Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bnwitt on October 29, 2017, 10:35:10 am
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So for quite some time I've been using 16 gauge 12' long power cords on my amp builds and it is a real bear to get them installed in the typical D hole strain relief busing. It seems everyone sells the same strain relief bushing which works well with 18 gauge power cords but not the larger 16 gauge cords. I am wondering if there is one available with a larger interior diameter for this purpose. Anyone know? As it is now I have to use a pair of pliers on the bushing and strike them with a hammer while pushing down to get the bushing to seat in the chassis hole.
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Barry - what I've done in that situation - (1) applied heat prior to squeezing with strain relief grommet pliars ( I made pliars from long handled adjustable pliars from harbor freight, ground the teeth off for a smooth surface)
(2) you can take a smaller rat tail file to the inside of the strain relief grommet to "open it up" a little.
But my final solution was to find a source of 10ft 18ga computer power cord and then snip the end off.. I found some cheap at wallly world dot com with US color coded wire.
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Hoffman, Mojotone and Partexpress (pretty common sources for amp parts, including the strain reliefs) both sell 18 gauge power cords. I'm sure Mouser sells them too, except searching their site is a nightmare.
Hardware store power cords tend to be larger... but getting a smaller cord may be as easy or easier than getting a larger strain relief.
I've used nail clippers to enlarge the inside of some of these strain reliefs, but only the ones meant for flat zipcord, not pre-shaped to a round power cord... basically, I bought the wrong ones and needed to enlarge them just to fit OPT wire, let alone a power cord. A file as mresistor suggests might be the best solution if you're already close to the final shape/size of the wire.
I've also run a power cord through a rubber grommet and achieved "strain relief" with a knot and/or loop around some component before making electrical connection inside the amp... I felt the result was reasonably durable and safe but I wouldn't 100% recommend this as a long-term or "best" solution.
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I quit using those D-hole strain reliefs when I discovered these. Much better and more secure. Several sizes and quantity packs available. 1/4, 3/8, and 1/2 NPT will likely cover any cord you would put on an amp.
Take a look...
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR0.TRC0.H0.TRS5&_nkw=Cord+Grip+Cable+Gland+&_sacat=0 (https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR0.TRC0.H0.TRS5&_nkw=Cord+Grip+Cable+Gland+&_sacat=0)
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https://www.wireandcableyourway.com/18-3-soow-portable-cord-600v-ul-csa.html (https://www.wireandcableyourway.com/18-3-soow-portable-cord-600v-ul-csa.html)
--pete
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Thanks everyone. I do prefer the 16GA over the 18GA cord and that is why I have this dilemma. The chassis I buy all have the D-hole in them and they are all the way to the left where I couldn't really cover them up with the rear plate. I'm familiar with the gland cord holders from my solar work but I've not seen them in a D-hole shape. I'd use them if I could get one that fits the typical chassis D-Hole
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Are you using the correct size bushing ? https://www.heyco.com/Strain_Relief_Bushings/product.cfm?product=Original-Strain-Relief-Round-2§ion=Strain_Relief_Bushings (https://www.heyco.com/Strain_Relief_Bushings/product.cfm?product=Original-Strain-Relief-Round-2§ion=Strain_Relief_Bushings)
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I'm familiar with the gland cord holders from my solar work but I've not seen them in a D-hole shape. I'd use them if I could get one that fits the typical chassis D-Hole
Don't hold your breath. Just continue to roll up your sleeve and crimp the hell out of that strain relief until your oversize power cord fits. :icon_biggrin:
Or you could use a step bit to ream that D-hole round and to the proper size. Probably take less than a minute once the step bit is chucked. :wink:
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Are you using the correct size bushing ? https://www.heyco.com/Strain_Relief_Bushings/product.cfm?product=Original-Strain-Relief-Round-2§ion=Strain_Relief_Bushings (https://www.heyco.com/Strain_Relief_Bushings/product.cfm?product=Original-Strain-Relief-Round-2§ion=Strain_Relief_Bushings)
Mresistor
Well all the usual vendors sell the same one. I'll check you'r link and see if I can get the correct one for the standard panel hole and cord size. Thank you sir.
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18AWG is rated to 10amps. 16awg is bigtime overkill. crimping down 16awg with a 18awg strain relief is worst thing you can do to that power cord.
--pete
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18AWG is rated to 10amps. 16awg is bigtime overkill. crimping down 16awg with a 18awg strain relief is worst thing you can do to that power cord.
--pete
I don't use 16 gauge for the power rating but for the toughness. I find the 18 GA cords too flimsy to put on an amp I hope to last 25 + years of gigging. I have lately been grinding the bushing for the 16 GA cord but that is hit and miss. I would prefer the correct size bushing.
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I used 16ga to wire some 0.1 Amp sense-wires from my fusebox to a meter. As you say, tough is good, especially when tapping raw 240V above a cellar floor.
But in that case I used electrical junction box fittings. These may not be right for a stage-amp's constant flexing. My case was more a fixed-install which doesn't move.
I always hated the Heyco. The "gland" fittings are better. I think that is what I used on a student/studio amp some years back.