So I have replaced C23 and C24 now as I was not happy with their ESR being so high and so different from one another.
And I replaced R254 the other day.
And I also had previously replaced R45.
So these are all brand new parts now.
I have ordered some resistors to replace R219 and R230.
I also previously replaced C517, C518, C523, C524 and C444 as they all had very high ESR and C517, C518 had bulged and were reading waaay low (13.2mF and 12.7mF).
I have probed over and over again all the parts on the SMD-L module which I have removed and I cannot find any shorts on any of the transistors or the diodes.
All the other resistors on the module seem to measure just fine, as do the two electrolytic caps C203 and C204.
I am struggling to find why R254, R219 and R230 and R45 had all burned out. Has anyone got any other suggestions?
Maybe to do with the power supply capacitors I previously replaced? I am seriously guessing here.
Something must have drawn too much current as mentioned, but what?
Or is it possible the resistors all just failed? It doesn't seem likely to me.
With the SMD-L module removed, I just took some measurements in the 'power on' state.
I just checked all my voltage rails and they all appear OK:
+46 = 50V
-46 = -50V
+37 = 39.4V
-37 = -39.3V
+18 = +18.3V
-18 = -18.3V
+5 = 4.99V
I just measured the voltage across R45 and R46 again.
I get 2.75V (84mA / 230mW) across R46 consistently.
However with R45 I get 3.54V (379mW), then the voltage quickly jumps to 4.0V (485mW) then the protect kicks in right away (probably because the SMD-L module is missing) and the voltage returns to 3.54V
Does this current seem high? or is this good? It is under the 500mW limit.