After sixteen years of reliable operation, the model 952452 power supply for my AOR 7030 receiver finally died.
I was tuning around listening to CW and datamodes stations that sounded like they all had raspy notes. A quick check on the PSU voltage with a voltmeter revealed it was sitting at 17v whereas it should be 15v. Substituting the PSU with another (AOR) 15v power supply cleaned up the raspy signals again so I decided to investigate if it was repairable.
Looking at the output with an oscilloscope showed 15v DC with 100Hz spikes up to 17v.
Firstly a visual inspection. The main reservior capacitor 4700µF/25v had popped the top so I removed this and tested with my Peak Electronics ESR Analyser. This revealed a completely open circuit capacitor.
As I don’t have a schematic diagram I drew one out. I’ll attach a PDF copy too…
AR7030_PSU PDF copy.
Some further checking after replacing the capacitor revealed I still had a high output voltage but reduced ripple. Measurements on the TO220 device (which turned out to be a BUZ71) showed it had failed with the gate very leaky to drain and source. I didn’t have a replacement to had but I do have a BUZ91 so after cheking some data sheets fit this as a temporary replacement. Now we have 15.2V with only 10mV of ripple. Apply some resistors to the output to load up to 500mA and check again – voltage and ripple have not changed. So now off to order the correct FET then I’ll replace and update with the final voltage and ripple figures!
If you have a AR7030 I suggest you measure the PSU voltage when you get the opportunity as that electrolytic will probably have dried out!