[BUILD] 1176LN Rev D DIY

[Echo North]

could you give me a rundown on how test those transistors. I'm going to double check the output pot wiring and look for cold solder joints now

Checked my wiring its fine and I went over all of the solder joints in the pre amp section just to make sure. Still getting 0v at C7. Just waiting for guidance on the transistor testing.

Compair the values on Q3, Q4, and Q14 to here:
http://mnats.net/files/1176REVD_VOLTS.pdf

You're measuring DC, unit on, no signal, referencing ground/common/0V whatever you want to call it.

Mike

 

[mgalimbe]

could you give me a rundown on how test those transistors. I'm going to double check the output pot wiring and look for cold solder joints now

Checked my wiring its fine and I went over all of the solder joints in the pre amp section just to make sure. Still getting 0v at C7. Just waiting for guidance on the transistor testing.

also could it be a bad output pot?

 

[Echo North]

could you give me a rundown on how test those transistors. I'm going to double check the output pot wiring and look for cold solder joints now

Checked my wiring its fine and I went over all of the solder joints in the pre amp section just to make sure. Still getting 0v at C7. Just waiting for guidance on the transistor testing.

also could it be a bad output pot?

Doubtful. Stuff like pots, transformers and other passives are HARD to damage. Semi conductors like diodes and transistors are VERY EASY to damage with static electricity and high soldering heat.

Mike

 

[mgalimbe]

could you give me a rundown on how test those transistors. I'm going to double check the output pot wiring and look for cold solder joints now

Checked my wiring its fine and I went over all of the solder joints in the pre amp section just to make sure. Still getting 0v at C7. Just waiting for guidance on the transistor testing.

also could it be a bad output pot?

Doubtful. Stuff like pots, transformers and other passives are HARD to damage. Semi conductors like diodes and transistors are VERY EASY to damage with static electricity and high soldering heat.

Mike

Ok thanks so how do I go about testing those transistors.

 

[Echo North]

could you give me a rundown on how test those transistors. I'm going to double check the output pot wiring and look for cold solder joints now

Checked my wiring its fine and I went over all of the solder joints in the pre amp section just to make sure. Still getting 0v at C7. Just waiting for guidance on the transistor testing.

also could it be a bad output pot?

Doubtful. Stuff like pots, transformers and other passives are HARD to damage. Semi conductors like diodes and transistors are VERY EASY to damage with static electricity and high soldering heat.

Mike

Ok thanks so how do I go about testing those transistors.

Posted the answer a few posts above.

 

[mgalimbe]

my apologies I missed it

So here are the values Q3

should be :12.5 getting: 1.78
"                  ":1.15 Getting 1.15 (ok)

Q4
all match up but 2 in different pin locations Ex: on mnats middle pin should be1.02 but reading 4.65, pin closest to c10 should be 4.2 but read 1.01 last pin should be .46  and it reads .42 so the middle pin and the pin closest to C10 are reading backwards.

Q14

should read 12 v but getting 10.47

 

[Echo North]

my apologies I missed it

So here are the values Q3

should be :12.5 getting: 1.78
"                  ":1.15 Getting 1.15 (ok)

Q4
all match up but 2 in different pin locations Ex: on mnats middle pin should be1.02 but reading 4.65, pin closest to c10 should be 4.2 but read 1.01 last pin should be .46  and it reads .42 so the middle pin and the pin closest to C10 are reading backwards.

Q14

should read 12 v but getting 10.47

The pins on the schematic don't match the pins on the PCB. You'll need to google the datasheet for each transistor and look at the drawing in the datasheet to figure out what is the base, emitter, and collector. It's super easy.

 

[mgalimbe]

my apologies I missed it

So here are the values Q3

should be :12.5 getting: 1.78
"                  ":1.15 Getting 1.15 (ok)

Q4
all match up but 2 in different pin locations Ex: on mnats middle pin should be1.02 but reading 4.65, pin closest to c10 should be 4.2 but read 1.01 last pin should be .46  and it reads .42 so the middle pin and the pin closest to C10 are reading backwards.

Q14

should read 12 v but getting 10.47

The pins on the schematic don't match the pins on the PCB. You'll need to google the datasheet for each transistor and look at the drawing in the datasheet to figure out what is the base, emitter, and collector. It's super easy.

Ok so here are the numbers as it relates to the proper pinout. The first number is what it should read and the second is what it actually reads:
Q3
B1.75      1.78
E1.15      1.15
C12.5    11.2

Q14
B12.5  11.1
E12        10.4
C30      29.06

Q4
B1.02    1
E.46        .42
C4.2      4.6

 

[Echo North]

Looks fine to me.

With the unit in GR OFF and feeding it a 1K 1dBu signal, (in/out midway) what is your AC voltage at the BASE of each of those transistors.

Again, AC this time.

Mike

 

[mgalimbe]

feeding a 1.55vac 1khz signal my AC at the BASE readings  Are:
Q3=17mv
Q14=0mv
Q4=20.9mv

 

[Echo North]

feeding a 1.55vac 1khz signal my AC at the BASE readings  Are:
Q3=17mv
Q14=0mv
Q4=20.9mv

Q2, Q3, and Q14 is what we're looking for.  Sorry type-o earlier.

Get the DC voltages for for Q2 like you did earlier, since we missed that one. Then the base in AC for each.

Mike

 

[mgalimbe]

feeding a 1.55vac 1khz signal my AC at the BASE readings  Are:
Q3=17mv
Q14=0mv
Q4=20.9mv

Q2, Q3, and Q14 is what we're looking for.  Sorry type-o earlier.

Get the DC voltages for for Q2 like you did earlier, since we missed that one. Then the base in AC for each.

Mike

The DC voltage for Q2 is all good B1.04, E.53 & C1.77
The AC voltage of Q2 at the base is .178v- feeding a 1.55vac kHz tone, meter off

 

[Echo North]

feeding a 1.55vac 1khz signal my AC at the BASE readings  Are:
Q3=17mv
Q14=0mv
Q4=20.9mv

Q2, Q3, and Q14 is what we're looking for.  Sorry type-o earlier.

Get the DC voltages for for Q2 like you did earlier, since we missed that one. Then the base in AC for each.

Mike

The DC voltage for Q2 is all good B1.04, E.53 & C1.77
The AC voltage of Q2 at the base is .178v- feeding a 1.55vac kHz tone, meter off

Maybe Q3 is bad or has a bad joint then.  Try reflowing the joints, if that doesn't work, I'd probably replace that one.

Mike

 

[mgalimbe]

feeding a 1.55vac 1khz signal my AC at the BASE readings  Are:
Q3=17mv
Q14=0mv
Q4=20.9mv

Q2, Q3, and Q14 is what we're looking for.  Sorry type-o earlier.

Get the DC voltages for for Q2 like you did earlier, since we missed that one. Then the base in AC for each.

Mike

The DC voltage for Q2 is all good B1.04, E.53 & C1.77
The AC voltage of Q2 at the base is .178v- feeding a 1.55vac kHz tone, meter off

Maybe Q3 is bad or has a bad joint then.  Try reflowing the joints, if that doesn't work, I'd probably replace that one.

Mike

After desoldering the joints of Q3 I now get an AC voltage with the 1.55vac sine wave at the BASE of 32.5mv. is that what we were looking for? the initial reading was only 17mv.

Also I have 2 other small issues one of the VU pads on the meter board (second to last)wouldn't hold solder, I followed the traces and heres how I presently have them wired. Does this look ok to you?

 

[mgalimbe]

feeding a 1.55vac 1khz signal my AC at the BASE readings  Are:
Q3=17mv
Q14=0mv
Q4=20.9mv

Q2, Q3, and Q14 is what we're looking for.  Sorry type-o earlier.

Get the DC voltages for for Q2 like you did earlier, since we missed that one. Then the base in AC for each.

Mike

The DC voltage for Q2 is all good B1.04, E.53 & C1.77
The AC voltage of Q2 at the base is .178v- feeding a 1.55vac kHz tone, meter off

Maybe Q3 is bad or has a bad joint then.  Try reflowing the joints, if that doesn't work, I'd probably replace that one.

Mike

After desoldering the joints of Q3 I now get an AC voltage with the 1.55vac sine wave at the BASE of 32.5mv. is that what we were looking for? the initial reading was only 17mv.

Also I have 2 other small issues one of the VU pads on the meter board (second to last)wouldn't hold solder, I followed the traces and heres how I presently have them wired. Does this look ok to you?

heres the pic of the ratio board

 

[mgalimbe]

mike

I went ahead and tested the rest of the transistors in the circuit they all look good however I noticed that I had Q11 in backwards. Unfortunately I destroyed one of the pins removing it. Just wondering if this would be the cause of my output pot not changing the VAC at the output XLR.

 

[Echo North]

mike

I went ahead and tested the rest of the transistors in the circuit they all look good however I noticed that I had Q11 in backwards. Unfortunately I destroyed one of the pins removing it. Just wondering if this would be the cause of my output pot not changing the VAC at the output XLR.

Possibly. Depends on a lot of factors.

Consider sending it in for repair. There are a number of issue and I can't even really wrap my head (digitally) around it.
http://www.hairballaudio.com/build-support-services

Certainly replace Q1 and Q11 and see what happens.

Mike

 

[mgalimbe]

mike

I went ahead and tested the rest of the transistors in the circuit they all look good however I noticed that I had Q11 in backwards. Unfortunately I destroyed one of the pins removing it. Just wondering if this would be the cause of my output pot not changing the VAC at the output XLR.

Possibly. Depends on a lot of factors.

Consider sending it in for repair. There are a number of issue and I can't even really wrap my head (digitally) around it.
http://www.hairballaudio.com/build-support-services

Certainly replace Q1 and Q11 and see what happens.

Mike
[/quote

Yes Mike you've been a GREAT help. I've ordered those transistors I'll install them and if that doesn't fix the problem I will send it to you. Thanks again for your patience and help.
Mike g.

 

[Echo North]

mike

I went ahead and tested the rest of the transistors in the circuit they all look good however I noticed that I had Q11 in backwards. Unfortunately I destroyed one of the pins removing it. Just wondering if this would be the cause of my output pot not changing the VAC at the output XLR.

Possibly. Depends on a lot of factors.

Consider sending it in for repair. There are a number of issue and I can't even really wrap my head (digitally) around it.
http://www.hairballaudio.com/build-support-services

Certainly replace Q1 and Q11 and see what happens.

Mike
[/quote

Yes Mike you've been a GREAT help. I've ordered those transistors I'll install them and if that doesn't fix the problem I will send it to you. Thanks again for your patience and help.
Mike g.

Good luck!

 

[mgalimbe]

just received a bunch of jfets and tested them for idss and Vp. Just wondering which number I should use to match them I have 2 that the idss is spot on but there is a difference of 20ma for the Vp.