[Lamu95]

Hi,
I've completed the 501 and the MP 573 kit. I managed to get all the voltage checks right in both units but the transformer (T1) on the 501 switcher was buzzing. It was audible just by ear and also through the MP 573. After some inspection, where I couldn't find any mistakes in the circuit, I plugged in the 501 again but now the transformer seems to be completely dead. I've made continuity checks and everything seems to be fine before and after the transformer. Also I'm reading 11.5 V at the input of the transformer but no voltage coming out of it.

 

For the switcher I'm reading:
+11.5V at the +12V input pin
0V instead of -19V
2.24V instead of +19V
1V instead of +55V

Could it be that I killed the transformer when I made the solder connection on the copper tape by applying heat for too long?

[JPK]

Were you able to solder the LM2586 heatsink tab to the PCB? This connection ensures good heat transfer from the case to the outside.
Check that the 2 regulators U1 & U2 are not touching any other pad or solder joint.
Can you check the switcher alone like in step 19 of the switcher assembly guide?
Is the LM2586 getting very hot?

[Lamu95]

You're amazing! I re-soldered the LM2586 tab to the pcb and the thing came back to life. The buzz is gone and everything works flawlessly.

Thank you!

[JPK]