BASSMAN AB 165

[Colas LeGrippa]

Hi,

Definitely there is more than one schem for a bassman AB165. The schem found here in the library shows a fixed bias, the one on my bench is a ''combo'' : fixed bias / cathode bias. Each cathode is tied to ground through a 150 Ohm resistor, with a negative voltage supply to the control grids. My question:  Are different AB165' s identified somehow or do we have to open the head to see how it was built ? So far as I can see, the schems are not reliable.  I suppose Mr Fender modified things as he felt that day...

[sluckey]

This schematic seems to match your amp description. Are you sure it's an AB165?

http://www.el34world.com/charts/Schematics/files/fender/BASSMAN_AC568.pdf

[Colas LeGrippa]

We are never 100% sure, but the sticker inside the amp is stamped AB165. All other components seem to be the same, only the bias seems different. Weird, no ?

[Colas LeGrippa]

Well, after examining the AC568 schem, I must admit it is what I have on the bench right now. Now, why is the original fender's sticker is stamped AB165 ? I presume the  tech was assembling his first AC568 after a bunch of AB165 and he picked up the wrong stamping tool. One difference for sure is the two 2.000 pF at the 6L6's shown on the AC568 schems are not in my amp.
Well thanks for finding the right one model, that's definitelay closer to what I got on my bench.

Regards
Colas

[HotBluePlates]

The AC568 was a later model; Fender didn't make both AB165's and AC568's at the same time.

But Fender was never one to waste anything. They probably had leftover AB165 labels, and stuck one in your amp. The tube lineup is the same, which is probably 85% of what Fender intended for the tube chart anyway.

And, there was no such thing as a combo-format AB165. They were heads only.

[Colas LeGrippa]

Thanx for your help, guys.

[Willabe]

One difference for sure is the two 2.000 pF at the 6L6's shown on the AC568 schems are not in my amp.

That's good. They kill the tone and your amp is stable (lead dress problems) with out them?


                             Brad     

[Colas LeGrippa]

I can't say if it is stable, it came in yesterday for service. I never install useless caps like these. Grid leaks , grid stoppers and good lead dress make stability. When you have to install small caps acrross everything to get a stable amp, you have a major problem hidden somewhere. Simpler is better. Less is more. White is black. Boys are girls. 

[sluckey]

Boys are girls.

Quick! You better go kiss your wife!   

[Willabe]

Boys are girls.

Quick! You better go kiss your wife!   

               

[Colas LeGrippa]

don't worry for that she's got kisses all over from her head to her toes.

(hope y'all know what I'm talking about, the way she wiggles that thing it really knocks me out.........Rick Derringer ).

[stratele52]

J'ai souvent vu des Bassman avec une étiquette mal identifiée comparé au chassis. le chassis n'était pas  le modèle imprimé sur l'étiquette.

I often see wrong Bassman 's number on label.

[Colas LeGrippa]

Il n'y a aucun numéro de modèle imprimé sur le chassis, seulement à l'intérieur du boîtier ( bizarre, non ? ) .Comme HBP écrivait hier, l'étiquette a été apposée pour le consommateur en général, pour l'identification des lampes, vu que les lampes sont les mêmes d'un modèle à l'autre. Le technicien, lui, doit se débrouiller.
Ciao!

[Colas LeGrippa]

yes it does

[Colas LeGrippa]

it's not mine, it's my customer's.....but if he doesn't come and get it, I'll keep it for myself without any problem