Proper way to run a '60's Supergroup

fenrisulfr
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Proper way to run a '60's Supergroup

Postby fenrisulfr » Mon Mar 07, 2011 10:12 pm

Sorry if this has been covered here, but apparently "Supergroup" is "too common" a search term to actually return any search results for so I couldn't find anything. I just got a late 60's Supgergroup MK1 100W and I've read/heard a few different things about how these should be run voltage-wise. I'm in the US and will be using US mains voltage. First thing I heard is that if you're running the SG in 110V mode, that you should use a variac to dial it down to 90-95V. I don't remember which forum I read this on, but the poster gave no reason as to "why", although everyone seemed to agree with him.. Next I heard that these should actually be set at the 240V setting, but run with a step up transformer from 110/120V to 240V. The amp runs fine for me plugged right into the wall and the guy I got it from says he never used a variac or anything, but that it does blow fuses from time to time and will definitely blow a fuse if you power it on and the volume is turned up. I actually tried to run it on a variac set to 95V and it would cut out and the power light would dim whenever you played any notes so I quickly disconnected it. Anyways any advise would be much appreciated so I don't blow up these precious Partridge transformers! Thanks.
Last edited by fenrisulfr on Thu Mar 10, 2011 2:56 am, edited 1 time in total.
1989 Pro Tube PT100
Late '60's (any help dating would be appreciated) Supergroup MK1 100W

fenrisulfr
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Posts: 15
Joined: Mon Mar 07, 2011 9:38 pm
Location: Southern California

Re: Proper way to run a '60's Supergroup

Postby fenrisulfr » Thu Mar 10, 2011 2:54 am

Nothing? ...so everyone here is running theirs straight into the wall off of modern mains voltage, not a care in the world then?
1989 Pro Tube PT100
Late '60's (any help dating would be appreciated) Supergroup MK1 100W

Gruppersoup
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Re: Proper way to run a '60's Supergroup

Postby Gruppersoup » Thu Mar 10, 2011 4:34 am

I always run mine w/a Variac to 100-110 v.
they work smoother and not the marginal dimming.
90-95 is the Van Halen territory for his "everything on 10 Brownsound," but slightly less volume.

fenrisulfr
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Joined: Mon Mar 07, 2011 9:38 pm
Location: Southern California

Re: Proper way to run a '60's Supergroup

Postby fenrisulfr » Thu Mar 10, 2011 6:38 am

Thanks for the response Gruppersoup! So you say "100-110V"... why the range of voltages from 100-110Vand not just set at, say, 110V? Also, when running the variac for this purpose, when turning the amp on, do you bring the voltage up slowly with the variac everytime you power the amp on, or do you just set the voltage on the variac and power the amp on/off normally?
1989 Pro Tube PT100
Late '60's (any help dating would be appreciated) Supergroup MK1 100W

HAL9000
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Re: Proper way to run a '60's Supergroup

Postby HAL9000 » Thu May 15, 2014 12:26 pm

I have a 1970 Supergroup 100 watt and measured the Partridge TG9684 power transformer output using a Variac. The tube filaments are working in the normal range at 110VAC/60Hz. Going below 105VAC/60Hz is below the recommended range for the tube filaments voltage. Going over 115VAC/60Hz puts the filament voltage above the recommended range. I run mine at 107.5VAC so that the power light will turn on.

For reference my wall voltage is 126VAC/60Hz, on the high side of the normal US range of 120VAC/60Hz +/-5%.


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