Since everyone was so helpful with my very first question, I figured I would ask about my next dilemma. Its surprising I get anything done but when its done, its to my liking.
I have been reading about safety capacitors and now I am up in the air on replacing the current .1uf paper capacitors on the AC line and .1 capacitor on the filament side with .1 safety (X,Y caps) of this Stromberg AU-42. I was originally going to replace them with orange drops, sorry I like orange drops, but after reading about safety caps, I am now wondering if it would be better choice.
I have been reading about safety capacitors and now I am up in the air on replacing the current .1uf paper capacitors on the AC line and .1 capacitor on the filament side with .1 safety (X,Y caps) of this Stromberg AU-42. I was originally going to replace them with orange drops, sorry I like orange drops, but after reading about safety caps, I am now wondering if it would be better choice.
On the primary side there is no choice other than X capacitors. No orange drops.
Paper capacitors will leak in older equipment, and should be removed.
Paper capacitors will leak in older equipment, and should be removed.
The problem with using paper or film caps is that they leak and if they fail they fail as shorts. If the X1/Y2 rated safety caps fail they fail open.
Also, you shouldn't use .1 cap. I've used .022 for a long time. I once asked if it would be better to use a .047 and I was told (by someone with a lot more technical know-how) that, while .022 was OK, that it would actually be safer to use .01 or .015 uf instead.
The safest you can do is to permanently remove them. Replace with protective
ground connection of chassies.
Non existent items cannot fail !
I would think that both would be the safest choice. If you plug into a circuit that is not actually grounded for some reason, or a circuit that has not been wired correctly, you'll still have some protection.
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There are several good videos out there on the dangers of using the safety cap on the input of a device. At the time they were implemented it was thought to be a good idea. I've removed mine from all my old radios and gear.
Rifa Evox Class X2 are paper if you like paper and cheap enough. Remember if above 100 nF a discharge resistance required. The transformer should be enough if the X2 cap the transformer side of the switch/fuse. 5CR< 2seconds is the rule. 470 nF was thought by Douglas Self to exceed needs.
https://cpc.farnell.com/evox-rifa/p...-x2-0-47uf-47r/dp/CA06048?st=470nf capacitors
I note there is a resistor inside that one or might be. If you search for the standard one it is without that. I have used the " wrong one " without problems by mistake. I think it was CPC who mixed that up. I remembered after posting. That type is as a switch suppressor.
https://cpc.farnell.com/evox-rifa/p...-x2-0-47uf-47r/dp/CA06048?st=470nf capacitors
I note there is a resistor inside that one or might be. If you search for the standard one it is without that. I have used the " wrong one " without problems by mistake. I think it was CPC who mixed that up. I remembered after posting. That type is as a switch suppressor.
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Looks like some conflicting answers here. The .1 caps that are original in this amp now are .1 Stromberg paper caps on the primary side and tube filament secondary side. These are the same type of caps used in the rest of this amp. I only thought about safety caps because I read about it and now I have this dilemma. I am still a bit confused and will need more research on which caps to buy for the primary and secondary side. Y2 caps I have read are used on secondary side (they open when fail), X1 caps are used for AC line to ground (fail short). Still a bit confused when they start talking about Y1/Y2 and X1/X2 types.
The X type is for across the AC line, not to ground.
https://www.hunker.com/13408990/differences-in-x1-x2-y1-and-y2-capacitors
https://www.hunker.com/13408990/differences-in-x1-x2-y1-and-y2-capacitors
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This is dangerous, connecting line to ground via an X1 cap ( or any cap)might
kill !
Just remove any caps connected between mains and chassies !
Y2 class as a rule are live or neutral to ground. 10 nF a maximum very often and very useful to remove common mode noise from radio sources. They often are two capacitors in series to enhance safety. Larger values can trip RCD circuit breakers.
Research info which is causing my dilemma:
“Across-the-line” capacitors should be replaced with type X2, X1/Y2 or Y2 safety capacitors.
•“Line-to-ground” line filter capacitors should be replaced with Y2 or X1/Y2 safety capacitors. (do not use X2 type).
A Y2 capacitor can safely be used in place of an X2 capacitor, but an X2 capacitor should not be used in place of a Y2 capacitor. This is because, although an X2-type capacitor would work and filter noise sufficiently, it would not meet the line-to-ground safety standards. Y2 safety capacitors are more robust, are able to withstand higher peak impulse voltages, and are designed to fail open as
opposed to failing short.
Class X capacitors are used in “across-the-line” applications where their failure would not lead to electric shock. Class X safety caps are used between the “live” wires carrying the incoming AC current. In this position, a capacitor failure should not cause any electrical shock hazards, rather, a capacitor failure “between-the-lines” would usually cause a fuse or circuit breaker to open.
“Across-the-line” capacitors should be replaced with type X2, X1/Y2 or Y2 safety capacitors.
•“Line-to-ground” line filter capacitors should be replaced with Y2 or X1/Y2 safety capacitors. (do not use X2 type).
A Y2 capacitor can safely be used in place of an X2 capacitor, but an X2 capacitor should not be used in place of a Y2 capacitor. This is because, although an X2-type capacitor would work and filter noise sufficiently, it would not meet the line-to-ground safety standards. Y2 safety capacitors are more robust, are able to withstand higher peak impulse voltages, and are designed to fail open as
opposed to failing short.
Class X capacitors are used in “across-the-line” applications where their failure would not lead to electric shock. Class X safety caps are used between the “live” wires carrying the incoming AC current. In this position, a capacitor failure should not cause any electrical shock hazards, rather, a capacitor failure “between-the-lines” would usually cause a fuse or circuit breaker to open.
By the way petertub, this amp already has .1 Stromberg caps in these positions and my dilemma is to replace them with safety caps and I really don't think I would just remove them. Most circuit designs have these but just wondering about safety cap replacement.
I assume that your goal is to restore the device to factory specification; this is is also my goal when I do a restoration. Unfortunately, it is not possible to replace the original paper capacitor with a modern safety type with same specifications, because it will violate safety standards. You may read EN60939 (for Europe) and UL1283 (for USA) to check the details. The maximum allowed leakage currents on residential applications are a lot lower now, compared to the past. There are good reasons for this change. The first one is related to safety. The way this capacitor was selected and fitted on old designs has proved to be a fire and shock hazard. The second reason is related to the need to interoperate with modern electronic devices. A high leakage current will overpower the input surge protection circuit of solid state electronic devices, and may cause damage to the audio source. Many people advocate the need to remove the capacitor completely. I support this approach on new designs: the line to ground capacitor is not needed anymore for hum suppression due to modern power distribution systems, and is not effective enough to filter out the radio frequency that may have been injected on the supply line by a switching mode power supply. For the restoration of a classic device, I feel instead that a capacitor should be preserved, because the device will look "incomplete" and less original without it, and also because the original designer was counting on the presence of a capacitor on this position, and removing it may have unintended consequences. I usually replace the original 0.01 to 0.1 uF capacitors with a 4.7nf "Y" safety rated ceramic disk capacitor. They are still widely used on modern power supply designs and have a 10Kv sourge capability, so the electric shock risk is very low.
Do remove them ! The do noting good ( if you want a mains filter, get a proper one). The only thing these caps add is security risks ( fire, shock )
Get them out !
okay I found the 5nf and 4.7nf safety caps. I think I will take pcan advice and replace both the .1 Stromberg paper caps on the primary side to ground and secondary side filament to ground with these 5nf safety caps and totally remove the .1uf caps.
More explicitly, replace the line cord with a three-wire with ground pin line cord. Connect the ground wire directly to the chassis where the line cord comes in.
This prevents an electrocution hazard from occurring if something (the transformer, or any other component connected to the line) shorts out to the chassis.
Benb, I always think about this when I am working on old gear but have never actually replaced the power cord with a 3-wire. I guess I figure if they came with 2 wire, they are meant to work in either polarity relatively safely and I use relative hastily. Some amps have a polarization switch, this one does not. I do tell customers about what you could notice if plugging in causes more noise, just reverse and see if it is better. Maybe there should be a thread on this to get everyone's opinion, I think I will do that.
Many old houses only had 2 wire supplies, but nowadays that is not the case, so I do not think there is any justification for leaving an old electrical appliance with just a 2 wire plug. The bits you are protecting them from are already at least 50 years old!
Doing the update in a sensitive way is another matter ...
Doing the update in a sensitive way is another matter ...