Robbie,Also, consider the fact that tying the fuse holder barrel tabs together, like the factory configuration, with 100V DC is not finger safe after removing the fuse.
I have been doing a lot of thinking about how to wire up the fuse holders...tie the barrels together like I have done or tie the top posts together...got examples of bothRobbie,
Eric has posted many fine pictures of best wiring practices in his upgrade threads. It is worth some of your time to look at how he dressed the wiring since you are at that stage of assembly right now.
OK, so that does put the 100V right there by the opening and ready to get your finger if you should stick it in there...Just to clarify, the top picture was posted in one of my threads, but not from one of my builds.
The side terminal of the fuse holder is tied to the center ring as shown in the picture below on the Left.
If you remove the fuse holder cap, that center ring is finger accessible and has 100V DC if the tabs are tied together like the factory.
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I disagree, by design if wired correctly, the fuse does not make contact with the tip until the cap and assembly is finger safe.But if you connect to the tip, when you are inserting the fuse you also run the risk of getting a little bite...
Mine seem to make contact a little sooner and if you tried you might get bit but nevertheless I'm reworking the lines to power up the tip as you recommended. I like your little loop in the connecting wire, not sure mine is going to look as neat but we'll see how they turn out.I disagree, by design if wired correctly, the fuse does not make contact with the tip until the cap and assembly is finger safe.
In the picture below, the fuse has not yet contacted the tip.
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Nice grab...Well, checked around town and nobody from auto parts stores to industrial supply houses had the shoulder bushings for the transformer isolation. I found some on Amazon and Ebay but the best I could do pricewise was some dude in France and a pack of 10 would cost about €12...delivered sometime in December. While I was looking around town, I did find some 25mm diameter PTFE stock...and I have a lathe...so I made my own bushings.
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I stole Mark's idea about using the heat shrink on the bolts and think it is going to work out quite nicely. I made the bushings different lengths so I could get engagement in the transformer core instead of the caps. I epoxy filled the corners and drilled the holes slightly oversize from the bushings to account for any deviations there might be...the bushings are a quite tight fit in the core.
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I put a little more heat and solder in the main cap lugs as Joe suggested and added some slack in the incoming AC line and am reworking the feeds to the DC fuses. (thanks, Eric)
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Drilled the heat sinks to 5mm to make sure there is clearance around the transistor leads. Had to MacGyver a chamfering tool as I didn't have a jobber length that would reach to the bottom of the fins. I know some of the holes look a little "wavy" but the top edge is smooth as a baby's butt. If I had thought about it I would have gotten a jobber length bit and drilled them from the transistor side so there wouldn't be any burr. (probably would have deburred the holes anyway just to be on the safe side) Still need to do a final cleaning (man that silicone paste is hell but brake cleaner works pretty well on it...wonder how well it would work for cleaning circuit boards or would it leave some residue?)
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And now, for the inspirational moment...sweet dreams
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My understanding of the stack-up puts the Teflon washers between the transformer and the chassis so the thicker shoulders shouldn't make any difference (other than making the bolts appear shorter) or do I understand wrong?Nice grab...
Your shoulders may be too thick on your Teflon shoulder washers. Check the clearance of the nuts to the body of the bulk capacitors in the cradles. Sometimes they hit and sometimes you are good.
OK, problem solved...just a quick trip back to the lathe and machine a shoulder in the shoulder...(it was 5mm thick to start with) and then top it off with a Teflon washer...You will need to electrically isolate the nut and washer from the inside of the housing if placing the bushing on the outside between the housing cradle.
The important part is isolating the bolt from chassis ground, not the transformer or cradle.
At a high level, the bolts pass through the transformer core and eddy currents are induced into the bolts.But I'm still curious about why basically everything has to be isolated from each other...
You mean like this?At a high level, the bolts pass through the transformer core and eddy currents are induced into the bolts.
The intent of this mod is to electrically isolate the bolts from chassis ground to prevent the eddy currents from potentially causing noise and offsets within chassis ground.
This is common practice in many sensitive test and measurement equipment.
The transformer mounting bolt bushings are typically mounted on the outside of the transformer bell and inside the chassis housing. I have multiple pictures on each of my build threads showing the bushings under the bolt head and under the nut.
Hang on a sec...do you put the transformer cradle directly in contact with the amp chassis? You don't say anything about putting a bushing between them so you are connecting them electrically. I checked my set-up and I don't get anything between chassis-bolt-transformer-chassis so I think I have accomplished the goal, right?The stack up is as follows (from the outside in):
Insert above into the transformer bell.
- Bolt
- Bushing
- Washer
After mounting the transformer to the chassis, place the following:
See below for pictures (the bushing is Black):
- Washer
- Bushing (through washer, chassis, cradle, transformer core)
- Nut
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