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Technical Assistance/Advice Thread


mwl168
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While building DYNAHI PS, I'm connecting the earth directly to the chassis with an exclusive screw as it was recommended by many.  You see thick black cable on the photo, excuse me I don't have green/yellow colored cable that is German rule.  I understand the purpose is for safety.   So the ground level have to be shared with the case surface overall.  However Modushop case components with cool black paint seems not conductive between them.   I had to peel the painting off below the washer on the bottom plate.   Then how can we ensure the electrical connection between parts, side heatsink front panel and top plate?   The supplied threads are also coated black and looks not conductive.   Originally made thread holes are also coated, so using chrome plated screw doesn't help anyway.   When the bottom plate is isolated from others, I see it's not useful to connect the ground wire to the bottom plate.   I know some mass production electrical products have a kind of metal wire net like parts between the external panels to guarantee low resistance between them.   Do you DIYers do so always?   Are you (Should I) so careful about the earth/ground connection between the case panels?   I'm wondering if I should connect DYNAHI PS ground to the chassis, too.

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For the case, the anodizing will isolate each panel from one another. Many people use a bit of sandpaper or abrasive to clear the anodizing in a small area in between panels, and where the PE ground is connected from the IEC terminal.

As for the PSU ground, I would not connect it to the chassis directly, but use a ground loop breaker (see https://www.diyaudio.com/community/threads/audio-component-grounding-and-interconnection.163575/).

For the case, once you are satisfied, I would check with an ohmmeter to make sure you have continuity.

Edited by Pars
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1 hour ago, Pars said:

For the case, the anodizing will isolate each panel from one another. Many people use a bit of sandpaper or abrasive to clear the anodizing in a small area in between panels, and where the PE ground is connected from the IEC terminal.

As for the PSU ground, I would not connect it to the chassis directly, but use a ground loop breaker (see audio-component-grounding-and-interconne).

For the case, once you are satisfied, I would check with an ohmmeter to make sure you have continuity.

I like using internal tooth lock washers for the grounding points. The teeth cut through the anodising and paint, and prevent the screws from loosening.

Also, I use more than one chassis grounding point (usually at the connection between the side and base plates), just to be absolutely sure.

Edited by Beefy
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Thanks Pars,  Yes, I'll make sure the contact between the housing panels.   As I have a motor tool, peeling coating shouldn't be big work.   I wasn't aware of the necessity of the ground loop breaker.   Unfortunately the link you gave me don't have active link to the Figures, but I think I got the most of contents.   I found the design of ground loop breaker on many sites and I'll apply it in my Dynahi PS.   I read that the amplifier chassis and the power supply chassis should be connected with an exclusive earth line not shared with the ground line of the power supply, right?   I think I can follow this, too.  As the number of wires in the umbilical cable is limited, it's a bit pain to lose one for earth though.

Thanks Beefy for the tips to use internal tooth lock washers.   It's nice to know that the teeth can penetrate the anodising coating.  When it's such easy, applying more than one grounding point should be easier.

For me it was good to confirm that you DIYers respect that grounding rule and spend much effort to guarantee it.  I'll follow your methods.

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  • 3 weeks later...

Do ya’ll think the Dremel (Moto) scroll saw would work okay on 1/4” thick aluminum? The manual says 20ga is recommended thickness… so I am guessing not… I am not sure what might be good for this - I need to cut a curved shape in the end of a piece of aluminum. 

 

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I see Jeff provided the proper HC advice?

If you have some scrap 1/4" aluminum, I'd try it with the Dremel. Aluminum is pretty soft, so it might work acceptably? You may go thru some blades, so some spare(s) would be a good idea.

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Transformer mounting: for an Antek 50VA, for mounting to a 3mm aluminum bottom panel, I would like to countersink the mounting bolt. Not sure what size of bolt Antek uses, but Avel Lindberg uses M5 bolts. Could I get away with countersinking an M5 in 3mm aluminum? Or would an M4 be big enough for the transformer (I'm thinking yes, but wanted my daftness evaluated before I do any drilling).

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Transformer is an AS-0532, weight 2 lbs. Maybe an M6? Playing around in Front Panel Designer right now and it will let me countersink a hole for 3mm panel past an M8. I guess it would hold OK if not abused too much?

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2 minutes ago, Pars said:

Transformer is an AS-0532, weight 2 lbs. Maybe an M6? Playing around in Front Panel Designer right now and it will let me countersink a hole for 3mm panel past an M8. I guess it would hold OK if not abused too much?

M6 should be fine for that - I would reach for a 1/4” screw on instinct so that checks out.

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Thanks Birgir and Marc. My main concern was countersinking something that large in a 3mm thick panel. You guys think that would hold alright? I guess if I have to, I could use a pan head and a washer if necessary. Just trying not to have anything hanging down.

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2 minutes ago, Pars said:

Thanks Birgir and Marc. My main concern was countersinking something that large in a 3mm thick panel. You guys think that would hold alright? I guess if I have to, I could use a pan head and a washer if necessary. Just trying not to have anything hanging down.

You could use a low profile socket head bolt / wafer head instead of a typical angled - I think FPE also has presets for a larger angle countersink (which exists for this reason) but make sure you can find the fastener before you order the panel l.

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@Pars: I used an M6, countersunk, to mount an AS-0518 on a Modushop Galaxy 388 base panel, which I believe is thinner than 3mm (supposedly 2mm). Also used FPE and FrontDesign. It turned out fine and looks plenty sturdy to me. I don't think the trafo will fall out.

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Yeah, I have used the button head screws before, and may just do that with no inset.

I was going to place the transformer in the vicinity of a chassis foot, so trying to think of ways that would allow me to place both where I wanted without worrying about interference.

I had also thought of raising the transformer up 5mm or so off the case floor, but coming up with something to do that with had me stumped a bit. The transformer is about 4" in diameter. It is a 2U case so I have plenty of clearance height-wise.

Edited by Pars
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