Okay, this is a very late update, but definitely not insignificant!

NickMattocks: I'm part of the (I've learned this about myself throughout the years) type of musician that likes to help out other fellow musicians in need, hence my update here; meaning, I have excellent gear, vintage and modern alike. If I have a friend who's in need and I have the means to help him out, then you can bet I'm gonna do whatever I can to help out! Since he had a wedding gig in Vegas, instead of loaning him my Hughes & Kettner TriAmp half stack --- which is a pain in the butt to lug around, or having him go direct into the PA, I programmed my Flextone for the type of tones he was gonna be working with, and voila... he was set!

Now, I haven't used my Flextone in over a year because I've been playing bass or gigging with my H&K guitar rig, but a few "Blues Night" gigs have been popping up lately and I thought it was time to pull out the leaf blower and blow the two-inch thick skin of dirt off my old girl and open her up to start troubleshooting. I checked both Celestion’s against another amp and those sounded fine – no crackling whatsoever --- next up was to replace the output IC’s. Check this out - I also came across the following Service Bulletin for the pre-2000 Flextone's…

Indications: Amplifier cuts out after a few minutes of high volume use.

Part Numbers affected: 30-51-6063 (output amp heat sink) and 12-30-3886 (output device)

Tools/Supplies Required: #2 Phillips screwdriver, heat sink compound

Repair Procedure

• Remove the (4) chassis screws on the top of the amplifier.
• Remove the (2) handle screws.
• Disconnect the speaker leads, remarking the location the leads
• Remove the (2) screws on the bottom of the chassis
• Remove the nuts on the 1/4" phone and the effects send and return jacks
• Slowly pull the bottom plate of the chassis off and when it pulls away, reach in and pull the ribbon connector from the main board.
• Look at the amplifier IC and see if the screw holding the output IC to the heat sink is in straight. If it is you can loosen the screws on the bottom of the heat sink and tighten the screw to 10-12 in lbs. If the screw is not straight, you may need to replace the heat sink. Also be sure that there is sufficient heat sink compound on the back of the IC. It should cover the back but not ooze out when the IC is secured tightly.
• Reassemble the unit

I figured if I was gonna be deep in and pulling out the main board and heat pasting both IC’s, I might as well replace ‘em both just to be on the safe side. Well, turns out, as I stated in my initial post, I was right (I sure do love patting myself on the back when I deserve it). I replaced both IC’s and I was back in business. I’ve seen forum posts using keywords such as Line 6 Flextone... “left channel noise” or “farting sounds” and “cuts out after 5 minutes” amongst others; so I thought, if there was a Service Bulletin written, then I’m sure my post will help so many people with their combo’s.

This project took me about five hours in total --- but keep in mind, there were laundry loads, smoke breaks, phone calls and visits in between. But it’s a fairly simple job for the experienced tweaker and a not-so-simple job for the soldering rookie! I would imagine this type of job would be in the neighborhood of $75-$120 for a certified tech to replace both amps if you can’t do it yourself; but it’s a super simple procedure. The IC amps I ordered through Digi-Key were $14.60 for the pair and the part# is LM3886TF-ND. I also used some Heat Sink Compound that you can get from Radio-Hack. You don’t need to spread it on thick --- all you need is a razorblade or something equivalent, and smooth it on like if you’re repairing a hole in drywall or leveling some concrete. Wipe off the edges and BOO-YA!

Hope this helps anyone out there with a pre-May 2000 Flextone II.

Musicians helping musicians baby! That’s what it’s all about! Hope I helped!

Thanks for the reply Nick and Andy!

~philthy