CL60 question

[john65b]

Hey all,

I understand that many use a single CL60 in lieu of a fancy softstart, but I have a question to ask...

Instead of putting a single CL60 on the mains, I thinking of putting two on the tranny secondaries before (or maybe after) the dual rectifiers.

The CL60 still effectively ramps the tranny, slowly loading the caps & rectifier as it does from the mains where it normally sits after the fuse.

I am considering this so I can "lose" more than the two volts (hopefully four - five volts) on each rail...

Is this not recommended?

Sorry if a lame Q...

[EchoWars]

Personally, I don't like thermistors for solid-state devices (unless we're talking about Class A) because of the wide range of current draw.

Bypassed with a relay after power supply charge, sure. No problem.

Not a lame question, but there have been lots of discussions 'bout this in the past.

[john65b]

Yup, we are talking class A...just realized I left that lil tidbit out...

[AndrewT]

Hi,
the CL60 on the secondary does a completely different job from a CL60 on the primary.
The Primary CL60 limits the start up current that flows while the transformer establishes the flux to allow it to perform as a transformer.

After this start up has happened, it is able to send power to the PSU.
The secondary CL60 limits the charging current going through the rectifiers and into the smoothing capacitors.

Both versions, primary and secondary, can be run without a relay bypass.
But I recommend a time delayed bypass for both. The primary time delay should be around 300mS, the secondary delay around 5S.

A thermistor on the primary modulates the supply voltage into a ClassA amplifier. The effect can easily be seen and measured at the output of the amplifier. Check my report on the Krell Klone KSA100.

[AndrewT]

http://www.diyaudio.com/forums/showt...68#post1265968

[john65b]

So the thermistor on the primary will unload the tranny and everything downstream, while on the secondary, just unload the PSU side (rectifiers and caps).

If I understand correctly, I would be aiding the reliability of the tranny keeping the CL60 on the primary, correct?

[AndrewT]

Originally posted by john65b
I would be aiding the reliability of the tranny keeping the CL60 on the primary,

probably not.
Transformers don't usually come to any harm due to switch on.
It's the other component performance that deteriorates, eg, switch contact burning, fuse blowing, circuit breaker opening, light dimming.