Only pros who are knowledgeable of electronic repair knows the amount of effort that you have put into make this video

That cap is for power-down detect. Actually a fairly common problem on various brands.

I just acquired this same amp and had it repaired. It works great  now. For sale 1500 bucks if anybody’s interested today’s date is March 29, 2026.

I had a similar issue with an HCA-750 I bought. Stuck in standby. But in my case that same circuit you drew is on a small board behind the front panel. This small board also has it's own power transformer, and it was the transformer that had failed, open secondary! There were no failed parts on the board, other than the  transformer. I used my bench supply to verify the board would work, which it did. So I subbed in a 12 vac wall wort transformer, and it worked fine. I later found a brand new board on Ebay for $50. So the amp is now back together the correct way, with the plastic safety cover over it

I'm glad to see you are going more in depth on your trouble shooting and showing your reasoning behind them.

Saw the lights momentarily dim when you switched it on! Nice find.

Your technique of trouble-shooting circuits is extremely refreshing and easy. For almost 20years I thought all the good electronics techinican just knew what the problem was before they studied the schematics.  Ive been wrong this whole time.

It's always the capacitors on youtube... it's never that simple with anything that comes across my desk, unfortunately.

Working capacitors block DC voltage, Good job!

@ 8:36  It looks like that capacitor got beat up by managing a constant ripple current that stressed it into an early demise. A lot of the "change all capacitors" crowd would either mistakenly replace that one with a audio grade capacitor with a low ripple current, hour and temp rating, only setting up another quick failure, or, get substitutions from Fleabay that are usually remarked cast offs that will also fail quickly. I hope you found a cap with a high ripple current temp, and hour rating for that one.

Nick, always love your videos. Short, concise and to the point. Coupled with clear explanations makes your site a winner.

nice work and great explanation. Parasound amps from this era suffered greatly from capacitor plague where the electrolyte dried out prematurely.

Great tips and great repairs! I have a Denon POA-2400 power amplifier with the same issues...i will be concentrating on the protection board, thanks to you!!

I really liked your presentation. Clean and precise. Please fix my Shurbourn!

Great to see proper troubleshooting being done. Thank you for sharing.

with the age of this amp and it being from the capacitor plague time i would recommend a full recap

Thank you so much for your expertise works.  Love them

Interesting video. Throughout my career I've found bipolar electrolytics to be particularly unreliable, even when they are used in lightly stressed low ripple locations. If a non polarised capacitor was essential for the replacement I would use ceramic for the lower values and film for the higher values.

thank you

Even faster method is to heat the top of the cap with a soldering iron for 5-10 seconds. Heating the cap will rise uF and lower ESR momentarily. If the unit comes out of protection your fault has been found. Quick n dirty method.