Tractor Beam update

[jimilee]

That's a sexy phaser

[Jules]

Great! Thanks a lot.

[Netnnk]

Is this how to assemble your own resistor arrays for the Tractor Beam?

*edit* Updated. Thanks, WormBoy!

[WormBoy]

Isolated looks good. For bussed, the bus needs to be directly connected to pin 1, so basically you would replace one of the outer most resistors with a jumper. As Brian explained in another thread: it does not matter whether that's the first or the last (quirk of the tractor beam design: both the first and the last pin of the bussed array are connected to ground, so one resistor is in fact unused). I would always quickly check the board with a DMM, just to make double sure  .

[greenskull]

Many thanks, I just received my boards today!
I didn't notice the Tractor Beam listed on the switching board doc..... what voltage zener do I need?
Also want to double check I need the charge pump chip. Thank you very much.

[WormBoy]

The Tractor Beam is on the last page of the switching board doc, in the schematic. States a 16v zener, but if you only run it on 9v, you can easily use something lower (it is only there to protect against overvoltage). The charge pump is in the photo in the TB build doc, and if you look at the opamp voltages, it is indeed used  .

[greenskull]

Thanks, Wormboy! I might need glasses.

[mark123]

When I'm matching the JFETs, what is the tolerance? How close do they have to be?

[287m]

When I'm matching the JFETs, what is the tolerance? How close do they have to be?

as close as possible
while we waiting Brian project jfet matcher, you can view NomNom docs

[mark123]

... you can view NomNom docs

I saw that mentioned but didn't know what it meant. I Binged it and figured it. Thanks.

From the Nomnom doc:

You want to find the closest matching voltage readings on these transistors. At least within 5% of one another, although I generally shoot for 1% or less. So, if a device reads ­0.75vDC, I would look for another one that measures ­0.74 to ­0.76v.

Exactly what I was looking for.  Since we're looking at Vgs I'm just thinking of picking up a semiconductor analyzer.

[mark123]

The Tractor Beam uses the TC7662B and the low ESR Electrolytics, correct?  It's not listed in the switching board "Used With" column but it is in the picture of the doc.

[madbean]

Correct.

[mark123]

*disregard*

[Lifeson-like]

Brian:
I received two Tractor Beam pcbs from you the other day (in a timely manner, as always). The first Note in the Tractor Beam build document states: "This project is built on the 'Enterprise' PCB... with a few modifications."  I'd be very interested in learning what those "modifications" were.  I've searched for the original build documents (and Bill of Materials) for the Enterprise, but have been unsuccessful finding them.  My question for any readers of this thread is: Does anyone have the original documents, including the schematic, for the Enterprise circuit?

Based upon audio clips I've been able to find, I still prefer the sound of the Enterprise, so would most like to build that circuit.  I realize that sound is very subjective and that much depends upon recording techniques and quality, but I've just been less impressed with what I'm hearing from the Tractor Beam circuit, as compared to the Enterprise circuit.  Be that as it may, any help finding the original Enterprise plans would be greatly appreciated.
Thanks