SVT-CL volume fluctuates while using -15dB input.

[L_Roy_Saint]

SVT-CL volume fluctuates while using -15dB input.  All tubes test ok.  Volume will either start at a lower volume and sudedenly jump after 20-30 minutes use or start high and drop by about half.  This repeats itself.  Sound familiar?

[PRR]

> while using -15dB input.

Dirty jack, bad solder joints on jack and resistors, bad resistors.

[L_Roy_Saint]

Thank you.  I will check it out.

[L_Roy_Saint]

SUCCESS!
The problem was the 0db input jack.  The two leads which make contact when the jack is vacant weren't making proper contact, causing the preamp to operate in unbuffered mode.  I cleaned the contacts thoroughly with alcohol and verified their continuity with a DMM.
While I had the preamp out of the unit I noticed alot of flux on the bottom of the pcb.  I cleaned this as well.