I have mounted the diodes how it shows on pcb but did notice that my +48v side resistors output - voltage and my -48v side output + voltage when im setting up bias.
This may be correct but I am not sure.
My boards didnt come with any circuit diagram or schematics all components are marked on boards.
They are meant to be exact coppies of krell ksa 50mk2 and they do look the same.
The only thing studying pictures of a real krell amp the dc pot was mounted the other way up so I tried turning mine but this made no difference I just had to wind the screw in to get the dc down to 1.6v.
The pot does work just I get the range of 3v dc to 1.6v dc.
I am now thinking my 2sc2240 / 2sa970 transistors may be fake as I got them from cricklewood electronics they sold me what turned out to e fake c2238B / A968B transistors.
Any ideas what can replace my 2SA970 / 2SC2240 transistors cant find them anywhere I dont trust ebay.
My boards are all in bits and I have ordered new output transistors / resistors to replace blown parts.
I ordered KSC1845FTA/KSA992F from rs components yesterday.
minimum order of 200 of each so I will have a few spares.
Looking for some more help please.
Replaced blown components
MJE15030 transistors
MJE15031 transistors
4148 diodes
25R5 resistors
2SC2240 transistors
2SA970 transistors.
My problem is without To3 output boards conected when I plug amp in my 100R resistors start to smoke.
Powered down streight away within a second so hope I done no other damage.
These 100R resistors come from pin 1 of A968B PNP transitor then go to +48v
Pin 1. C2238B NPN transistor go to -48v.
Removed and tested all 4 diodes they are ok.
Sorry I feel so stupid but did say it was my first amp build.
Where I substituted parts got my part numbers muddled up so had my pnp and npn in each others places.
Hi sorry I missed this post about diodes.
At D1 and D2 I get 26.7v one way nothing the other.
Thought I would check 4148 diodes I get 0.5v both ways the +48v.
On -48v side I get 36v both ways round.
I have tried changing these diodes with same results any idea or is this correct.
This is a little confusing, D1 & D3 are 1N4148, D2 & D4 are 27v zenners.
Can you measure the voltage at D1 anode, pot wiper and D3 cathode as shown,
and could you also measure the D4 zenner voltage, (all measurements wrt 0V).
PS, sorry about the crappy schematic, it's the only copy I have.
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My circuit is different from one you have shown me its after 1983 version krell ksa 50 mk2 simular as early krell ksa 100 I believe.
Dave, this is your schematic, trust me
Thank you does this picture help.
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