That wold be my guess also.
The construction is kind of funky and while the output is bandswitched the driver isn't.
I know that amp pretty well, used to sell them and repair them as a kid when I worked for a retailer who sold both amateur and CB stuff.
It was built to be cheap-cheap-cheap and they used a voltage doubler to produce only about 1000Vdc, which always seemed silly to me. This was to save probably $2 on the transformer, at the time. They also did some other funky things like instead of switching from operate to standby bias, to go to standby they literally shut off the B+ altogether, using a relay. That seemed like an accident waiting to happen.
And if I recall correctly, this was a 2-driving-4 amp with a pretty powerful driver stage, so if you hit that with more than about 4W, you'd just blow up everything.
A government which robs Peter to pay Paul can always depend on the support of Paul.
If it came without the transformer, that's a bit strange, since the transformer is part of the amp.
This model has the transformer in an external cabinet with a connecting cable. Finding a replacement transformer has proven more difficult than I anticipated. All of the 300-330V transformers are less than 500mA. Most are around 20mA. If anyone has a suggested vendor I would appreciate it.