Lesser known PV rock amp Peavey Valve King 100. Everyone always thinks of 5150 and Butcher. Strangely they chose to call it a VALVE King which is the name a European person would typically use for TUBE. This one has done the rounds so many times it eventually needed new power valves/tubes and a burnt screen grid resistor replaced.
Screen grid resistors are located under power amp PCB (right) so you have to remove the board and some of the back panel stuff to get it out. VK100 has a strange value of screen grid resistor, 330 ohm. Most screen grid resistors for power tubes tend to be in the 470 ohm to 2.2K range. Anyway one screen grid resistor was burnt and not wanting to mix and match and not having any 330 ohm in stock I decided to replace all four with 470 ohms which is the most standard value chosen for 6L6GC power tube anyway. Much to my surprise the customer said it sounded way different. Not in a good way! He said it sounded “bad” and “thin” with “weak palm mutes,” so typically not what you’re looking for in a Valve King, especially knowing this player! I ordered up some 330 ohm / 5W and he was happy as can be. In some amps it’s a good idea to up 470 ohm screen grid resistors to 1K or 1.5K so it is not so punishing to the power tubes (V4) and I think there is not really much of a noticeable sound difference. What a surprise with the VK100, or maybe the player just really knows his tone. PV ValveKing100 schematic and parts list supplied by Peavey because they are so great with their product support.