Projects for next hollidays (the world smallest VBITNGC??)

[Franz G]

... things are moving

I am sitting at my desk, the schematics nearly ready to post here.

In the meantime, I can show you two details about the d-sub connector, used for the power supply (NEVER connect some computer devices to it

1. Bridge between pin 1 and 3

You can recognize the yellow isolated wire between pin 1 and 3. The purpose of this bridge, is to activate the switch on delay. The NE555 timer and the relay are not grounded, as long as no plug with this bridge is connected. As soon as you connect the plug, the delay count 20 to 30 seconds before delivering power for the LM3875's. Disconnecting the plug immediately switches of the power stage of the amp. Just for the sake of your speakers

2. How to connect thick cables to 9 pin D-sub

I inserted a thin piece of wire at the end of the thicker litz-wire and soldered it. Attach a piece of shrinking tube and you can solder it to the very small pins safely.

Next postings: the psu-schematic. Followed by a exact grounding and 9pin scheme within the next days.

Have fun!
Franz

dont forget: lethal voltages in this project!

[VT67]

Ha, things start to move here!
Looking forward to the PS schematic.
Thanks for the update Franz

Regards

[Franz G]

Looking forward to the PS schematic.

... but just handdrawn. And Zang will have to review it (I think, Zang must be sleeping right now at this time).

Here a draft from the grounding scheme, but from a "prototype" version. I will adapt it within the next days, as I feel very obliged now.

And I am really courious about all the new mini hybrid amps! Looking forward.

Franz

[Franz G]

Here we go: draft of part 1, including high current part, tube filament voltage and delay circuit. Part 2 coming soon.

Subject to be reviewed by Zang.

I plan to include the drawings (hopefully in better quality) in a pdf document to send it out.

Some comments:

1. Bypass caps for diodes

I did not draw them. They are optional, depending on your taste and diode type. On the board, you will find space for 8 caps parallel to D1 to D8.

2. Discharge resistors

Normally, they are not needed for LM-powerchips, as the chips itselfs are discharging them after switching of the amp. But with the remote PSU box, you can disconnect the cable and the caps are staying charged. So, better dont forget this resistors.

Franz

P.S.
I did not reduce the size of this drawing, otherwise you never could read my writing

[troystg]

You assume we could read your writing if it were this big....

"P.S.
I did not reduce the size of this drawing, otherwise you never could read my writing "

[Franz G]

Troy (and all others, of course):

here is the voltage doubler, the greinacher circuit, for the anode voltage. My recommendation: use fast FRED diodes.

More news within the next days.

Kind regards
Franz

[planet10]

Originally posted by Franz G
draft of part 1, including high current part, tube filament voltage and delay circuit

Franz... i had trouble readng bits of your map so this will need QC. I also don't think you meant to put 12.6V onto the filaments....

dave

Edit: map attached updated 27-oct-05

[Franz G]

Hi Dave

What a surprise! Many thanks.

I reviewed it, my result:

- add a primary fuse 1.6A slow for 220VAC
- Optionally, you can connect 8 caps in parallel to the diodes for the high current voltage
- the second caps in the high current part are just 1000uF.
- the rectifier in the filament part is a bridge type.
- the trimmer in the filament part has a value of 4.7k
- The trimmer for the NE555 is a 200k type
- between pin 3 and 4 of the NE555 is the relay coil for the delay connected.

Could you please correct your drawing and include the anode voltage part?

Would be great, when you could send it to me in high resolution:

franz.gysi at tiscalinet.ch, my spam account. Please add appropiate subject, so I can find the message.

Kind regards
Franz

[digi01]

Franz,the attached is my review psu sch.

thanks dave,your draw looks very clear


EDIT: photo updated.

[Franz G]

Nearby perfect, Zang!

Many thanks.

For the first review, I just remark the voltage of the T2 is too high, resulting in a DC of +/- 117V.

I recommend about 45VAC for the tranny, resulting in +/- 63VDC, according to Duncans PSU Designer.

I leave now for work and will do a exact review this evening.

Franz