Hi,
It's hard to find notes on the web on safely mounting torriodal tx's.
Just checking some things:-
-the bolt through the torroid should never touch the chassis ? (I think the core can go or is live)
-the on/off switch needs to be a dual switch to switch grnd, and live ?
(Is that there incase the cable is reveresed?)
-the chassis should be grounded (to stop the case going live)
-rubber on top, and bottom of core.
Any other safety issues?
I may opt for a chasis mount tx..
Kind regards,
Ashley.
It's hard to find notes on the web on safely mounting torriodal tx's.
Just checking some things:-
-the bolt through the torroid should never touch the chassis ? (I think the core can go or is live)
-the on/off switch needs to be a dual switch to switch grnd, and live ?
(Is that there incase the cable is reveresed?)
-the chassis should be grounded (to stop the case going live)
-rubber on top, and bottom of core.
Any other safety issues?
I may opt for a chasis mount tx..
Kind regards,
Ashley.
Hi,
About to order the stuff for a gainclone. I feel building the power supply should be done first.
This is the plan..
-Double throw switched fused rated for 5A
-Transformer primary wired to switch contacts
-Insulating sheath / boot covering live contacts
-Calculate correct slow blow fuse value
-Transformer bolted to case as per guidance.
-Ground connection to case (measure resitance to check safety)
Is it better to use fastons or solder on switches ?
Any other power supply safety tips ?
About to order the stuff for a gainclone. I feel building the power supply should be done first.
This is the plan..
-Double throw switched fused rated for 5A
-Transformer primary wired to switch contacts
-Insulating sheath / boot covering live contacts
-Calculate correct slow blow fuse value
-Transformer bolted to case as per guidance.
-Ground connection to case (measure resitance to check safety)
Is it better to use fastons or solder on switches ?
Any other power supply safety tips ?
I prefer the fastons... make sure the blade thickness is matched from blade to terminal.
Soldering is completely possible and would be more vibration resistant... not an issue here really. Sometimes switches and breakers can be damaged by the soldering heat. The switch will tell you what it wants. Faston spades means fastons... lugs mean soldering.
Soldering is completely possible and would be more vibration resistant... not an issue here really. Sometimes switches and breakers can be damaged by the soldering heat. The switch will tell you what it wants. Faston spades means fastons... lugs mean soldering.
> -the bolt through the torroid should never touch the chassis ?
>(I think the core can go or is live)
No, the core can't go live, and the bolt can directly touch the chassis. The important bit to remember is that you must NEVER allow a short circuit loop to form around the core; therefore, if the bolt is mounted on the chassis on one side, the other side must be free/unconnected. This isn't normally a problem if you just take the trafo, plus the two rubber sheets and the metal cover that are normally supplied, bolt it to the chassis and leave it alone otherwise.
>-the on/off switch needs to be a dual switch to switch grnd, and live ?
>(Is that there incase the cable is reveresed?)
For best safety, you should indeed switch both live and NEUTRAL. These are the two pins in a 2-prong mains plug. GROUND is the third, and it MUST NOT EVER be switched.
>-the chassis should be grounded (to stop the case going live)
Yup.
As for clearance, jus make sure nothing can make a short from the mounting bolt top to the chassis, and keep low-level signals away from the transformer. Other than that it's not critical.
>(I think the core can go or is live)
No, the core can't go live, and the bolt can directly touch the chassis. The important bit to remember is that you must NEVER allow a short circuit loop to form around the core; therefore, if the bolt is mounted on the chassis on one side, the other side must be free/unconnected. This isn't normally a problem if you just take the trafo, plus the two rubber sheets and the metal cover that are normally supplied, bolt it to the chassis and leave it alone otherwise.
>-the on/off switch needs to be a dual switch to switch grnd, and live ?
>(Is that there incase the cable is reveresed?)
For best safety, you should indeed switch both live and NEUTRAL. These are the two pins in a 2-prong mains plug. GROUND is the third, and it MUST NOT EVER be switched.
>-the chassis should be grounded (to stop the case going live)
Yup.
As for clearance, jus make sure nothing can make a short from the mounting bolt top to the chassis, and keep low-level signals away from the transformer. Other than that it's not critical.
Do I need a power switch ?
Hi,
Thank you for the tips.
The Double throw switched and fused IEC inlet I can buy are suitable for class II applications but the fused IEC inlets I can get are suitable for class I applications.
Do I need a power switch?
Without a power switch I assume that at the electrical wall socket I will be switching very large currents.
Hi,
Thank you for the tips.
The Double throw switched and fused IEC inlet I can buy are suitable for class II applications but the fused IEC inlets I can get are suitable for class I applications.
Do I need a power switch?
Without a power switch I assume that at the electrical wall socket I will be switching very large currents.
ash_dac said:
Scratch off any paint/oxidation under ground screw. Please note that if you have ANODIZED aluminium case it requires sometimes real heavy scrathing to remove anodization. (most pre-made 19" aluminium rack stuff is anodized for example.) Use "star washer" between ground wire lug and case. http://www.randyray.com/TMC/images/RFShield/StarWasher.jpg
Use 2nd nut to make sure that ground connection cant became loose.
Hi,
that safety ground connection must be direct from mains input cable to permanent connection. Do not use a terminal block for the safety earth.
Each conductive panel should have it's own direct connection back to the safety earth. This is often omitted for removable lids etc. But best practice is separate direct connection for every panel.
If you need to make any extra connections to the safety earth then ADD and extra nut/fixing above the original nuts. DO NOT design in a need to dismantle the safety earth. It must be permanent (welded lugs are best).
The safety earth is (probably) the most important aspect of any mains powered project. Do not take any shortcuts or skimp on the understanding for the need and implimentation.
that safety ground connection must be direct from mains input cable to permanent connection. Do not use a terminal block for the safety earth.
Each conductive panel should have it's own direct connection back to the safety earth. This is often omitted for removable lids etc. But best practice is separate direct connection for every panel.
If you need to make any extra connections to the safety earth then ADD and extra nut/fixing above the original nuts. DO NOT design in a need to dismantle the safety earth. It must be permanent (welded lugs are best).
The safety earth is (probably) the most important aspect of any mains powered project. Do not take any shortcuts or skimp on the understanding for the need and implimentation.
Hi,
I insulate (two layers of self adhesive insulating tape) the top washerplate and nut of the toroid fixing to ensure that accidental contact can never be achieved.
Someone leaning heavily on a thin lid can cause sufficient deflection to contact the washer plate or the nut if the plate is not heavily dished.
Similarly dropped tools (during maintenance) could temporarily short to chassis.
I insulate (two layers of self adhesive insulating tape) the top washerplate and nut of the toroid fixing to ensure that accidental contact can never be achieved.
Someone leaning heavily on a thin lid can cause sufficient deflection to contact the washer plate or the nut if the plate is not heavily dished.
Similarly dropped tools (during maintenance) could temporarily short to chassis.
AndrewT said:
Hi,
My amplifier case NAD3130 is built out of small panels screwed together. So I assume it will need six grounds!
Yes it's very important safety, and this is one reason I haven't built an amplifier yet! (still looking at the potential hazards)
I have seen many DIY designs with 'exposed' mains contacts on input switches. Is there any reason for this ? (insulating boots are cheap)
Ash,
For the purpose of safety, panels screwed together are considered connected. Coatings and platings can affect things here though. Make your ground connection to the plate you would consider to be the MAIN plate. Then make sure that all metal that could accidentally become live has a secure electrical connection to this main plate.
For the purpose of safety, panels screwed together are considered connected. Coatings and platings can affect things here though. Make your ground connection to the plate you would consider to be the MAIN plate. Then make sure that all metal that could accidentally become live has a secure electrical connection to this main plate.
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