Sorry. 

"Bad" means some unwanted clipping on the clean channel in one amp. The Peavy Forum suggested retightening the screw grounding the power amp to the heat sink , and that seemed to help, but it still breaks up a bit near max volume which is to be expected, right.

In the other amp, it means awful clipping like a starved fuzz, a MID control that seems to have no effect, and no signal to the reverb tank.

So maybe the op amp driving the reverb went band and/or something further up stream near the input.
Should I move my question to The Newcomer's Forum?

Hello. New forum member here, and a proud owner of two of three Peavey Blazers. Why two of three? Well, I was so impressed by this little amp that I wanted another to use with for stereo delays. Unfortunately the second one I got for $12 didn't work right. So recently I found a third for less than $50 which works fine...so far.

Unfortunately, the first one and the second one seemed to go bad at the same time which could be caused by:

A. Manufacturing defects... :duh
B. Using them together in stereo without proper grounding.  xP
C. Unplugged cables lying on a static-charged carpet.   
D. Swapping the stock 4Ω speakers in both each with an 8Ω Jensen C8R. :loco
E. None of the above. 

Can we rule out D?

The data sheet for the TDA2040 suggests it will work fine with an  8Ω speaker, and indeed I found the amp sounded better that way.

OR could the speaker dampening circuitry in Transtube amps make it susceptible to damage?