EZ 1290 Success!

[rp3703]

So this has been quite the journey. I have to admit I sort of lost interest at a few points along the way but I finally made it through to the end and it was well worth it. I would like to say right away that the EZ1290 boards worked perfectly right from the start. Same with the parts kit form ALM. Even when I tested them with the oscilloscope, both preamps tested perfect with no adjustment necessary. Besides the complexity of trying to figure out how to fit two EZ1290’s with their transformers and a power supply all into a 1U rack unit, the biggest problem I had with this project was with my choice of power supply. Instead of using the JLM PSU as suggested in the instructions, I chose to go with another PSU. The MNATS Variable +48V sold by Hairball. At this point I would like to state that the difficulty I experienced was no ones faults but my own and not the designer of the EZ1290, Madriaanse. I wanted to house the PSU inside the same 1U case that the preamps would be housed in so that there will be only a power cable out the back. No wall wart or separate PSU box. Anyhow, I chose to go with the MNATS Variable +48 since it fit the bill and was cheap. BAD IDEA! This PSU is not bad design wise but the actual PCB is crap. The circuit traces and solder pads are so small, it's next to impossible to even solder the components on. This was such a problem that some of the traces on the PCB broke. To remedy this, I had to scrape quite a bit of solder mask off and solder bridges to reconnect parts to the traces. My PCB required six fixes. I don't mean to be overly critical of the MNATS PSU but I have done a bunch of research on PSU design and even designed one for an 8 channel API 312 I built myself. This one is just plain bad. Regardless, I was able to fix the problems I had with the PSU and once remedied, the preamp worked excellently and tested perfect right from the start. I would like to thank Madriaanse and ALM for making it possible to build a two channel 1290 for less than $500. Way to go.

 

[madriaanse]

nice work! love the 1u layout. no hum?

 

[ATGuitar_Ninja]

Nice, seriously though, no hum from that toroid power transformer in channel 2 there?

 

[rp3703]

Just to reiterate, the MNATS variable + phantom power supply is a complete piece of shit. The solder pads are so weak, they cannot even hold the weight of the components soldered to them. Find something else.

 

[Flatpicker]

Just to reiterate, the MNATS variable + phantom power supply is a complete piece of shit. The solder pads are so weak, they cannot even hold the weight of the components soldered to them. Find something else.

This is really funny because I went down that same road around 7 years ago when I built a pair of EZ1290's with the MNATS PSU and spent a good amount of time scraping off solder mask and solder bridging just as you described. I ended up mounting the 24V regulator vertically with an oversized heatsink on it.

At first I was considering a Neve-gray front panel with Marconi style knobs, but then I realized, no, 1290 clones should be bright red with chickenheads, lol.

 

[Flatpicker]

I actually rolled my own PS circuit and board to replace the MNATS one (I just know one of those kludged connections is going to open up one of these days) but haven't ordered the boards yet. When I get it built and tested out, I'll share it on Osh Park so others can just purchase it for their neve-ish needs.

 

[rp3703]

Mine was working fine and then it started making a buzzing sound at 120HZ. Turned out to be one of the bridge diodes busted through it's solder pad. I took it all apart, which is not easy in a 1U rack and fixed it by scraping a bunch of solder mask off. I put the whole damn thing back together and now the 48V doesn't work. I can measure 24V across the diodes but nothing from that point on. The PCB is such a POS. Why would you take the time to design a PCB and put such small solder pads for your components to mount to?
I'd like to find an external switching PSU and just toss this linear one but have not had any luck. For now I guess I'm just going to have to scape solder mask off all the pads and hope that it will last me for a few years.
Nice red front panel. Do you find that you use the trim much? I skipped that option and wonder if I should have included it.

 

[Flatpicker]

Yeah, I've always had a thing for bright red panels. It's like they say "Look at me - I'm special" haha.

You know, I don't find myself using the trim all that much so you're probably just fine without it.