Emma TranMORGrifier Problem/Debug

[rocket8810]

I swear this has become the story of my life. I get 3-5 great builds, then one where something is off that I can't figure out. I just built the TranMORGrifier and the only way I can describe it is that it just sounds like its farting. I followed the layout to the T, with 2 changes, a 100nF in place of the 10nF for the input cap so I can make this more usable for bass, and I had to use a 20k linear pot in place of the 20k log as I ran out of 20k linear pots. I'm also using an Intersil CA3080e IC.

The output control works, but the ratio control seems to alter the output too, and I can't tell what the attack and release controls are doing since the only sound I get out of it is this farting sound, with a little sustain, fuzzy/crackling/gated decay.

I checked for solder bridges, checked the wiring, cuts, and double links, and the diode position, but it all seems good. I need some direction to figure out whats going on. I was thinking it could be the IC, so I tried another and I still have the same issue. I've checked the transistors to see if they are all good, and they test fine, so I was thinking it could be the bias of the transistors, but I don't know what they should be.

I haven't built a compressor before, and not sure why it would sound like a fart.

Here are the Voltages Readings.
IC
Pin 1: 0.000V                   Pin 8: 0.000V
Pin 2: 4.60V                     Pin 7: 9.33V
Pin 3: 4.60V                     Pin 6: 0.717V
Pin 4: 0.000V                   Pin 5: 0.662V

Q1                       Q2                       Q3                       Q4                       Q5
E  0.010V              E 0.312V               C 9.03V                C 9.03V                C 9.33V
B  0.410V              B 0.111V               B 0.00V                B 0.00V                B 9.00V
C  9.33V               C 9.32V                 E 0.00V                E 0.00V                 E 8.15V

FYI: The readings on Q5 change when the attack and release pots are turned.

Here's the Schematic


Here's the Vero layout


Here are some pictures of the board top and bottom respectively.


FYI: some of the poly caps are physically larger or smaller, but are the correct values. They're just different versions of the Panasonic ECQ's.





As usual, thanks for any help you can give so I can get this working and finally have a compressor.

[PRR]

Q1 Base gets +3V through 1Meg from the bias string. We expect Q1 Emitter to be at least 1.5V.

Get the voltage on C8. If +3V, find where it isn't getting to Q1.

[jimilee]

How are your polarities? I'm getting confused looking at it on my phone.

[rocket8810]

Q1 Base gets +3V through 1Meg from the bias string. We expect Q1 Emitter to be at least 1.5V.

Get the voltage on C8. If +3V, find where it isn't getting to Q1.

I'll check that tomorrow. My only question is when looking at the schematic isn't C8 the 10nF cap that links C of Q2 with the B of Q3? So on the vero isn't the 10nF in the lower right hand corner after the 1M resistor?

Also, jimilee the polarities of the electrolytics are as they appear in the layout, so they should be correct unless something's wrong with them.

[rocket8810]

Q1 Base gets +3V through 1Meg from the bias string. We expect Q1 Emitter to be at least 1.5V.

Get the voltage on C8. If +3V, find where it isn't getting to Q1.

Ok, I checked the voltages at C8 as well as C2, since C2 connects to the emitter of Q1.

On the side of C2 that's on row 2, connected to pin 2 of the IC, I get 3.82V, but on the side that is next to the Emitter of Q1 I get 0.001V.

On the side of C8 that's on row 14, connected to pin 2 of the IC, I get 9.50V, but on row 15 that connects the Collector of Q2 to the Base of Q3 of I get 0.001V.

The 15k resistor that connects to the 1M resistor to Q1 I get from row 1 2.90V, and the other side right next to the 1M resistor I get 0.44V.

I checked the resistor value to make sure its 15k, and it is. Why could I loose so much of the voltage, because it doesn't seem that have the voltage drop that much.

[PRR]

Maybe I'm not reading the schematic good. Are there two "C8"s??

I was looking at the divider string, from +9V to Gnd, which seems to be 39K 15K 27K.

If we squint and think all three resistors are the same, you'd figure 9V 6V 3V 0V.

With the real values we still get 3.0V at the top of the 27K.

I'm not looking at rows so I don't know where this is on your vero.

[rocket8810]

Ok, I see where you are talking about. I'm sorry for the quality of the schematic, its the only one I could find while I was building it. If I'm looking at that divider string then the cap is C6, I think. Which would be a 10uF electrolytic.

When I follow the path I get the following from top to bottom.
39k - 9.38V, 2.90V
15k - 2.90V, 0.44V
27k - 0.44V, 0.00V
10uF - 0.44V, 0.00V

[PRR]

> 39k - 9.38V, 2.90V
> 15k - 2.90V, 0.44V
> 27k - 0.44V, 0.00V
> 10uF - 0.44V, 0.00V

"If we squint and think all three resistors (39K, 15K, 27K) are the same, you'd figure 9V 6V 3V 0V."

Not 2.9V and 0.44V.

Most likely mess-up is that you have _2.7K_ where you think is 27K. (Your voltages suggest 2.655K.) Red-stripe instead of orange-stripe. Alternatively you got 390K and 150K where should be 39K and 15K, but that seems less likely.

[rocket8810]

> 39k - 9.38V, 2.90V
> 15k - 2.90V, 0.44V
> 27k - 0.44V, 0.00V
> 10uF - 0.44V, 0.00V

"If we squint and think all three resistors (39K, 15K, 27K) are the same, you'd figure 9V 6V 3V 0V."

Not 2.9V and 0.44V.

Most likely mess-up is that you have _2.7K_ where you think is 27K. (Your voltages suggest 2.655K.) Red-stripe instead of orange-stripe. Alternatively you got 390K and 150K where should be 39K and 15K, but that seems less likely.

Thanks Paul. I took a look at them, and you were right. There was a 2.7k not a 27k in that spot. Once I replaced it with the right resistor it worked perfectly. Thanks a ton. BTW, how were you able to tell what the voltage should have been between each of those resistors? Knowing how to figure that out would be an amazing think to have in my debugging toolbox, if you know what i mean.

[PRR]

> how were you able to tell what the voltage should have been between each of those resistors?

The R11 R12 R13 string looks like a Voltage Divider.

Read: http://en.wikipedia.org/wiki/Voltage_divider

Yes, the R11 R12 R13 string plus side-branches is more complicated than the introductory examples. However the R2 and R10 side-branches are "large resistors"; 150K and 1Meg compared to around 30K. Unless they go some place wild, they will have little effect.

R11 R12 R13 is three resistors, not two as in simple examples. However it is the SAME idea. Try simple cases. Try three identical lamps across a 30V outlet. You would expect 30v/3= 10V per lamp.

To quickly do three different resistors does take practice. And it is wise to do it several different ways to check for mental mix-up.

Since all three are orange-stripe, I pretended they WERE identical, which gives 1/3rd across each or 9V/3 is 3V at the lower one.

Noticing that 39K+15K (54K) is exactly twice the 27K means this approximation happens to be exact (probably easy for the designer).

Finally: You report 9.38V-2.90V= 6.48V across the "39K". I ass-umed (trial assumption) you used a real 39K here. 6.48V/39K is 0.166mA. The "15K" has 2.90V-0.44V= 2.46V across it and the _same_ 0.166mA through it. 2.46V/0.166mA says 14.8K, which is near-enuff to 15K. Now your "27K" has 0.44V across and the same 0.166mA through it, that's 2.65K (not 27K).

[jimilee]

Is it as awesome as the video on tagboard makes it out to be? I'm thinking I need to build one.

[rocket8810]

Is it as awesome as the video on tagboard makes it out to be? I'm thinking I need to build one.

honestly it's the only compressor i built, so i don't have a lot to compare it to, and i modded mine to handle bass frequencies, but yes it's awesome. it's fairly transparent, adds maybe a touch of warmth, and if you play with the controls you can get some real nice overdrive from it too. i really love it. i do want to try to build some other compressors like the pigtronix philosophers twin, cause i've heard great stuff about it.

[Lars F]

The schematic is on a photo bucket link, so can't be viewed anymore, does anyone still have it?

Thanks,

Lars

[Slowpoke101]

Here is the circuit. Not very clear though and no pin numbers on the chip, but...

[Lars F]

Thanks!

Lars

[Mark Hammer]

In view of how very similar it is to an MXR Dynacomp, why not get a PCB for one of those and simply do any parts substitutions required.

[Lars F]

For me, it's because I just repaired my original and was curious about the circuit.

Regards,

Lars