Bias pot mounting for plexi and JTM 45

Info for maintaining and tweaking your amp to perfection.

Moderator: VelvetGeorge

Post Reply
User avatar
VelvetGeorge
Site Owner
Posts: 7220
Joined: Tue Oct 14, 2003 5:12 pm
Just the numbers in order: 13492
Location: The Murder Mitten
Contact:

Bias pot mounting for plexi and JTM 45

Post by VelvetGeorge » Wed May 23, 2007 12:03 pm

Thought I would share how I've been mounting the bias pots lately. It's a little more secure.

I bend the rounded tabs out to the side and solder them to the top of the bias circuit ground terminals.

One pointed contact goes to the bias cap lead and the other gets a 47k-68k resistor as normal.


george
Attachments
bias pot wiring.jpg
bias pot wiring.jpg (72.5 KiB) Viewed 16064 times
Check out Plexi Replicas for my personal amp builds...
Image

User avatar
Joe Popp
Senior Member
Posts: 302
Joined: Tue May 29, 2007 9:13 pm

Post by Joe Popp » Thu May 31, 2007 9:04 am

George:

What is the red stuff on your solder joints? Nail polish to prevent corrosion? Or is it some super solder paint?

Loving the site and the parts you just sent!

User avatar
guitar007
Senior Member
Posts: 1154
Joined: Thu Nov 10, 2005 8:28 pm
Contact:

Post by guitar007 » Thu May 31, 2007 12:12 pm

Joe Popp wrote:George:

What is the red stuff on your solder joints? Nail polish to prevent corrosion? Or is it some super solder paint?

Loving the site and the parts you just sent!
Yeah...what's it called and where can we get it. 8)
~guitar007

User avatar
Joe Popp
Senior Member
Posts: 302
Joined: Tue May 29, 2007 9:13 pm

Post by Joe Popp » Wed Jun 06, 2007 6:28 am

Aha!! found it

The infamous Red Sharpie! I'm new and catching up on all of the old threads...

Wallace
Senior Member
Posts: 182
Joined: Sun May 21, 2006 4:04 pm
Location: London, England.

Post by Wallace » Wed Jun 06, 2007 3:48 pm

that looks pretty thick for a sharpie :shock:

stokesdead
Senior Member
Posts: 254
Joined: Fri Jun 16, 2006 11:18 pm
Contact:

Post by stokesdead » Wed Jun 06, 2007 10:23 pm

liquid electrical tape?

Loganp
Senior Member
Posts: 88
Joined: Thu Oct 04, 2007 12:28 am
Location: Burlington, Ontario

Post by Loganp » Sat Dec 15, 2007 9:01 pm

question about this Bias pot. I am at the point of testing all the voltages and final tweaking of my amp and bias. Should i solder the bias resistor and pot on now then tweak it as needed. or wait till i test all the voltages and am actually ready to set the bias?

User avatar
toner
Senior Member
Posts: 2582
Joined: Sun Dec 03, 2006 7:57 pm
Location: Iowa

Post by toner » Sat Dec 15, 2007 11:33 pm

Solder every connection before turning the amp on.

User avatar
mjbrown
Senior Member
Posts: 68
Joined: Fri Aug 24, 2007 12:57 pm
Location: Little Rock, AR

Re: Bias pot mounting for plexi and JTM 45

Post by mjbrown » Mon Oct 27, 2008 12:29 am

The red stuff is what Marshall used starting in 1968 and onwards for Quality Control on the solder joints (I believe)
I think the closest equivalent to this today is Glyptal (this is what high-performance
engine builders coat the porous cast iron inside engine blocks for better oil flow/circulation.)
Just do a search for it.

User avatar
chubs
Senior Member
Posts: 701
Joined: Tue Feb 20, 2007 8:23 pm
Location: Near Ottawa, ON Canada

Re: Bias pot mounting for plexi and JTM 45

Post by chubs » Mon Oct 27, 2008 9:17 am

Actualy... I asked George not too long ago and his answer was:

""Red Insulating Varnish. Like they use in alternators and motors.
I get it from Allied.
VG""

User avatar
syscokid
Senior Member
Posts: 619
Joined: Mon Oct 27, 2008 2:25 pm
Just the numbers in order: 13492
Location: Groovy Beach, CA.

Re: Bias pot mounting for plexi and JTM 45

Post by syscokid » Mon Jun 01, 2009 10:29 am

chubs wrote:Actualy... I asked George not too long ago and his answer was:

""Red Insulating Varnish. Like they use in alternators and motors.
I get it from Allied.
VG""
What happens when you have to R&R a component with this "varnish" on the solder?
"When I'm on stage and first plug in, and I feel a rush of air in my balls... That's when I know my guitar is sounding good!" -Leslie West

User avatar
Structo
Senior Member
Posts: 1219
Joined: Mon Jun 08, 2009 7:07 pm
Just the numbers in order: 7
Location: Salem, Oregon

Re: Bias pot mounting for plexi and JTM 45

Post by Structo » Fri Jun 19, 2009 1:33 pm

I just use a red sharpie.

The purpose for me to do this especially when I get a customers amp in is to inspect the solder joints.
As I move through the amp I color the tops of the joints, that way I know I have looked at it.

Plus it looks cool as hell and when the customer sees it I tell them that is for quality assurance and means I have thoroughly checked through the amp. 8)
Tom

Don't let that smoke out!

wrea398
Senior Member
Posts: 649
Joined: Thu Nov 26, 2009 10:06 am
Just the numbers in order: 7

Re: Bias pot mounting for plexi and JTM 45

Post by wrea398 » Sun Dec 20, 2009 7:39 am

The original stuff is called "Glyptol". It's made for just this kind of "anti corrosion" use. It is red insulating varnish. You can get it on the web or a good electrical shop. The original stuff is more transparent and rustier in color.

Twistingcrow
Senior Member
Posts: 312
Joined: Tue Nov 25, 2008 8:48 am

Re: Bias pot mounting for plexi and JTM 45

Post by Twistingcrow » Sun May 20, 2012 9:04 am

wrea398 wrote:The original stuff is called "Glyptol". It's made for just this kind of "anti corrosion" use. It is red insulating varnish. You can get it on the web or a good electrical shop. The original stuff is more transparent and rustier in color.
It's actually called "Glyptal", with an "a" instead of the "o"... But any efficient search would have found it anyway... Pretty tough to find though, especially in the EU...

maxwedge572
Senior Member
Posts: 117
Joined: Mon Jun 28, 2010 12:10 am
Just the numbers in order: 7
Location: Concord, Ca USA

Re: Bias pot mounting for plexi and JTM 45

Post by maxwedge572 » Mon Feb 10, 2014 1:13 pm

This too funny! :lol:
I've had a quart of unopened Glyptal for about 35 years! I used to be into hot rodding and they used to paint the valley area (where the cam and push rods are) of V8 engine blocks with this stuff because it was really slippery. The oil would drain back to the pan faster.

Is this what they really used? I think that this what I have is a bright red and the marshal stuff looks much darker. I haven't tried to look but maybe they have different tints.

Image
Scott

Post Reply