08/2000 : "Chatter Fix" [1] [2] [3] [4] ---[1]--- Yeah, good posts. The problem isn't with 2.0 per se - it's version 1.2 or 1.3 that needed a resistor change to the hardware to accompany the software. Anyone upgrading from 1.3-1.5 up to 2.0 should be fine. Going from 1.1 (or possibly 1.2) up to 2.0 requires the resistor change. Way to be on top of this, guys! John Fera (PEAVEY) ---[2]--- Hi all, I was able to fix the "chatter" problem in my Tubefex last night. Combined with the new v2.0 update that I've already installed, I have what seems like a brand new processor! I'm very impressed, not to mention extremely happy!! The fix for my unit was very simple, and I'll be glad to share my experience. Hopefully it will help some other TubeFex owners with the "chatter" problem. First, let me mention I have an older unit that came with v1.1 firmware. With that version I wasn't getting the "chatter." But, when I installed the new v2.0 upgrade chip the problem began. John Fera has already explained that a software change had been made to change the control of the motor/pot. Anyway, I called Peavey parts department yesterday to get a schematic. While talking to Nate in parts, I asked him if there was a motor/pot kit to fix the problem. He passed me to Gene in the Service department. Gene was kind enough to explain the "big secret" to the fix over the phone. Thanks Gene!! It's simply a matter of changing out one resistor! If you feel comfortable with working on your own unit, I'll explain the process. On the other hand, if you are not familiar with working on PCB's and doing clean soldering jobs, do yourself a favor and take it to a qualified technician. Also, you'll have to do some disassembly to get to the bottom of the board to solder. The part certainly won't cost much, and the labor shouldn't be much. A qualified technician should be able to perform the modification within a half hour. So, here's how to accomplish the task: First, locate the resistor in question. To do so, take the top off of the unit and have the front facing you. Look over near the right/front of the circuit board. Locate the (3) large capacitors. These are parallel (vertical) and glued to one another. From the middle capacitor, follow straight down (toward the front). You should see a diode and then (2) resistors all in parallel (horizontal) to each other. The resistor in the *middle* is the one to change out. Change that resistor to a 1/4 watt 1.3k ohm. The existing one should be a 1.8k ohm. If you have a unit that you bought used, you might want to check first to see if the resistor change has already been made. It'll save you some time and trouble. Also, if you have the 1.3k ohm already installed, then there is something else wrong with the unit. Time to take it to a technician. Unfortunately the bottom of the TubeFex doesn't come off. So, you'll have to attack the situation from above. You may wish to remove your tubes before starting so they don't get damaged. Remove all screws from the bottom. These hold the circuit board to the case. Remove the screws located on each side of the back of the unit. There are (2) on each side. Remove the (2) screws/nuts holding the heatsinks on the right/front side. Unplug all of the ribbon connectors and pull all of the knobs off of the front pots. You should now be able to *carefully* pull the entire circuit board up from the back to get underneath. If the board doesn't come up easily, you've missed a screw somewhere. Double check and try again. Do not force the board. It should come up with little resistance. Anyway, there are two short wires (red and black) that are soldered to the board and to the front display unit. You'll have much better and easier access to the bottom of the board if you unsolder these two wires from the main circuit board. Be certain to remember what order they were in, so you can solder them back properly when done. Carefully remove the old resistor from the board and solder in the new 1.3k ohm. Take your time, and do a clean solder job! Now, reverse the procedure to put the unit back together. Make sure you resolder the red and black wires, plug all ribbon cables back, and get all screws back in place and tightened. That's it! Turn the unit on, and hopefully you'll have the same results I did. If you're fairly proficient and comfortable with working on electronic equipment, it shouldn't take much more time to actually perform the procedure than to read the above explanation. I hope this helps some of you. Good luck, and please post your results here when you've done the modification. ---[3]--- I dug up 2 quotes from Service, for what it's worth: "The earlier versions of software in the Tubefex were written so the motorpot normally did not have to travel far from preset-to-preset....it would pretty much stay in the same spot. The newer presets in 1.3 and above made the pot swing more severely.....also the PID controller for the motor was changed a bit to allow for these extreme position changes. Replacing the belt on the motorpot assembly requires complete disassembly of the part....you must bend the tabs holding the metal to the phenolic board, remove the motor, carefully remove the slider shaft which also includes the wipers.....string the belt into place, then re-assemble this entire thing while hoping the belt stays put long enough and hoping the tabs will bend back into place tight enough so there is not slack or slop in what needs to be a tight mechanism.....attempts to do this have resulted in replacing the assembly anyway. One other thing.......since the older spoftware kept the pot pretty much in one spot, the rest of the carbon trace never really gets used......it oxidizes just like any other pot does with age. I have fixed many of these units over the phone by suggesting the customer spray the pot with a deoxit like Cramolin Dn5 or "Tweak"......then run the pot back and fourth a few times......does the problem go away? As far as the claim that removing the "plastic shroud" off the end of the motor......this is there to actually assist in keeping tension on the belt and keeping it from jumping off the gear.....removing it would make no difference." "...the motor pot does not need to be replaced with the newer softwares above 1.2....HOWEVER a resistor change must be made. The customer must check R1431 towards the front of the unit by the motor control IC. It must be a 1.3kohm resistor....if it isn't, then a 4.7k resistor must be paralleled across R1431. If the change is not made, the motor pot will go nuts when presets are changed. As far as offering the update overseas, that is a yes.....Peavey UK has been waiting for a while. One word of warning....if someone has used their Tubefex for quite a while and THEN upgrades to 1.5 or whatever, the belt on the pot goes through quite a shock with the newer version (it has to travel farther and faster for some of the presets). Sometimes the wear on the belt is too much, and the "chattering pot" syndrome will occur......the only option here is to change the entire assembly." John Fera ---[4]--- A 1.3k ohm resistor will have a color code of: Brown, Orange, Red with a Gold tolerance band indicating 5%. Ray