Thank you for accepting my request to join. I'm a Newbie with a 15 year history of lurking around here at the forums. Glad to finally make my first post! This is my '79 Session 400 that I purchased 'used' back in 1984 at Guitar Resurrection in Austin, TX. I needed a loud budget amp for my electric guitars; and this has been my goto amp ever since. It's been everywhere with me including my most recent 23 year stint in Japan.
Read about Brad Sarno's Session 400 mods and Ken Fox's kits here at the forums fifteen years ago. Ordered all the parts from Mouser and had it shipped to Japan. However just as I was preparing to apply the mods, my amp blew during a thunderstorm. Wasn't able to devote the time I needed to repair the amp and apply the mod until my recent retirement. Devoted some time to troubleshooting the amp and applying the mods. Troubleshooting took a while (I'm not an amp tech and my only electrical skills are using a multimeter and soldering) because everything was testing fine according to my multimeter. Long story short, I replaced all the TO-92, TO-220 transistors, one ceramic disc capacitor on the power PCB, and one TO-3 transistor on the rear panel. Also, disassembled, cleaned, and re-greased all the potentiometers.
Just finished taking my Session through the paces; and WOW! 15 years is a long time to wait, but I don't remember this amp sounding this good! A powerful amp with an amazing voice. Whether I'm playing single-coil, humbuckers or P90s the Session 400 really delivers. I've also found with some tweaking, my acoustic electrics even sound amazing through this amp!
Although the new power caps (10,000uF/63V) have a smaller footprint than the original 6,000uF/45v they really improve the amps headroom. I also found that the bass signal cleans up considerably for electric guitar when C6's value is 2.2uF/35V instead of the original value of 22uF/25V. Finally, one of the concerns I've always had with this amp is that the power PCB is secured with screws in each of the 4 corners. At volume, the power PCB flexes and vibrates quite a bit making cracked solder a real serious issue. There used to be some foam sponge under the power PCB (to prevent vibration?); but I found some white edge mount PCB clips at Amplified Parts; and secured the power PCB with two clips.
So my Session 400 sounds the best it's ever sounded and I can't be more pleased with the results. Just love the discrete component circuitry of these amps. It's such an elegant, versatile, and sensitive amp with a beautiful voice! I would have been completely lost had it not been for the wealth of information available here so thank you very much Steel Guitar Forums, Brad Sarno, and Ken Fox for being such a helpful resource!
KenO
