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Posted: Sun May 09, 2010 9:19 am
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stratele52 wrote:
I don't think polarity ( ground switch) is dangerous if you replace your 2 prong AC wire for a 3 prong ( with ground).

It is the 2 prong wire make it dangerous.

You should never use an amp without a ground plug


You are correct, sir. However, the grounded 3-conductor plug now commonly used with most gear obviates the need for a polarity switch since AC wiring is (for the most part) polarized. Thus, a polarity switch becomes redundant. But it also frees up that switch to be used for other interesting purposes. I used the now-unneeded polarity switch on my original '65 Princeton Reverb to add a "standby" function to the amp, thus extending tube life -- no holes drilled in the chassis and the mod is instantly reversible if desired. Likewise on my DRRI I used the polarity switch (which is in fact a dummy -- not connected to anything) to switch between the dual secondary taps of the custom output tranny I installed. Thus I can safely run either 4Ω or 8Ω loads at full power without fear of meltdown. Again, no holes drilled and the mod is virtually invisible.

Arjay


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Posted: Sun May 09, 2010 12:39 pm
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Good idea Retroverbial to use the polarity swich for stanby.Thank's for the hints.


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Posted: Sun May 09, 2010 2:24 pm
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To convert an AA764 Princeton or Princeton Reverb's polarity switch to perform the standby function (assuming you've already installed a fully-grounded 3-conductor power cable and removed the "death cap"), connect the B+ feed off of pin 8 of the rectifier tube socket to the side of the switch with two lugs on the same side. A single lug is sufficient. Next, connect the opposite side of the ground switch to the B+ supply (at the 1K resistor terminal on the main board).

HTH

Arjay


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Posted: Mon May 10, 2010 4:54 pm
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Very interesting, Arjay. Does this standby switch present a "no-load" condition on the rectifier tube? Art

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Posted: Mon May 10, 2010 4:57 pm
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It functions precisely the same as the standby switch on the larger Fender platforms.

Arjay


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Posted: Mon May 10, 2010 6:10 pm
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Thanks, Arjay. I think a standby thread might be cool. Art

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Post subject: Re: Silverface
Posted: Fri May 28, 2010 8:29 pm
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mytelecriesblues wrote:
I want to know what makes Silverface amps so cheap. Is it because they are poorly made?

My buddy has an old fender champ (Silverface, circa 1970) and it is amazing and I was considering looking for an old silverface Deluxe Reverb or Princton.

Since I have little knowledge of these amps i would like to know if i am wasting my money.

Help me out, Nic.


Well, I guess it is what the market bears. I recently bought a 78 Vibrolux Reverb for 350. I saw a mid 60's Vibrolux Reverb go for over 4 grand!

I actually prefer the sound of this silverface to all of my blackface amps. But I am a jazz guitarist and prefer a more darker tone.

I think the labor skills might have declined in the 70's for Fender a bit if you look and compare soldering and lead dress.


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Post subject: hijacked
Posted: Wed Jun 23, 2010 7:43 pm
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It's still an interesting fact, to us that give a sh*t about EARLY SF amps.[quote][/quote]


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Post subject: Re: Silverface
Posted: Wed Jun 23, 2010 8:15 pm
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jazzgene wrote:
mytelecriesblues wrote:
I want to know what makes Silverface amps so cheap. Is it because they are poorly made?

My buddy has an old fender champ (Silverface, circa 1970) and it is amazing and I was considering looking for an old silverface Deluxe Reverb or Princton.

Since I have little knowledge of these amps i would like to know if i am wasting my money.

Help me out, Nic.


Well, I guess it is what the market bears. I recently bought a 78 Vibrolux Reverb for 350. I saw a mid 60's Vibrolux Reverb go for over 4 grand!

I actually prefer the sound of this silverface to all of my blackface amps. But I am a jazz guitarist and prefer a more darker tone.

I think the labor skills might have declined in the 70's for Fender a bit if you look and compare soldering and lead dress.


Lead dress was sloppy in the 70's. I'll tell you what, my 76 Twin only saw a shop once for a recap and retube in 34 years, my 74 Champ has yet to see a shop. The sloppy lead dress didn't seem to hurt the reliability. I'd rather have sloppy lead dress than cheap thin boards, insufficient wave soldering, thin traces and ribbon connectors that look like they were borrowed from my old desktop. :wink:

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Post subject: Re: Silverface
Posted: Wed Jun 23, 2010 10:59 pm
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63supro wrote:
cheap thin boards, insufficient wave soldering, thin traces and ribbon connectors that look like they were borrowed from my old desktop. :wink:


Aw c'mon now, Supro......that's progress!

:mrgreen:

Arjay

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Post subject: Hijacked
Posted: Thu Jun 24, 2010 12:08 am
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Hey Teberwein, are you trying to steer us back on topic ? If so, you're spot on ! One aspect of why the Silverface amps are cheaper, could reflect the CBS ownership change. Although the changes in labor force, circuits, components, and manufacturing techniques did not change on Jan 1, 1965, a certain public acceptance did change, when valuing these amps years later. IMO the Silverface cosmetic change was similar to the change of the Ford Falcon body style to the Mustang body style. The same frame, engine, trans, and running gear, but that's not how the unit was/is accepted by the public today. Just my view. Art

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Posted: Tue Jul 13, 2010 1:31 pm
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on the much-maligned pull boost silverfaces:

when my Princeton Reverb was getting its mods done, I asked if the pull boost made a difference to the sound vs. a regular pot.

My amp tech replied, "Only if you pull it out."

So I left mine as is.

Now that pull boost is a nasty sound, but it's got me thinking that with a switchcontrol on the front and a 1/4" switch jack in the back, it could be good for something else... suggestions?

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Post subject: Grounding question
Posted: Wed Nov 10, 2010 5:19 pm
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Hi,

Saw the topic of grounding come up and I want to know, if I add a three prong cable, I assume bringing the green or ground wire to the chassis is the method - yes? It is what I have done on smaller tube projects, but I wanted to be sure - I am working on a Silver Face SR and it REALLY needs a new plug and cable.

Also, was it normal to have a general coating of brown gunk all over the inside of the chassis? The one I am working on is horrible in this regard. Serial Number is A29XXXXX and the wiring is all cloth covered. Tube location sheet says it is an AB763 circuit - how can I confirm exactly what circuit it actually is without resorting to schematic? Is there an identifiable method using the layout pictures that are available?

Regards, Chris


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Post subject: Re: Grounding question
Posted: Wed Nov 10, 2010 7:06 pm
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taskerc wrote:
Hi,

Saw the topic of grounding come up and I want to know, if I add a three prong cable, I assume bringing the green or ground wire to the chassis is the method - yes? It is what I have done on smaller tube projects, but I wanted to be sure - I am working on a Silver Face SR and it REALLY needs a new plug and cable.

Also, was it normal to have a general coating of brown gunk all over the inside of the chassis? The one I am working on is horrible in this regard. Serial Number is A29XXXXX and the wiring is all cloth covered. Tube location sheet says it is an AB763 circuit - how can I confirm exactly what circuit it actually is without resorting to schematic? Is there an identifiable method using the layout pictures that are available?

Regards, Chris


The first step to determining the circuit revision is to find out when your particular amp was made. Go here for a pretty comprehensive serial number list......

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

1968 represents the last of the cloth push-back wiring. Subsequent amps used plastic insulation and the lead dress itself grew sloppier with each passing year.

Your assumption regarding the installation of a proper ground is correct. Most techs will install a donut lug on the ground (green) wire of the new power cable then attach it solidly to the chassis using one of the mounting bolts for the power tranny.

The brown gunk you reference is probably nicotine residue. Hard to properly clean from a chassis's innards -- most folks leave it alone rather than risk further self-inflicted damage to the amp trying to remove it.

HTH

Arjay

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Post subject: Re: Grounding question
Posted: Wed Nov 10, 2010 8:35 pm
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Retroverbial wrote:

The first step to determining the circuit revision is to find out when your particular amp was made. Go here for a pretty comprehensive serial number list......

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

1968 represents the last of the cloth push-back wiring. Subsequent amps used plastic insulation and the lead dress itself grew sloppier with each passing year.

Your assumption regarding the installation of a proper ground is correct. Most techs will install a donut lug on the ground (green) wire of the new power cable then attach it solidly to the chassis using one of the mounting bolts for the power tranny.

The brown gunk you reference is probably nicotine residue. Hard to properly clean from a chassis's innards -- most folks leave it alone rather than risk further self-inflicted damage to the amp trying to remove it.

HTH

Arjay


Thanks Arjay!

I did the check you mentioned already and found it to be 1967 but form this I was not able to better understand if I "really" have an AB763, as listed on the tube position paper or if it was one of the other variants listed there. In my forum trawls it appears that the relationship between circuit type written on tube sheet can differ from reality.

But I guess more importantly , should I really care which circuit variant I have?

I may post a picture tomorrow - if the brown gunk is really nicotine, this amp has some SERIOUS stories to tell :-) It truly is gunked up.

I am quite jazzed about this project now and I probably should not mention I found this in a Garage sale and offered $50 and it was accepted. And moreso, I plugged it in (even though I probably should have been more careful) and it worked, well mostly. Hum, and some functions not right but it made music, and quite nicely at that given that the 'lytics Caps are all candidates for replacement. In the strip down I found the handle screw retainer thingy wedged into the works near the power supply section. I am lucky that powering it up did not blow it up. It has all the original blue molded caps still and looks like it has not been modified as of yet.

But it is a silverface with black speaker cloth and no edge trim on speaker baffle. Being a Canadian variation it has "Radio Speakers of Canada" 10"ers in it. So I am not sure exactly what it is in reality. Front panel has black lines (why is this important? I have seen it mentioned a good few times).

Thanks again!

Regards, Chris


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