Bride of Zen, Bride of Son of Zen

[mjf]

attenuation at the output:
e. g. paralell a 10k res to your 10k pot - this gives you a "5k pot load" similar to the original schematic and decreases the output signal.

 

[darrr]

Good idea I must try. On your diagram is R3 100k which isn't in the original BoZ.

 

[mjf]

r3 100k is only for sim purposes (e. g. input impedance of an amp.......)

annother option......if you build in a 820 ohm res instead the 1k drain res (or
paralell a 4,7k res to the 1k ) the gain will decrease.......(around 4 x)

 

[mjf]

.....and at last.......lower r12 (10k) to 4,7k or so..... attenuates the signal a bit.......this is a little bit crude, but it helps.
(or you try out to change r3 at the output with 4.7k .......)

 

[darrr]

I suppose that your r3 is useless in my BoZ I'll change and listen until I get to the best sound. Thank you for your help

 

[darrr]

Something wrong with one channel. After few hours of listening music I measured bias and now it's looking like this. I cant increaese bias becouse now pot is in max position

 

[mjf]

i guess the boz was hot......
are the voltages in the normal region when the boz is cooled down?


(all transistors in the boz need a proper heatsink!)

 

[darrr]

voltages are the same when it starts and after few minutes.(3.0 on beginning , 3,4 after few minutes) Heatsinks of course are installed. Irf on this channel is colder than the other.The same r104(1K)

 

[darrr]

I withdrew a few turns on P102 and now the measurements look like this.

 

[mjf]

.......yes, the current is low.....less heat.

the boz has only a few parts to measure, so check every res (ohm) with your dmm......

is the 100uF (c102) electrolytic cap built in the right way?

if they all are correct, search for a bad soldering point/lost connection.

......and the 1uF input cap not to forget......

 

[darrr]

I'll check. Now I have p102 on max and bias is 2,8v if plugged in rca with CD but wihout rca it's 5,0v. Second channel still 5,6v. Caps are in good direction.
I found- R105 is ca. 70k but I'm 100 % sure that it was correct 100k

 

[mjf]

........input cap 1uF could be damaged......

 

[darrr]

not 100k? should I change channel to check it?

 

[mjf]

you can solder out the 1uF cap and measure again.......

 

[darrr]

wow. There is 2,9v on input before 1u.there are 1u/400v jantzen audio. what kind can I replace? maybe some bigger for example 3u3?

 

[mjf]

.......you mean 2,9V on the node 6,2k and 100K (without cd-player connected)?

1uF is big enough i think , this gives you low pass frequency lower than 2Hz....

 

[darrr]

Yes, I unplugedd CD an 2,9v was on rca in. I soldered it out - there is 10Mohm on cap. Now all points measured looks ok ,

 

[darrr]

I am concerned about that problem with cap-what was the cause of damage becouse everthing was ok

 

[darrr]

I am concerned about that problem with cap-what was the cause of damage becouse everthing was ok

I have replaced the damaged jantzen cap with a cheap replacement and now all voltage values ​​are stable.

 

[mjf]

a damaged cap at the input is a rare event.........