Scott R307 - no protection circuit?

[amphead4]

Just picked up a Scott R307 receiver, circa 1977. I don't know the specs but seems to have a decent amount of power.

When switched on, the speakers play the audio immediately with no delay. Is this expected or a defect in the protection circuit?

If there is no protection circuit, I suppose there's a risk of DC from the power supply being fed to the speakers if an output transistor shorts, unless the output is capacitively coupled. I measured the DC offset before connect speakers and it was 0.02 and 0.03.

Is anyone familiar with this receiver and able to confirm what normal startup is like?

 

[ryuuoh]

According to a video I watched, looks like there is no relay protection.

 

[amphead4]

Was that on youtube?

 

[ryuuoh]

Yes.

 

[ConradH]

Download a service manual from Elektrotanya or elsewhere and see what the schematic looks like. Lots of gear didn't have relays for protection, as there are other ways to do it. Lots more gear just had current limiting, but no DC detection. It's no sin to put some in-line fuses in the speaker leads to protect them (the speakers, not the leads), though the purists will cringe at the thought. There are also aftermarket solid state solutions. Personally it's never been much of a concern and I've had as many problems with flaky relays as output devices.