N72 step 47 issues .46 volts on Q6

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N72 step 47 issues .46 volts on Q6

Postby Gl1tch106 » Sat Jun 21, 2014 12:25 pm

I recently built an N72 and I'm experiencing problems during step 47

When measuring from J1 with negative probe in pin two and positive probe on Q6 I get .46 volts

when measuring Q1-Q6, Q1-Q3 function properly, but the others, not so well.

Here are their voltages

Q4 Collector 1.153 Base .015 Emitter .000
Q5 Collector .47 Base 1.15 Emitter .47
Q6 Collector .47 Base .47 Emitter .01

Also after scouring the forums I checked resistor 39, 40, and 49 as many people seemed to find their problems with these three but all are functioning properly

Oh! And I just bought a brand new battery for my DMM :p
Gl1tch106
 
Posts: 4
Joined: Sat Jun 21, 2014 12:19 pm

Re: N72 step 47 issues .46 volts on Q6

Postby Gl1tch106 » Sat Jun 21, 2014 12:48 pm

It is SO mind blowing what re-flowing your solder joints can do ^.^

Even the ones that look professional, redo em, you might fix the problem :D

So I am able to successfully bias to 22.2 volts with ease

however my C B E measurements on Q4-Q6 are as follows

Q4 C 5.9 B .9 E .3
Q5 C 22.2 B 5.9 E 5.3
Q6 C22.2 B 5.3 E 4.7

granted step 48 mention voltages can vary a little, my question is whether or not I should worry about a whole volt of difference?

Thanks guys!
Gl1tch106
 
Posts: 4
Joined: Sat Jun 21, 2014 12:19 pm

Re: N72 step 47 issues .46 volts on Q6

Postby Gl1tch106 » Sun Jun 22, 2014 7:31 am

Well, upon testing signal flow the sound has absolutely no low end and is slightly distorted when testing with a dynamic mic, condenser mic seemed to have less of a high pass filter effect, but seemed just a tad more distorted. No tracking with the n72 this afternoon :p rather back to the forums and quadruple checking my work. Any suggestions appreciated :)

Also built an A12 and it sounds absolutely amazing :D
Gl1tch106
 
Posts: 4
Joined: Sat Jun 21, 2014 12:19 pm

Re: N72 step 47 issues .46 volts on Q6

Postby Gl1tch106 » Sun Jun 22, 2014 4:43 pm

Reflowed transformer joints, everything works great and the pre sounds amazing! Headroom for days :D
Gl1tch106
 
Posts: 4
Joined: Sat Jun 21, 2014 12:19 pm


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