• Hello and Welcome to HiFiVision.com - an online community for the home entertainment and tech enthusiasts!

    If you would like to ask a question, participate in a discussion and view attachments please Register yourself.

Power amp DC protection circuit.

Marantz offers at HiFiMART.com

diesel engine

Active Member
Joined
May 17, 2013
Messages
113
Points
28
Location
Kollam, Kerala
The photo shown is the protection circuit of the famous medium power AF amp published in Elektor magazine Nov. 1990. The circuit seems promising. But I am confused about the way the relay is driven. There are two transsistors (T26 and T25) in series handling the relay current. out of them one is a low power BC546 and the other a BC880 Darlington. Why one relatively high power darlington and the other a low power when the current to be handled seems to be the same? any thoughts? My reason and logic failed to understand this. Expect somebody shed some light on this.
 
SPONSORED ADS

Attachments


SPONSORED ADS

Fantastic

Well-Known Member
Joined
Jun 1, 2010
Messages
868
Points
93
Location
Third Rock
The BC880 is a PNP Darlington in a TO92 package. It is not a power device.
The BC880 along with the Capacitor next to it would act as a delayed turn on. To minimise the base current ( which loads the capacitor) he has used a PNP Darlington. You can very easily do this other ways to protect for DC and also have a delayed turn on. Relay coil current must be below 60mA I think.
 
Last edited:
SPONSORED ADS

Top