Testing solid state amp with no load...

[alchemy]

Just wanted to double check something with you folks more knowledgable! I have a Ampeg SVT 350h to repair, and looking at the schematic it shows test points and numbers for scoping it. It says "no load", and everything that I can find says it's OK to run a solid state amp without a load, but being as I rarely work on solid state stuff and that I have only ever fed signals and scoped tube amps (with a load), I want to make sure I am proceeding correctly.

Is it OK?
Any other tips for troubleshooting solid stae amps?

[R.G.]

Although there are always exceptions to any general rule, it is generally fine to test a solid state amp with an open circuit on its output. If the schemo says "no load" then they really mean it - don't hook up a speaker or dummy load for the test.

[Wilder Amplification]

Most SS amps are not transformer coupled. Due to this they can handle an open load condition just fine. It's actually a great way to check everything up to and including the pre-driver transistors.

When scoping the output of a complimentary symmetry push pull amplifier with no load connected, you're testing the pre-drive transistors only. As long as you have signal here with no load, everything up to the pre-drivers is good. However, if you apply a load and your output signal goes to nothing, that means that your "current carrier" transistors (i.e. the transistors that are strapped in parallel with each other that the pre-driver transistors control and carry the majority of the load current) aren't coming on.

Of course, if you apply a load and you end up letting the magic smoke out, start looking for shorts.