Biasing Silveface Deluxe Reverb

OLAF MELCHER · June 7th, 2006, 02:21 AM

Hi,

can anybody tell me if my Silverface Deluxe Reverb from 1971 has an adjustable fixed bias (seems so) and where to locate the bias pot ?

Thanks

Olaf

JohnnyCrash · June 7th, 2006, 03:22 AM

Yes, bias pot.

You'll have to remove the amp chassis from the cabinet.

Inside it's the small flat-head screwdriver adjusted pot... it's a small 10k deal.

It'll be on the end of the amp/board that is closest to the big power transformer as opposed to the end where the preamp tubes/inputs are.

If you're not sure how to bias - I'd leave it alone and have an amp guy do it... if you've got a multimeter and know what you're doing - go for it. It's not hard if you know what you're doing.

Silverface Deluxe layouts are hard to find... at least for me :)

Schematics are everywhere though...

If that didn't help I should have another shot... too bad rum's all I've got left :(

OLAF MELCHER · June 7th, 2006, 06:08 AM

Thanks Johnny - very helpful.

Best regards

Olaf

TDPRI · June 7th, 2006, 09:52 AM

I got a "Bias King" just for this purpose and it makes biasing even easier.

Here's a link:
http://www.biasking.com/

Paul Green

LK · June 7th, 2006, 08:52 PM

There should be a adjustment hole ( it will look like a 1/4 guitar jack on the underside of the amp chassis) You can adjust the bias here with a flat blade screwdriver, if you have a bias rite. Very easy to find.

LK

jackleg · June 8th, 2006, 11:50 AM

shouldn't one be cautious when trying to bias an amp from the inside, due to possibility of electocution? 450+ volts and the amperage that these amps carry could be lethal. unless you are experienced, stay away!!!

LK · June 9th, 2006, 08:05 PM

Be very cautious about doing anything inside the chassis of a amp. If you use the adjustment on the underside of the chassis you have nothing to worry about, as you are not touching anything inside the amp.

LK

JohnnyCrash · June 9th, 2006, 08:11 PM

You still have to be able to use the meter to check the voltage while adjusting...

Like I said though, "if you know what you are doing"...

Otherwise you could end up with dead power tubes, or worse yet, a dead guitar player!

-Danger High Voltage-

June 7th, 2006, 02:21 AM	#1 (permalink)
OLAF MELCHER TDPRI Member Join Date: Feb 2005 Location: Western France Age: 47 Posts: 63	Biasing Silveface Deluxe Reverb Hi, can anybody tell me if my Silverface Deluxe Reverb from 1971 has an adjustable fixed bias (seems so) and where to locate the bias pot ? Thanks Olaf __________________ jazzjoker

June 7th, 2006, 06:08 AM	#3 (permalink)
OLAF MELCHER TDPRI Member Join Date: Feb 2005 Location: Western France Age: 47 Posts: 63	Biasing Silveface Deluxe Reverb Thanks Johnny - very helpful. Best regards Olaf __________________ jazzjoker

June 7th, 2006, 03:22 AM	#2 (permalink)
JohnnyCrash Poster Extraordinaire Join Date: Mar 2005 Location: Lost Angeles and Orange County Posts: 7,128	Yes, bias pot. You'll have to remove the amp chassis from the cabinet. Inside it's the small flat-head screwdriver adjusted pot... it's a small 10k deal. It'll be on the end of the amp/board that is closest to the big power transformer as opposed to the end where the preamp tubes/inputs are. If you're not sure how to bias - I'd leave it alone and have an amp guy do it... if you've got a multimeter and know what you're doing - go for it. It's not hard if you know what you're doing. Silverface Deluxe layouts are hard to find... at least for me :) Schematics are everywhere though... If that didn't help I should have another shot... too bad rum's all I've got left :(

June 7th, 2006, 09:52 AM	#4 (permalink)
TDPRI Administrator Poster Extraordinaire Join Date: Mar 2003 Location: TDPRILAND Posts: 5,725 36 Photos	I got a "Bias King" just for this purpose and it makes biasing even easier. Here's a link: http://www.biasking.com/ Paul Green

June 7th, 2006, 08:52 PM	#5 (permalink)
LK TDPRI Member Join Date: Nov 2005 Location: Markesan, WI Posts: 52	There should be a adjustment hole ( it will look like a 1/4 guitar jack on the underside of the amp chassis) You can adjust the bias here with a flat blade screwdriver, if you have a bias rite. Very easy to find. LK

June 8th, 2006, 11:50 AM	#6 (permalink)
jackleg TDPRI Member Join Date: Aug 2004 Posts: 95	shouldn't one be cautious when trying to bias an amp from the inside, due to possibility of electocution? 450+ volts and the amperage that these amps carry could be lethal. unless you are experienced, stay away!!!

June 9th, 2006, 08:05 PM	#7 (permalink)
LK TDPRI Member Join Date: Nov 2005 Location: Markesan, WI Posts: 52	Be very cautious about doing anything inside the chassis of a amp. If you use the adjustment on the underside of the chassis you have nothing to worry about, as you are not touching anything inside the amp. LK

June 9th, 2006, 08:11 PM	#8 (permalink)
JohnnyCrash Poster Extraordinaire Join Date: Mar 2005 Location: Lost Angeles and Orange County Posts: 7,128	You still have to be able to use the meter to check the voltage while adjusting... Like I said though, "if you know what you are doing"... Otherwise you could end up with dead power tubes, or worse yet, a dead guitar player! -Danger High Voltage-