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31 Oct 2014

UREI Trick or Treat

Happy Halloween!

In our ghoulish gear crypt, we’ve recently witnessed two frightening re-animations! For the longest time, we’ve had not just one, but two broken UREI 527a graphic EQs stashed away. Often, either Chris or I would pass by the PlethoraTone Lab Bench, and shoot a wistful, longing glance toward their vintage, 1970’s, American hand-made corpses. Would we ever hear their 27 bands of inductor-based equalization loveliness?

I decided this week, I could take it no longer… I re-animated them. Mwa-hahaha!

UREI 527a EQsFirst, a little history. These UREI 527a EQs were made circa 1973 – it’s as if they were over 200 years old in people years! (Dogs age slightly faster than electronics, in my opinion.) They feature a classic circuit design (much of the EQs are discreet) with 10dB cut or boost for each of the 27 bands. There’s a beefy output transformer, and they can really add some nice mojo to electric guitars, drums, or whatever. They are musical and capable of some nice crunchy effects if pushed hard. Our problem was they just didn’t work! Not just one. Both of them! What was the statistical likelihood of that happening?

After much trial and error, I uncovered the primary key to our sonic woes: corrosion.

Corrosion had impaled the switches to failure, and this was their evil trick. Harnessing the amazing power of contact cleaner and Deoxit, both of these equalizing beauties snapped back to life. While inside, I also choose to recap their power supplies, as the 8 electrolytics’ replacements were totally straightforward.

However, what was not straightforward was the infamous sliders – all 54 of them (27×2). While fine electronically, these potentiometers are a bad physical design, and to add insult to injury, the lubricant used at the factory was more like rosin or brown sticky goo that had been infused with rubber cement. Q-tips, a small scraper, denatured rubbing alcohol, and water with mild detergent were used to clean the the 108 track faces, tops, and bottoms. Often times it was picking off pieces smaller than a pin head. Meticulous and time-intensive, yes – but it gave me a chance to listen to a bunch of great music.

After spraying MCL on the interior conductive paths, things were quite a bit better, but still a fight to adjust. The final modification of moving the entire fader assembly forward was the ace in the hole!

So now for Halloween, we can enjoy the aural treat of classic multi-band LC equalization. And so can you, at PlethoraTone!

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