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I did a UPS project for B.A.R.T. in the mid 90's. I'd go out there 2-3 weeks at a time. We worked 11:00 PM to 5:00 AM because the train didn't run then. Not much to do during the day. I visited all of the surplus shops in the San Jose area more than once. Near Berkley there was a surplus...

I believe I remember seeing this circuit in Audio Magazine sometime in the 70's. The Leach concept is just a phase inversion circuit. As I recall some of the Hafler amps had a strapping circuit. Look up the pro 500. I think the downside is, in bridged mode, an 8 ohm speaker effectively...

Years ago I rebuilt quasi comps with all 2SD555's and/or MJ15024's and had troubles. No amount of base stoppers, decoupling caps, and pouring over the service bulletins stopped it. Reusing RCA 410's as drivers improved things somewhat. I never knew why. What did the 410's do differently?

Got a schematic?

Lee, Triacs, to use a popular term, are binary. Unlike a bipolar transistor that can operate in a linear state (such as amplifier output transistors), triacs are either turned on or turned off. They do not operate linear. A triac is, for all practical purposes, 2 SCR's operating in reverse...

Thanks Nav for elevating this post to the next level.

Same here. I check the pins to make sure they are straight and then proceed with Lee's technique. It works.

What's the asking price? I don't need any amplifiers, but I like everything UREI because of the quality design and construction.

...Or send them to me and I'll eventually put them in someone's amp who doesn't want to convert to full comp. The important thing is you do not sub "superior" transistors for the applications Joe has called out above. Doing so creates oscillations that can not be cured.

I have a dozen or so amps with names such as Crown, BGW, Hafler, Dynaco, Phase Linear (10X or so) Marantz, Sony, Advent.. If I saw a URIE local for $300 I’d jump on it. I don’t care what the specs say. It’s great gear.

4 Fluke meters qualify as a science fair project.

I got to work with some UREI gear decades ago. There is no better build quality and reliability. UREI was designed with the pro in mind who was willing to pay for reliability and simple but functional gear, night after night.

I've got 2 sound technology analyzers sitting the garage. Had them given to me when a local shop closed. Haven't found the time to check them out. Also have to S.T. oscillators. Same status as analyzers. Does anybody work on them. Can't find any docs on them..

My brother bought a 3 phase, 208 VAC, 7.5 H.P. dust collector. To power it in his house I bought a variable frequency drive (VFD) intended for single phase 240 VAC in and 3 phase out. I built a box with start/stop push buttons and a pot to control ramp rate. Uses a 8" flexible pipe from the...

The power supply is as simple as it gets. A rectifier and caps. If the ripple is less than 100mv and ripple frequncy is 120 Hz, it's good.

I try to check emails once a day. As for the spam folder where I found Daves' messages and several others, not very often. Maybe I need to start checking it more frequently.

"I have tried several times to contact wattsabun with no success" Hm, that's a puzzler. I did get distracted by post 19. Didn't see anything in email accounts. No PM's.

1. Read the attached manual, especially troubleshooting/testing transistors. 2. Read the attached manual, especially troubleshooting/testing transistors. 3. Read the attached manual, especially troubleshooting/testing transistors. 4. If you refuse to read the manual, don't ask for more...

Well Mark, I think you said it for me. I call it a triac board as that is a term that many people recognize. Yes the triac mounts on the back of the board with the Phoenix connector on the top of the board. I use a 45 degree Phoenix connector to make it easier to land the wires. I don't...

Well, yes, to a certain degree. The stock 400 doesn't have a power switch. The board was intended for the 700 that has a power switch. That switch is is subject to failure. The board does the actual power switching. It uses the existing switch on the 700 to control a solidstate triac that...