Originally Posted by Ngr
if the amp was working with the smashed rectifier it means that there must be a solid state one installed directly on the tube base (it's just a few diodes).
pic is not very clear. I have one that is just a tube base with a black resin cover masking the diodes installed inside the tube base itself.
you can take off the insulating tape (unplug the tube base from the amp first) and see what's inside. You should see 4 diodes soldered on the tube pins.
No need to change to tube rectifier. Modern tube rectifier (AC30 uses a GZ34) are not very reliable.
So keep your SS one and replace your preamp and power tubes. Just remember to use standby switch with solid state rectifier to avoid wearing tubes too fast.
I'm going to second this recommendation and appraisal of what is under the tape.
Definitely check under the tape to see if it's a tossed together SS rectifier made up of 4 diodes. If those components are not in there, I would venture to guess that somebody installed an SS rectifier under the plate somewhere - especially since you say that it looks like somebody has done some work inside.
Obviously, if you take it apart to check, you need to be super-extra careful not to touch ANYTHING in there. I have an AC20CC1 (the 1x12) and it's the same amp. I've gone through mine and they have sectioned off the power caps and power transformer leads into a separate compartment, basically to keep folks from accidentally killing themselves via electrocution.
Given the seriousness of the voltages lurking around in the power section of an amp, I feel compelled to always mention the warning of caution. If you're not already experienced with discharging capacitors, then I'd just have someone qualified to take a look at it.
The SS rectifier will definitely be more reliable and quieter provided the diodes used are quality components. The amp will be a little smoother and ever so slightly less "angry", perhaps, as is typically the case with an SS rectifier. But then again, as with mic preamps, it all depends on where the circuit is being "leaned upon" to get it's character. I won't venture to hypothesize beyond that.
Hope this helps,