All things G1176 - the new "repost" thread.

[Terby]

Mikko,

B ist beta (hfe), the gain of the transistor.

The difference betwen the various BC107 you mentioned below is also hfe, with the "A" type being the lowest

I have used BC107B's in my 1176 with success.

  Andreas

 

[JW]

Hey guys,
On this test jig, can someone tell me which way the base, emitter and collector of the transistor are oriented? Also, what's a good frequency to feed the transistor? 1K

http://www.axtsystems.com/index.php?view=article&catid=34%3A1176ln&id=46%3A1176lnfets&option=com_content&Itemid=62

 

[Andrew]

FET instead of BJT, so it's Drain, Gate, Source respectively from top to bottom I believe. The test is setup with DC voltages. You could measure Id with a 1k resistor across Vds.

Andrew

 

[JW]

Thanks Andrew ,

When you say top to bottom, do you mean clockwise starting with the top? Also, what is "Id," (other than part of the psychic apparatus?)

 

[Andrew]

You're welcome 8)

Drain connected to 10k, Gate to top of 5M, Source to ground. Id is drain current which is the y-axis on the plot. I was wrong before. Id should be found by using:

Id = (10V - Vds)/10k...you can see how the plot is formed by varying Vgs, since Vds will vary in response to Vgs.

Andrew

 

[skal1]

Hi

just two question i am building mnat rev j  boards and i can  see two R15's one is on the ratio board the other on the main pcb ,my ? is what is the of R15 on the main board...

sorry where is R50


thanks in advance


skal1

 

[SaMpLeGoD]

Hi all,

I've finished my 1176 REV D with pushbuttons, all seemed to be ok!
I regulate the Q Bias normaly, regulate the Null trimmer as well (with that jumper getting the R44 out of the circuit).
Well, so far so good, but when I put back the R44's jumper on the normal position, the VU in GR mode don't reach the "0", stays on the -18 and the compression don't work... the input and output pots works very well, both increases the gain, but it seems like there's no Threshold point... so, don't compress...
I wired my out trafo (EA5002) like the original one, it has 4 wires on the secondary so, i connect the orange and yellow togheter, leave the blue for the + (hot), red for the - (cold)... the shield is connected directly to the star ground.. well, I think I wired correctly, appears to be normal.
I'm still reading the meta, but so far there's no problem like this... anyone have any idea about what's happening?
I'm still searching

Merry Christmas to everybody

Eddie  ;D

 

[dean.winter]

Hi All,
I'm building my first 1176 (in fact, my first ever anything) and I'm having a problem with the power supply.  When measuring at R85 and VR1 I get a nice steady +30 at VR1 but only a -0.7 at R85.  First, what I've done so far:
Checked the resistance of R85 R86 R87 and R89 and all appear to be fine.
Checked the capacitors C23 C24 C25 and C26 by using an ohmmeter and making sure that resistance climbs as the cap charges
Checked CR7 CR8 CR9 CR10 - all show the same forward voltage drop.  CR6 shows a different value (but I assume that's to be expected)
At the zener (CR6) I also show -0.7.  Same -0.7 at C24.
I've removed the IC at IC1 so that only the socket is in place.

A couple of questions:
First, I have fully stuffed the board (Dumb...I know...I can only plead inexperience).  Will the presence of the other components in the PCB affect the value when measuring at R85?  That is, could I be getting a perfectly reasonable and valid reading that is just being affected by a trimpot or something?

Second, assuming the answer to the first question is "no, you should always see -10 at R85", can someone offer me some advice or point me at some existing information on how to troubleshoot this going forward?

Thanks in advance for the help, and happy holidays.

Dean

 

[skal1]

Hi dean are you using the on board supply or the mnats psu


regards

skal1

 

[dean.winter]

I'm using the on board supply.

Dean

 

[skal1]

OK then ,first check the ac coming out of secondary of the transformer to the board ,tell me what you get +v and -v


regards

skal1

 

[dean.winter]

Hi Skal,
Forgive my ignorance, I'm really very new at this.  I'm not entirely sure which part of the board I should be checking, but after a bit of searching I think you're referring to the two outer pads under the 3 pin header that connects the transformer secondary to the PCB.  I'm measuring AC at each of them and reading 26.7 at each.  Let me know if I should be measuring something different, and thanks again for the help.

Dean

 

[skal1]

ok that seems alright  i am new to this as well .check voltages on both sides of R86 and r85 to see what you get.


regards

skal1

 

[dean.winter]

R85 on one side shows -13 and on the other shows -0.7 (the -0.7 is the -10v test point)
R86 on one side shows -13 and on the other shows -25.3

Dean

 

[skal1]

Did you check R86 and R85 out of the circuit ? if  you did not de solder these two  resistors and check again should 1KOHM


Regards

skal1

 

[dean.winter]

Ah...my apologies, I thought you were asking for DC volts on each side of R85 and R86.  OK, I de-soldered and checked each resistor.  Each resistor measures 1k (well, .995 in once case, .996 in another) out of the board.  I soldered each one back in and measured resistance on the R85 and R86 pads, still 1K.  Plugged it in and measured voltage, still the same -0.7 at the R85 test point.

Thanks again
Dean

 

[skal1]

what is the -voltage at cr6? it should be -10v check

regards

skal1

 

[dean.winter]

Getting a -0.7 at CR6...same as R85.  FWIW also seeing -0.7 at C24.  Just to make sure, the presence of other components shouldn't affect the -10 reading at R85, right?

 

[skal1]

is this on both sides of cr6


regards

skal1

 

[dean.winter]

No, just on one side.  The other side reads 0, which I think is appropriate...the "g1176 for beginners" document floating around out there (http://www.google.com/search?q=g1176+for+beginners&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-USfficial&client=firefox-a) says that one side should read -10v and the other 0.

Dean