ABDX - no delay

[muehring]

Hi all.  Question about the signal path for the abdx.  I'm getting dry output, but no delay and have nothing on pin 7 of IC2.  I tried two different ICs in IC2 with the same result.  I'm not sure the signal is getting to IC2.  Should I have a somthing on pin 6 of IC2 even if that IC isn't working?  I traced the signal to the left side of C4 and R7.  That seems to be where it stops.  Nothing on the right sides. 
Thanks!

[madbean]

It's normal to not hear the signal at the inverting input of IC1A, but you should have something at the output (pin1). If there's no output there, you need to investigate. Take some voltage readings on the IC, check your soldering on the IC pins.

[muehring]

Great, thanks for the quick reply!  I think that confirms what I was thinking.  I'll focus on getting a signal on pin 1 of IC1A.

[madbean]

Sure. After that, take a listen to pin6 and pin7 of IC2. Those are the input/output of the compander.

[muehring]

I am still trying to make progress on the signal getting to the sa571, but haven't succeeded yet.  I tried a different lf353 and checked continuity on all the components in the area.
Here are my voltage readings:
LF353
4.66
4.66
4.66
0
4.66
4.66
4.66
9.2

SA571
1.21
1.80
1.80
0
1.80
1.80
3.09
1.80
.85
1.80
1.80
9.20
1.80
4.71
4.71
1.80

V3205D #1
0
4.07
2.33
2.33
0
1.86
4.06
8.18

V3205D #2
0
4.06
2.57
2.57
.125
6.6
4.06
8.19

3102 - Clock
8.19
4.07
0
4.07
4.01
4.01
4.01
7.67

Any help is appreciated.

Thanks!

[muehring]

Just bumping this, because I still need help.  I'll post some pictures later.

[muehring]

I'm back.  I waited to revisit this build until I could finish populating my second abdx board.  My first parts order got lost in the mail so it took awhile.  I just finished populating it and I'm having the exact same problem as the first.  I'm not getting a signal on pin 1 of IC1A.  I'm getting a signal on pin 2 and the sides of C4 and R7 that are connected to pin 2.  The sides of C4 and R7 connected to pin 1 I get nothing.

Here are some photos.  I'm hoping something will stand out to someone as populated wrong or is it possible both of my LF353s are bad?  They're labeled LF353P and are from Tayda.
Thanks for your help.

[Scruffie]

Power to your BBDs is wrong, you should have near 8v2 on Pins 5 & 8, seems power is being grounded by your readings up there...

Pins 2 & 6 (clock) should be the same and near half supply too and you have those readings as being 2 & 7 by the looks of it.

Take v3205 readings again on both builds.

[muehring]

Scruffie, thanks for your help.  I did have pins 5-8 on the BBDs reversed in the readings above so pin 8 is actually the one I'm getting no voltage.  I checked continuity with ground on all the pins and only pin 1 is connecting on both BBDs.  
Pin 8 seems to be getting the correct voltage on the newer build.
For the clock I'm getting around 4.1 on both 2 & 6.  Pin 7 on the clock is a little less at 4.02.  Not sure I'm following you with what you're saying about the clock readings.

   Original Build:      Second Build:
IC1 - LF353      IC1 - LF353
1   4.63                   1   4.67
2   4.63                   2   4.67
3   4.6                   3   4.67
4   0                   4   0
5   4.6                   5   4.67
6   4.61                   6   4.67
7   4.63                   7   4.67
8   9.28              8   9.39
         
IC2 - SA571N      IC2 - V571D
1   1.01                   1   1.05
2   1.8                   2   1.92
3   1.8                   3   1.92
4   0                   4   0
5   1.81                   5   1.92
6   1.8                   6   1.92
7   3.08                   7   3
8   1.81                   8   1.92
9   1.81                   9   1.92
10   4.72                 10   5.37
11   4.72                 11   5.37
12   1.81                 12   1.92
13   9.24                 13   9.39
14   1.8                 14   1.92
15   1.81                 15   1.92
16   0.84                 16   0.91
         
IC3 - V3205D      IC3 - V3205D
1   0                   1   0
2   4.08                   2   4.11
3   2.34                   3   3.86
4   2.34                   4   3.9
5   8.19                   5   8.25
6   4.07                   6   4.11
7   1.86                   7   0.83
8   0.16                   8   7.72
         
IC4 - V3205D      IC4 - V3205D
1   0.02                   1   0
2   0                   2   4.11
3   2.59                   3   3.82
4   2.59                   4   3.84
5   8.19                   5   8.26
6   4.07                   6   4.11
7   6.62                   7   1.48
8   0.19                   8   7.72
         
IC5 - CD3102GP      IC5 - CD3102GP
1   8.2                   1   8.26
2   4.07                   2   4.11
3   0                   3   0
4   4.07                   4   4.11
5   4.01                   5   4.07
6   4.14                   6   4.15   
7   4.02                   7   4.02
8   7.67                   8   7.73

[jimilee]

I'm building one of these as well and i have only put on the resistors, is there a reason you left out D3 on both and also are the jumpers set correctly? It's hard to tell from the pictures.

[Scruffie]

Scruffie, thanks for your help.  I did have pins 5-8 on the BBDs reversed in the readings above so pin 8 is actually the one I'm getting no voltage.  I checked continuity with ground on all the pins and only pin 1 is connecting on both BBDs.  
Pin 8 seems to be getting the correct voltage on the newer build.
For the clock I'm getting around 4.1 on both 2 & 6.  Pin 7 on the clock is a little less at 4.02.  Not sure I'm following you with what you're saying about the clock readings.

   Original Build:      Second Build:
IC1 - LF353      IC1 - LF353
1   4.63                   1   4.67
2   4.63                   2   4.67
3   4.6                   3   4.67
4   0                   4   0
5   4.6                   5   4.67
6   4.61                   6   4.67
7   4.63                   7   4.67
8   9.28              8   9.39
         
IC2 - SA571N      IC2 - V571D
1   1.01                   1   1.05
2   1.8                   2   1.92
3   1.8                   3   1.92
4   0                   4   0
5   1.81                   5   1.92
6   1.8                   6   1.92
7   3.08                   7   3
8   1.81                   8   1.92
9   1.81                   9   1.92
10   4.72                 10   5.37
11   4.72                 11   5.37
12   1.81                 12   1.92
13   9.24                 13   9.39
14   1.8                 14   1.92
15   1.81                 15   1.92
16   0.84                 16   0.91
         
IC3 - V3205D      IC3 - V3205D
1   0                   1   0
2   4.08                   2   4.11
3   2.34                   3   3.86
4   2.34                   4   3.9
5   8.19                   5   8.25
6   4.07                   6   4.11
7   1.86                   7   0.83
8   0.16                   8   7.72
         
IC4 - V3205D      IC4 - V3205D
1   0.02                   1   0
2   0                   2   4.11
3   2.59                   3   3.82
4   2.59                   4   3.84
5   8.19                   5   8.26
6   4.07                   6   4.11
7   6.62                   7   1.48
8   0.19                   8   7.72
         
IC5 - CD3102GP      IC5 - CD3102GP
1   8.2                   1   8.26
2   4.07                   2   4.11
3   0                   3   0
4   4.07                   4   4.11
5   4.01                   5   4.07
6   4.14                   6   4.15   
7   4.02                   7   4.02
8   7.67                   8   7.73

Right, the new build voltages are better for the most part so we'll focus on that one

The only thing off is your Bias voltage on Pin 7 of both BBDs, it's very low, should be near half supply... adjust the trims, if it wont get near 4.1V check values for R19 & 20 and 25 & 26 and what value did you use for R55 and R27? You may need to reduce them if the trim will not get the voltage up to 4.1V +/-1.5V.

I'm building one of these as well and i have only put on the resistors, is there a reason you left out D3 on both and also are the jumpers set correctly? It's hard to tell from the pictures.

Bean suggests to in the build docs for certain build set ups... however as far as I can see from the schematic it should be in there for the 3205 version.

[jimilee]

[/quote]

Bean suggests to in the build docs for certain build set ups... however as far as I can see from the schematic it should be in there for the 3205 version.
[/quote]
I've read the BOM ove and over and I don't see where he suggests leaving off D3. I see where he suggests leaving off D1 and the last 3 resistors though. I'm building the 3008 version and it's a bit intimidating. Sorry for the hi-jack.

[muehring]

Thanks!  I'll try to get the voltage up on pin 7 and check those resistors.  Do you think that would effect the signal at pin 1 on the LF353?

For D3 it depends on the clock you're using.  Here is the info from the build docs:
NOTE: if you are using the MN3101 with the v3205, you must use D3 to approximate the correct Vgg voltage for pin8 of the clock (14/15 of Vdd). In all other cases (including when using an MN3102, BL3102 or v3102) you should omit D3. The 3102 variety clocks automatically generate the correct Vgg voltages needed in each case.

[jimilee]

Thanks!  I'll try to get the voltage up on pin 7 and check those resistors.  Do you think that would effect the signal at pin 1 on the LF353?

For D3 it depends on the clock you're using.  Here is the info from the build docs:
NOTE: if you are using the MN3101 with the v3205, you must use D3 to approximate the correct Vgg voltage for pin8 of the clock (14/15 of Vdd). In all other cases (including when using an MN3102, BL3102 or v3102) you should omit D3. The 3102 variety clocks automatically generate the correct Vgg voltages needed in each case.

And there you have it, thank you. I think I"m just going to put mine on the back burner for a while.

[Scruffie]

I've just noticed you used multi-turn trimmers, you probably haven't made a value mistake and you're just gunna have to sit there and turn them for ages to get the bias voltage up  while checking for signal at the output of each BBD.

Get them up to about 3V on Pin 7 before you start checking for signal and then keep turning.