1001

CP4500 Stereo Bus Compressor / Re: Signal loss when CP4500 is on

« on: January 12, 2021, 04:30:09 PM »

My V+ and V- are reading a little hot
No problem here, it is your lunchbox which is a little hot.

Can you do the voltage checks shown here and report the ones which are wrong?

1002

CP4500 Stereo Bus Compressor / Re: Test Pin Difficulty

« on: January 12, 2021, 04:24:53 PM »

This is a problem that comes with some PCB batches, when the coating is thicker.
What we do in this case is insert the pins upside down, solder from the top side of the PCB and cut the sharp end above the ring.

1003

EQP501 Passive Equalizer / Re: When will this be back in stock?

« on: January 10, 2021, 08:57:31 AM »

Probably 2 weeks from now.

1004

EQ573 Equaliser / In case your EQ573 doesn't work as expected

« on: January 09, 2021, 09:34:48 AM »

Check the usual suspects:

• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (electrolytics, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
• Flipped IC's or transistors,
• Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.

Check the DC voltages:
Next, without any input signal, connect the voltmeter black probe to 0V (TP4 for EQ573) and note the DC voltages you get at the points shown on the picture below. Compare with the expected results (more or less 10%).
EQ573-II:


EQ573:


Try to follow the signal
Send a good constant sine signal on input, like 100Hz - 2VAC measured between pins 2&3 of the input XLR.
All controls on OFF, source switch on XLR.
Connect the voltmeter black probe to TP4 and trace the signal on:
-  TP1: 0.53VAC
-  TP2: 0.46VAC
-  TP3: 0.30 VAC
The reading should follow the input signal level.
The place where the signal drops will give you hints on where to look for.

1005

EQP501 Passive Equalizer / Re: EQ worked for awhile then stopped

« on: January 08, 2021, 05:41:00 PM »

I would recommend that you start a new one because all the transistors are DC connected and one failure usually causes other cascading failures.

1006

EQP501 Passive Equalizer / Re: EQ worked for awhile then stopped

« on: January 08, 2021, 08:20:44 AM »

It looks like your SK25 is the culprit. This will be confirmed if you get any DC voltage on TP2.
- Check that R1 is not touching the vertical PCB and the diode D5,
- check that the 4 solders on each vertical PCB are making good contact,
- check that all the component leads are trimmed as short as possible. None must be touching any component underneath.

1007

EQ573 Equaliser / Re: Placement of Capacitors Ceramic (docs-20)

« on: January 06, 2021, 11:48:38 AM »

Yes correct.

1008

501 Single Host / Connecting the auxiliary jack

« on: January 06, 2021, 11:33:00 AM »

Jumper settings
- To connect the auxiliary jack to the module output:
T   R
o o o
o-o o Out+
o o o
o o-o Out-
o o o
o o o
o o o
o o o
o o o
o o o

- To connect the auxiliary jack to the module input:
T   R
o o o
o o o
o o o
o o o
o o o
o o o
o o-o In-
o o o
o-o o In+
o o o

1009

CP4500 Stereo Bus Compressor / Re: 9db less output on the right channel

« on: January 06, 2021, 08:44:06 AM »

Great news!

1010

EQP501 Passive Equalizer / Re: eqp510 5dB drop in level once engaged with all pot values at 0

« on: January 06, 2021, 08:41:05 AM »

Check the usual suspects and try to follow the signal as described here.
The makeup gain is defined by R13/R12. Check their value.

1011

EQP501 Passive Equalizer / In case your EQP501 doesn't work as expected

« on: January 06, 2021, 08:31:16 AM »

Check the usual suspects:

• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (electrolytics, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
• Flipped IC's or transistors,
• Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.

Check the DC voltages:
First check the supply voltages as described in the setup guide.
Next, without any input signal, connect the voltmeter black probe to 0V and check you get no DC voltages on TP2. Any DC voltage higher than a few millivolts shows that the DOA is the issue.

Try to follow the signal
With all pots at 0, Send a constant 100Hz - 2 VAC sine signal on the input, measured between pins 2&3 of the input XLR.
Connect the voltmeter black probe to 0V and trace the signal.
- On TP1 you should get about 1.3 VAC- On TP2 you should get about 1.15 VAC
The reading should follow the input signal level.
The place where the signal drops will give you hints on where to look for.

1012

CP4500 Stereo Bus Compressor / Re: 9db less output on the right channel

« on: January 05, 2021, 03:55:04 PM »

With Threshold at +15, is the meter resting at 0?

1013

LA502 Optical Compressor / In case your LA502 doesn't work as expected

« on: January 04, 2021, 07:38:24 PM »

1. Check the usual suspects:

• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (electrolytics, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
• Flipped IC's or transistors,
• Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.

2. Check the DC voltages:
First check the supply voltages as described in the setup guide.
Check you get no DC volts on TP1. Any DC above a few millivolts here shows that there is an issue.

3. Try to follow the signal

Send a good constant sine signal on input, like 1VAC measured between pins 2&3 of the input XLR. PEAK at 0.
Connect the voltmeter black probe to 0V and trace the signal on:
- R2 right pin: Should be at 0.7VACand follow the input voltage.
- REV1.3: R5 low pin should be at 0.5V when GAIN is on 100.
- REV1.4: R5 right pin should be at 0.5V.
- TP1: should go above 10V when GAIN is at 100.

Check the input transformer coils resistance

1    3    5
o  .  o  .  o

              BOTTOM VIEW

o  .  .  o  o
10      7  6

1-5  ? 2 kohms
6-10  ? 2 kohms

Check the output transformer coils resistance

1    3  5  5  6    8
o  .  o  o  o  o  .  o  PRIMARY

      BOTTOM VIEW

o  o  .  o  o  .  o  o  SECONDARY
16 15    13 12    10 9

1-3  ? 10 ohms (5 ohms if in circuit)
6-8  ? 10 ohms (5 ohms if in circuit)
9-12 ? 12 ohms
13-16 ? 12 ohms

1014

CP4500 Stereo Bus Compressor / Re: 9db less output on the right channel

« on: January 04, 2021, 07:21:37 PM »

Can you check if you get the correct voltages ?
https://www.soundskulptor.com/forum/index.php?topic=3.msg3#msg3

1015

CP4500 Stereo Bus Compressor / Re: burned led

« on: January 04, 2021, 04:25:11 PM »

The current limiter in the LED's are the relays and resistors R104 & R105.
Check that diodes D19 and D20 are not reversed.
Check the value of  R104 & R105.
Check you don't have a short circuit between some pins of CN2a & CN2b.
Check there is no mistake in the wiring of the meter.

1016

News and updates / Welcome to the Sound Skulptor forums

« on: December 29, 2020, 11:15:29 AM »

Here we can find help on build issues, share experiences and discuss products.

1017

MP512 Microphone preamplifier / In case your MP512 doesn't work as expected

« on: December 29, 2020, 08:32:23 AM »

Check the usual suspects:

• Check you didn't leave the polarity switch on the center position (=mute),
• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (electrolytics, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
• Flipped IC's or transistors,
• Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.

Check the DC voltages:
First check the supply voltages as described in the setup guide.
Next, without any input signal, connect the voltmeter black probe to 0V and check you get no DC voltages on TP2. Any DC voltage higher than a few millivolts shows that the DOA is the issue.

Check the DI input
Check you didn't forget to remove the JMP1 jumper.
Check you didn't swap the 2 transistors on the DI board.
If the DI input works then the issue may be in the switching between DI and XLR. Check the 2N7000 on the DI board. This component is sensitive to static electricity and is better handled without your shoes on (body grounded).

Try to follow the signal
Send a constant 100Hz - 100mVAC sine signal on the input, measured between pins 2&3 of the input XLR.
Check the level with the preamp connected because the input impedance of the preamp may pull the signal down.
Connect the voltmeter black probe to 0V and trace the signal.
On TP1 you should get about 750mVACOn TP2 you should get more than 10VAC, depending on the position of the gain potentiometer.
The reading should follow the input signal level.
The place where the signal drops will give you hints on where to look for.

1018

MC624 Monitor Controller / Frequent mistakes

« on: December 27, 2020, 03:42:45 PM »

Connectors soldered on the wrong side
Do not try to save the connector! This will very likely damage the PCB which cost 100 times more than the connector.
Instead, split the connector into pieces with cutting pliers until you are able to remove the pins one by one.
Next empty the holes with a de-soldering pump (this one works great : Jonard Industries DP-100).

1019

EQ573 Equaliser / Frequent mistakes

« on: December 27, 2020, 08:52:43 AM »

Swapped IC's
The 2 IC's on the IN/OUT daughter board are different. Don't swap them and insert them carefully in the right direction.
The pin 1 of the NE5532 is identified by a small recessed circle on the body.

Tips on how to solder the long 2x40 pins header
The main issue here is when you heat some pins for too long, they start to move because the plastic part which hold them together starts melting. The solution is to lay the header on a damp sponge while soldering the pins. The water in the sponge prevents the parts getting too hot.

1020

First Aid / Frequent mistakes

« on: December 20, 2020, 09:15:52 AM »

You are not looking at the correct documentation
If you accessed to the documentation through the site Support/Technical documents menu, you may not be looking in the right place. The kits evolve in time, and we keep every versions of their documentation.
Only take your documentation at the url address marked on your kit box, something like https://www.soundskulptor.com/docs-xx.html.

Component soldered in the wrong place
Do not try to save the component! This will very likely damage the PCB which cost 100 times more than most components.
Except for transformers which are also expensive, cut the components pins with cutting pliers in order to be able to remove the pins one by one.
Then empty the holes with a de-soldering pump (this one works great : Jonard Industries DP-100).

Untrimmed component leads
Check that no component lead is able to touch the chassis plate, the test pins in particular.

Soldering too fast
When making a solder joint, beginners are often afraid of heating too much the components resulting in a lot of dry joints. It is necessary to put enough heat on the component pins so that the solder can flow into the hole. 2-3 seconds heating with an iron set to 300-320°C (507-610°F) is not a problem for most components.
The only components that may suffer from to much heating are the pin headers when the plastic part that holds the pins together start melting, messing the pins position. For these, you can press the component on a wet sponge while soldering.

1021

First Aid / In case your module doesn't work as expected

« on: December 20, 2020, 09:04:50 AM »

Check the usual suspects:

• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (electrolytics, tatalum's, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
• Components in the wrong place like IC's or transistors,
• Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.

1022

SK25/SK99 Discrete Op-Amp / In case your DOA doesn't work as expected

« on: December 17, 2020, 11:47:34 AM »

1. Check the usual suspects:

• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (diodes, transistors),
• Flipped transistors,
• Trim all the component leads as short as possible. Nothing must touch the PCB below.

2. Also:

• make sure R1 is not touching the vertical PCB and the diode D5,
• check you didn't flip the power transistors Q9-Q10,
• check that the 4 solders on each vertical PCB are making good contact,
• check you didn't reverse the LED (it must light up),
• check you didn't swap D4 (Zener) with one of the 1N914.

Other than this, the DOA's are very difficult to repair, I would recommend that you build a new one.

1023

CP5176 FET compressor / In case your CP5176 doesn't work as expected

« on: December 17, 2020, 11:33:04 AM »

1. Check the usual suspects:

• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (electrolytics, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
• Flipped IC's or transistors,
• Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.

2. Check the DC voltages:
First check the supply voltages as described in the setup guide.
Check you get no DC volts at the output of the DOA on L1 top pin. Any DC above a few millivolts here shows that there is an issue with your DOA.
Next, without any input signal, connect the voltmeter black probe to the 0V pin and note the DC voltages you get at the points shown on the attached picture. Compare with the expected results (more or less 10%).


3. Try to follow the signal
Send a good constant sine signal on input, like 1VAC measured between pins 2&3 of the input XLR.
Connect the voltmeter black probe to 0V and trace the signal on:
TP1, TP2, L1 top pin.
The reading should follow the input signal level.
The place where the signal drops will give you hints on where to look for.

4. Check the side chain
Input on 10
Out on 10
Attack on 0
Release on 10
Input signal sine 100Hz, 100mVAC
Jumper JMP1 on 2-3 [o o-o o o]

AC level on TP3:

• Ratio 2 : 0.65 VAC
• Ratio 4 : 1.3 VAC
• Ratio 8 : 2.1 VAC
• Ratio 12 : 3.4 VAC
• Ratio 20 : 5.9  VAC
• Ratio SLAM : 6.6 VAC

DC level on TP4:

• Ratio 2 : 0 VDC
• Ratio 4 : -0.5 VDC
• Ratio 8 : -1.3 VDC
• Ratio 12 : -2.5 VDC
• Ratio 20 : -5.5 VDC
• Ratio SLAM : -0.6 VDC

DC level on JMP1 pin 1:

• Ratio 2 : 0.6 VDC
• Ratio 4 : 0.9 VDC
• Ratio 8 : 1.2 VDC
• Ratio 12 : 1.9 VDC
• Ratio 20 : 2.3 VDC
• Ratio SLAM : 7.9 VDC

DC level on TP6:
      -4.5 to -1.2 VDC depending on P6

DC level on TP5 with jumpers JMP1 on 2-3 and 4-5 [o o-o o-o]:
      0.32 VDC

1024

MP573 Microphone preamplifier / In case your MP573 doesn't work as expected

« on: December 16, 2020, 06:41:09 PM »

Check the usual suspects:

• Check you didn't forget the jumper on CN1,
• Check you didn't leave the polarity switch on the center position (=mute),
• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (electrolytics, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
• Flipped IC's or transistors,
• Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.

Check the DC voltages:
First check the supply voltages as described in the setup guide.
Next, without any input signal, connect the voltmeter black probe to TP2 and note the DC voltages you get at the points shown on the attached picture. Compare with the expected results (more or less 10%).



Check the DI input
Check you didn't forget to remove the JMP3 jumper.
Check you didn't swap the 2 transistors on the DI board.
If the DI input works then the issue may be in the switching between DI and XLR. Check the 2N7000 on the DI board. This component is sensitive to static electricity and is better handled without your shoes on (body grounded).

Try to follow the signal
Send a good constant sine signal on input, like 0.5VAC measured between pins 2&3 of the input XLR. Check the level with the preamp connected because the input impedance of the preamp may pull the signal down.
Connect the voltmeter black probe to TP2 and trace the signal on:

• Input transformer pin 7: 0.9VAC,
• TP1: 4.8VAC (Gain=40, TRIM=Min),
• output transformer yellow wire: 8.4VAC (Gain=40, TRIM=Min).

The reading should follow the input signal level.
The place where the signal drops will give you hints on where to look for.

In case you need to remove the input transformer follow these steps

• Remove the 4 screws on the Carnhill transformer (2 in front and 2 in the back).
• Remove solder on the 7 pads of the back daughter board and remove it. Use a desoldering pump.
• Remove solder on the 9 pads connecting the transformer in/outs on the front daughter board and remove the transformer. Be careful when removing the front daughter board not to pull the transformer front plate with it because it is not attached anymore

To verify the transformers DC resistances
CARNHILL VTB1847 (unplugged) :

• Yellow-Orange : 7.6 ohms
• Red-Brown : 6.4 ohms
• Blue-Green : 21 ohms
• Violet-Black : 21 ohms

CARNHILL VTB9045 :

• 2-4 : 24 ohms
• 3-5 : 24 ohms
• 7-9 : 144 ohms
• 8-10 : 142 ohms

1025

CP4500 Stereo Bus Compressor / Frequent mistakes

« on: December 15, 2020, 12:25:17 PM »

Connectors soldered on the wrong side
Do not try to save the connector! This will very likely damage the PCB which cost 100 times more than the connector.
Instead, split the connector into pieces with cutting pliers until you are able to remove the pins one by one.
Next empty the holes with a de-soldering pump (this one works great : Jonard Industries DP-100).

IC's in the wrong place
There are 3 different kinds of 2x4 pins IC's: Don't mix them up!
They usually don't like being powered in the wrong place and are likely to die.

Conductive solder flux
Some solders leave a slightly conductive flux residue on the PCB. This will mess the side chain circuit which works at very high impedance. The symptom is a meter that doesn't stay at 0 with no input signal. It can stay at the right or at the left of the 0, changing slowly.
The solution is to completely immerse the 3 PCB's in isopropyl alcohol during 10mn at least, shaking and brushing the surfaces. A simple clean without immersing won't be enough.
You should check your solder before committing. Put the 2 probes very close to each other on a spot without any track but with some flux residues. Set the ohmmeter to megohms. If you get any reading then it is not good.
One recent example of solder which had this problem was the WBT-0800 with halogen free flux.