funkstar101
New member
below is a link to an amplifier project that i have had running for about 6 years. its the A. Riedl pa300.
http://www.reber.si/ojacevalniki/PA300/PA300.htm
the problem: a single turn trimpot that keeps losing its set point value once it has been adjusted. when the amp was just completed it was thought that the change was due to the gain on the finals settling down but its 6 years on and the amp plays fine except for this problem. every 3 months i check this value only to find that where the quiescent voltage was at 27 mvolts, it has dropped to 6-10mvolts. this trimpot is used to set the quiescent voltage of 27mvolts for the finals. it appears that no other values in the circuit because when adjusting the trimpot the pointer always settles at the same physical location again.
current cause of the problem (i think): view here. http://www.mantech.co.za/ProductInfo.aspx?Item=14M1598.
can anyone on the forum recommed a better quality drop-in trimpot or suggest a reason why this set value keeps changing. with my most recent adjustment it feels like there is a contact spot on the track and 1 pot cannot adjust anymore. is fixed at 17 or so millivolts.
http://www.reber.si/ojacevalniki/PA300/PA300.htm
the problem: a single turn trimpot that keeps losing its set point value once it has been adjusted. when the amp was just completed it was thought that the change was due to the gain on the finals settling down but its 6 years on and the amp plays fine except for this problem. every 3 months i check this value only to find that where the quiescent voltage was at 27 mvolts, it has dropped to 6-10mvolts. this trimpot is used to set the quiescent voltage of 27mvolts for the finals. it appears that no other values in the circuit because when adjusting the trimpot the pointer always settles at the same physical location again.
current cause of the problem (i think): view here. http://www.mantech.co.za/ProductInfo.aspx?Item=14M1598.
can anyone on the forum recommed a better quality drop-in trimpot or suggest a reason why this set value keeps changing. with my most recent adjustment it feels like there is a contact spot on the track and 1 pot cannot adjust anymore. is fixed at 17 or so millivolts.
