Lets talk bias tools.

Rob (PA) · December 14th, 2003, 10:31 PM

Ok tuners, lets discuss bias probes (I guess that's what they are called) I am starting to work on my own amps, and I need to get a pair for working on the various Fenders and 122/147 amps I have been previously farming out. What's the general consensus out there on what type I should get? As always, thanks in advance!

Lyle Caldwell · December 14th, 2003, 10:56 PM

Weber makes a good'un. www.webervst.com

JDO · December 14th, 2003, 11:28 PM

that's what i use. i'm cheap so i just got the one that you plug into a meter. if i had it to do over again, i would get the bias rite with all the options. it would just be easier.

Cam · December 14th, 2003, 11:44 PM

I can't remember what web site I pulled the info from, but I made my own. It is a single probe though which is kind of a pain switching between tubes to strike an average setting. But it works. I'm thinking about ordering a "real" one.
If I find the website, I'll edit this post.

JDO · December 14th, 2003, 11:56 PM

Quote:

Originally Posted by Cam

I can't remember what web site I pulled the info from, but I made my own. It is a single probe though which is kind of a pain switching between tubes to strike an average setting. But it works. I'm thinking about ordering a "real" one.
If I find the website, I'll edit this post.

hoffman has info and sells the stuff to make it.

Cam · December 15th, 2003, 01:08 AM

Thanks for the reminder. I did this:
http://www.hoffmanamps.com/biascurrent.htm

Except I didn't use an old tube base. I had both the mail and female sockets and soldered the wires as in the diagram and used a pcv tube to separate them.

jazzguitar · December 15th, 2003, 03:36 PM

I don't like them. You unplug the tubes, plug in the device, do your whatever, unplug the device and reinsert the tubes. I rather do the measurements inside (using the transformer voltage drop method) which is more precise and does not wear the tube sockets.

But to each his own, and the bias gadgets are pretty good for people who don't like to work near wires charged with 400V.

11 Gauge · December 15th, 2003, 03:38 PM

I'm fairly pleased with it. The literature is fairly decent and can sometimes serve as a first aid kit if you're working with tubes that you are unfamiliar with.

I've got the model that lets you toggle between 1 of 2 power tubes, so you can check your match on the fly.

My gripe with this unit? The parts of the gizmo that install in between the socket and tube are quite beefy - LARGER than the base of the tube. as such, you can run into clearance problems, and most tube retaining mechanisms have to be removed (i.e. most Fender amps, where the tubes hand down and require something to keep them from falling out).

It's great with amps that are biased hot though, as I can periodically check up on things to make sure everything's okee dokee...

eryque · December 15th, 2003, 04:48 PM

can pulling out the tubes a coupla times really cause that much wear? i prefer to open the thing up as well, but just because i know how to do it and i'm too cheap to buy a bias probe.

Cam · December 15th, 2003, 06:35 PM

11 Guage, I figure the next time I go to bias, I will sit my fender amps upside down to do it.....easier to see and find the bias pot plus any fallout of tube is prevented.

WrapAround · December 15th, 2003, 11:32 PM

I use a BiasRite from WeberVST. Alternatively, resistors can be installed so that you can measure it at pin-8 to ground. I'm just too lazy to do that to my amps. ;)

Teleologist · December 16th, 2003, 09:55 AM

I do it the dangerous way, but I'd suggest a probe you use with a DMM. You're going to need one anyway if you plan to do anything beyond simple re-biasing. If you need a DMM, Fluke's are expensive but are 'lifetime' type tools. The models that can measure capacitance, check diodes & transistors, and measure True-RMS AC are especially usefull.

11 Gauge · December 16th, 2003, 01:06 PM

I got a new one a couple years back and the prices have really come down - mine was under $200 and does even more than I need it to.

If you work on amps a bunch you really owe it to yourself to buy a Fluke. In a matter of minutes i can check voltage, amps, capacitance values, resistance values, and even diode polarity within any particular project. I really love being able to check caps - often times their value is not listed. Or the value may have drifted or not even be anywhere close to what it is suppossed to be.

Any ampmeister should own a Fluke or something similar.

Rob (PA) · December 16th, 2003, 04:25 PM

Good point about the kind that hooks right to a VOM. I have a couple Flukes in my pile of tools for work (an 87 and an 85III) plus the old Simpson 260. I never even thought to try reading it that way- I saw a couple on eBay from SRS, theirs take your own VOM. Looks as though thats the way I'm gonna go. Thanks again folks!

Rob (PA) · December 16th, 2003, 04:26 PM

Good point about the kind that hooks right to a VOM. I have a couple Flukes in my pile of tools for work (an 87 and an 85III) plus the old Simpson 260. I never even thought to try reading it that way- I saw a couple on eBay from SRS, theirs take your own VOM. Looks as though thats the way I'm gonna go. Thanks again folks!

December 14th, 2003, 10:31 PM	#1 (permalink)
Rob (PA) TDPRI Member Join Date: Apr 2003 Location: Embreeville PA (West of Philadelphia) Posts: 10	Lets talk bias tools. Ok tuners, lets discuss bias probes (I guess that's what they are called) I am starting to work on my own amps, and I need to get a pair for working on the various Fenders and 122/147 amps I have been previously farming out. What's the general consensus out there on what type I should get? As always, thanks in advance!

December 14th, 2003, 10:56 PM	#2 (permalink)
Lyle Caldwell Tele-Holic Join Date: Mar 2003 Posts: 535	Weber makes a good'un. www.webervst.com __________________ "Everybody sings about Memphis, but nobody ever does anything about it."

December 14th, 2003, 11:28 PM	#3 (permalink)
JDO Tele-Holic Join Date: Mar 2003 Location: Pittsboro, NC Posts: 603	that's what i use. i'm cheap so i just got the one that you plug into a meter. if i had it to do over again, i would get the bias rite with all the options. it would just be easier. __________________ clean as a whistle

December 14th, 2003, 11:44 PM	#4 (permalink)
Cam Tele-Afflicted Join Date: Mar 2003 Location: Snow Piles Alberta Canada Posts: 1,022 7 Photos	Home made job I can't remember what web site I pulled the info from, but I made my own. It is a single probe though which is kind of a pain switching between tubes to strike an average setting. But it works. I'm thinking about ordering a "real" one. If I find the website, I'll edit this post. __________________ Relic Schmelic! Play the darn thing! Wipe it down after and put it in it's case!

December 15th, 2003, 01:08 AM	#6 (permalink)
Cam Tele-Afflicted Join Date: Mar 2003 Location: Snow Piles Alberta Canada Posts: 1,022 7 Photos	Yeah Hoffman that was it: Thanks for the reminder. I did this: http://www.hoffmanamps.com/biascurrent.htm Except I didn't use an old tube base. I had both the mail and female sockets and soldered the wires as in the diagram and used a pcv tube to separate them. __________________ Relic Schmelic! Play the darn thing! Wipe it down after and put it in it's case!

December 15th, 2003, 03:36 PM	#7 (permalink)
jazzguitar Tele-Meister Join Date: Mar 2003 Location: Germany Posts: 280	I don't like them. You unplug the tubes, plug in the device, do your whatever, unplug the device and reinsert the tubes. I rather do the measurements inside (using the transformer voltage drop method) which is more precise and does not wear the tube sockets. But to each his own, and the bias gadgets are pretty good for people who don't like to work near wires charged with 400V.

December 15th, 2003, 03:38 PM	#8 (permalink)
11 Gauge Friend of Leo's Join Date: Mar 2003 Location: The East Coast Posts: 3,091 10 Photos	I've got the Bias King I'm fairly pleased with it. The literature is fairly decent and can sometimes serve as a first aid kit if you're working with tubes that you are unfamiliar with. I've got the model that lets you toggle between 1 of 2 power tubes, so you can check your match on the fly. My gripe with this unit? The parts of the gizmo that install in between the socket and tube are quite beefy - LARGER than the base of the tube. as such, you can run into clearance problems, and most tube retaining mechanisms have to be removed (i.e. most Fender amps, where the tubes hand down and require something to keep them from falling out). It's great with amps that are biased hot though, as I can periodically check up on things to make sure everything's okee dokee... __________________

December 15th, 2003, 04:48 PM	#9 (permalink)
eryque Poster Extraordinaire Join Date: Mar 2003 Location: albany, ny [not chicago] Posts: 7,241 44 Photos	can pulling out the tubes a coupla times really cause that much wear? i prefer to open the thing up as well, but just because i know how to do it and i'm too cheap to buy a bias probe.

December 15th, 2003, 06:35 PM	#10 (permalink)
Cam Tele-Afflicted Join Date: Mar 2003 Location: Snow Piles Alberta Canada Posts: 1,022 7 Photos	Upside down.... 11 Guage, I figure the next time I go to bias, I will sit my fender amps upside down to do it.....easier to see and find the bias pot plus any fallout of tube is prevented. __________________ Relic Schmelic! Play the darn thing! Wipe it down after and put it in it's case!

December 15th, 2003, 11:32 PM	#11 (permalink)
WrapAround Tele-Holic Join Date: May 2003 Posts: 804 14 Photos	I use a BiasRite from WeberVST. Alternatively, resistors can be installed so that you can measure it at pin-8 to ground. I'm just too lazy to do that to my amps. ;)

December 16th, 2003, 09:55 AM	#12 (permalink)
Teleologist Tele-Meister Join Date: Nov 2003 Location: Chicago Posts: 382	I do it the dangerous way, but I'd suggest a probe you use with a DMM. You're going to need one anyway if you plan to do anything beyond simple re-biasing. If you need a DMM, Fluke's are expensive but are 'lifetime' type tools. The models that can measure capacitance, check diodes & transistors, and measure True-RMS AC are especially usefull. __________________ Keep on Twangin'

December 16th, 2003, 01:06 PM	#13 (permalink)
11 Gauge Friend of Leo's Join Date: Mar 2003 Location: The East Coast Posts: 3,091 10 Photos	More on Flukes- I got a new one a couple years back and the prices have really come down - mine was under $200 and does even more than I need it to. If you work on amps a bunch you really owe it to yourself to buy a Fluke. In a matter of minutes i can check voltage, amps, capacitance values, resistance values, and even diode polarity within any particular project. I really love being able to check caps - often times their value is not listed. Or the value may have drifted or not even be anywhere close to what it is suppossed to be. Any ampmeister should own a Fluke or something similar. __________________

December 16th, 2003, 04:25 PM	#14 (permalink)
Rob (PA) TDPRI Member Join Date: Apr 2003 Location: Embreeville PA (West of Philadelphia) Posts: 10	Good point about the kind that hooks right to a VOM. I have a couple Flukes in my pile of tools for work (an 87 and an 85III) plus the old Simpson 260. I never even thought to try reading it that way- I saw a couple on eBay from SRS, theirs take your own VOM. Looks as though thats the way I'm gonna go. Thanks again folks!

December 16th, 2003, 04:26 PM	#15 (permalink)
Rob (PA) TDPRI Member Join Date: Apr 2003 Location: Embreeville PA (West of Philadelphia) Posts: 10	Good point about the kind that hooks right to a VOM. I have a couple Flukes in my pile of tools for work (an 87 and an 85III) plus the old Simpson 260. I never even thought to try reading it that way- I saw a couple on eBay from SRS, theirs take your own VOM. Looks as though thats the way I'm gonna go. Thanks again folks!