26

TS500 Tape Simulator / Re: TS500 different version out of phase?

« on: October 25, 2023, 09:21:31 AM »

Right, it was corrected in REV1.5.

27

TS500 Tape Simulator / Re: TS500 different version out of phase?

« on: October 23, 2023, 05:51:37 PM »

Here it is

28

MP573 Microphone preamplifier / Re: How much deviation of the voltages is acceptable during setup?

« on: October 21, 2023, 09:34:32 AM »

The measured voltages depend on the actual PSU of your lunchbox so a 10% deviation is acceptable.
Plugging in the output transformer should show a small decrease in the V+ voltage.
If it doesn't, check your output tansformer connections, verify the output transformer DC resistances.

29

MU524 Vari-Mu Tube Compressor / Re: My Problems begin at step 6 of setup

« on: October 21, 2023, 09:27:17 AM »

TP1 = TP2 UNSTABLE
This is for VAC, right?

Remove U4 and check again step 6. Does it change?
Remove the front panel and measure the AC voltage on TP3 and TP4. It should be 1.8VAC.
Is the input transformer T1 in the correct direction, label facing to the back?
Did you check this : Make sure that capacitor C12 do not touch the transformer daughterboard pins. It is very close and if the pins can pierce the insulation the circuit will oscillate.

30

CP554 Diode bridge compressor / Re: Suddenly no output! Help please

« on: October 17, 2023, 09:23:16 AM »

Send a constant sine signal to the input and check if you can measure it with your AC voltmeter on TP1 and TP2, against 0V.
It must vary in level with the input signal and the compressor makeup gain.

31

MP573 Microphone preamplifier / Re: noise floor issue

« on: October 17, 2023, 09:17:49 AM »

It doesn't matter.
We are just testing in case a defective cap generates the noise.
You can use any cap with a voltage similar or higher and a value similar or higher.

32

MU524 Vari-Mu Tube Compressor / Re: MU 524 build problems

« on: October 16, 2023, 09:02:52 AM »

If you are stuck troubleshooting your mu524, I recommend sending it to us for verification. Contact me here.

33

MU524 Vari-Mu Tube Compressor / Re: MU 524

« on: October 16, 2023, 08:37:11 AM »

34

MP573 Microphone preamplifier / Re: noise floor issue

« on: October 16, 2023, 08:35:41 AM »

Try removing C24.
Try replacing C8 and C27 (for testing you can use any larger value).
Try replacing Q4.

35

MP573 Microphone preamplifier / Re: MP573 No input after assembling

« on: October 14, 2023, 04:10:54 PM »

These values are all good.
I start being short of ideas, maybe it's time for you to send us the unit for a check?

36

CP5176 FET compressor / Re: No audio passing on my 5176

« on: October 14, 2023, 04:03:30 PM »

Part number: H2RA-20-UA
https://www.digikey.com/en/products/detail/adam-tech/PH2RA-20-UA/9830622?s=N4IgTCBcDaIAoAkwCUCCBaMAGdBVVIAugL5A

37

MP573 Microphone preamplifier / Re: MP573 No input after assembling

« on: October 13, 2023, 03:34:27 PM »

Left side of R42 stays at 1
1Volt DC ?

This point should be 24V.
Please measure the DC voltage of both sides of R24 against 0V.
Also measure the DC voltage on TP2 against 0V (should be -9V).

38

MU524 Vari-Mu Tube Compressor / Re: MU 524

« on: October 13, 2023, 12:03:52 PM »

Sorry, yes P2.
It seem P2 does not go down to 0 Ohm.
Can you check directly on the pot, between the center pin and each side pin, after disconnecting the front PCB?

39

MP573 Microphone preamplifier / Re: MP573 No input after assembling

« on: October 13, 2023, 11:56:21 AM »

There is something really wrong in the DC values in H, I, J, L.

I repeat: The issue is around Q4...Q6, R40...R47, C24...C29.
Check the value, direction and solder joints on these components.

With the output transformer disconnected, what DC values do you get on G, H, I and on the left side of R42?

40

CP5176 FET compressor / Re: No audio passing on my 5176

« on: October 13, 2023, 11:08:28 AM »

Check the solder joints on transformer T1.
Check the solder joints on connectors CN3a and CN3b.
Check if you can measure the input signal between the 2 side pins of pot P1.

41

MU524 Vari-Mu Tube Compressor / Re: MU 524

« on: October 12, 2023, 12:12:40 PM »

These values are good.
With power off and still no IC's, measure the minimum resistance value of P1 between pins 6 and 7 of U1. It should go from 0 to 2k2.

42

CP5176 FET compressor / Re: No audio passing on my 5176

« on: October 12, 2023, 08:22:42 AM »

Check the value of R15, R14, R9 (by color code).
Check the direction of C12, C11, C6.
Try to follow the signal in TP1, TP2, L1 top pin.
The DMM must be set to AC volts. The voltage you read must vary with the position of pot P1.

43

MP573 Microphone preamplifier / Re: MP573 No input after assembling

« on: October 12, 2023, 08:06:23 AM »

I- 1.10
Your value in point I: is it negative or positive ?

44

MU524 Vari-Mu Tube Compressor / Re: MU 524

« on: October 12, 2023, 07:59:51 AM »

Check values of R1, R2 and P1.
In step 3 initial conditions,
Do you hear the pure input tone at the output or is it hum or noise?
What are the AC and DC voltages you get on TP1 & TP2?

45

MP573 Microphone preamplifier / Re: noise floor issue

« on: October 11, 2023, 11:49:52 AM »

Look for reversed electrolytics or tantalum between C24 and C29.
Is the V+ voltage correct?

Can you try the following:
Create a temporary short circuit between pins 2 and 3 of U2 (you can carefully use a small screw driver) and listen if it reduces the noise. If it does, then the noise source is U2 and it needs to be replaced.

46

MP573 Microphone preamplifier / Re: MP573 No input after assembling

« on: October 11, 2023, 11:26:46 AM »

The issue is around Q4...Q6, R40...R47, C24...C29.
Check the value, direction and solder joints on these components.
Check the connections of the output transformer (no short circuits between adjacent wires).
Check the output transformer coils resistances (unplugged: Yellow-Orange : 7.6 ohms, Red-Brown : 6.4 ohms, Blue-Green : 21 ohms, Violet-Black : 21 ohms)

47

AB528 Microphone preamplifier / Re: AB528 phantom power issue

« on: October 11, 2023, 11:13:44 AM »

This looks like a bad solder joint.
You could leave the pre on, waiting for a failure and when it happens, check if you can measure the signal on TP2, TP3 and TP4. this would narrow the search field.

48

MU524 Vari-Mu Tube Compressor / Re: MU 524 build problems

« on: October 11, 2023, 11:04:56 AM »

on the tube heater slow start test. i am getting 2.5 dcv with the tube in and 33.5 dcv with the volts removed.
You can try to shunt R39 (18R) with a little wire to remove the slow start circuit.

i am also wondering if that is normal or if that is because the tube is bad?
If the tube doesn't get the proper heater voltage, it is normal that all the other results are wrong.

i took the tube that was sent in to a local electronics place that has a tester for that tube and it didnt check out so i know its bad.
If confirmed, we will send you a new tube.

49

MP573 Microphone preamplifier / Re: noise floor issue

« on: October 09, 2023, 03:36:43 PM »

Your measured voltages are good.
Can you measure the noise AC voltage level on the output?
Do you get the same noise after removing the jumper on CN1?
Do you confirm that the noise doesn't vary in level with the -/+10dB potentiometer?

50

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.