AML EZ1073 500 Series

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Joeblutak

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Joined
Jul 24, 2021
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5
Location
London
Hi all,
I've been having a bit of trouble with an AML EZ1073 500 series pre that I've built. It largely seems to be working - the relay clicks on and it amplifies sound all good, however the sound is rather thin and tinny, any bass is gone and it's slightly crunchy and quiet. I've gone back through the instructions and checked over everything, reflowed solder joints and made sure my transformers are in the right way round etc but I'm at a bit of a loss as to what might be causing this - does anyone have any ideas what might be the source of the issue? I've built a few pedals before but this is my first preamp build.
The other issue with it is that the phase switch makes the signal significantly quieter when it is in regular phase as opposed to opposite phase.
Cheers,
Joe
 

[email protected]

New Member
Joined
Jan 21, 2021
Messages
9
G'day Joe,
I'm having trouble with my ez1073 too.
I finished building an AML ez1073 500-series a couple of weeks ago and I wonder if my problem is similar to what you're experiencing. When I power up the unit with an SM58 connected the signal is clean and strong, then 20-30 seconds later the signal fades to very weak and crunchy (distorted). I've checked component orientation, re-soldered most of the joints on the main PCB to ensure no cold solder joints, but no change to the problem.
I was able to calibrate the 90mV across TP1 & TP2 without issue. Any issue for you?
Could you try something for me? Power down your ez1073 and wait for 10-15 mins. With a mic plugged in, switch the ez1073 on and see if you have a reasonable signal for approx 15-30 seconds before the signal fades out. This may confirm we're looking at the same issue.

If you have any tips for me I'd be very interested.

As a point of interest, I've built five CAPI 500 series pre-amps, two CAPI 1176 compressors and a DIYRE OLA5 opto-comp without issues. But this DIY AML ez1073 project has me stumped.

Any assistance appreciated.
Al
 

Joeblutak

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Joined
Jul 24, 2021
Messages
5
Location
London
Hey Alan, the issue with me is that the signal is weak and crunchy from the get go! I've been through the same checking process as you but still no change also - despite the fact I've managed to calibrate the 90mV as well.
I tried powering up and waiting, but it's hard to tell as the signal seems as crunchy and tinny as when I turn it on.
 

[email protected]

New Member
Joined
Jan 21, 2021
Messages
9
G'day Joe,
Thanks for getting back to me and appreciate the feedback. Sounds like your issue may be a little different to mine. I have re-soldered every joint on the main PCB but no change. This week end I'm going to check every capacitor within the whole circuit. I've performed a visual inspection of the Cap directions best I can with the unit assembles. I think the next step will be removing the smaller PCBs from the main PCB for a more detailed inspection of solder joints and cap directions.
I'll forward another update when I've completed this weekend's circuit check, including any observations that I think may be of assistance to your problem diagnosis.
Cheers,
Al
 

iambeatmenace

Member
Joined
Mar 1, 2014
Messages
12
I have an issue with my AML ez1073 500 series module and I was hoping to share with you for a solution as the AML folks haven't been of much help because it's a kit I bought and apparently, they don't offer troubleshooting and advice when something goes wrong.

I have a few questions and might need some help if anyone has the time to walk me through a few things. I got 2 kits and I followed the instructions to the T (or at least, I thought I did) and eventually built both.

Problem is the completed AML pres put out phantom power (led comes on) but nothing else works. I realized this during the step I had to calibrate the voltage pots etc and the readings were all null so it's pretty obvious actual current isn't passing through but phantom power very likely is as the LEDs on the unit come on.

I messaged Colin of AML only to be told they don't offer support for kits and thats the reason for the option to buy pre-assembled which was a pricy decision I couldn't afford at the time. I have learnt my lesson the hard way.

I wanted to know if there was a way anyone could be of help to help me diagnose what might possibly be wrong; or, alternatively, at the very last resort have them sent to you to be checked etc.

Any help and/ or assistance will be very much appreciated. Thanks and have a lovely week guys.
 

FarisElek

Well-known member
Joined
Oct 26, 2019
Messages
438
G'day Joe,
I'm having trouble with my ez1073 too.
I finished building an AML ez1073 500-series a couple of weeks ago and I wonder if my problem is similar to what you're experiencing. When I power up the unit with an SM58 connected the signal is clean and strong, then 20-30 seconds later the signal fades to very weak and crunchy (distorted). I've checked component orientation, re-soldered most of the joints on the main PCB to ensure no cold solder joints, but no change to the problem.
I was able to calibrate the 90mV across TP1 & TP2 without issue. Any issue for you?
Could you try something for me? Power down your ez1073 and wait for 10-15 mins. With a mic plugged in, switch the ez1073 on and see if you have a reasonable signal for approx 15-30 seconds before the signal fades out. This may confirm we're looking at the same issue.

If you have any tips for me I'd be very interested.

As a point of interest, I've built five CAPI 500 series pre-amps, two CAPI 1176 compressors and a DIYRE OLA5 opto-comp without issues. But this DIY AML ez1073 project has me stumped.

Any assistance appreciated.
Al
If it fades after some time it sounds like it's overheating. Is it properly attached to the heat sink with the thermal shield and all. I fixed a friend's unit that was terrible at soldering and understanding how important these little pieces were for the electronics to function properly.

Also, he soldered everything from the top. Don't do that....tape it with masking tape and solder from the bottom (opposite side the resistor, capacitor, etc sits)
 

[email protected]

New Member
Joined
Jan 21, 2021
Messages
9
If it fades after some time it sounds like it's overheating. Is it properly attached to the heat sink with the thermal shield and all. I fixed a friend's unit that was terrible at soldering and understanding how important these little pieces were for the electronics to function properly.

Also, he soldered everything from the top. Don't do that....tape it with masking tape and solder from the bottom (opposite side the resistor, capacitor, etc sits)
Hi Faris,
Thanks for your reply and an interesting idea regarding the transistor heat sink. This DIY build include thin insulation mats TO220 & TO247 that wedge between the transistors and its heat sink. I checked a few images of other ez1073 builds to check that I had the insulation mats the correct way around. Seems correct, and would be difficult to get them mixed up given they're significantly different in size.
However, along the same train of thought, I wonder if a supply voltage or current to the transistor is too high, generating too much heat. Any ideas?

Regarding the soldering, this is my sixth pre-amp build but my first problem I haven't been able to solve. It's also my first AML kit build. I've also built two CAPI FC526 (1176 clones) without issue and they were considerably more complex. (Got me puzzled how one could solder from the top of the board - lol).

Anyways, any further tips will be greatly appreciated.

Cheers,
Al
 

[email protected]

New Member
Joined
Jan 21, 2021
Messages
9
I have an issue with my AML ez1073 500 series module and I was hoping to share with you for a solution as the AML folks haven't been of much help because it's a kit I bought and apparently, they don't offer troubleshooting and advice when something goes wrong.

I have a few questions and might need some help if anyone has the time to walk me through a few things. I got 2 kits and I followed the instructions to the T (or at least, I thought I did) and eventually built both.

Problem is the completed AML pres put out phantom power (led comes on) but nothing else works. I realized this during the step I had to calibrate the voltage pots etc and the readings were all null so it's pretty obvious actual current isn't passing through but phantom power very likely is as the LEDs on the unit come on.

I messaged Colin of AML only to be told they don't offer support for kits and thats the reason for the option to buy pre-assembled which was a pricy decision I couldn't afford at the time. I have learnt my lesson the hard way.

I wanted to know if there was a way anyone could be of help to help me diagnose what might possibly be wrong; or, alternatively, at the very last resort have them sent to you to be checked etc.

Any help and/ or assistance will be very much appreciated. Thanks and have a lovely week guys.
Hi there,
I'm having issues with my ez1073 build as well. Maybe we can help each other.
Did you complete the bias test and adjust to 90mV? Any issue?
I also have phantom power working, and a condenser mic will work for approximately 30 seconds before the signal attenuates and the small, low level, remaining signal starts to distort heavily.
Have you checked all the basics? E.g. Large Electrolytic Capacitors, the 5 diodes, and the BC550C transistors are all facing the right way?
I've also gone over all my solder joints, but still experience the same problem symptom.

Any other observed symptoms when testing your pre-amps, that you could describe?

Al
 

[email protected]

New Member
Joined
Jan 21, 2021
Messages
9
Well, I'm a bit stumped regarding what I fixed, but my ez1073 has been working flawlessly for a few days. All I did was inspect as many components as possible, measured what I could to confirm values, pretty much gave up on finding anything wrong. So I plugged it in to my API 500V just to get it out of the way.
A few days back I plugged a P-bass in just to see what would happen and the ez1073 sounded fine. I then tested a few mics, low and behold, no problem. Condenser mic, dynamic, ribbon, etc. I've been randomly testing for a few days and it's still working. No idea what I did but seems to be fixed.
I did leave it in the rack powered up for a few days. I wonder if simply having power running through it has altered something.
I'll report back if anything changes.
 

[email protected]

New Member
Joined
Jan 21, 2021
Messages
9
G'day Joe,
After your message I plugged in a condenser mic to my ez1073 and it worked flawlessly for an hour. I hadn't used it for a few weeks but your inquiry sparked my curiosity.
What signal did you use for calibration? The calibration instruction states -40dBu (7.75mV) but no frequency, so I used 1kHz. You?
I found 7.75mV RMS challenging to obtain and I'd be interested in how you performed the calibration.
The pre appears to be working find, but I'm sure it's not calibrated accurately.
 

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