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Post subject: Fender Bronco
Posted: Wed May 25, 2011 8:23 pm
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Location: Redding Ca
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My Fender Bronco 69 or 70 ? Cool little amp.

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Post subject: Re: Fender Bronco
Posted: Wed May 25, 2011 8:50 pm
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The best way to determine the date is to examine the EIA codes found on the trannies, pots, and (if it's still original) the speaker. There may be a date ink-stamped within the chassis innards as well. Cosmetically, the '69 and '70 models are identical. My little Bronco is a '68 -- easily identifiable with its silver/black/blue grill cloth, drip-edge molding, and snowman knobs......

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They're cool little porch weasels.

Welcome to the forum, BTW

Arjay

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Post subject: Re: Fender Bronco
Posted: Wed May 25, 2011 9:01 pm
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1968-1969 would have the silver frame around the grill cloth so I think mine is early 1970's.

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Post subject: Re: Fender Bronco
Posted: Wed May 25, 2011 9:15 pm
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The quickest way to definitively determine the vintage is to pull the upper rear cover, turn the amp upside down, look inside, and make a note of the stamped tranny codes.

You'll see two lines of characters on each, stacked vertically. The first set will read "220XXX" which is Fender's in-house part number. The second set wil be formatted "606XXX" or "831XXXX". These numbers indicate who made the component and when. The 606 is Schumacher's ID while 831 was assigned to Better Coil & Transformer (this latter company was a second-source used by FMI when amp production surged after the CBS buyout and Schumacher could not meet the increased demand). You may find a mix of these tranny brands which is perfectly legitimate. The next digit following the subcontractor's ID (or two digits in the case of a BCT tranny) will be the last digit of the year in which the part was made. The final two numbers indicate the week within that year.

Best of luck, HTH

Arjay

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Post subject: Re: Fender Bronco
Posted: Thu May 26, 2011 1:34 am
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I have a Bronco as well , looks identical .
Have not had it long and was a bit dissapointed with it as it it nowhere near as loud as my Vibro Champ .
I have not had it looked at yet as my amp guy is away for a while .
I only bought it because I have the matching Bronco guitar and as I say I was a bit underwhelmed by the amp . I do love the Vibro Champ though .


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Post subject: Re: Fender Bronco
Posted: Thu May 26, 2011 2:09 am
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Likely your amp is ready for a tune-up......

Tubes, cap can, bias and bypass caps, cathode resistor. If done competently, it shouldn't require any further servicing for several years.

Arjay

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Post subject: Re: Fender Bronco
Posted: Thu May 26, 2011 11:52 pm
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As far as I know, the Bronco has the identical (or near identical) circuit as the SF Vibro Champ. Like Arjay said, recap the puppy. Then, check voltage at specific points labeled on the schematic.

All ok... maybe go for new tubes. Or at least swap the 12AX7 for a known good one. Try out the amp. Still not up to par? Try a known good 6V6GT. Not better? Try a good 5Y3GT rectifier.

http://www.ampwares.com/schematics/bronco_ab764.pdf

Good luck. A good amp to restore. Done right, will have killer tone.


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Post subject: Re: Fender Bronco
Posted: Fri May 27, 2011 12:01 am
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Some of the very first examples of the Bronco Amp actually left Fullerton with a Vibro Champ tube chart stuck in the cabinet. Comparing those early Broncos with the original AA764 blackface Vibro Champ schematic, I find no differences whatsoever.

Arjay

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