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Old 17th January 2001, 01:47 AM   #11
FYC is offline FYC  Hong Kong
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There must be something wrong if you need to use a 100k VR to get to 18V at the drain. With what you describe, certainly you need to recheck your complete wiring and your MOSFET. MOSFET are easily killed by statics, or it run into oscillation due to connection problems.

Don't give up, my Zen amp work perfectly immediately after hook up, and was so far so good. It is not a terribly difficult project.
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Old 17th January 2001, 05:54 PM   #12
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Please, stop saying it's not a difficult project!

This is my first analog circuit!
To prove my predisposition to digital, I just remembered yesterday that the G is for Grid not Gate. Sad.

Thanks for the help though. It's appreciated. I wouldn't have gotten this far without you guys. Especially Vince. Thanks man.

I think I will get that circuit board. I'm going to keep the power supply part separate though. My father made me an aluminum case that has a separate section for the power supply. And, I'll remember to check the diagram for the connection of the small transistor. I'm going to start over with new FETs. So, I'll be starting with a clean slate.

Thanks,
pixie
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Old 18th January 2001, 01:38 AM   #13
FYC is offline FYC  Hong Kong
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My appology, G in MOSFET is Gate, Grid is for tube. My mistake.

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Old 19th February 2001, 03:14 PM   #14
peted is offline peted  United Kingdom
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Hi Pixie et al - hope you got it going! Others said it's not difficult - I agree - your probs have got to be due to zapped mosfets, bad wiring, etc. Give it another go - hand check all the bits like vdi_nenna said that could cook before inserting, wire mosfet leads & remove only when wired the rest (is this overkill?). Resistors - cute new(?) coding scheme - are you getting them right - DON'T always rely on the supplier doing so either).

I'm building beefed up Zen Revisited - 4amp bias, 50v psu, twin paralleled channels working into 4ohm spkrs. 2 of 4 completed channels worked first time - but you need to set bias point (as advised by NP) for symetrical clipping ('scope) - it's NOT 1/2 supply volts - rather more like 60% - that cooks the lower mosfet more too - beware the h/sinks.

I'll report results (& any more hints) in due course... Not put these 2 together yet... Most difficult (in a domestic environment) is the heatsink with these things. 80% of my effort - high bias, high volts - VERY big h/s ( Great results (

Pre-amp will be BOZ - NP says it'll be fine into the 500ohm i/p (2 parallel amps). BOZ as published (5K o/p pot) will have a very skewed volume curve into Zen Revisited with it's much lower i/p impedance too. I've worked out stepped attn. resistor vals to hopefully match the two - we'll see..

Cheers to all

Pete
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