Bandido Questions

[Molzar]

I’m working on Bandido project. I’m using Gary’s schematic and board designs as a reference and I have a few questions:

1) Gary’s schematics / notes specify +9V for IC 1 (4024), but Gary’s PCBs has this connected to +5 V. I looked at the component spec (I’m using OnSemi) and power requirements are +3 /18 V. Is there any reason for the +9V?

2) I’m omitting the original battery check circuit (in favor of Gary’s Bat Check). Do I need to tie down pins 1,2,3 of IC 3 and 10,11,12 of IC 4 to gnd? Or should just let them float?

3) Outside of the caps used in the oscillation circuits, is there any advantage in using poly caps over ceramic discs?

Thanks,

Molzar

[porkluvr]

what page are we on?

I am sure many will be happy to help you, but would you please post a quicklink to the schematic you refer to, so that we can all be sure that we are all looking at the same page?

[Max]

Hi Molzar,
I think you mean that circuit of the picture... if not please send yours.

OK

1. works about the same. 4024 is cmos device so could work with voltages of +3V only. I think Gary connected to +5 on PCB cause it's stabilized voltage and not just on +9 line from battery cause of maybe of the thought about eventual spurious signal propagation on battery line...after he modified the schematic... but then also the input signal is always in the 0-5V range (due to T2 interface) so no need of +9 supply.

Also there's no differences about audio performances this way... cause 4024 gives only the GND level to be used with the pull-up action of comparators: so it's absolutely safe and right using +5V there on PCB.

2. you can omit passive stuff too... and tie 2,3 of IC3 to gnd and 12 of IC4 to gnd; if you have already all mounted there... just pull out of circuit the 1K resistor with label R13

3. Just about stability: poly are better of MKT or similar type to gain more stability. Ceramics are good just for small values here.

Best regards,
Max

[Molzar]

Hi porkluvr and Max,

The schematic is as below, Gary's most recent. The 4024 shows +9V.

This is my first VLF and pcb design. I omitted the original "Bat Chk" so I wasn't sure what was good practice with the open pins. I've seen both Poly and Disc used so I just wondered which was best.

Thanks for your reply, I read many of your posts, very good information.

Best Regards,

Molzar

[Max]

Hi porkluvr and Max,

The schematic is as below, Gary's most recent. The 4024 shows +9V.

This is my first VLF and pcb design. I omitted the original "Bat Chk" so I wasn't sure what was good practice with the open pins. I've seen both Poly and Disc used so I just wondered which was best.

Thanks for your reply, I read many of your posts, very good information.

Best Regards,

Molzar

Hi Molzar,
if this is your first VLF pay much attention on PCB assembly and cleaning... very important.

If you need a very good VLF with more support by the forum you can build the Golden Sabre ... many people had success with it than with bandidoII.

Anyway, it's your choice... I found bandidoII very good thing if right tuned and with good coil so the only drawback is some lack in informations about assembly... components values (e.g. caps) etc but you can do with bit more efforts and search of old posts a nice detector.

Kind regards,
Max

[Molzar]

Hi Max,

The Golden Sabre is already on my list (maybe next?), but I thought some of the proper components (ie LM30 would be difficult to obtain so I choose Bandido first. I haven't read through all thousand or so the posts on TGS so maybe I find available good replacement parts there.

The coils seem a bit difficult, I probably try a DD first as this seems simpiler, but that is down the road a bit, right now just concentrating on PCB / component selection.

Thanks for advice.

Best Regards,

Molzar