QSilver
Super Member
I was using my SA-7500 yesterday with the preout connected into a SPEC 4. After about an hour I started to notice that the SA-7500 was getting quite warm and this amp usually runs only slightly warm. After another 30 minutes I began to hear the protection relay clicking on and off. I turned the amp off and open the case and hooked a DMM into the speaker outputs and watched the DC voltage and powered it back up.
For the first 30 minutes it stabilised but the power transistors on the right of the amplifier were starting to get warm. After 30 minutes or so, the DC started to dance around rapidly and the relay began to click again - at one point the DC peaked at about 1V as the protection kicked in.
I turned it off and left it over night and when I come back to it now with the multimeter on, the amp has been on an hour and is staying cool and the DC is moving around 3.2-4.6mV.
I find it strange that its running in and out of protection one day and not the next. The amp was made in 1976 and is all original as far as I can see.
For the first 30 minutes it stabilised but the power transistors on the right of the amplifier were starting to get warm. After 30 minutes or so, the DC started to dance around rapidly and the relay began to click again - at one point the DC peaked at about 1V as the protection kicked in.
I turned it off and left it over night and when I come back to it now with the multimeter on, the amp has been on an hour and is staying cool and the DC is moving around 3.2-4.6mV.
I find it strange that its running in and out of protection one day and not the next. The amp was made in 1976 and is all original as far as I can see.