unclej Posted February 8, 2006 Report Share Posted February 8, 2006 a customer dropped off a big fender amp yesterday with an "occasional" problem that has nothing to do with my question. i noticed that the master volume control had been removed and asked him about it and the last tech modded it that way for him. he didn't know why and neither do i. what do you gain by doing that? Quote Link to comment Share on other sites More sharing options...
croaticum Posted February 8, 2006 Report Share Posted February 8, 2006 only thing on my mind is that you gain yourself a pot that you needed and were ti cheap to buy one! Quote Link to comment Share on other sites More sharing options...
unclej Posted February 8, 2006 Author Report Share Posted February 8, 2006 only thing on my mind is that you gain yourself a pot that you needed and were ti cheap to buy one! now why didn't i think of that? Quote Link to comment Share on other sites More sharing options...
Paul Marossy Posted February 8, 2006 Report Share Posted February 8, 2006 Is it a silverface Twin Reverb? A lot of people do partial blackfacing to those amps, and the master volume control gets removed... Quote Link to comment Share on other sites More sharing options...
unclej Posted February 9, 2006 Author Report Share Posted February 9, 2006 Is it a silverface Twin Reverb? A lot of people do partial blackfacing to those amps, and the master volume control gets removed... no paul..it's a 60's era vibrolux reverb..but i'm still curious..what do you gain (pun intended) by removing it on even a silverface twin reverb? Quote Link to comment Share on other sites More sharing options...
Paul Marossy Posted February 9, 2006 Report Share Posted February 9, 2006 what do you gain (pun intended) by removing it on even a silverface twin reverb? Some people feel that it hurts the tone, and that it should be removed. In general, silverface Fenders are frowned on- everyone seems to think that a blackface is better. I however think the silverfaces are excellent sounding amps, and I personally like the master volume control. I think it makes them more versatile. I have no inclination whatsoever to touch anything in my sf Twin Reverb. Now, why would someone do this on a 60's Vibrolux? Y our guess is as good as mine. I would expect the answer would be "to get it to break up sooner". One good mod to do the silverface Fenders is to add a bias adjustment pot, in addition to the hum balance pot (that was the bias adjustment pot in the blackface amps). This way, you get the best of both worlds. Here's how it was done in my amp: http://www.diyguitarist.com/GuitarAmps/TR-BiasMod.htm Quote Link to comment Share on other sites More sharing options...
unclej Posted February 10, 2006 Author Report Share Posted February 10, 2006 what do you gain (pun intended) by removing it on even a silverface twin reverb? Some people feel that it hurts the tone, and that it should be removed. In general, silverface Fenders are frowned on- everyone seems to think that a blackface is better. I however think the silverfaces are excellent sounding amps, and I personally like the master volume control. I think it makes them more versatile. I have no inclination whatsoever to touch anything in my sf Twin Reverb. Now, why would someone do this on a 60's Vibrolux? Y our guess is as good as mine. I would expect the answer would be "to get it to break up sooner". One good mod to do the silverface Fenders is to add a bias adjustment pot, in addition to the hum balance pot (that was the bias adjustment pot in the blackface amps). This way, you get the best of both worlds. Here's how it was done in my amp: http://www.diyguitarist.com/GuitarAmps/TR-BiasMod.htm thanks as always for your help and the link. i don't know who worked on this amp last but i have some doubts about his skill. not just what appears to be a needless mod but the problem was that sometimes you'd turn the amp on and it would power up...sometimes not and it would shut off completely most of the time after the customer started playing. took a minute to find the problem but the hot wire running from the jewel light to the first power tube was just stuck through the hole in the lug..not even soldered. and he had put all 12ax7's in instead of the 12at7's and 7025's that were supposed to be there. by the way..is there a secret handshake for techs after they get their first big shock while re-tensioning tube sockets when the haven't drained all the caps but didn't check before they started working on it? man, i remembered some cuss words that i learned in turkey that i thought i had forgotten. Quote Link to comment Share on other sites More sharing options...
Paul Marossy Posted February 10, 2006 Report Share Posted February 10, 2006 by the way..is there a secret handshake for techs after they get their first big shock while re-tensioning tube sockets when the haven't drained all the caps but didn't check before they started working on it? man, i remembered some cuss words that i learned in turkey that i thought i had forgotten. LOL. I haven't had that pleasure yet, but I have been zapped by 120VAC at the IECC socket a few times... Quote Link to comment Share on other sites More sharing options...
lovekraft Posted February 10, 2006 Report Share Posted February 10, 2006 No secret handshake, but you do learn a new dance step or two. Quote Link to comment Share on other sites More sharing options...
Opencan Posted February 13, 2006 Report Share Posted February 13, 2006 i think its more of a undesired handshake. its called twitching. never got a real good zap from an amplifier (yet), but i've got not-that-a-few shocks from engines, computers, and what not. and here its 230VAC... its a bit more annoying. i got to a point that the thing i hate the most about getting shocked is going all the way to the raise the switch... Quote Link to comment Share on other sites More sharing options...
JoeAArthur Posted February 13, 2006 Report Share Posted February 13, 2006 Ok... I'll add my $0.02 to the original question. If you have a 60s era Vibrolux Reverb with a master volume control - it ain't stock. To me, that's enough reason to remove it. Fender only added master volume controls in the early-mid 70s and after 1968, all of those amps would have been silverface (not that it is a bad thing, just a fact). However, Fender did revert back to blackface cosmetics sometime in the early 80's. I think the Vibrolux did get a "pull-boost" switch sometime after 1976-77... but I don't have anything that proves it, but if you have a blackface Vibrolux reverb with a "stock" master volume control, chances are pretty good that it is one of the early 80 models, and not a 60s. Why remove the master volume on silverface amps. Several reasons. First, the master volume control as installed is a "loudness" design - there is a "bright switch" style cap that is connected to a tap on the master volume pot. This cap will boost treble at a low enough control setting... and cut treble when the control is above the tap point. Cutting this cap out will restore a lot of the "shimmer" found in the earlier non-master-volume amps. The master volumes with the pull boost amps introduced additional treble cutting networks. Some of these are not obvious... something like a resistor and capacitor in series IIRC. Removing these networks along with the master volume also restores a lot of presence to the amp. oops... ran out of change. Quote Link to comment Share on other sites More sharing options...
Paul Marossy Posted February 13, 2006 Report Share Posted February 13, 2006 If you have a 60s era Vibrolux Reverb with a master volume control - it ain't stock. To me, that's enough reason to remove it. Fender only added master volume controls in the early-mid 70s and after 1968, all of those amps would have been silverface (not that it is a bad thing, just a fact). Doh! That didn't even register the first time. That's correct, when CBS bought Fender they tweaked all of the existing designs and went to the silverface graphics. And the mv control was added sometime in the mid-70s. So, a mv control would not be stock. Maybe your amp is not from the 60s? the master volume control as installed is a "loudness" design - there is a "bright switch" style cap that is connected to a tap on the master volume pot. This cap will boost treble at a low enough control setting... and cut treble when the control is above the tap point. Cutting this cap out will restore a lot of the "shimmer" found in the earlier non-master-volume amps. The master volumes with the pull boost amps introduced additional treble cutting networks. Some of these are not obvious... something like a resistor and capacitor in series IIRC. Removing these networks along with the master volume also restores a lot of presence to the amp. Thanks for explaining that. I never did fully understand why people want to take the mv control off of the silverface amp, but now I get it. Quote Link to comment Share on other sites More sharing options...
unclej Posted February 13, 2006 Author Report Share Posted February 13, 2006 well, it's a moot point now as the customer has picked it up but that also explains why the hole where the volume control was removed really didn't look like it belonged where it was. i would imagine that someone added it before this guy bought it and the last tech removed it. Quote Link to comment Share on other sites More sharing options...
Paul Marossy Posted February 14, 2006 Report Share Posted February 14, 2006 well, it's a moot point now as the customer has picked it up Yah, but a good discussion. Quote Link to comment Share on other sites More sharing options...
lovekraft Posted February 14, 2006 Report Share Posted February 14, 2006 If anybody's interested in what Fender did (and to whom, with what) at any given, you can refer to the Fender Field Guide ( courtesy of Ampwares) - pretty accurate, and since it includes schematics for most models, it's easy to see the evolution of various amps over time ( as well as the gradual triumph of marketing over musicality - but I digress! ). Definitely worth a bookmark. Quote Link to comment Share on other sites More sharing options...
Paul Marossy Posted February 14, 2006 Report Share Posted February 14, 2006 Yeah, the FFG is a great source of information. That's where I learned most of what I know about Fender amps... Quote Link to comment Share on other sites More sharing options...
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