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Messages - JPK

Pages: [1] 2 3 ... 33
1
CP554 Diode bridge compressor / Re: CP554 Setup step 6 and 7
« on: September 25, 2023, 04:29:52 pm »
Were you able to adjust the bias in step 5?
Check if you can measure a signal on TP1, against 0V, with your DMM on AC volts. It should increase with the gain makeup.
Same thing on TP2.

2
CP554 Diode bridge compressor / Re: CP554 setup-guide point 13
« on: September 23, 2023, 09:49:48 am »
The side chain circuits are on board 2. So it is normal that you don't get any compression without board 2.
Can you do the measurements on the side chain shown here?

3
CP5176 FET compressor / Re: Trouble with FET setup
« on: September 19, 2023, 04:19:32 pm »
Can you go through the "Check the side chain" tests here?

4
CP554 Diode bridge compressor / Re: CP554 setup-guide point 13
« on: September 19, 2023, 04:14:21 pm »
Make sure the sidechain switch is on INT.
Check the sidechain as shown here.

5
TS500 Tape Simulator / Re: Way to adjust head bump amount
« on: September 16, 2023, 10:05:52 am »
R29 sets the bump level:
Decrease (5k) --> more bump
Increase (20k) --> less bump 

6
LA502 Optical Compressor / Re: Two LA502 with different output levels
« on: September 13, 2023, 08:58:10 am »
It is normal, the configuration of the gain stage has changed between these 2 versions.
I am sure it is possible to convert a REV1.3 into REV1.4 but it will require quite some tracks cutting and re-wiring.

7
AB528 Microphone preamplifier / Re: AB528 DI not working
« on: September 13, 2023, 08:52:15 am »
Send a 1VAC sine signal into the DI input and check if you can measure it on U2 pin1 (the square pin) against 0V. You should read 1VAC on the meter.
Also check there is no DC voltage on this pin.
If all OK, the issue must be on relay RLY1.

8
MP573 Microphone preamplifier / Re: MP573 - No low end
« on: September 08, 2023, 10:36:42 am »
These are good.
Check the solder joints of the input transformer pins and of the daughter board to main board connections.
Next try to follow the signal like said here: https://www.soundskulptor.com/forum/index.php?topic=5.msg5#msg5

9
LA502 Optical Compressor / Re: Two LA502 with different output levels
« on: September 07, 2023, 09:03:15 am »
Can you tell me what are the revision number on both units? there have been some design changes over time.

10
MP573 Microphone preamplifier / Re: MP573 - No low end
« on: September 06, 2023, 10:28:16 am »
Can you check the input DC resistance: ohmmeter between pin2 and pin3 of input XLR, power on, Z switch on 1200. Should read about 48 Ohms.
Next check the output DC resistance: ohmmeter between pin2 and pin3 of output XLR, power off. Should read around 42 Ohms.

11
AB528 Microphone preamplifier / Re: Noisy/Clicky
« on: September 06, 2023, 10:15:06 am »
Check that the 48V is present on both microphone balanced lines (input XLR pin2 and pin3), against lunchbox chassis.
Check the solder joints on R1, R2, C1, SW1, RLY1, RLY2, RLY3.
Try removing C1, in case it is damaged.

12
DI503J Triple DI and Re-Amp / Re: Old vs New
« on: September 06, 2023, 10:08:14 am »
👍

13
MP566 Tube microphone preamplifier / Re: Stops working after some time after years in use
« on: September 06, 2023, 10:07:12 am »
Great news!

14
DI503J Triple DI and Re-Amp / Re: Old vs New
« on: September 02, 2023, 10:27:22 am »
Do the units sound the same when DIST is off (up)?
If so, the issue is somewhere in TR1, C9, C10, C11, R17, R18, R19, L1.
Check the value and solder joints on these components.

15
MP566 Tube microphone preamplifier / Re: Stops working after some time after years in use
« on: September 02, 2023, 10:20:04 am »
Yes you should upgrade the PTC's to 300mA ones.
In the mean time you could short them with wires. The PTC's are there to prevent shutting down the whole lunchbox in case of a module failure.

16
AB528 Microphone preamplifier / Re: AB528 DI not working
« on: September 02, 2023, 10:15:51 am »
Does the XLR input still pass through when there is a plug in the DI input?

17
MP566 Tube microphone preamplifier / Re: Stops working after some time after years in use
« on: August 26, 2023, 11:18:19 am »
Just make sure it doesn't get too hot 👍

18
AB528 Microphone preamplifier / Re: Noisy/Clicky
« on: August 21, 2023, 05:26:58 pm »
Does the preamp work apart from the noise?
Does the noise level depend on the position of the pot?
Does it depend on the gain switch position?
What is the DC voltage on Q5 collector, taken on the heatsink? Should be about -0.5V.
Check that all your electrolytic caps are in the correct direction.

19
CP554 Diode bridge compressor / In case your CP554 doesn't work as expected
« on: August 18, 2023, 11:49:03 am »
Check the usual suspects:
Forgotten solder joint,
Bad solder joint (reflow suspicious joints),
Reversed components (transformer,s 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:
Check the supply voltages as described in the setup guide.

Check the side chain:
Set the compressor as described in step 9 of the setup guide.
Remove the jumper on JMP1.
Inject a 1VAC sine signal into the input.

Threshold switch position     TP4 & TP5 AC voltage    JMP1 pin1 DC voltage
+6dB    0.11V    0.14V
  0dB    0.22V    3V
-6dB    0.45V    10.8V
-21dB    2.4V    15V



20
CP4500 Stereo Bus Compressor / Re: Comp not engaging when ‘in’
« on: August 17, 2023, 05:02:49 pm »
The unit stopped compressing on both channels at the same time, right?
Check if you get some side chain signal on TP11. It is a negative going DC level which reflects the input amplitude.
Then check if it is also present on TP12, added to a voltage controlled by the makeup pot.

21
MP566 Tube microphone preamplifier / Re: Stops working after some time after years in use
« on: August 16, 2023, 04:50:06 pm »
I don't think it is the tube. More probably the high voltage converter U5 or a resettable fuse PTC1 or PTC2.
The high voltage converter doesn't like being very hot.
When it happens again check the high voltage (+225VDC) on TP2 as well as the heater voltage (-4VDC) on TP8, against 0V.

22
CP554 Diode bridge compressor / Re: JMP1 Missing CP554
« on: August 16, 2023, 04:41:01 pm »
Sorry for the missing bit.
Is it the header missing or the jumper?
It wouldn't be convenient to solder it because you will need moving it during the setup.
Email me here so we can send you one.

23
CP4500 Stereo Bus Compressor / Re: Comp not engaging when ‘in’
« on: August 10, 2023, 05:33:33 pm »
Does the makeup potentiometer increases the output level?

24
CP4500 Stereo Bus Compressor / Re: Meter Light not working
« on: August 04, 2023, 06:26:04 pm »
First thing to check is the meter connector. Make sure the contacts are inserted the right way round with the latch in the side rectangular hole.
The meter is controlled by U21 pin 1 via the trimmer T4 and resistor R100. The FET Q1 inhibits the meter when the compressor is bypassed.

25
AB528 Microphone preamplifier / Re: AB528 in a Trident Deca Dent chassis?
« on: August 02, 2023, 04:05:52 pm »
Yes, the PTC resistors we are talking about are in the lunchbox.
Some of our modules also have one or two, but not the AB528.

Things you could check on the AB528:
- Swapped power transistors Q5 and Q6,
- Reversed diode,
- With the phase  switch on center (which disconnects the out TX) check the voltage across resistor R33 at power up. It should not go over 100mV.

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