Pine model 203 Tube Amp - hot chassis grounding question - diyAudio
Go Back   Home > Forums > Live Sound > Instruments and Amps
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Instruments and Amps Everything that makes music, Especially including instrument amps.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 8th February 2012, 01:49 AM   #1
diyAudio Member
Join Date: Feb 2012
Location: Ontario
Question Pine model 203 Tube Amp - hot chassis grounding question

I'm working on an old Canadian made Pine (Paul) model 203 guitar amp that has a hot chassis and am about to install a Triad N-68X isolation transformer. I have studied the circuit and something just isn't making sense to me with regards to grounding. Now I've read "The Plan" website where the guy installs an N-68X in another old guitar amp but still I feel I'm missing something.

To the point...

In the attached picture you can see I have a secondary side live line (yellow arrows) coming off the on & off switch that after a resistor\capacitor combination goes right to the red X on chassis. I have this thought in my head that if I connect the mains ground to the chassis and secondary side's white static wire to the chassis I'm going too make smoke. I've checked continuity from chassis to switch and it's dead but still

Attached Images
File Type: jpg hotpine1.JPG (141.9 KB, 79 views)
  Reply With Quote
Old 8th February 2012, 01:58 AM   #2
kevinkr is offline kevinkr  United States
diyAudio Moderator
kevinkr's Avatar
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Please put a power cord with ground on this amplifier before you use it, and in conjunction with installing your isolation transformer.

There should be no connection between the mains and the chassis once you install the transformer. Connect the line cord hot (black lead) first to a fuse, then the power switch and then one primary lead of your isolation transformer. The neutral (white lead) from the line cord goes to the other primary connection ONLY.

Ground one side of the secondary of your isolation transformer to chassis and the other side goes to the rectifier and filament string. (Connection removed from non line side of the power switch prior to installing the isolation transformer.)

Moving this thread to I&A since it is a guitar amp. Please note the message at the top of the tubes/valve forum.
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
  Reply With Quote
Old 8th February 2012, 03:15 AM   #3
diyAudio Member
Join Date: Feb 2012
Location: Ontario
Thanks Kevin and sorry about where I originally posted this, should have looked up first.

I have it wired like you mentioned, mains hot to a fuse then to a new toggle switch that I mounted in one of the 4 input jack holes. One side of the primary to the new switch, the other to mains neutral. The green is mounted to one of the screws that secures the N-68X to the chassis.

On the secondary side your saying negate the original switch and fuse then connect a line to the chassis and the other to the filament string? This method sounds similar to how the guy that wrote The Plan did it sans the bridge rectifier part.

What about that static shield white wire on the secondary side? What is it's purpose?
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
MR-78 Hot Chassis kman Analogue Source 18 16th March 2009 07:35 PM
chassis grounding question mnr102 Solid State 2 12th July 2008 09:14 AM
Entech 203.2 DC offset question theAnonymous1 Digital Source 3 4th February 2007 01:30 PM
Tube preamp question...also, chassis layout jim_vt Tubes / Valves 1 22nd January 2006 12:01 AM
Jolida tube amp grounding??? kpars Tubes / Valves 4 4th November 2002 10:39 AM

New To Site? Need Help?

All times are GMT. The time now is 01:06 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2