AML ez1073 build and troubleshooting thread

[Delta Sigma]

All AML ez1073 build and troubleshooting posts.

I wanted to post a question about an ez1073 pre but could not find a build thread. I found the original @Slenderchap feeler thread and tonnes of individual problem threads. I'm personally not a fan of a new thread popping up every time someone has an issue so I thought I could make this thread for future ez1073 problems.

Colin, any opinion on that? I figured both EQ and pre posts could stay here since there could be issues related to connecting the pre and add-on eq.

 

[Delta Sigma]

My ez1073 issue:

A friend contacted me for help with his ez1073. Symptoms were a thin sound at low gain settings, then the signal dropping completely when the gain is stepped up three or four steps. This doesn't line up with the extra gain stage. He brought it over and it was dead. LED lights when phantom is engaged, but no audio at all. I don't own any 500 series gear, so I don't have an extender. When I pulled the unit out, the heat sink felt fairly hot.

Anyone deal with something similar before? I'm suspecting the regulator, but I'm really not sure.

He's ordering an extender so I can actually troubleshoot, but I thought I'd take a stab in the dark and see if anyone had similar issues.

 

[EarthTone]

It’s easy to mix up the trimmer resistors for the input voltage and the output level during calibration. Once I accidentally mixed them up and almost fried the big resistor at the top of the circuit. Thankfully I cut off power and it only smoked a little and nothing got damaged and that big resistor value didn’t change and the pre has been working great for a long time since then, several years. But it is something to check for if they tried to calibrate it themselves. I’m not in front of my computer right now so I can’t give you layout data but it’s the big grey resistor that takes the brunt of an over-voltage if that happens, and if it fails, anything behind it would potentially be cooked as well... Look to see if the big grey resistor is burned/measure it for correct value and check visually on anything else down the line as well.

Also could easily be a transformer wire became detached. The little thin transformer wires are sometimes soldered on poorly and one of mine came loose once. I put it back with some solder and that one also still works great.

Hmmm what else comes to mind to check for… Nothing immediately. I’ve built a bunch of these so if anything else comes to mind I’ll post back. Hope you figure it out.

I’m convinced this build is the best value to tone quality ratio in the preamp game. These pres sound incredible. I have 8 (4 rack 4 500) with all stock parts and helped a friend build 3 for himself as well and they are amazing.

 

[Delta Sigma]

It’s easy to mix up the trimmer resistors for the input voltage and the output level during calibration. Once I accidentally mixed them up and almost fried the big resistor at the top of the circuit. Thankfully I cut off power and it only smoked a little and nothing got damaged and that big resistor value didn’t change and the pre has been working great for a long time since then, several years. But it is something to check for if they tried to calibrate it themselves. I’m not in front of my computer right now so I can’t give you layout data but it’s the big grey resistor that takes the brunt of an over-voltage if that happens, and if it fails, anything behind it would potentially be cooked as well... Look to see if the big grey resistor is burned/measure it for correct value and check visually on anything else down the line as well.

Also could easily be a transformer wire became detached. The little thin transformer wires are sometimes soldered on poorly and one of mine came loose once. I put it back with some solder and that one also still works great.

Hmmm what else comes to mind to check for… Nothing immediately. I’ve built a bunch of these so if anything else comes to mind I’ll post back. Hope you figure it out.

I’m convinced this build is the best value to tone quality ratio in the preamp game. These pres sound incredible. I have 8 (4 rack 4 500) with all stock parts and helped a friend build 3 for himself as well and they are amazing.

He bought it assembled from a builder on Kijiji (Canadian Craigslist). I'll check that resistor though! All the transformer wires were OK.

The schematic is laid out really well, but I printed it 11x17 at work and found it hard to read the text at home. I hope it's the drawing and not my eyes getting old!

I regretted not printing out the PCB layout. Could find anything on the board! Beautiful PCB design though. I love seeing so much crammed into a 500 series unit.

 

[Voyager10]

Just to check - it's this one here, right?
https://www.audiomaintenance.com/downloads/ez1073pre_colourbook.pdf
Generally the first step with debugging analogue circuits is to measure the DC voltages at various points, so you'll need an extender or other way of powering it while you measure.

I guess you've got a multimeter. Any other test equipment? A bench power supply can be really useful, as is a signal generator. (An old phone or iPod with a headphone output which can run a 'tone generator' app makes a great signal generator for the audio range).

 

[KraftWerk]

I had similar issue with my Aml ez 73. Symptoms was the same...Thin sound and pot not responding on upper levels.2 days I was searching for mistake. It was my fault. Bad soldering between motherboard and stage 2 . Be sure that soldering paste go out on booth side.