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X-100-3 Safety/Death cap question

Let us know if you ever get them. My recent Mouser order was shipped by some method where UPS hands it off to the USPS. UPS tracking is very sketchy and USPS has no tracking until the handoff. From the sketchy UPS tracking info, it appears that this package took over a week just to get part way across Texas. Another nail in their coffin. (Meanwhile, DigiKey order was on the doorstep in 3 days.)
 
I got stuff from Mouser a couple days ago. FedEx 2 day since it was the same price as ground. No problems.
 
that UPS -> USPS hand-off thing has never worked well for me. Takes much longer and its the same price as other options that get here more quickly
 
Don't know why a "death cap" is even needed for a transformer-powered unit. Series string radios that work off the line, yes. Most equipment comes with 3-wire power cords, and that eliminates any need for one.
 
These were made decades before most homes in the US even had 3 wire plugs. Not that it really matters since this doesn't actually have a line to chassis cap.
 
The X-100-3 has a snubber cap (C4) on the secondary side of the power transformer - just before the rectifiers. This is intended to remove noise. A safety cap is needed in this position to ensure the chassis doesn't become energized. To assist in preventing an energized chassis a safety cap should be used for C4.

Safety caps are self-healing in that if a short starts happening inside the cap, it will burn away some of the plate which will eliminate the short. Plenty of info on the internet about X and Y types of caps. I usually buy Y rated caps as they take it a step further than X rated caps, but that is me.

There is no cap on the primary side so this is not about line grounding or polarization - it is on the secondary side which feeds the DC power section.
 
it really doesn't need to be a safety cap. Consider C2A. It sits between the same transformer secondary and chassis, and caps of that value don't exist with those ratings. The 0.01 is next to a diode that is basically shorted to chassis for half the waveform. If either shorted it wouldn't do anything besides blow a fuse. There isn't a path from the transformer secondary to anything outside the chassis so its not a shock hazard.
 
gadget73 said:
it really doesn't need to be a safety cap. Consider C2A. It sits between the same transformer secondary and chassis, and caps of that value don't exist with those ratings. The 0.01 is next to a diode that is basically shorted to chassis for half the waveform. If either shorted it wouldn't do anything besides blow a fuse. There isn't a path from the transformer secondary to anything outside the chassis so its not a shock hazard.
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Good to know. So I've been over-engineering by using Y rated caps for that. I learned something today!
 
over-doing it won't hurt anything thats for sure. After all I use 630v rated caps in AA5 radios that only see about 150 volts. Thats more because I'm too lazy to special order parts, but on the other hand I know its not going to lose that cap.
 
The safety caps aren't required for secondary use, but are rated for AC use and have very high surge voltage ratings - so still a good choice.
 
I have pair of McIntosh MC-30 amplifiers, and I replaced the power cords with 3-wire ones, and grounded the chasses. They work fine, and I now have the safety of a grounded chassis on them.
 
egellings said:
I have pair of McIntosh MC-30 amplifiers, and I replaced the power cords with 3-wire ones, and grounded the chasses. They work fine, and I now have the safety of a grounded chassis on them.
Click to expand...

:beerchug:

When I electronically restored my 30s almost 6 yrs. ago, I replacement power cord grounded them as well, and like you I experienced no issues, as well as rewiring the transformer`s primary`s additional tap for 120 volts instead of the factory normal default of 117 volts which put the filament voltages in their rated range now that they are powered in the common mains ~ 120 volt range.

They seem to be happy and trouble free for my effort.
 
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