Hi to you all
If we are going to teach a member to do fault finding then let?s show him/her how to do it the right way and not by simply changing all the components on the board. Doing that or rather advising a member to do so is pointless as that member is NOT learning a thing from it (only to change components) and any fool can change parts at random (although sometimes it is a last resort) further more it will only cause further frustration the next time that he/she has a problem.
Rather let us show our member?s how to do fault finding by the process of elimination He/She will have a far greater sense of satisfaction having found the fault by them selves (and with a little bit of help from there friends) and will have acquired a good base for fault finding. I know that this is a time consuming process (at first) but we will all be gaining from in the future should that member have (and will) have a new problem that member will have done those preliminary test?s and will be able to inform us better about the fault if he/she has not already solved the problem.
By the way I am not attacking you Cornelius and I do hope that you will not take my comment in the wrong way I am merely bringing fourth my point of view and opinion.
Here is the way that I would proceed
1) Do we have Audio? (Well we had) check for audio out (disconnect the battery pack) connect pin 8 IC6 to +9v and pin 1 to neg (for a brief moment) if there is audio GOOD and remember that there is no way that a shorted coil could have damaged the 555 (IC6).
2) Do we have a pulse on the coil? (replace battery pack) Disconnect the coil set DVM to AC switch on is there a reading? Yes GOOD that will mean that TIP31A and IC1 is OK
3) Check IC4 pin 6 IC7 pin 10 and IC5 pin 6 for signal you should be able to do it with a PC scope mine goes up to 20 Khz you can get it at.
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http://www.zeitnitz.de/Christian/Scope/Scope_en.html
by the way there is an under score between Scope and en should one of you want to write down the address.
4) Failing that proceed to check the transistors the most probable one to my opinion that could get damaged would be the TIP31C but Aliman did a check on it and has found it to be OK good initiative on his part way to go. Check all the other transistors but do be aware that some are ECB and some EBC NPN and PNP.
5) Next would be the diode?s, cap?s and resistor?s if you still do not find a fault then it could be that there is a setting between VR1 and the control pot (the big knob) having done all of that and it still does not work go thought all the solder points check all wiring for continuity (this should be point number one) and finally if you till have not found the fault then replace the IC?s one by one but that would be my last resort.
Best regards
Xavier
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Xavier
