MaxHart85231281734137 Posted January 11, 2010 Share Posted January 11, 2010 hey guys I recently got given an electroharmonix micro synth guitar pedal( because it is broke and dont work right) and if I can fix it well theres a new pedal for cheap ( hopefully) ...... heres the deal, it powers up fine, LED light is one, and the so called bypass channel works, its kinda a light fuzzy bosted sounding channel, no true bypass on this pedal, the when i push the button to change it to the FX channel of the pedal, there is a lot of loss in volume...and the signal seems to cut in and out..espically when moveing the sliders up and down, some times i can get it to come in but it is very week? does any one here know what that may be? I opened it up and there dosnt seem to be any damage or "fried" wires in there... one more thing I read online and tried is that there is a trim pot? located inside of it, i turned it and it seems to increase the volume of the fx but it cuts in and out when i turn it, there is also an other trim pot located near this one that seems to have no affect at all when i turn it?any experince or ideas? or know of a place that i can send it to get repaired?thanks heres a pic of it Link to comment Share on other sites More sharing options...
cGil Posted January 11, 2010 Share Posted January 11, 2010 Odd that EH has no obvious links on their web menu regarding product repair service! http://www.ehx.com/products/micro-synthesizer But it doesn't hurt to contact 'em direct and ask. info@ehx.com Gil... Link to comment Share on other sites More sharing options...
twanger Posted January 12, 2010 Share Posted January 12, 2010 My first thought whenever volume is cutting in and out and you get that gritty scratchy sound is to get some Caig (NOT Craig!) Deoxit ( http://store.caig.com/s.nl/sc.2/category.188/.f I use the D5) and spray all the pots then slide all the sliders or twist all the knobs a few times each, spray it again then use a paper towel and wipe up the dirt/dribblins then plug it in and see what happens. About 94% of the time this fixes it. It's real good for volume and tone pots on your guitar too! Just don't let it dribble on a nitro finish. If the cleaning doesn't fix the problem then at least you know you have good clean pots! Next to check out will be the simple things because it's always the simple things that will get you. The thing to do here is to double check your cables first and make sure that they are passing signal as they are supposed to. If this does NOT work, repair your cable. If it does work we move on to the next simple thing which is the input jack on the unit. Here you need to check at least 3 things: 1) make sure that your plug is connecting to the correct portions of the jack. You must see it happen with your eyes! 2) make sure that your plug is connecting to CLEAN portions of the jack. If they're not clean...well you know what to do 3) make sure the wires that are supposed to be connected to the jack are indeed connected. If not, solder or make clean terminal connection. Now is where the simple stuff can get tricky. This happens to many cheap 1/4" phone jacks and some good ones - the prong that connects to the tip of your 1/4" phone plug can actually slide just a little bit. To explain this you need to be looking at a 1/4" phone jack. Look at the threaded part where you insert your plug...on the other end of that hole is another hole where the plug comes out and moves toward the final connection point. Look at this hole where it comes out. You will notice a brown wafer. this brown wafer is a phenolic plastic insulator. Wher the prong for the tip of your plug connects to the jack is just under this wafer. On the opposite side of the prong connection is a solder lug or terminal lug.. Visualize it as being straightened out and looking sort of like this: =======O== That "O" near the end is a ring that fits around the hole that your plug is coming through. That hole is not just for the pleasure of your plug...it is also the ground connection. Pretty handy, huh?! If the crimp at the center of the wafer is even the slightest bit loose it will allow that "O" to slide a bit and make a sort of contact with the ground. This kills volume and can ugly noises! Now after all of that explanation you can take the time and test it and all it requires is straight tip screwdriver and a very sharp eye. Put the tip of the screwdriver somewhere on the tip prong, preferably at the bend near the wafer and give it slight push so the prong will slide laterally. If it slides, you have a bad jack. If it does not slide the jack "should be" ok.. If it's a bad jack get out the soldering iron and replace it. If all the simple things check out ok it's time to move on to the slightly more delicate task of pulling the chips and cleaning their sockets and reinserting them. This is a delicate task so DO NOT be in a rush. If the chips are old/dirty this may take a little longer and may require unorthodox methods and bit of gentle (read: GENTLE!) force to remove the chips. Before removing ANY chips do note that there is a mark on each one in a corner. Make a note of this position because the chips need to re-inserted in there proper position. there are special tools for removing and inserting chips and most folks do not have these tools so you must improvise if you do not have them. Typically I use a small straight tip jeweler's screwdriver and a fine jaw set of needlenose pliers. take the screwdriver and slowly and gently wedge it between the bottom of the chip and the plastic block in which the chip is sitting. STOP! If there is no block and the chip is soldered directly to the pc board PROCEED NO FURTHER. Find a qualified repair person or send the unit to EH for repair. If the chip IS in a block proceed with the screwdriver and gently pry up one end of the chip. DO NOT try to pry it out You simply want to get a little lift on one end. Now repeat on the other end of the chip. Now repeat on the first end then the other end as many times as are necessary to get the chip out of the block. Once out, inspect the chip for straightness of the pins/legs. If necessary straighten the legs being VERY GENTLE! While inspecting use your sharp and look for cracks on the chip. Spray some Deoxit in the block and dab up all excess. Now it's time to re-insert the chip. Carefully line up ALL the legs. When you are sure all pins are aligned with their proper holes apply an even, gentle downward pressure on the chip with eithe your finger or the handle end of a screwdriver or similar tool with a suitably large handle end to cover the whole chip. If there is more than one chip repeat until all chips are cleaned and re-inserted. Now clean up your mess and put you tools away have a smoke and get a cup of coffee. this gives the unit a little extra drying time and helps you relax. Plug it all in turn it on and give it a test run. If it works...Rock ON! If it doesn't work you've just eliminated most of the problems inattentive technicians would miss. Now you know that you've done all that you can and you can feel confident that it really is time to send the unit to EH or some qualified technician for repair or replacement of bad chips. Unless you have the necessary meters, scopes and signal generators on hand to test and further diagnose and then repair the unit it's time to send it off to a tech. Considering the age of the unit and the problems you described the above procedures will most likely fix the problem. Good luck with it and let us know if it works! Link to comment Share on other sites More sharing options...
m-theory Posted January 12, 2010 Share Posted January 12, 2010 Here's your schematic: http://files.effectsdatabase.com/docs/schematics/eh_microsynth.pdf Link to comment Share on other sites More sharing options...
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