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Post subject: Silverface Twin dating question
Posted: Wed Jan 15, 2014 10:14 am
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Aspiring Musician
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I'm trying to date this Silverface Twin but it seem's contradictory as far as the dating methods I've read. The tranny's have EIA606-945 and 916 ('69?) and the ser# tag or tags is F954040 ('79 - '80?). What's with all the bonus tags? It does have a push pull master volume pot that isn't labeled on the faceplate.

Image

Image

Image

Thanks for any info.


Last edited by upnorth on Wed Jan 15, 2014 10:19 am, edited 1 time in total.

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Post subject: Re: Silverface Twin dating question
Posted: Wed Jan 15, 2014 10:18 am
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Try this................

http://www.superiormusic.com/page195.htm

Hopefully Arjay will chime in.........................

Tranny is either 69 or 79, does this have a master volume?


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Post subject: Re: Silverface Twin dating question
Posted: Wed Jan 15, 2014 10:42 am
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After a little more research I'm thinking this is a SF135. I could use layout if anyone knows where to get one. It seems the schematic is easy to find. It has ruptured caps, so all the electro's need to go.


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Post subject: Re: Silverface Twin dating question
Posted: Wed Jan 15, 2014 11:40 am
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upnorth wrote:
After a little more research I'm thinking this is a SF135. I could use layout if anyone knows where to get one. It seems the schematic is easy to find. It has ruptured caps, so all the electro's need to go.


Indeed, it's an ultra-linear 135-watt chassis from 1979.

You'll need filter caps rated for 600 VDC. And be sure to inspect the power-rail resistors for evidence of thermal degradation. Replace if necessary.

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: Silverface Twin dating question
Posted: Wed Jan 15, 2014 1:36 pm
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This thing's got some iron!


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Post subject: Re: Silverface Twin dating question
Posted: Wed Jan 15, 2014 2:30 pm
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I'm apparently missing something here. Is there more than one schematic for this 135 amp? I'm not seeing enough cap's on the schematic for the '79 135 Twin.

Thanks.

Image


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Post subject: Re: Silverface Twin dating question
Posted: Wed Jan 15, 2014 2:55 pm
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upnorth wrote:
I'm apparently missing something here. Is there more than one schematic for this 135 amp? I'm not seeing enough cap's on the schematic for the '79 135 Twin.

Thanks.

Image


*Somebody's* been in there before.

And looking at his handiwork, I'm not altogether certain of his competence.

:roll:

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: Silverface Twin dating question
Posted: Wed Jan 15, 2014 3:21 pm
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I'm starting to wonder if this is even what it's supposed to be. This thing is capped more like a Super Twin than 135.

Image

Image

Image

Image


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Post subject: Re: Silverface Twin dating question
Posted: Wed Jan 15, 2014 4:31 pm
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Those look to be EV drivers of some persuasion......Force 12's? EVL12's?

Definitely some *serious* work for a roadie.

:shock:

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: Silverface Twin dating question
Posted: Wed Jan 15, 2014 5:53 pm
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upnorth,

That is a UL 135 power rail. It has original OEM Mallories ("235" mamanufacturer's code, both 1978 and 1979 dates). There should be two 220mfd/285VDC first filter stage caps. Three 20mfd/500VDC caps for the gain stages. A 80mfd/75VDC and 70mfd/100VDC cap for the bias supply. All under the doghouse.

The bypass caps all appear to be original Mallories. The Blue Blob Paktron coupling caps appear to be OEM. These were commonly used by Fender in later SF amps. Not the world's best tone creatures (IMHO).

The 2700-ohm, 10-watt "sandbox" resistor (tan color), which is in the power rail --- is on the far right side of photo, next to the chassis wall. It's on the terminal strip with the two 100k-ohm, 1 watt leveling resistors of the first stage power rail.

There is a white 30k-ohm, 20-watt resistor "sandbox" resistor between the rectifier tagboard and the main circuit tagboard. The actual power ratings of the two sandbox resistors maybe wrong on the schemo. The tan one on the far right (by the chassis wall) looks like a 20-watt. And the white one, by the main circuit board looks like a 10-watt one.


The bypass caps all appear original, too.

http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: Silverface Twin dating question
Posted: Wed Jan 15, 2014 6:16 pm
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BMW2002Ti wrote:
upnorth,

That is a UL 135 power rail. It has original OEM Mallories ("235" mamanufacturer's code, both 1978 and 1979 dates). There should be two 220mfd/285VDC first filter stage caps. Three 20mfd/500VDC caps for the gain stages. A 80mfd/75VDC and 70mfd/100VDC cap for the bias supply. All under the doghouse.


I've just never seen wires pinched between the caps like that before. The doghouse on mine (a '78) is wired pretty neatly.

I concur with the assessment though -- the UL model is an altogether different animal from the original BF or SF editions.

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: Silverface Twin dating question
Posted: Wed Jan 15, 2014 7:42 pm
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Arjay,

Yeah, a bit sloppy. Maybe Lupe was on vacation, that day.

:lol:


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Post subject: Re: Silverface Twin dating question
Posted: Wed Jan 15, 2014 8:36 pm
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Or celebrating Cinco De Mayo.

:wink:

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: Silverface Twin dating question
Posted: Wed Jan 15, 2014 9:28 pm
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Aspiring Musician
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Thanks for the encouraging info. I didn't see three 20uf's, only one, on the schematic I was reading so I got concerned. I'll just replace them all with the same values. There is one that is a 5uf/50v (If I remember right it's for the tremolo so a 25/50 could work) I can still get from at least one supplier, but the rest including replacements for the 220/285's, are easy to find.

Thanks again. I just need to figure out how to get it out of the basement when I'm done. Maybe dime it with a 335 using speaker propulsion, strapped on with a helmet of course.


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Post subject: Re: Silverface Twin dating question
Posted: Wed Jan 15, 2014 9:35 pm
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Never mind my comment about the missing 20's. I must have needed a nap, because I sure didn't study the schematic enough. I see em' all now. Old and blind, that's me.

Thanks for the help!


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