Hi Rick,
I see that you say that those two 680R resistors measure alright but are they browned? Just because they still measure doesn't mean they didn't get hot. It might just be that the 47R went first before they got hot enough to fail. I can't find the schematic for the MK2. Double check that you have all the right transistors in the right place and that the layout matches the schematic. I can't think of anything else right now.
I see that you say that those two 680R resistors measure alright but are they browned? Just because they still measure doesn't mean they didn't get hot. It might just be that the 47R went first before they got hot enough to fail. I can't find the schematic for the MK2. Double check that you have all the right transistors in the right place and that the layout matches the schematic. I can't think of anything else right now.
AHH. Good Point! Will have to get some in. The Combo Pic shows R22. No Schematic i can find, so i will use the Std AX11 one. Thanks
Rick
On this pcb there is wrong polarity on 2N5551... use BC546 or reverted 2N5551 pins (E-B-C to C-B-E)... and use 0,22R/5W instead 22R/5W
Regards
AH.. Thank you for correcting this. Will get the new parts & post results in a few days.
Yes the MJE15030 & MJE 15031 have shoulder washers under the M3 screws. The MJ15003/004 also have insulators. There is No Short from the Heatsink to anything. Thanks for looking .
R22 =0.22R The silkscreen in post #5155 is ok.
Transistors are wrong placed.
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Why do you say that? Pinout for 2N5551 is EBC. It is reversed on the silkscreen in post #5155. BC546 will work fine in those positions.
Yes Mile did "nail" it. I replaced all 3 2n5551 & installed correctly.Replaced 22R with R33/5W i had on hand. Powers up but now have +25V on Spk Out. Bias settles at 90mv.
I got this from POST#2201, pg221 by Wiljj78.
Rick
