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EQ573 Equaliser / Ceramic Capacitor Issue

« Last post by cmcclellan on September 27, 2025, 04:15:39 AM »

I ordered two EQ573 kits and just got around to building them. The two kits have different variations of ceramic capacitors provided. The issue lies in the ceramic capacitors 471 and 470. To be clear, the BOM states that you need five ceramic capacitors reading 470 (47p) and five ceramic capacitors reading 471 (470p).

The first EQ573 kit provided three ceramic capacitors reading 470, two reading 471, five reading K2J and one capacitor reading K1J. These are pictured below. There is nothing in the BOM reading K1J or K2J.





The second EQ573 kit provided three ceramic capacitors reading 470, three reading 471, and then four reading K2J.
These are pictured below.


It seems I should have been provided five 470 ceramic caps and five 471 for each kit. Am I misunderstanding something with the other capacitors provided? Any clarification is appreciated. Thanks.

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MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« Last post by soundguy937 on September 18, 2025, 06:48:38 PM »

Thanks a million, definitely taking notes on my mistakes.

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MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« Last post by JPK on September 18, 2025, 05:48:33 PM »

Hello, your module is repaired.
There were two problems.
The first was the broken 2n7000 (be careful of static electricity, this component is very sensitive) and the second was the defective solder on the tube's PCB. I think the solder you're using isn't the best quality for proper soldering. I noticed some residue due to the solder. The connection to the tube wasn't perfect (there was noise in the tube and the tube's balance voltage was impossible to achieve).

The module has been calibrated and reassembled. It's ready to use!

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MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« Last post by soundguy937 on September 18, 2025, 04:39:22 PM »

My unit should have arrived late last week. Do you have an eta when you or your staff will be able to take a look at it?

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MP566 Tube microphone preamplifier / Re: MP566 fault troubleshooting help needed.

« Last post by JPK on September 16, 2025, 05:50:42 PM »

The L272 has become difficult to find these days.
You can replace it with a TCA0372DP1.
Like any other integrated circuit, it can be killed by overvoltage on any pin, a short circuit on some pins and by overheating.

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MP566 Tube microphone preamplifier / Re: MP566 fault troubleshooting help needed.

« Last post by mrevans on September 15, 2025, 09:01:37 PM »

Thanks for the fast reply! I followed your instructions, and I can measure 12V between V- and TP8 and 225V between 0V and TP2 on both units. 
I will replace the U4 on both of them and let you know if they work fine now.
They both failed at the same time. I think it was a problem related to the 500 Rack PSU where  I had mounted them. One voltage rail was having problems.
I do not think they overheat. In your experience, what is the most common failure cause of the L272?

Cheers. 
Jorge

77

MP566 Tube microphone preamplifier / Re: MP566 fault troubleshooting help needed.

« Last post by JPK on September 14, 2025, 04:39:05 PM »

The problem is on U4 or U5 or U6 or U7 or several of these.
Remove U4 and create a small jumper with a little piece of wire, between pins 2 & 3.
Place the voltmeter between 0V and TP2 and power on. If the high voltage is present then U5 is OK.
Remove the jumper and place anotherone between pins 1 & 2.
Place the voltmeter between V- and TP8 and power on. If the 12V is present then U6 and U7 are OK.
If both tests are OK, you just need to replace U4.

Did the 2 pres broke down at the same time? Did they overheat?

78

MP566 Tube microphone preamplifier / MP566 fault troubleshooting help needed.

« Last post by mrevans on September 12, 2025, 02:01:03 PM »

Hi, I have a pair of MP566 that I have used for some years, suddenly stopped working. I have followed the guides and read the forum for clues or maybe solutions. 
from the test guide
1. There is no short circuit on v+ or v- and GND
2. I get 0Vdc  when testing the High voltage between TP2 and 0V
3. On 1 unit the v+ is 15.9V and the V- is around+7V, on the second unit  the v+ is -6.5V and V- is-16V. 
4. The current consumption on the rails is 400mA on one and 30 mA on the other. 
5. I read in one of the threads to remove U1 U4 and the Tube   to check if the V+ rail and V- rail would get +16 V and -16V respectively.  I removed U1, U4 and the vacum tube on both units and  I do get +16V on V+ and -16V on V- . 
6. I am looking for the next steps to follow since on the other threads there was another issue. Regarding a reversed diode.

Thank you! Please let me know what other tests should I do. I am suspecting that either U1 or U4 are damaged, but how to test that?. The revision of the board I have is 1.5
BR Jorge

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Discussions about the products / Re: Christmas wish-list new modules suggestion!

« Last post by JPK on September 09, 2025, 11:39:45 AM »

Thank you for the clarification.

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Discussions about the products / Re: Christmas wish-list new modules suggestion!

« Last post by Lud on September 08, 2025, 06:57:07 PM »

And a U47 or 48