ESL bias supply the GE way

[stokessd]

When I look in my own audiostatics (commercial brand) they did make their HV-supply directly run from the mains, so without any transformer at all.
These speakers are pretty aged (though completely refurbished) and possibly audiostatic may use a different aproach these days.
I don't know to what extend this may lead to dangerous situations, to itself or to other equipment. But these hv-supples seem to work very reliable.

I rebuilt a set of ES50's and they did NOT hook directly to the mains. They used the ever-polular filament transformer backwards driven from an AC output wall-wart.

http://quadesl.com/pdf/es50_schem.pdf


Sheldon

[MJ Dijkstra]

Hi Sheldon

I've refurbished ES50, ES100, ES200 models and I know about the others.
All of them have their HV directly from the mains with no transformer. I assume their models going to US did have a (external) transformer because of regislations which differ from Europe.

[jan.didden]

Why would you use Staticide on HV stuff? Staticide is designed to provide a creep resistance to bleed off static.
I wouldn't want any creep resistance on my HV stuff!

jan didden

[geraldfryjr]

A staticide provides for a nice high resistance and consistent coating on the diagphram. jer

[chinsettawong]

Originally Posted by janneman

Why would you use Staticide on HV stuff? Staticide is designed to provide a creep resistance to bleed off static.
I wouldn't want any creep resistance on my HV stuff!

jan didden

Can you suggest anything better?

Wachara C.

[MJ Dijkstra]

I've got some bottles EC-coating left over from a batch....
Expiration date 5-6-2011

Send me a p.m. if interested

[kavermei]

Originally Posted by geraldfryjr

Thats the method I had used here.


how can test the stator insulation and mylar coating?


Just make sure that recovery time of the diodes is suitable for the frequency that you are driving them them with. jer

That's about it. But there's really no need for the 555. Just drive the bases of the transistors from a feedback winding (mind the phase ;-) ). That way the inverter will automatically adjust its frequency to the load, so you don't need to trim the frequency for maximum output voltage.

Kenneth

[geraldfryjr]

That an excelent way to solve the oscillator issue,Kenneth.

The only reason I did it the way I did was because my transformer had a rather sharp
Q and I wanted it to have a variable output voltage and I wasn't sure if the output regulation and oscillator startup would be relieble if I varied the supply voltage feeding the FET's.

Another method that maybe more relieble once the resonate frequency of the transformer is detrimined is to drive the transformer with a small power opamp such as an LM2003 or LM1875 driven by an opamp sinewave oscillator fed through a volume control to determine the output voltage level. jer

[kavermei]

Yes indeed! With my approach, the frequency can change depending on the amount of leakage current, and so on. That's true.

Fortunately most of this is remarkably uncritical in practice :-)

Kenneth

[stokessd]

I build something similar to the link above. Here's the schematic, it's been working well for me for about a decade:

http://quadesl.com/speaker/diyesl/hv_supply.pdf


Sheldon