Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Swaping preamp boards on JL amps
Swaping preamp boards on JL 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 10th January 2009, 07:28 AM   #1
ItsCustom is offline ItsCustom  United States
diyAudio Member
Join Date: Jan 2009
Default Swaping preamp boards on JL amps

Hi, I accidentally burned one of the preamp boards (with leds on it) on the JL 300/2. I don't have time to find replacement components, I found another JL 300/4 that is willing to donate one of its daughters. After I swap the boars do I have to adjust anything?
  Reply With Quote
Old 10th January 2009, 05:21 PM   #2
1moreamp is offline 1moreamp  United States
diyAudio Member
Join Date: Dec 2005
Location: Northern California
You should check your bias to the outputs. Other then that I am fairly sure you will be OK. There is a two pin jumper style plug on the board for each channel a simple comparison with a voltmeter is a good start. I like to O-scope the outputs on all channels just for good measure keeping a eye out for crossover notch distortion.

And unless your good to excellent at de-soldering the daughter board will be difficult to remove, and you could damage the main board thru-holes if your not careful. Its simpler to just cut out the old board then remove the header pins one by one safely. I cut the right angle as the pins bend over and go into the daughter board. This will ease the pin removal and reduce your chances of damaging the thru-holes on the double side main board. I have seen many boards damaged by others and its not a pretty sight, and it can pretty much trash the amp if your not careful....That's about it, Good luck on your project....
  Reply With Quote
Old 11th January 2009, 01:16 AM   #3
Perry Babin is offline Perry Babin  United States
diyAudio Member
Join Date: Nov 2003
Location: Louisiana
ChipQuik ...

The best thing since sliced bread.

You'll never damage another via (almost guaranteed).

If you use it, apply the flux liberally and use a length of the CQ alloy about 3/4 the length of the row of pins. Run the iron with the CQ along the pins to distribute it evenly. After it's distributed, place your iron's tip on top of each header pin and gently move the pin around in the through hole. This will work the alloy down into the via.

Run the iron back and forth along the pins (without EVER touching the board or pads). This will heat all of the pins at once. With a relatively hot iron (~750F), the pins will pull free with essentially no force after about 6-10 pass of the iron along the pins.

If you can't quite get them all hot enough at once, use a heat gun to preheat the board. This will help prevent board from soaking so much heat from the pins.

After using the alloy, you must remove as much of it as possible. Desolder the pads and pins. Add new solder and desolder once again.

I agree, the bias will probably need to be adjusted. Since JL doesn't publish the recommended voltage across the test points, measure the voltage on the other 3 channels and set the 4th channel to match. Don't try to measure from the top of the board, there's too great a risk of shorting to the busbars. Measure the voltage from under the board.
  Reply With Quote


Swaping preamp boards on JL ampsHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Tube Preamp Popping on Source Input Change (?) / 6DJ8 Preamp On Chip Amps Travis Clarke Tubes / Valves 3 16th October 2008 04:52 AM
ZV9 boards and preamp colonelkernel8 Pass Labs 7 8th August 2007 09:15 PM
Group buy on parts boards for amps, ps gearheaddruid Group Buys 0 26th May 2006 01:36 AM
new to speaker swaping...help mickyb Multi-Way 3 8th March 2004 08:49 PM
Circuit boards For Aleph amps labjr Pass Labs 16 10th May 2003 03:11 AM

New To Site? Need Help?

All times are GMT. The time now is 04:11 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio