That appears to be derived from an old (now) RCA circuit. Note the transistor types 40xxx all RCA type numbers.

Definitely not HiFi, but this amp if I remember rightly was originally used as a guitar amplifier. It will not produce anything like 150w not with those transistors, but should get close to half that. i cant remember who the designer was at the moment.

What wattage are you looking for, just the power amp or pre as well? What power supplies are available or do you want that as well?

What impedance is your speaker? Check the data sheet for the 3118, It will work down to about 5v supply when the output will be about 2w into 4 or 8 ohms.

More likely is you have blown one or more output transistors.

Just to clarify the PAM8302 are not made by Adafruit.  They are made in China and available from ALI Express for cents not dollars if you are willing to wait weeks for delivery.

Maybe its got an ARTEC QDD in it? https://www.amazon.com/QDD2-Quadra-Distortion-Driver-Effects/dp/B007XIW07S

Buy it!  Easy to fix if broke.

Often when an output device goes short it can affect the driver transistor in this case the 15031. Dont remove it just keep an eye on it when youve replaced the faulty output. BTW here's a link to a Peavey transistor list of equivalents. http://matthieu.benoit.free.fr/cross/competitive/Peavey_Transistor_Cross.pdf

The Peavey T-max appears to be hybrid with a Solid State power amplifier.  If it's a loud humm not affected by the volume control, disconnect the speaker immediately or it will be destroyed, and check for DC on the output terminals. If DC is present more than a few millivolts, then it is likely one or more output devices haxe expired.  You will need a schematic diagram and a conversion table for the proprietary codes Peavy use for their semiconductors.
Tony

(edited to correct typo)

As I dont know where in Australia Rod lives, I can only use the information displayed on his web site and that is what he quotes. UK VAT must also be added (20%) and also the local Royal Mail charge for collecting this from me. This is not known but Rod estimates it at about £8.00. The P68 board costs US$32 (£22 approx). Unfortunately I am not prepared to pay this for one board no matter how good, even though the ones I have used before are certainly good quality.

Yes I know about Rod and have already used a number of his boards, but I am not prepared to pay his ridiculous shipping charges of US$24.50 from Oz to UK for a board when all he has to do is stick it in an envelope.

Looking for a suitable project to build for a bass amplifier, I found this board (bare PCB) on Ali Express . https://www.aliexpress.com/item/32942076982.html?spm=a2g0s.9042311.0.0.5d434c4dzHmGDd . Does anyone know anything about it, especially the schematic as one is not supplied, only giving component values on the board? Has anyone bought and assembled it?

Tony

12a?7 valves have a 12v6 heater between pins 4 & 5 and a centre tap on pin 9. for 6.3 v common pins 5 & 6 and feed supply between these and pin 9.  AC or DC  doesn't matter.

 Has anyone tried to use one of those Piezo preamps sold for ukuleles like this on Ali Express https://www.aliexpress.com/item/33048124904.html?spm=a2g0o.cart.0.0.5e793c00tS3Zyw&mp=1 on a magnetic pickup?