cobra149

Thanks. The 9v batteries I use are 280ma 8.4v NiMh. So would I use a 10v zener reference instead ?. Also What resistor would I use to give me 28ma c/10 in this circuit. Thanks.

Hi, found this circuit on the net. I have attached the schematic and a drawing of the pcb layout. Just need to know if it will correctly charge a 9v battery safely, and if the pcb I have drawn is correct. Thanks in advance for any help.

@Hero999 Thank you so much. I have tested the 40673 re your instructions and it is indeed faulty. Thanks and regards

Hi, thanks for the reply, though I should have mentioned that I am a complete novice in electronics. I am not quite sure of what you mean, do I apply 5 volts directly to one of the gate legs ?. And if I see a high resistance ....is the mosfet in good condition ?. Sorry for my lack of knowledge on this matter , and thank you for your reply

Hi, please can any one tell me how to test if a 40673 mosfet is blown. Can I test this with a digital multimeter, if so how do I go about it ?. Pic attached. Thank you.

Great, thanks for the schematic I can visually see the problem now. The thought of getting 22v variable sort of took over when I spotted this pc Atx mod on other sites. But when I think of it, I probably wouldnt have needed that voltage much in the real world. The -12v , & in fact all other - rails have now been snipped off the psu, to be gone for ever. So I am now happy with 1.2v to 10v with a real 0v. I will go with +12v and + 5v on the other binding posts. It was so kind of you to put some time into this, to avoid me having any further problems down the road. Best Regards.

Hi, Thanks for that. In view of your knowledge on this matter I have decided to do away with the -12v and +12v idea to get variable voltage from 22v down. I wasnt aware of the theory of how it would behave when used. Would I now be ok to use my variable pcb to vary the +12v and black 0v gnd wire. I realize that I will only get about 10v down to 2v variable adjustment with +12v input on the lm317 But I would rather go with safety if using the +12v and 0v is safer than the +12v and -12v method to . Thanks

Hi, thanks for the reply, the psu is showing correct voltages on all post terminals.As I have fitted an lcd volt meter to the face off the psu cabiinet. I think the lcd meter could be the small load required thats making the Atx give the correct voltages. The -12v gnd from variable pcb is showing 0v. And the lcd meter - + connected to the variable terminal output posts. The 317 has an overkill heatsink fitted ,and the 317 is external to the pcb using 3x 16 guage wires. So the reg is really cool after hours of usage. I will use a 1A fuse to protect any items connected to the variable output as you suggest. Not exactly sure what you mean about an osciliscope would short the -12v varaible terminals and cause the 317 to overheat ?. Thanks again.

Hi, please could some kind soul help me with correct fuse ratings to protect the atx psu when connected to electical items. Picture is attached. I:E if any attached items, go bad , I need the fuse to blow instead of the atx psu continuing to give loads of current. Thank you.

Hi, can any one help , I want to build a pcb with a reed relay that will trigger on any transmitted RF signal (front end protection in mind ). Hope this is possible, rather than using 12v tx on rear of radio to trigger the relay. This way it would be more portable to connect to any second receiver using 9v battery. So what would I need to ad to the circuit in front of the relay to detect the RF , that will switch the relay ?. Thanks.

@audioguru Thanks for the reply. What do you suggest adding to this circuit to improve it ?. Also what about my original question on Axial inductor instead of air or ferrite wound coil for the 20uH ?. Regards

Hi, please can some one answer wether I could use an axial inductor in this circuit instead of a wound coil for the required inductance of 20uH ?. Drawing attached. Thank you.