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Post subject: Dating / Worthwhile buy: Fender Eighty Five
Posted: Fri Aug 23, 2019 5:50 pm
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Hi All,

So... I have the possibility of picking up a Fender Eighty Five cheaply (under $100) and I’m trying to work out whether it’s a good buy.

It will likely need a replacement treble pot due to crackling and intermittent signal at some points (or the current one cleaned) and it has a background hum when turned on (not too loud but audible in a quiet room). Can anyone who has one tell me if a slight hum is usual on these amps?

It is also missing the foot switch.

From the serials I’ve seen on other advertised Eighty Fives it is pretty low (LO-015XXX) and has the made in USA logo but also has black knobs. It seems possible that it was a first run before the cost cutting red knobs were added although it seems that black knobs were also used in the last production run (but those did not have the made in USA on the logo and I would expect a higher serial).

Does anyone have any thoughts on this?

I’ll add some photos when I have a moment.

Thanks,

D.


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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Sat Aug 24, 2019 3:10 pm
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Hum is not normal, amp should be quiet

Issue with Filter caps ? bad ground, transistors ?

Owner manual ;

https://www.fmicassets.com/Damroot/Orig ... der_85.pdf

Pots ;
https://www.guitarpartsresource.com/amp_electrical.htm


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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Sat Aug 24, 2019 3:39 pm
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Thanks!

I can do the pot myself but I don’t trust myself to check/replace the caps so if the hum is loud enough to be problematic then I’ll likely take it in ...


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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Sat Aug 24, 2019 10:15 pm
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The hum may just be me being overly picky.

Any thoughts on whether it’s an early or late example?


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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Sun Aug 25, 2019 12:49 am
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The hum may come from a bad solder on filter caps ; just reaheat.


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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Sun Aug 25, 2019 2:29 am
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stratele52 wrote:
The hum may come from a bad solder on filter caps ; just reaheat.

If I'm going to take the time to open up a 25+ year-old amp that's likely never been serviced you best believe I'm going to replace every electrolytic cap on that chassis.

But hey, that's just my maintenance philosophy......

Arjay

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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Sun Aug 25, 2019 2:48 am
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I have so many electronics gear with more than 25 years old and filter caps are good.
25 years ago was yesterday for me :lol:


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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Sun Aug 25, 2019 12:21 pm
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stratele52 wrote:
25 years ago was yesterday for me :lol:

Don't pull that merde on me, pal.

I've got rolls of solder older than you.

:lol:
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: Dating / Worthwhile buy: Fender Eighty Five
Posted: Sun Aug 25, 2019 2:44 pm
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The black knobs came after the red knobs, in an attempt to make them look a bit more like traditional Fender Amps. These are well made good sounding amps, and if you can score one under $100, then even with a visit to an amp tech is still going to get you a good deal. My guess is the amp has the crappy Illinois Caps in it and at 25 years they likely need replacement. Just make sure the tech uses some good quality caps like F&T's and you'll have a dang fine SS amp!

:mrgreen:

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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Sun Aug 25, 2019 8:10 pm
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Got it for $60 in the end...

Should have some deoxit here on Tuesday for the pot and then I’ll see whether it needs a visit to the tech.

It didn’t come with a foot switch but I think I might just use pedals on a single channel unless I find one cheap.

*** does anyone have a 3? button foot switch they don’t need?

I did think the black knobs were the later ones - is the serial being lower than red knobs I’ve seen irrelevant?

Thanks again for the help.


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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Sun Aug 25, 2019 11:14 pm
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It's possible that a previous owner merely swapped the knobs. To many, the red knobs were a reprehensible sacrilege.

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: Dating / Worthwhile buy: Fender Eighty Five
Posted: Tue Aug 27, 2019 3:39 am
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I’ve found a local amp tech to look at the amp. Do the following prices sound reasonable?

“Replacing Filter Capacitors on most Fender and Ampeg models costs $100 which includes a complete diagnosis and general overhaul of amp (see following description of General Overhaul).


A General Overhaul of an amplifier costs $75 and includes diagnosing circuitry and components, checking and adjusting voltages, reconditioning all potentiometers, jacks, switches, and socket pins, and re-soldering connections and pcb pads.”


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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Tue Aug 27, 2019 9:47 am
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The prices are reasonable if the job is done competently.

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: Dating / Worthwhile buy: Fender Eighty Five
Posted: Tue Aug 27, 2019 9:52 am
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This era of Fenders have control shafts that are easily damaged by simply pulling off the knobs. They are on tight enough to pull the metal shaft out of the plastic rotating contact. The contact looses spring pressure against the resistance strip and crackles.
Use a slot screwdriver on each side of the skirting and alternately pry gently until it loosens.
You can see the damaged ones by pulling on the shafts gently and comparing the crackly ones to the quiet ones. Pull gently on the crackly one while you rotate it. It should clean up.
If you pull the control and remove the back cover, you can push the shaft back through the plastic disk and super glue it back into position. Back that up with epoxy and you have a good repair.

Reconditioning the pots usually means spraying some solvent inside. While this removes some dirt, it also removes the lubrication grease. This takes away the damped feel of the knob turning. More importantly, it exposes the aluminum shaft to oxygen. This allows the shaft to corrode and seize up the shaft.
I recommend not cleaning a control unless there is an actual fault. Then I recommend removing and opening up the control for a proper cleaning.
Using a thin strip of cardstock and solvent, place the cardstock between the wiper and the resistance element. Hold the shaft and rotate the control to wipe the entire length of the resistance strip. This will put pressure on the cleaning strip and substrate right where it needs to be cleanest.
Next, push a clean wet strip between the secondary wiper contacts and rotate the shaft until its clean.
Repeat on the other side of the wiper contact.

If you pulled the shaft to clean the pot, clean it with solvent and recoat the shaft and bushing with siiicone grease. I use the bulb grease found on many autoparts counters. This restores the dampened feel to the knob.
I regrease the metal wiper contact with lithium grease. If the shaft was removed, this is easy. If you have to skinny it between the wiper and the substrate, another strip with just a drop of grease can get in there. If you get grease on the resistance element, clean it off.

I've never had to recap Fender SS amps.
Resolder jacks and big resistors.
If you have it opened up, drop a TLE2072 or an OPA2134 in IC1 and the reverb circuit. You'll get more bang for your buck over recapping.

There are major differences in the drive channels of the Fender 85s. The early version A have a chassis that is silver in the back. The later version C have a black chassis in the rear. These have 3 times the gain of the silver back in the drive Channel.


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Post subject: Re: Dating / Worthwhile buy: Fender Eighty Five
Posted: Tue Aug 27, 2019 5:10 pm
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As far as I know this guy should be good. He builds/sells boutique amps and does repair work for a number of the local stores and specializes in Fender.

Regarding the black vs silver chassis, is that on the inside or outside of the back? I’ll ask the tech to take some photos when it’s out.

The hum sounds like all of the clips of filter cap hum that I’ve found so I’ll ask him what he thinks prior to recapping...

Does anyone know which foot switches will work with this amp? I’d be happy with a single button channel switch or a 2 button channel + reverb.

Thanks for the help/info...


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