Turntable Motor Power supply

[Salas]

Not looking to start a war here!

I don't understand this very well, so I am relying on you guys.

Like I said, it will be over a week before I am ready to order parts, so we have time to come to a concensus... Maybe shoot the middle between the values suggested by each? Not sure.

Its not intuitive always but the fact that the saturated low pinch off Jfet under Vbe circuit has been used by hundreds of people in my regs, plus the photos driving the turntable in the link you got it from, should give some food for thought. LT Spice I showed too.

Anyway since it has been explained before by syn08, here is it for Steerpike:

''All points on the Id=f(Vgs) with Vgs=Vds (it's a parable) are called "incipient saturation". For each of these points, keep the Vgs and add a |Vp| to Vds. This is "saturation" in Walt's sense.

Example: A LSK170 has Vp=-0.6V and Idss=10mA, that is, at Vgs=Vds=0, Id=10mA. Therefore, at Vgs=0V and Vds=0+|-0.6V|=0.6V the LSK170 is in saturation.

In contrast, the region where Vds<Vgs is called "linear region" and the JFET is essentially a voltage controlled resistor.''

Me I have made it and it drives my friend's Walker TT on Maxon. Gave you all info in the original link. Have nothing more to add.

 

[Steerpike]

it can give steady IDSS.

Might as well use an ordinary fixed resistor - it's cheaper.

 

[Salas]

It degrades the loop gain by 6dB and creates DC level cyclic shift. Been there, done that.

 

[Jim Leach]

Hello guys!

I'm back from my honeymoon and ready to get back to this project (on top of all the other projects...)

So, do we feel we are good to go with what we have?
Can I do a BOM and order parts?
Any other suggestions we might want to add before I order stuff? i.e. do I need more than just the components- what transformer should I be picking up etc. I need to know everything!

Thanks again guys! Looking forward to putting this together!

 

[Salas]

From me nothing more to add. You got the original link to my experiment and schematic on post #7 plus what we discussed here.

 

[Jim Leach]

Does this look like a good transformer for this circuit?

If I'm not mistaken, I can get 30V out of this (but maybe I'm mistaken?).

Universal R Core Transformer for Tube Pre-Amplifier new - eBay (item 250614623647 end time May-13-10 05:50:54 PDT)

I will keep looking meanwhile...

Found this one- (R 26-08 on the list) which may be better..

http://cgi.ebay.com/50W-R-Core-Tran...pt=Vintage_Electronics_R2&hash=item439e86d6cf