Fender Studio 85 amp, caps, bump, sound

[ricci]

Hi everybody, i have a 1987 Fender Studio 85 amp on which I had replaced almost all the electrolytic caps, some ceramic cement resistor, some diodes and some TL072s. I also wanted to replace the two 2200 uF caps on the power supply but they told me that if they work it is not necessary.

In the meantime, however, I bought two equivalent Jamicon caps (1970 uF) and two Samwha (2100 uF), much smaller than the originals (the diameter is half), and I would like to know if in your opinion it is worth putting them in place of the originals or do you say which could be bad quality? Both Jamicon and Samwha have ESR around 0.15% and Vloss 0.6%.

Could the sound change with the replacement ?

Could I solve the bump I have when I turn the amp on and off ?

Many thanks

[The Dude]

Firstly, a schematic would help.

There's not much point in replacing parts that aren't bad. Ceramic caps and wire wound resistors rarely go bad, so I'm not sure why you'd replace them. Shot gunning is not an effective troubleshooting method. If your original electrolytics are good, leave 'em alone.
First test: Leave the unit's power switch on and power up/down by plugging in and unplugging the amp. Does it still thump? If not, your power switch could be arcing. Some power up/power down thump is normal in many amps that don't have some sort of "slow on" or soft start feature. It's not something I'd probably worry about unless it was excessive and could damage the speaker.

[ricci]

I replaced the 5W wire resistors with 10W equivalents because in 35 years of use the pcb had become brown due to the heat, while I haven't touched the ceramic caps, only the polarized ones. The bump was annoying for me but for now I put a jack in the headphone input so the speaker isn't affected. But the thing that interested me most concerned the 2200 uF polarized caps which perhaps after all this time will have dried up.

In reality I had opened the amp to repair the reverb which was emitting a hiss and I fixed it with a new TL072 but at that point I said to myself...why not change all the electrolytics ? Ok, so I leave the 2200 uf ones, since they don't give me problems. I attach the diagram and link that I followed for the work