Bartell/hohner amp, bias question

[Stuff4bikes]

Anyone familiar with these? All I have is the chassis, no enclosure or speaker.

Can someone explain the bias method on this amp...I am fairly new to this stuff but I cant remember seeing this method.

[Latole]

https://bartell.vintageusaguitars.com/2021/05/19/ca-15-mini-bass/

Google ; " honer contessas CA 15 amp"  and you'll many informations

What are you looking for ? Is amp working or not ?
You want to add a speaker ? Any 8 ohms 20 watts (or more) speaker will work .
Whant to built cab ?

[Stuff4bikes]

Just some random question.....

It says bass amp....how does a guitar sound through it.....
How did the chassis mount originally.
I have noticed different variations online. Mine has a toggle and fuse on the front right side. Mine doesn't say hohner on the front.
Some had a 12" speaker or a 15"
They made a guitar and bass CA-15, it sounds like.....what's the difference....

[Stuff4bikes]

I put a 2amp fuse in, powered it up with my dim bulb and it sounds pretty good. No hum that I hear.....everything looks factory except it looks like cap can was changed....

[st]

Fixed bias, it seems. But something's wrong in the supply on the schematic. Who drew that? Pics of actual circuitry?

[Stuff4bikes]

Fixed bias, it seems. But something's wrong in the supply on the schematic. Who drew that? Pics of actual circuitry?

I got it from a bartell fan site. Its stated he owns this amp and several others and he drew/put the schematics on line.....
I will get some pics tomorrow of the circuitry.

[Latole]

Fixed bias, it seems. But something's wrong in the supply on the schematic. Who drew that? Pics of actual circuitry?

It is a fixed bias.
AC voltage for bias circuit is wrong;
What it should be ;

[Latole]

Two modifications I would make would be to rewire the heater.
Unplug the ground side of the transformer and the heater side to install a wire. The two wires feeding the heaters should be twisted together.

I would add an artificial ground with two 100 to 220 ohms resistors. ( screen shot )  ; http://www.valvewizard.co.uk/heater.html

And I'll add 3 prong grounded power cord.

This modification would make the amp quieter and safer.

[PRR]

Pin 8 V2 is surely higher than 80V, more near 100V-110V DC. I dunno if the parts can drift that much or just a typo.