wharefedale pro s-1500 overheating

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   As the title says ,left channel o this amp is overheating at idle in 40 secords the heatsink is so hot you cannot touch it. 

 I measured all transistors ,diodes ,resistors ech. Everything seems fine. 

 Does anyone know how to adjust the 3 trimmers of the pcb as well as the test points? Forgot to say that i didn't measure any components off pcb for any possible ''leaks'' of any kind.

  Any opinion and knowledge is very welcome. Thanks in advance....

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d.antonis Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 04 January 2009 Location: greece Status: Offline Points: 49	Post Options Post Reply Quote d.antonis Report Post Thanks(0) Quote Reply Topic: wharefedale pro s-1500 overheating Posted: 26 July 2019 at 1:13am
	As the title says ,left channel o this amp is overheating at idle in 40 secords the heatsink is so hot you cannot touch it. I measured all transistors ,diodes ,resistors ech. Everything seems fine. Does anyone know how to adjust the 3 trimmers of the pcb as well as the test points? Forgot to say that i didn't measure any components off pcb for any possible ''leaks'' of any kind. Any opinion and knowledge is very welcome. Thanks in advance....

kedwardsleisure Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4947	Post Options Post Reply Quote kedwardsleisure Report Post Thanks(0) Quote Reply Posted: 26 July 2019 at 11:10am
	The trimmers will be +ve and -ve current limit and bias. I dont have the bias figures to hand but if you measure the good channel idle current then set the other one to match, should be ok. If you're lucky it's just an open circuit bias pot. The bias pot will be around the 100-ohm value and ISTR is shunted by the heatsink thermistor. I think the circuit is similar to the QSC RMX1450. Bear in mind it could be getting hot for other reasons, eg RF oscillation, small dc offset causing a crowbar condition etc, component in the bias stabilisation circuit failed. that sort of thing. Wharfedale will supply diagrams if you speak to them nicely.
	Kevin North Staffordshire

d.antonis Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 04 January 2009 Location: greece Status: Offline Points: 49	Post Options Post Reply Quote d.antonis Report Post Thanks(0) Quote Reply Posted: 26 July 2019 at 3:06pm
	Thanks for the tips. I will start measuring the ''good'' channel as a first step to compare measurements. And of course it is one of many QSC clones... Edited by d.antonis - 26 July 2019 at 3:08pm

d.antonis Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 04 January 2009 Location: greece Status: Offline Points: 49	Post Options Post Reply Quote d.antonis Report Post Thanks(0) Quote Reply Posted: 03 August 2019 at 11:31am
	Problem found. A dirty trimmer was guilty for the overheating ,cleaned it and the amp's fever went down to normal operating temperatures. Thankss everyone....