Author Topic: MP566 not working

July 19, 2022, 09:17:32 PM
Read 4237 times

narekm97

  • Newbie
  • *
  • Posts: 1
  • Karma: +0/-0
    • View Profile
Hello, 

When I connected my MP566 to my lunchbox, I turned on the power and got a red light on the LED. After around 5 seconds the LED light went out and I couldn't get any signal through the preamp. Not sure where to look for the problem 

July 20, 2022, 05:58:04 PM
Reply #1

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
Check again the voltages then follow these tests: https://www.soundskulptor.com/forum/index.php?topic=209.msg981#msg981
JPK

December 06, 2023, 05:38:47 PM
Reply #2

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
I have the very same problem as described above.

I also checked Topic: "In case your MP566 doesn't work as expected" - there are no "usual suspect" to be found on my build.

Neither the DI nor the Mic in let any signal through.

What should I do?

December 07, 2023, 09:30:28 AM
Reply #3

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
Try to follow the signal as described in the same place here.
It will tell you where to look.
JPK

December 07, 2023, 10:54:40 AM
Reply #4

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
Thank you for replying.

I was not able to follow the instructions to "follow the signal" - I am new to this DIY stuff and I simply don't know what to do with the instructions.

Since this is my first build, I might have done something wrong, although I took special care to insert all the components in the right direction.

This is what happenes:
- I turn on the power of my R6, the LED flashes red for about a secont or two then it goes out
- the device emitts a faint smell, so I think some components are heating, the tube is not getting warm and the tube does not light up

Here is, what the test-restults are:

Test 1 (Short circuit test) -> 2,72 MOhms (If I got the test right, since there is no GND test pin on my board)

Test 2 (High Voltage Test) -> 0,03V and decreasing over time to 0

Test 3 (Low Voltage Test) -> -0,02 and rising to 0

Test 4 (Signal Check) -> I read 1,63V between OV and TP4, the LED stays off even if I max out the Output potentiometer

If you know what that means; I would be greatful to get any advice how to find and fix the problem.

December 08, 2023, 11:32:38 AM
Reply #5

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
There is something wrong around U4, D14, D15, R47...R50.
Check value, direction and solder joints.
JPK

December 08, 2023, 07:25:45 PM
Reply #6

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
Thank you. I checked the components you told me:

U4 - direction ok, solder joints ok

D14 - direction ok, solder joints ok

D15 - direction ok, solder joints ok

R47 - 330k - ORG-ORG- BLK- ORG-BRN measures at 105 kOhm

R48,49,50 - 47k - YEL-VIO-BLK-RED-BRN measure at 41kOhm

So there is one difference in R47... is that the problem?



December 11, 2023, 10:22:28 AM
Reply #7

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
From the picture I can see that you have the wrong IC in U4 (OPA134 instead of L272/TCA0372).
The OPA134 goes in U1.
JPK

December 11, 2023, 02:46:03 PM
Reply #8

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
Thank you. I switched the ICs and now it tests as follows:

Test 2 (High Voltage Test) -> 223,7V

Test 3 (Low Voltage Test) -> 0,0 V

Test 4 (Signal Check) -> LED stays off all the time. I measure 0,003 VAC with in and out turned on to max.

Where else can i look for problems?

December 11, 2023, 05:17:07 PM
Reply #9

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
You have probably destroyed the TCA0372 by putting it in the wrong spot. Maybe both IC's.
JPK

December 14, 2023, 04:07:16 PM
Reply #10

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
Thanks for your help.

I replaced both ICs - but nothing changed. It still does not work.

Test 1 (Short circuit test) -> 2,72 MOhms

Test 2 (High Voltage Test) -> 223,8V

Test 3 (Low Voltage Test) -> -0,04 and rising to 0

Test 4 (Signal Check) -> LED stays off all the time. I measure 0,003 VAC with in and out turned on to max.

What could it be?

December 15, 2023, 08:57:03 AM
Reply #11

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
The heater is not working.
Check the tube heater by measuring the resistance value between TP8 and V- (with power off): ~12 ohms.
If you don't get this value, check on the tube itself between pins 4 and 5 (bottom view).
JPK

December 15, 2023, 09:14:14 AM
Reply #12

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
I measure:

between TP8 and V- => 12,3 ohm - Sometimes wildly jumping up to 15 to 20 Ohms

between pin 4 and 5 of the Tube (bottom view): 16 ohms and rising

between pin 5 & 6 (bottom view): 12,2 Ohms
« Last Edit: December 15, 2023, 09:37:55 AM by heimito »

December 15, 2023, 11:46:09 AM
Reply #13

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
between pin 5 & 6 (bottom view): 12,2 Ohms
Do you confirm. This is totally uncorrect.
Can you check again the tube when disconnected?
JPK

December 15, 2023, 01:49:21 PM
Reply #14

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
You are right. I was off by one pin.

I measured again with the tube disconnected: 127,5 Ohms.

Do I need a new tube?


December 18, 2023, 06:19:22 PM
Reply #15

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
Is that between pins 4 and 6 (not sure from the photo).
If true, then you need to replace the tube. Contact us here.
JPK

December 29, 2023, 01:31:28 PM
Reply #16

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
Thank you - I replaced the tube, now audio is coming through. But very very quiet.

The sound is not distorted or anything, but very quiet.

Here is what I did:

I set the Input Level on my apollo twin to 3/4 (that is 52dB)
I set the MP566 Input to 10 and output to 10

With the Gain Switch to low: I receive 46dB of level
With the Gain Switch to mid I receive 20dB of level
With the Gain Switch to hi: I receive 36dB of level (yes, acutally quieter than with mid)

Still seems something to be wrong. What else could I do?

December 29, 2023, 05:40:50 PM
Reply #17

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
Try sending the signal via the DI jack and check if it is louder?
Try to follow the signal
JPK

January 01, 2024, 03:05:31 PM
Reply #18

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
I re-checked:

Audio-Check:
POT in & POT out set to 10
Apollo Twin set to 65 dB input (fully turned up) - Noise is at 46dB constant

Code: [Select]
Line-in:     |  High-Z in:
Lo:  -27 dB  |  Lo:  -18 dB
Mid:  -5 dB  |  Mid: -18 dB
Hi:  -25 dB  |  Hi:  -36 dB


Then I followed the signal. I sent the 1000Hz sine to the line-in, measuring 0,5V between 8 and 10 of the extender

Code: [Select]
    | black probe | red probe
------------------------------
TP1 |  0,142 V    |  0,207 V
TP3 |  0,137 V    |  0,217 V
TP4 |  0,164 V    |  0,227 V

January 03, 2024, 10:44:55 AM
Reply #19

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
    | black probe | red probe
------------------------------
TP1 |  0,142 V    |  0,207 V

The value on TP1, TP3, TP4 are measured against 0V (black probe on the 0V test pin).
The value on TP1 should be around 3VAC with the gain switch on MID.
Do you get a better level when sending the signal on the DI input?
JPK

January 08, 2024, 03:36:09 PM
Reply #20

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
Thank you for clarifying.
I remeasured: black probe to oV - red probe to TP1, TP3, TP4.

Code: [Select]
    | Line-in |  DI in
-----------------------
TP1 |  0,0V   | 0,496V
TP3 |  0,0V   | 0,0V
TP4 |  0,0V   | 0,0V

Same results for Gain Switch lo, mid and hi
Potentiometers did not affect the measurement

I got 0,496V on pin 8 and 10 of the extender - my multimeter showed 1,044kHz - so the input should be right.

January 09, 2024, 10:18:09 AM
Reply #21

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
You have 2 issues here.
- The input signal not reaching the first triode: Check the connections on RLY1, transformer T1, potentiometer P1.
- The tube amp gives no output: Check the connections on the tube, on potentiometer P2.

Check the usual suspects.
JPK

January 09, 2024, 04:10:13 PM
Reply #22

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
I checked all the connections. Solder joints look okay to me, only T1 looks a bit strange.

I remember having trouble soldering the 90° connectors of the tube PCB (A) to the Main PCB. The solder just didnt stick correctly.

Please find attached pictures of the joints.

Should I resolder?


RLY1


T1


P1


Tube socket


PCB Connector


P2


January 09, 2024, 04:56:19 PM
Reply #23

JPK

  • Administrator
  • Hero Member
  • *****
  • Posts: 1052
  • Karma: +31/-0
    • View Profile
This solder joint on T1 looks bad:



Should I resolder?
Do not hesitate to reflow any suspect joint. Your iron should be hot enough, around 320-350°C.
JPK

January 28, 2024, 11:41:11 AM
Reply #24

heimito

  • Newbie
  • *
  • Posts: 23
  • Karma: +0/-0
    • View Profile
I finally got the time, to resolder and do the tests again.

The signal is now coming through louder
- Pot IN and Pot OUT turned to max
- input level on my apollo is turned to max (65dB)
- Signal is louder but only in position mid gain (solid level up to 0dB)
- but Signal is very very noisy.

Test 4 (low voltage check) -> -15V

Test 5 (signal check)

Code: [Select]
    |          Line In         |/|           DI In          |
    |   Lo   |   Mid  |   Hi   |/|   Lo   |   Mid  |   Hi   |
----|--------|--------|--------|/|--------|--------|--------|
TP1 | 0,271V | 3,043V | 3,043V |/| 0,496V | 0,496V | 0,496V |
TP3 | 0,000V | 0,006V | 0,000V |/| 0,000V | 0,000V | 0,000V |
TP4 | 0,001V | 0,019V | 0,001V |/| 0,002V | 0,002V | 0,000V |

What else should I try?