ok, couldn't wait ;-) so i replaced q104 ... measures the same as the other one, still no change on the output voltage... so next step is replacing irf9530?
so i replaced q106 and have still the same output voltage...😡
regarding the vref section - i have 2 red leds and d201 jumpered
regarding the vref section - i have 2 red leds and d201 jumpered
Q104 is BC550 and not BC560 by any chance, right? Is there any voltage drop across VR106? What happens if you short it across?
q104 is bc550, no voltage across r106 so i guess shorting it wont make any difference - tried just in case, but it doesn't ;-)
The Vref components should not be changing current with different test loads. Q103 is supposed to give their current. Something allows communication. Take those Q103 and Q105 out and make sure they test normally like working in an idss test. Also look for any solder bridge or blob in the board that shorts something.
i tested them before putting them in, but i will try again... what is really wierd is that i looked again at the "pinout" of the 117gr and the pcb and now i am totally confused... it seems like drain and gate are connected together the way i mounted them ... could it be possible that the orientation suggested on the pcb is not right for this fet? attached a picture showing the way i mounted it.
edit - scratch that, mounted the right way, just got confused by what is what ;-)
edit - scratch that, mounted the right way, just got confused by what is what ;-)
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yay, looks like we are getting somewhere ... i replaced 303 and 305 and now i get 8,5vdc output with the trimpot at max ... doesn't make sense they mesaured ok, but whatever ;-)
I guess i replacing r103 with a 2k should get me to the 10V? 🙂 thanks so much for your patience
I guess i replacing r103 with a 2k should get me to the 10V? 🙂 thanks so much for your patience
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Yes, a higher r103 should do that. Maybe some joint was cold or a jfet intermittent. Anyway congrats for having it working.
im building for the ba-3 front end. I bought the minikit from teabag. it's a little confusing on the led theme for me. i have 6 red and 4 green. i'm reading the guide but don't know if i have to measure or match leds or just put them with no criteria.
thanks
thanks
I don't know maybe for spares. Small Leds are easy to overdo with the iron. Especially when reworking a board. That flat head type he had chosen is tighter for random Vf than various others nonetheless. The main impact of parts tolerances will be in how much CCS current someone gets vs what he may expect. Biggest contributor will be the MOSFET with its Vgs differing by sample. R101 can always be chosen differently to compensate for any gross off target result. In general when you target say 300mA and you end up with 285mA and 325mA in two channels when you have 100mA basic consumption from the load you don't care. Because you already have rich hot-rod that will cover any extra demand and that CCS difference will not make any interesting difference in the MOSFETs transconductance. Just always measure voltage drop across R101,(201,301) and divide by its value so to know what the CCS really runs when finishing a build so to have a picture.
P.S. Now that I think more of it maybe he sends six reds so you could also use all red Leds (choose R101 accordingly) and it looks uniform when it lights up 
Ok. Thanks.
I asked some posts back if i have to hotrod for the ba-3 preamp. If i am not making wrong deductions, and if the ba-3 is 50ma hungry per channel, the total is 100ma and if this is correct don't i need to have a 200ma margin? So, 300ma is the total that i need to have. Just thinking. If so, the 300ma value exceeds the 200ma in the manual for a normal use. That's why i asked if i have to use the Mur820 . This thinking could be totaly wrong if the 200ma spare current is too much.
I am sorry, i am really in the beggining of my learning curve and my function is not exponencial! 🙂
I asked some posts back if i have to hotrod for the ba-3 preamp. If i am not making wrong deductions, and if the ba-3 is 50ma hungry per channel, the total is 100ma and if this is correct don't i need to have a 200ma margin? So, 300ma is the total that i need to have. Just thinking. If so, the 300ma value exceeds the 200ma in the manual for a normal use. That's why i asked if i have to use the Mur820 . This thinking could be totaly wrong if the 200ma spare current is too much.
I am sorry, i am really in the beggining of my learning curve and my function is not exponencial! 🙂