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Post subject: help dating silverface twin reverb possibly 1970 not sure
Posted: Thu Jan 27, 2011 1:11 am
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I picked up this beauty at musicians discount in mesa Arizona and i am pretty sure that it is a 1970 through my research but I had some doubts notably i have not seen any twins with the silver serial sticker still attached and serial number and as low as 0021. I have read about EIA numbers but as a complete novice to tube technology i am not sure which is the transformer in the last image attached the box to the left number is 606934, box in the middle number is 606-0-15, and the box on the right number is 606930. Per multiple charts i assume that the left and right box indicate parts made in 1969 in the 30th and 34th week and the middle box indicates made in 1970 15th week. Fender's site asks to allow 6 month buffer on parts as could have been in storage before using. The tube chart is missing and the speakers look like someone had replaced the originals with a pair of JBL MI-12 which sound awesome but are of no help for dating the amp. My final theory is that this a 1970 and was 21st off the assembly line what do you think?

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Post subject: Re: help dating silverface twin reverb possibly 1970 not sur
Posted: Thu Jan 27, 2011 1:21 am
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The amp does indeed seem to be a 1970 model, judging by the tranny numbers and the composition and construction of the cabinet. If you remove the chassis you may find a date ink-stamped on the inside, adjacent to the power tranny and bias-balance circuit. That silver sticker on the rear of the chassis is NOT something that Fender applied. If you peel that back you'll find the "official" Fender serial number stamped into the chassis.

Arjay

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Post subject: Re: help dating silverface twin reverb possibly 1970 not sur
Posted: Thu Jan 27, 2011 1:28 am
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thank you for the quick reply i was reluctant to alter anything on the amp but i had a feeling there would be the embossed serial number behind the sticker ill take that off and open the chassis see what the guts look like


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Post subject: Re: help dating silverface twin reverb possibly 1970 not sur
Posted: Thu Jan 27, 2011 1:31 am
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Use caution.

There are things within that have the potential to injure or kill.

Arjay

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Post subject: Re: help dating silverface twin reverb possibly 1970 not sur
Posted: Thu Jan 27, 2011 2:08 am
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Sure enough the serial number is A 23373 which indicates a 1970. I took out the chassis but i do not see any stamped numbers here is what i'm looking at

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Post subject: Re: help dating silverface twin reverb possibly 1970 not sur
Posted: Thu Jan 27, 2011 2:15 am
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That's the AA270 chassis. Here's the schematic for it......

http://web.archive.org/web/200610201016 ... _schem.pdf

HTH

Arjay

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Post subject: Re: help dating silverface twin reverb possibly 1970 not sur
Posted: Thu Jan 27, 2011 2:28 am
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impressive i have spent about 3 days doing research and you gave me the proper evidence it's a 1970 in a matter of minutes I emailed JBL to see when they manufactured JBL-12 speakers i'm guessing early 80's do u have any prior experience with these?


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Post subject: Re: help dating silverface twin reverb possibly 1970 not sur
Posted: Thu Jan 27, 2011 2:35 am
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I have no user experience with JBL's "MI" series although as I recollect, they were designed in the mid '80s to compete with Celestion's V30 and G12M Greenback. The design was somewhat of a U-turn from their earlier "D" and "K" series which used a short-throw cone, a large-diameter voice coil and a rare-earth magnet structure. The MI's are ceramic, with a 2-inch coil.

Here's some archival material relating to your speakers......

http://www.jblpro.com/pub/obsolete/MI_Series.pdf

HTH

Arjay

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Post subject: Re: help dating silverface twin reverb possibly 1970 not sur
Posted: Thu Jan 27, 2011 2:58 am
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Yeah i read the same manual unfortunately it did not have any sort of date on it but the speakers sound awesome and rated at 150 watts each i have a ton of clean headroom i'll just wait and see what JBL has to say i gave them all the serial numbers i just wanted to get as much info on the amp as possible. One last question is this silverface model 85 or 100 watts model?


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Post subject: Re: help dating silverface twin reverb possibly 1970 not sur
Posted: Thu Jan 27, 2011 8:57 am
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From EIA Numbers and the picks i would date it to 1970


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Post subject: Re: help dating silverface twin reverb possibly 1970 not sur
Posted: Thu Jan 27, 2011 10:21 am
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DKH wrote:
One last question is this silverface model 85 or 100 watts model?


According to my 1970 Fender catalog, the AA270 circuit was rated for 100 watts @ 4 ohms ("220 watts peak music power").

Arjay

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