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Post subject: this Fender Bassman? aa864 or aa165 or ab165
Posted: Fri Dec 04, 2015 9:19 am
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I have got a Fender Bassman blackface.
I've red on the internet that the Fender tubechart could give incorrect information about the amp model, because Fender used to use old tubecharts on newer models.

Pictures:
http://www.tdpri.com/forum/amp-central- ... ost6697720

Please, could anyone tell (by those pictures) if this Bassman is a AA864 or AA165 or AB165 model?

Already thanks
Lex


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Fri Dec 04, 2015 9:54 am
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My WAG is AA864.

This photo has bias pot and 220k-ohm grid-to-ground resistors on the 6L6GCs. Plus, the 100k-ohm/82k-ohm phase inverter anode plate resistors of AA864:

http://www.tdpri.com/forum/attachments/ ... g_1703-jpg



This photo has the 820-ohm/100-ohm global feedback network of the AA864:

http://www.tdpri.com/forum/attachments/ ... g_1704-jpg


AA864 schemo:

http://bmamps.com/Schematics/fender/bas ... _schem.pdf


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Fri Dec 04, 2015 10:04 am
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BMW2002Ti wrote:
My WAG is AA864.

This photo has bias pot and 220k-ohm grid-to-ground resistors on the 6L6GCs. Plus, the 100k-ohm/82k-ohm phase inverter anode plate resistors of AA864:

http://www.tdpri.com/forum/attachments/ ... g_1703-jpg



This photo has the 820-ohm/100-ohm global feedback network of the AA864:

http://www.tdpri.com/forum/attachments/ ... g_1704-jpg


AA864 schemo:

http://bmamps.com/Schematics/fender/bas ... _schem.pdf


Thanx BMW2002ti


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Fri Dec 04, 2015 10:13 am
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I reverted my AB165 back to AA864 circuitry. So much better for guitars. Not sure about basses --- haven't tried one through the amp.

Nice that you have an OEM blackface. Saves quite a bit of modifications.

:)


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Fri Dec 04, 2015 10:43 am
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BMW2002Ti wrote:
I reverted my AB165 back to AA864 circuitry. So much better for guitars. Not sure about basses --- haven't tried one through the amp.

Nice that you have an OEM blackface. Saves quite a bit of modifications.

:)



The output-transformer has been replaced, cause the amp wasnt working at that time. So its not fully original anymore...
I dont know how much of a difference it will be in sound, between the original and the new output-transformer?


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Fri Dec 04, 2015 10:54 am
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The date stamped on the chassis is unambiguously 1965. The bias-adjustment configuration (if original) seems to reflect the AA165 circuit, which was identical to the earlier AA864 revision.

The follow-on AB165 layout introduced the bias-balance pot.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Fri Dec 04, 2015 11:03 am
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Retroverbial wrote:
The date stamped on the chassis is unambiguously 1965. The bias-adjustment configuration (if original) seems to reflect the AA165 circuit, which was identical to the earlier AA864 revision.

The follow-on AB165 layout introduced the bias-balance pot.

Arjay


Thanks for your answer, Arjay.
So, which model do you think it is, according to you?


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Fri Dec 04, 2015 3:35 pm
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Arjay is correct. I didn't see the date stamp on the chassis. AFAIK, the AA165 only differs from the AA864 in the filter cap used in the bias supply. AA864 list the 25mfd/50VDC. The AA165 lists 50mfd/50VDC. Your unit's bias board has been worked on, so can't see what the OEM parts were:

http://www.tdpri.com/forum/attachments/ ... g_1707-jpg


See layout of the AA165:

http://bmamps.com/Schematics/fender/bas ... _schem.pdf

versus AA864:

http://bmamps.com/Schematics/fender/bas ... _schem.pdf


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Wed Jan 13, 2016 5:05 pm
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Circuits (AB175 or AA864) are not really crucial ... or at least not in this case.

This is an AB165 ..

https://www.youtube.com/watch?v=_N8wNmi9B40


What you think? :mrgreen:


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Wed Jan 13, 2016 5:53 pm
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Nikola, think this is an early 1965 Bassman. It has bias pot circuit, if I remember correctly. AA165.


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Wed Jan 13, 2016 10:35 pm
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Steve, if you scroll down where the comments are, you'll see the owner stating:


"Stock AB165 1965. The key elements is that I retubed and Recaped the amp and used Scumback speakers. ...."

8)


.. and:

"Your too funny... Actualy, you're hearing probably one of the most common Fender circuits around. The STock AB165 circuit can be found from '64 all the way into '74-'75 I believe. This video, though not perfect, just goes to show you don't need crazy cash to get this sound. We over think our gear I think...


:mrgreen:


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Post subject: Re: this Fender Bassman? aa864 or aa165 or ab165
Posted: Sat Jan 16, 2016 8:03 pm
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You are correct. I was getting excited about seeing a real AA165. My UNICORN! :lol:


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