As someone who's captivated with small tube amps, I recently purchased a previously owned Fender 600, supposedly with some minor problems. After getting it home and plugging it in, I couldn't really find any specific issues. Seemed to play fine, just seemed a bit lame. At wide open volume I got a bit of grit out of it, but it clearly it's a candidate for some mods from stock! In this thread it's my plan to document my approach to changing this thing from its existing ho-hum stature to a respectable little screamer. As this is NOT a 'sky's the limit' project, I'm setting a few basic limits. First, the 'iron' in the amp will stay! No new Power or Output transformers to be used. This means sticking with a 4 ohm speaker. Second, no 'added' transformer for purposes of adding a tube rectifier! If found necessary for 'noise' reasons, a small choke might be added, but the SS power supply rectifier stays. Finally, its got to all work within the confines of the original chassis and cabinet. So, as I plan my attack on the amp itself, my first modification was to address the cabinet, as well as the 6" speaker. In that regard, I decided to shoe-horn in an 8" speaker, which took a bit of creativity. For starters, the original baffle board had to go. A trip to Home Depot produced a small piece of 3-ply 3/16" plywood for all of $4. A quick zip with a circular saw and I cut it to the roughly 10" X 6.5" dimensions that matched those OE baffle. I placed it into the cabinet and traced the opening area, then cut it out. I also marked the 4 mounting holes for drilling. Because the speaker mounting screws had to come from the front of the new baffle, I then glued a front frame using bands of paint stirring sticks. I then did some test fitting! This test fitting revealed the need to have to make a slight modification to the cabinet itself. Basically I had to cut out about 1/2" of the bottom of the cabinet at the inner front. This allowed me to drop the new speaker in about 1/2" lower than the current bottom of the cab. This provided the needed clearance at the top of the speaker to the amp chassis. As to the new baffle board, once all measured up, holes got drilled to mount it to the cabinet, as well as install the speaker mounting screws. Those were set into the baffle using some JB Weld. That will hold them firmly when tightening the nuts that hold in the speaker. I then painted it flat black. Now at the point of affixing the new grill cloth, then mounting the board into the cab, then mounting the speaker. Plan to do that tomorrow. Pictures to be provided then as well. I'll give it a quick test listen, then it will be on to the mods to the amp!!