Welcome! Need support, you got it. Or share youe ideas and experiences.
Return to K&K Audio / Lundahl Transformers
67.103.29.164
In Reply to: RE: R115 on Maxxed Out Board posted by KevinC on December 09, 2012 at 09:10:05
I can bias the right channel @1.8 VDC, but the left seems stuck at 2.4 VDC or higher no matter which way I turn the trimmer. I have tried with a few sets of tubes with same results. How do I use the battery to test the CCS? I have Rev 3 board with an additional upgrade from you from a few summers ago with involved another set of CCS's
Follow Ups:
Remove the tube from the socket. Assuming your DVM has a DC current measuring capability, set it up for the mA DC range. The - battery or PS terminal should be connected to the end of C112 closest to the heat sink. The red DVM probe needs to be connected to the + battery terminal and the black DVM probe connects to the end of C111 closest to C112. You should read the current passing through the CCS directly on the meter at this point and be able to adjust it. The 9V battery doesn't provide enough voltage for a really precise adjustment, but will do for your diagnostic purposes.
Kevin Carter
K&K Audio
www.kandkaudio.com
OK I did this with a 9v battery. Trimmer R115 indeed did adjust the mA DC from about 5 to 40 so I guess the trimmer works. What does this say about the CCS and why this channel won't balance? What is the next step?
Any joy?
Kevin Carter
K&K Audio
www.kandkaudio.com
I kept getting bizarre readings whether checking mA Dc with the battery or V DC with the tube installed. It would read different with and without the screwdriver touching the trimmer's adjust screw or simply just up and down in values for no reason. I changed the trimmer and now it seems to hold bias correctly at 1.8 V DC. I have not had time to reinsert it into my system, but will do so tomorrow morning. If you do not hear from me, assume it makes joyous music. If not, I will respond again. Happy holidays!
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: