Ghia Clone Noise On Powerup

[mtbrider405]

Hey guys,

I have built 3 Ghia clones two for friends and one for myself. I am using a layout I drew that's on a board small enough to fin in the Hammond chassis.

The first one powered up fine the first time and has ever since.

The second and third both, on initial power up and one or two other times since then, made a crackle sound and then a very loud low to high pitch signal sweep sound, then go quite and sound normal. That is only time I've heard it and I have no idea what might be causing it. Again, its not every time you turn it on. Just the initial and a couple times since. Other than that, they sound great.

I just can't afford to have a loose canon so to speak floating around. I need to know that they will be quite on power up every time.

Any thoughts and/or help would be much appreciated!

Thanks,
Jason

[Structo]

Have you tried a different rectifier tube?

On the schematic I have the standby switch is shown before the reservoir cap.

Could it be a bad cap that is charging slow, then the noise stops when it is charged?

If you are using a 5Y3, that is a directly heated cathode and it should be fine to not use the standby switch since the B+ will ramp up slowly as the 5Y3 warms up.

[mtbrider405]

Hi Structo, thanks for the reply.

Bad cap sounds reasonable. None of the 3 amps have standby switches and they are all using 5Y3's.

Still not really sure where to go from here. Add a standby switch?