oscillation in power supply filter caps

If the caps are bad, there could be an increased load on the transformer causing it to vibrate.

also one of the down stream components could be failing causing the circuit to oscillate this could potentially do serious damage so if in doubt take it to a local tech. 

You are right to replace the caps. Hopefully the caps you ordered are not merely electrically the same but "designer" ie better sounding. Cheap caps do indeed sound cheap. Swapping out caps for higher quality is one of the surest, easiest mods you can make. Probably second only to diodes.

Anyway, swapping them out would be a good time to check those transformers. Some are bolted straight to the chassis. If that is the case you might want to try putting O-rings or rubber washers between the transformers and the chassis. Or if the VTL already has them they will be hard, maybe even cracked after 30 years, so there you go.

Thank you for the tips, I will check out the transformers and I have to make up new power cords as they didn't come with any.

Also one of the fuse holders is damaged and I was thinking of replacing both with better ones, they are at 15 amps each, any thoughts on replacements and from who.

Littelfuse makes a copper alloy/tin plate holder(click on the pic to see the pdf/download). Acme fuse holders are silver-plated and inexpensive: https://www.partsconnexion.com/fuses-holders-clips.html .

There’s always the silver plated audiophile fuse holder from Acme Audio Beep! Beep! to consider. Not for the timid. 😬

Hello, I replaced the four filter capacitors and now I have a minor amount of resonance in all the caps now. what gives or is this normal

Does anyone know what the bias is on the VTL 225 with kT90's?

Hello, I replaced the four filter capacitors and now I have a minor amount of resonance in all the caps now. what gives or is this normal

What is meant by 'minor amount of resonance in all the caps now'?
What are you hearing through the speakers?

^^^^ also wondering what does “oscillation” sound like through the speakers?