Ok but I do'nt see the opto isolator correlation to polyprop motor caps. Please go on . As for the 1000s of hours of test would years of use over the rating suffice or is there some other lab rating that will do ? The stress of dc bias and resulting failure is not to be taken lightly some examples of such would help there should be from the manufactures web sites. Regards
"Motor caps" rated at a certain AC voltage must withstand shutoff transients of 6 to 10 times running voltage. That is what motors put out if not transient suppressed. If you put a scope in a factory AC line, that is what you will see. So that sort of explains why film motor caps are so huge. I imagine the 1000 VDC rating of my 500 VAC genilec caps in my organ is very conservative. I don't expect to ever replace them, not at the current a 5AR can deliver to them. Heat is one thing that really kllls plastic film. Won't get much of that in hifi service, unless the mounting postition is wrong.
I am planning on using a 5R4WGB in the place of a GZ34/5AR4.
Main difference, apart from difference in price, is that the 5R4 needs a 4uF input capacitor ...
http://www.r-type.org/pdfs/5r4wgb.pdf
I am planning on using a 4.7uF motor run capacitor, so a little off spec.
My transformer is a toroid - 750VCT. Do I need an input resistor? The application (Tubelab SSE) does not have one specified for a 5A4 since the DCR of the standard transformer (Hammond) is sufficient.
I'll stick a couple of 1n4007's in series with the plates - am I being unduly nervous?
Interestingly, I bought the tubes from a surplus store in the UK. They are ruggedised, so have a funny base, but are NOS. However the stock was no longer listed at the surplus place (Langrex) and now appears to be in China? The guys at Langrex did say the Chinese are hoovering up stock - is this the shape of the future? Stock moving East, and getting a 250% price hike in the bargain?
Main difference, apart from difference in price, is that the 5R4 needs a 4uF input capacitor ...
http://www.r-type.org/pdfs/5r4wgb.pdf
I am planning on using a 4.7uF motor run capacitor, so a little off spec.
My transformer is a toroid - 750VCT. Do I need an input resistor? The application (Tubelab SSE) does not have one specified for a 5A4 since the DCR of the standard transformer (Hammond) is sufficient.
I'll stick a couple of 1n4007's in series with the plates - am I being unduly nervous?
Interestingly, I bought the tubes from a surplus store in the UK. They are ruggedised, so have a funny base, but are NOS. However the stock was no longer listed at the surplus place (Langrex) and now appears to be in China? The guys at Langrex did say the Chinese are hoovering up stock - is this the shape of the future? Stock moving East, and getting a 250% price hike in the bargain?
Typical Operation. NOT a max limit.
It can handle "any" capacitor if the source (transformer) resistance is sufficient.
Thanks for all the help. With a primary voltage of 238v and secondary of half of 750v (centre tap), primary resistance of 9.2 ohms and secondary of half of 122, I get a calculated resistance of 83 ohms in series with each plate. Hence I will need to supplement that with another 17 ohms on each plate.
I have a 200 VA transformer with heater taps, so assuming 100ma to each plate in normal operation, then I calculate 1.7 volts dropped, less than 0.2w, so 1w resistors should be fine.
I have a 200 VA transformer with heater taps, so assuming 100ma to each plate in normal operation, then I calculate 1.7 volts dropped, less than 0.2w, so 1w resistors should be fine.
.... and then I come with the experience of many decades, and comment that I think that obsession with motor run caps is overrated. Especially these days of better quality electrolytics ....
Yes, there are still low quality electrolytic caps. But by now this would have sorted itself out. I hesitate to mention brands; I have mostly used Philips and JJ electrolytic caps, not least so because of their comparative availability locally. I never had a failure from one of these (several 100 samples).
As to what 'sounds' better; I always steer clear of that subjective subject. Same value caps have no sound in themselves; unless woefully miscalculated they should make no audible contribution.
As said though, temperature and frequent charging/discharging cycles, particularly where fast forced rise times are concerned (e.g. ripple), are a capacitor's enemies. One should check these parameters before placing just any capacitor in a particular circuit.
Yes, there are still low quality electrolytic caps. But by now this would have sorted itself out. I hesitate to mention brands; I have mostly used Philips and JJ electrolytic caps, not least so because of their comparative availability locally. I never had a failure from one of these (several 100 samples).
As to what 'sounds' better; I always steer clear of that subjective subject. Same value caps have no sound in themselves; unless woefully miscalculated they should make no audible contribution.
As said though, temperature and frequent charging/discharging cycles, particularly where fast forced rise times are concerned (e.g. ripple), are a capacitor's enemies. One should check these parameters before placing just any capacitor in a particular circuit.
For what it’s worth, and at the risk of upsetting some, the best sounding modern oil caps I have used are the GE 97F series. I prefer these over CSC and ASC caps of the same value. BUT I don’t use any of these in my equipment these days. For modern caps, I prefer Jensen radial electrolytics which, to my ears, sound better and they happen to be a lot smaller so more convenient to use. Lastly, I also prefer the sound of BlackGate WKZ series caps over all others including the Jensens. Unfortunately they are long gone.
Having replace e-caps 4 times in the ST70, I hate them with a passion. I've got 8 pieces of equipment lined up for the workbench that need new e-caps. Now my main ST120 amp I use 14 hours a day, that I re-ecapped with 3000 hour service life CDE caps in 2011, (the longest life 3300 uf 80v in stock that day) needs it again! The 50 uf 440 VAC 1000 vdc Genelec polypros I put in my H-182 organ will likely NEVER need replacing. Pity a polypro 3300 uf 80 v cap would be the size of a dorm room refrigerator, and cost $$$$.
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Indianajo,
I can obviously not fault your experience; I was not there. In contrast my amplifier remained switched on for the last some 15 years, discounting vacations and the sometimes power cuts that we have here in summer (thunderstorms). They are Hitanos, 2200µF 63V, working under some 40V each; in the p.s. seried wirh divider resistors. In a few other places I also use electrolyics.
The only relevant factors are ripple, temperature and brand. Thus the difference must come in in some of those factors? As said before I also use Philips (valve amplifiers), thus higher voltages. I must include my workplace, where many hundreds of electrolytic caps. were used.
??? ???
I cannot hazard a guess. Certainly in your case I would agree with you, and I will not enter into argument wth you; our experiences were different. Also it will be a little thick to argue that by chance you were unfortunate to only acquire bad examples while only good ones came my way. I cannot begin to think of reasons why; each of us will have to (re-)examine our own cases of application.
I can obviously not fault your experience; I was not there. In contrast my amplifier remained switched on for the last some 15 years, discounting vacations and the sometimes power cuts that we have here in summer (thunderstorms). They are Hitanos, 2200µF 63V, working under some 40V each; in the p.s. seried wirh divider resistors. In a few other places I also use electrolyics.
The only relevant factors are ripple, temperature and brand. Thus the difference must come in in some of those factors? As said before I also use Philips (valve amplifiers), thus higher voltages. I must include my workplace, where many hundreds of electrolytic caps. were used.
??? ???
I cannot hazard a guess. Certainly in your case I would agree with you, and I will not enter into argument wth you; our experiences were different. Also it will be a little thick to argue that by chance you were unfortunate to only acquire bad examples while only good ones came my way. I cannot begin to think of reasons why; each of us will have to (re-)examine our own cases of application.
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