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1965 MARSHALL JTM WITH 105-110 VOLTAGE TAP NO 120 VOLT TAP CAN I RUN IT ON A 120 LINE SAFELY PLEASE READ THANKS !


 
9/14/2000 10:17 PM
MICHAEL
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1965 MARSHALL JTM WITH 105-110 VOLTAGE TAP NO 120 VOLT TAP CAN I RUN IT ON A 120 LINE SAFELY PLEASE READ THANKS !
Hello !!  
 
I recently purchased a 1966 jtm-45/100 which is a 100 version of Marshalls jtm these were the 1st Marshall 100 watt models. The voltage taps in the back say 105-110, 200-210, 220-230 & 240-250. I had Victor Mason from plexi paradise fix up the amp he insisted that I run it at either 105 or 110 he even sold me the variac to use with it, he told me he would not guarentee the reapirs unless I ran it at this voltage, he spefically told me not to run it into a 120 volt line so I have a $ 160 variac he sold me to use with the amp it sounds great and works fine. After posting my previous question on Variacs I am concerned. Well I know you guys know the answer thanks for the help - what would you do if it was your amp ???
 
9/14/2000 11:07 PM
Peter S
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Micael,  
Use the variac. Set it to 105vac. Get the amp biased at that voltage. Make a plastic label up and tie wrap it to the back of the amp indicating that the amp must be used with a variac at 105VAC. You will have to make sure that your tech understands this......dont assume that just because he/she's a tech that they will be paying attention. Once the bias is set to run the amp at 105vac everything will be cool. Never experiment with different voltages using the variac no matter how tempting it may be. NEVER LET ANYONE BORROW THE AMP!!!!!!!!!!!!  
 
Peter S
 
 
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9/15/2000 1:49 AM
Troy
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Better yet, go to the GEO website (sorry don't have url handy, but it's linked on Ampage somewhere) and have a tech build you the vintage voltage adapter. That way you don't have to worry about anyone messing with your Variac.  
 
Troy
 
9/15/2000 2:48 AM
Don Symes
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www.geofex.com  
 
Mount it INSIDE the head hooked to the original power inlet. That way you never even need think about it.
 
9/16/2000 4:20 PM
Peter S
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Michael,  
Don and Troy gave you excellent advise. As I told you before, the variac is very risky buisiness. Using the Vintage Voltage Adapter is much sfer and far less expensive. Go for it!  
 
Peter S
 
9/16/2000 12:22 AM
Hamilton
Don and Troy, thank you and my JTM-50 says thank you. I was not about to haul my variac to the gig but the tone out of this amp is one of my favorites, thus that poor ol' thing saw 117-120 vac ALOT.  
 
Today I installed a 12 volt 3 amp AC transformer and the power transformer now sees 104 vac. My plate voltage went from 496 to 427 vdc and the filament was 6.8, now at 6 vac. You guys are great!
 
9/16/2000 3:40 AM
MICHAEL
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Re: 1965 MARSHALL JTM WITH 105-110 VOLTAGE TAP NO 120 VOLT TAP CAN I RUN IT ON A 120 LINE SAFELY PLEASE READ THANKS ! PETER S ARE YOU THERE ???
HEY THANKS FOR ALL THE INFO -- PETER S WHAT DO YOU THINK ABOUT DON & TROYS ADVISE
 
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