some schematic questions by newbie help!

[Raj1]

Hi,


Regarding this schematic,

http://www.ultranalog.com/cdenhancer...ancer2_3a5.pdf



The 3A5 filaments are on pins 1 and 7,

With + 2.5 volts going to pin 1 and F2 going to pin 7

is this correct?

in the schematic which pin is connected to ground via the 150 ohm
resistor?

Also does anyone have pin data for the AZ1 rectifier???

I'd just like to make sure I'm doing this right, to avoid mishaps, as the voltages are lethal and I'd like to be around to actually hear it work!


Thanks
Raja

[fdegrove]

Hi,

On the 3A5 the heater is 1 & 7 with pin 4 as the midpoint.

This allows for either series or parallel heating:

2.8VDC @ 0.11A or 1.4VDC @ 0.22A. (According to my RCA datasheet)

in the schematic which pin is connected to ground via the 150 ohm

That would be your cathode resistor, so pin #4 can be used.

Also does anyone have pin data for the AZ1 rectifier???

Yep.
It's going to cost you an O-scope though...

Cheers,

[Raj1]

Hi,

Thanks, the O-scopes in the post

(It was made by the tailor who made the emporer's new clothes )

Well I've never used tube re's before and I found it kinda weird that the 4 v ac supply is also connected to the dc output from the rectifier

Still I don't supppose I have to understand why???

I have managed to find a cheapo solution for my tmains transfo's,

for the 100v supply and 3A5 2.5 v supply
http://www.maplin.co.uk/products/mod...718&Products=1

and for the rectifier 4v supply

YJ50E on this page
http://www.maplin.co.uk/products/mod...91&Products=11

Can I drop the voltages on all these to the requirements with the use of resistors???


Thanks
Raja

[Paul Barker]

The rectifier chosen is directly heated, this means that the cathode from which we get HT (also known as B+) is heateddirectly by application of 4 volts across both ends.

Therefore the 4v supply to this cathode (known in this case as a filament) stands at the dc potential of the output of the rectifier. Therefore the heater supply must not be used for any other valves and it must not be grounded in any way.

4v is impractical when buying modern transformers, but yes you can use resistors to drop the voltage. Why not instead a 6.3 volt rectifier so you can utilise a 6v secondary? What is the main circuit so we can predict needs of rectifier?

[Raj1]

Hi Paul,

Here's the schematic for the output stage

http://www.ultranalog.com/cdenhancer...ancer2_3a5.pdf


So by your above post even though the 4 v ac supply is connected to the same pin as the B+ output as long as no other circuits are using this winding there will be no problem. I was trying to get my head around how there's no ac leakage into the circuit, but I understand now.

Thanks
Raja

[Paul Barker]

EZ80 or EZ81 would do B9a socket easy to obtain 6.3v heaters easy to feed.

These are indirectly heated so heater winding is not at HT potential.

[fdegrove]

Hi,

These are indirectly heated so heater winding is not at HT potential.

No, the IDHT is part and parcel of the final result...

Cheers,

[fdegrove]

Hi,

My apologies;

The DHT and as such the DHR is part and and parcel of the final result.

Cheers,

[Raj1]

Hi,

Should the 3A5 positive heater supply be connected to pin 1 or 7????

http://www.mif.pg.gda.pl/homepages/f.../049/3/3A5.pdf


thanks
Raja

[fdegrove]

Hi,

That doesn't matter, it's left floating.

Cheers,