safe at turn on

[susomora]

hi guys ,
one more question ; will the thermistor thing (used on the ST35 ) work fine on my 5e3 guitar amp ?
Cheers SUSO

[EWBrown]

If you are using tube rectification, then it isn't necessary. For solid state rectification (and large value PSU caps) then it will help to eliminate the initial power-on "slam" as the transformer and SS diodes are briefly looking into what amounts as a short circuit, as the bulk caps are at zero volts. THe additional few seconds of "warm up" time that the CL-90 offers, will act as the electrical version of a vehicle's shock absorbers.

In a tube-rectified PSU, the lCL-90 really doesn't add anything useful.

/ed B

[susomora]

thanks Ed for the answer and the explanation . Valuable stuff . The day I'll build something Trainwreck'ish I'll remember it .
Cheers
SUSO

[TD_Madden]

I came across a similar situation when refreshing a '66 Vox AC50. It uses a "Brimistor" (Brimar's name for it) to limit the onrush to the power-supply caps at turn-on time. Since I know the Weber Copper Caps include this function, I replaced it with a couple thermistors-in-parallel that Ted Weber sent to me. Works fine.

As it is, I'm using this amp with a Weber Browner to keep the wall a/c down to 115v (as originally designed)....keeps the heaters right on 6.3v.