Members tb303orys Posted July 23, 2011 Members Share Posted July 23, 2011 Hi there guys! I recently bought a used Microwave XT and it appears not to be working. I can barely make it sound something on just a patch or two but i am getting a crackly sound. Very awful sound. I opened it up to find out that 1 of the 4 transistors on the bottom board is burned. They 2 are in line. Looking as if they are standing in a queue. The good one is the s170/ph77. The other one is burned completely and I cannot read anything on it just a 9 on the edge. The synth was taken by me to a pro electrician and he needs me to tell him the part number for that transistor. Is there anyone willing to read the markings on there for friendships sake please? I will pay for the info. Just ask a price. There's nothing else i can do. The seller insists that i did this to the synth. It appears he spilled something in the synth long time ago. I really need the service manual or schematics to fix the synth which seem to be impossible to find. I am very very disappointed, gutted!!! Please help me. oratiosh@gmail.com The board is MWMB REV 2.0 LAYER 4. please see photo for transistor identification. Cheers Tio Link to comment Share on other sites More sharing options...
Members realtrance Posted July 23, 2011 Members Share Posted July 23, 2011 That's too dark to see, but it's probably a standard component; Waldorf did not manufacture their own transistors. Just look at the other, non-burned one, gather whatever numbers and info you can for that, and then Google search that info to see what you come up with. Looks like an easy part to replace, fortunately, if that's the only damage. OTOH it doesn't look like any kind of spill on the board so there might be somewhere else in the circuitry that overloaded this transistor, in which case replacing it will just end up with another burned one (cheap experiment to try replacing it, in any event). Waldorf is still in business so you might try contacting them...... Link to comment Share on other sites More sharing options...
Members tb303orys Posted July 23, 2011 Author Members Share Posted July 23, 2011 I found the damaged part.It is BS250/ TO92/ P-FET.Problem is that i cant buy it from over here as none seems to carry it in stock.Any alternative parts?Can someone help? Link to comment Share on other sites More sharing options...
Members tb303orys Posted July 23, 2011 Author Members Share Posted July 23, 2011 OTOH it doesn't look like any kind of spill on the board so there might be somewhere else in the circuitry that overloaded this transistor, in which case replacing it will just end up with another burned one (cheap experiment to try replacing it, in any event). it's pretty clear there was some brown liquid or whatever that left all that brown residue. Link to comment Share on other sites More sharing options...
Members tb303orys Posted July 23, 2011 Author Members Share Posted July 23, 2011 There are modifications that prove that this unit was in trouble before. It appears that mod number 1 is a normal transistor with a metal plate stuck on it. No voltage regulator according to some board photos floating on the net. What about mod 2? That thing is not original as its legs are not soldered though to the other side of the board as there are no holes. Mod 3 is even better. Was that factory made? You can even see on the back which parts have probably been already replaced due to the solder paste that makes that caramel colour. As you can see the legs of the intact transistor look as if the transistor has been replaced. According to another owner, that same transistor is S170/PH34. Mine reads S170/PH77. So this means THAT one has been replaced too. What i'm saying is that with the mods done, if i get to replace the burned transistor the unit will probably burn something else or worst get destroyed but will not fix the problem. Am i right? Link to comment Share on other sites More sharing options...
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