoolBlueGlow


post.marcel@...
 

Hi Keith,

Happy to help. As with most things, I am standing on the shoulders of giants here. My main profession is in IT, and electronics is definitely not my forte. It took me therefore many hours to research all the parts but I couldn't have done it without this forum, eevblog and all the people contributing there, as well as the amazing parts selection interface from mouser and digikey and a whole bunch of other resources that would have taken me an impossibly long time to understand.

Things I left out from the video was that there were a couple of caps out of spec and one resistor (R1010 on the A2A1 board) that had gone open circuit. I already spent 4 hours editing the video and didn't want to go down in too much more detail.

If you have been following the eevblog forum posts for the 2465B teardown you'll read that there are some issues that you probably should be aware of though:
- the aging battery in the DS1225Y memory chip that holds your scope's calibration data
- the (probably) leaky capacitors on the A5 board (on the side of the case)

The calibration is a real pain to do if you don't have the right tools, so if you can, check my other video on displaying the calibration data (https://www.youtube.com/watch?v=Tu1j-fImuv8) and just make a video of the values that are in your scope. It's a really simple thing to do and it doesn't require opening the case or anything. Once you have that video, write down the numbers so it will be so much easier when you need to reprogram another memory chip. I've added instructions in the video comments on how to enter the diagnostics monitor mode.

If something ever goes wrong with your 2445B begin reading at chapter 6 of the service manual, it's got a super helpful troubleshooting section.