Cambridge Audio Azur 651a Integrated Amp

savatage1973

Addicted Member
Just a quick question for those that might be familiar with this amp. I recently acquired one for a system in a spare bedroom.

Azur651%20paj%C5%A1l.jpg

The amp seems to run a little hotter than I would expect, but the "hot spot" is not over the main output heatsinks, but rather, from the small bank of heatsinks (middle right in the photo). Everything works/specs fine, and I haven't even popped the hood to look at anything, but what are those sinks for and why would they be hotter than the mains?
 
They're almost certainly heatsinks for three power supply voltage regulator chips, likely supplying +5 volts and bipolar 15 volts based on the service manual for the Azur 540A. I couldn't find a manual for the 651A, but it appears to be similar.

The regulators running quite warm is normal, as long as they're not smoking or hot enough to char the circuit board.
 
I have the same amp and it's hot in the same spot, so I guess it's normal.
Probably not a problem, however I solved it with this:
https://www.acinfinity.com/component-usb-fans/multifan-s2-quiet-usb-cooling-blower-120mm/
(for Europe, it's probably cheaper and faster to order from Amazon - I found it on Amazon Deutschland).
It is very silent, and the lowest speed is enough to remove all heat.

PS: I found this thread while looking for information on removing the obnoxious APD (Auto Power Down) function.
User manual says it's "permanent". I don't have the service manual unfortunately.
Any idea if it's possible to disable it, maybe even with an hardware modification if necessary?
 
get a service manual for the 651a. they are very detailed with large schematics for each
and every function and you can find the exact circuit very quickly. there's probably a timing
circuit you can adjust or eliminate.
 
Thank you for your suggestion, I asked Cambridge Audio for a technical manual and they sent it very quickly.
You're right, the circuits are very clearly identified: there's an APD Trigger board schematic, gerbers, and an APD Trigger Cable that I tried to disconnect but had no effect! Very strange. I am sure this is due to my very limited knowledge of electronic circuits. Perhaps it works the other way around? i.e. the trigger keeps the amp ON instead of turning it OFF?
 
I uploaded a service manual for this amp yesterday

All that goes to the APD board is L/R input, +15/-15, +5, GND and a APD trigger. Surely taking the APD board off will disable it without stopping the amp from working.
Screenshot 2023-11-22 220248.png

Well it works fine, took out this pictured APD board, and no more powering off.
apd.jpg

Well this amp has me stumped. It is still powering off without the APD board.
 
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