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Messages - JPK

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851
MP566 Tube microphone preamplifier / Re: Hum at 60hz
« on: March 01, 2021, 05:01:55 PM »
Yes the tube stage makes the noise but not necessarily the tube itself. More probably one the switching regulators for the heater or the high voltage.
TP2 is the high voltage line and TP8 is the heater voltage.
Find out which one has the 80Hz hum.

852
News and updates / Re: Modules availability
« on: March 01, 2021, 04:55:53 PM »
10-15 days from now.

853
MP566 Tube microphone preamplifier / Re: No Mic Input And Saturation on DI
« on: February 25, 2021, 06:31:09 PM »
The No Mic issue may come from a damaged 2N7000 (Q1). This component is sensitive to static electricity and is better handled without your shoes on (body grounded).
You can check this by creating a short between the 2 extreme pins of this component. It should activate the mic relay.


Quote
I have a click between the Low and the Mid but nothing for the High
This is normal, the high gain is directly controlled by the switch, without a relay.

Do you have a gain variation between the mid and high gain?
Check the DC voltage on TP4. it should be close to 0.

854
EQP501 Passive Equalizer / Re: Signal passes through unit, but no EQ
« on: February 25, 2021, 06:17:50 PM »
Congratulations!

855
MP566 Tube microphone preamplifier / Re: Hum at 60hz
« on: February 24, 2021, 09:31:35 AM »
The output is the floating secondary of a transformer.
So you can only do measurements differentially between the hot and cold.
The audio connection to the output of the pre must be done with a balanced cable.

856
MP599 Microphone preamplifier / Re: Test procedure, Tp2 élevé
« on: February 22, 2021, 06:13:11 PM »
C9 possible.
C6 C7 C20 C21 je ne crois pas.

857
MP566 Tube microphone preamplifier / Re: Hum at 60hz
« on: February 22, 2021, 03:58:56 PM »
You can start looking to where the noise appears in the signal path:
Scope on AC, high gain. Check TP1, TP2, TP3, TP4.

858
First check the unit in a lunchbox that has another module in. If the other module still works when the MP573 fails, then the issue is not in the lunchbox.

Quote
starts making scratchy noises once it gets up to temperature
This is often caused by a bad solder joint the gets worth when getting warm.
Try reflowing the joints around the power transistor.
Next, try to follow the signal when it fails.

859
EQP501 Passive Equalizer / Re: Signal passes through unit, but no EQ
« on: February 22, 2021, 03:37:15 PM »
Check again the VDC on TP2 after removing U1.
If the large offset is still there then the issue is in the DOA.
If not it is around U1a, R10...R16, C17.

860
MP599 Microphone preamplifier / Re: Test procedure, Tp2 élevé
« on: February 22, 2021, 03:33:07 PM »
Sur le module D, the servo U1 empire l'offset au lieu de le réduire.
Il y a donc un problème quelque part entre R11...R17, C13, C14, U1.
Vérifiez les soudures. Nettoyez le PCB des résidus de flux.

861
MP573 Microphone preamplifier / Re: Troubleshooting MP573
« on: February 19, 2021, 06:50:36 PM »

Quote
yellow-orange: 23,8
red-brown: 19,4
These values are not correct. Did you measure with the transformer unplugged?

862
CP4500 Stereo Bus Compressor / Re: True bypass?
« on: February 19, 2021, 05:35:05 PM »
Is this on both channels?

863
MP566 Tube microphone preamplifier / Re: Hum at 60hz
« on: February 19, 2021, 05:33:19 PM »
It is not possible to mount the transformer the other way round. It is only EDCOR who changed the aspect.

864
MP599 Microphone preamplifier / Re: Test procedure, Tp2 élevé
« on: February 19, 2021, 05:27:32 PM »
Les pin 5 et 8 de U1 ne sont pas connectées. Le voltmètre dit n'importe quoi.
Il est normal que en fonctionnement, les mesures varient dans le temps car le DOA chauffe faisant varier l'offset.
Il semble que le D ait un problème. Avez-vous essayé de permuter les OP07 ?
Est-ce que la LED fonctionne normalement ?

865
News and updates / Re: Modules availability
« on: February 19, 2021, 05:09:16 PM »
Stock update on first post.

866
MP599 Microphone preamplifier / Re: Test procedure, Tp2 élevé
« on: February 18, 2021, 09:15:37 AM »
Sur le module D :
Vérifiez valeur et soudures de R16...R18, C13, C14, U1.
Vérifiez que les tensions d'alim arrivent bien sur U1 (pin4 et pin7 ).
Essayez de permuter les OP07.

867
CP4500 Stereo Bus Compressor / Re: True bypass?
« on: February 17, 2021, 12:06:42 PM »
Sorry, still not understanding.
What you should have if the unit is working properly:
IN button released: The signal goes through unaffected,
IN button depressed: The signal goes through compressed.

868
CP4500 Stereo Bus Compressor / Re: True bypass?
« on: February 17, 2021, 11:14:00 AM »
Do you mean no sound at all when off?
Or the compression continues when off?
On both channels?

869
Do you also have the short when the IN switch is off?

870
EQP501 Passive Equalizer / Re: Signal passes through unit, but no EQ
« on: February 17, 2021, 11:03:46 AM »
Send a strong sine signal (2VAC across cold and hot) to the input and check if you get 1.3VAC on TP1.
If not the issue is in the input stage. Check solder joints and components value of R1...R9, C1...C9, U1.
Check the supply voltages presence (- & + 15V) on pins 4 and 8 of U1.

871
MP573 Microphone preamplifier / Re: Troubleshooting MP573
« on: February 17, 2021, 10:32:54 AM »

Quote
1.: in the diy-kit, the Resitors R31,R39,..., R68 (eight in total, labled as '47k' in the component list) were in my case 10k Resistors.
This was an error on our part on some kits. You did well replacing them by the correct 47k (you should have told us so that we could replace them...).

Quote
The capacitor I soldered is labled '4n7j100'
This a 4.7 nF and it should go on C26.
C34 must be labeled 0,47.

Quote
L: 0,0
Check the connections to the output transformer on CN2.
Check the solder joints and also look for any short circuit between wires.
Also check the DC resistances of the output transformer.



872
MC624 Monitor Controller / Re: MC624 build
« on: February 17, 2021, 10:14:19 AM »
U3, U6, U8 = LM4562.

873
MP599 Microphone preamplifier / Re: Test procedure, Tp2 élevé
« on: February 16, 2021, 06:26:40 PM »
On parle bien ici de valeurs de tensions continues avec l'entrée audio déconnectée ?
Reaites les mesures avec le gain au minimum.
Et comparez avec des mesures sans U1, c'est à dire sans le servo.

874
MP566 Tube microphone preamplifier / Re: Hum at 60hz
« on: February 16, 2021, 11:53:08 AM »

Quote
If I were to change tube - which model should I chose?
ECC81 or 12AT7.


Every tube is microphonic to some degree. The ECC81 is considered not very microphonic.
Regarding the hum, do you have access to an oscilloscope? It would let you find out where the hum comes from. Is it the tube, or U6, U5, U2?

875
  • 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.

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