Post by yoder on Feb 13, 2015 14:39:00 GMT -5
SE-160 MK1 DYI UPGRADE TO PREVENT TURN ON/OFF THUMP
Note: The modification below requires using potentially dangerous voltages. In making the modification you agree to assume liability for any damage or injury resulting from exposing yourself, others, or pets to this high voltage hazard. If you do not feel that you possess the skills, knowledge, or common sense necessary to safely make the modification, then DO NOT ATTEMPT TO MAKE THE MODIFICATION.
The text below describes the modification and the desired results. This PDF will provide you with step-by-step instructions and has detailed photos for more clarity. (Please be patient as the PDF downloads...it takes a little time with all of the images despite being optimized.)
Several have noticed that power cycling the amps can lead to large cone excursions. Below is an effective and simple solution that doesn’t require taking the PCB out:
STEPS
1) solder a 22k ohm resistor across the leads of a 4700 uF cap (16V or 35V electrolytic, available at Radioshack etc.)
2) Connect this 4700 uF caps POSITIVE lead to right leg (right, as viewed from the front of the amp) of the 12V zener ("12V") (other side than the transistors are on) and connect the NEGATIVE lead to the ground leg of the LED ("LED", leg towards the rear).
See pink arrows in the picture below.
RESULTS:
Adding a 4700 uF cap across C23 (330uF, 16V) gives:
30 sec delay from POWER ON to connecting speaker, 9 sec from POWER OFF until disengages speaker. Adding a 22kOhm resistor (1/8W or higher) across these caps for rapid cap discharge to get: 36 sec delay from POWER ON to connecting speaker, 2.5 sec from POWER OFF until disengages speaker.
Do not use smaller R than 22k as it may never reach the 12.5V to disengage the relay.
Larger than 22k will reduce the benefit of speedy discharge.
This R ensures that when amp is turned off and back on there won’t appear any serious DC at the speakers. This way no serious cone movement is ever seen, except a slight one ~1 sec at turn off or during rapid power cycling.
Submitted by: Justus V Verhagen
More mods at: co-bw.com