Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Planobilly on December 12, 2016, 04:00:08 pm

Title: A new fault/sound I had never seen before
Post by: Planobilly on December 12, 2016, 04:00:08 pm

Hi Guys,

I just repaired a Fender Blues Deville 212. The drive channel made a sound like a small motorcycle and got louder as the master volume was turned up. I had never seen a amp act just like that. I assumed the issue was a cap somewhere and that was a correct assumption. I found a defective 22uf filter cap and problem solved.

Motorboating I have listen to but motorcycling was a new one on me...lol

Anyone have any idea how a bad cap actually causes the sort of noise/oscillation?

Cheers,

Billy

Title: Re: A new fault/sound I had never seen before
Post by: HotBluePlates on December 12, 2016, 05:14:43 pm

So you had motorboating which was a few-Hz higher in frequency than what you usually hear...  Mechanism will be exactly the same.

The ear tells you there is a big difference between setting your trem to minimum speed (maybe 4-6Hz) and maximum (maybe 10-12Hz), but that depends on your perspective (doesn't look like a lot when just talking numbers).

Title: Re: A new fault/sound I had never seen before
Post by: Planobilly on December 12, 2016, 06:12:46 pm

Thanks for the feedback. No pun intended..lol

Just a strange sound I had just never experienced before.

Cheers,

Billy