LM338's for one channel getting way hotter than the other

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Each channel is regulated separately, on totally separate boards. The only difference between the two channels is that one is using Panasonic FC's before the regulators, and one is using "R.M" caps pulled from an amp. The one with the FC's gets FAR hotter than the "R.M" board. The heatsinks are identical and before I put the FC's on I really don't remember either getting that hot at all.

So really, I am just curious as to why it's getting so hot? Could it actually be something to do with the FC capacitors? There doesn't seem to be any issues, even playing with the volume on the pre all the way up, and both boards are giving the same voltage outputs (+/-28.5v) and have the same voltage being fed to them (~35v after the bridge rectifiers).

I'm confused [ again ]
 
That's right, only one of the boards is running hot.

I will try disconnecting the amp board from it hopefully later and let you know if it cools down, though I wouldn't have thought oscillation would have been a problem. The two amp boards are identical, and the other regulator board doesn't get hot. Along side that the amp board connected to the regulator board that is getting hot.... isn't getting hot at all, which is supposedly a sign of oscillation :)
 
head_spaz said:
Swap the amps... with their respective PSU boards.
Amp-A to PSU-B, and Amp-B to PSU-A.
See if the same PSU runs hot, or when switching, the other PSU shows the same symptoms. This way you can isolate whether or not it's the PSU or the AMP.

Simple diagnostics.

I put the other amp board on the hot channel, still gets hot. Doesn't seem like the grounding made any difference after all either!

Maybe it's just this capacitor "burn in" doing it? I could swear with the old caps it didn't get this hot... hm...
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.