Guest " " Posted November 5, 2006 Share Posted November 5, 2006 I am looking for high uf ( couple hundrd uf's) 500 volt to 550 volt caps. There seem's to be an abundance of high uf 450 volt caps with max surge of 525 volts at really low prices. Can a medium volt cap be put in series to increase the voltage rating of the pair, while reducing the uf rating? Would two 300 volt 1500uf caps in series equal a 600 volt 750uf cap? Does anyone know of a supplier of high uf 550 volt caps? Quote Link to comment Share on other sites More sharing options...
dlb945 Posted November 5, 2006 Share Posted November 5, 2006 Yes, you are on the right track. For an example of replacement boards go to the SDS Labs site. On this site you will see several power supply circuit boards for tube based equipment. I have used these on several rebuilds and the results are outstanding. Here is a pointer to the Dynaco Stereo-70 board. I'm sure this information will help answer your questions. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 5, 2006 Share Posted November 5, 2006 JJ Electronics makes a 550 V cap Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 5, 2006 Share Posted November 5, 2006 JJ Electronics makes a 550 V cap No they make a 500V cap there is no surge rating listed for the JJ line of caps. They seem to hold up well with 480V on them but I would never trust them to hold up in the long run to surges above 500V. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 5, 2006 Share Posted November 5, 2006 I am looking for high uf ( couple hundrd uf's) 500 volt to 550 volt caps. There seem's to be an abundance of high uf 450 volt caps with max surge of 525 volts at really low prices. Can a medium volt cap be put in series to increase the voltage rating of the pair, while reducing the uf rating? Would two 300 volt 1500uf caps in series equal a 600 volt 750uf cap? Does anyone know of a supplier of high uf 550 volt caps? Tell me more about the particular application and what is currrently used in the amp and I'll point you in the right direction. Do you have a schematic? If the amp has 500V on these caps and room exist to run caps in series then I would suggest you use the 385V series from JJ telsa but the highest uF rating they produce is 800uf @ 385V AES stocks this cap or the 350V to 450V United chem-con KMH series caps. You will also need to install balancing resistors for the best results. Usually 100k to 240k will work to even out the load on both caps in series. You want caps designed for high ripple current application's. Oh and yes running two caps in series takes the effective value of the cap down to 50% of the value of one of the caps used and double the voltage rating of the single cap. Craig Quote Link to comment Share on other sites More sharing options...
Guest " " Posted November 5, 2006 Share Posted November 5, 2006 Thanks all for the comments thus far. I guess one of our american manufactures of tube amp equipment cut the "capacitor class" during engineering school. I was checking a tube amp that had a very faint, but audible hum. The main power supply capacitor was rated at 450 volts with a 525 volt max surge value. Power supply voltage was 496 volts. The faint hum went away when I dropped the line voltage from 125 volts down to 105 volts which resulted in a 452 volt power sullpy voltage. So I am on the hunt for 550 volt or above caps. Second choice, putting lower voltage caps in series. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 5, 2006 Share Posted November 5, 2006 You're right, Craig, they don't make a 550V cap. They make a 560V cap. Couple friends of mine have bought them, but I haven't had a use for this voltage rating up to this point. I'm surprised you don't know about it. Speakerfritz: I was 10 volts off on that, but you might check the following link. This place has been excellent. https://ssl.eurotubes.com/cart/index.php?page=view_products&category_id=5&sub_category_id=27 Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 5, 2006 Share Posted November 5, 2006 Speakerfritz: Available are 50X50/560V or 500uf/560V Caution: Make sure you know what kind of capacitance the rectifier tube you're using is rated for. For example, I've seen 5AR4s used with input caps of 100uf, which can cause premature failure of the tube in equipment where that aspect of the design was neglected. I would have to go check to confirm this, but off the top of my head I believe I remember the 5AR4 max. cap rating being 40Uf. Don't ignore those specs and extend the life of your tube and quipment. Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 5, 2006 Share Posted November 5, 2006 Make that 60uf. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 5, 2006 Share Posted November 5, 2006 You're right, Craig, they don't make a 550V cap. They make a 560V cap. Couple friends of mine have bought them, but I haven't had a use for this voltage rating up to this point. I'm surprised you don't know about it. Speakerfritz: I was 10 volts off on that, but you might check the following link. This place has been excellent. https://ssl.eurotubes.com/cart/index.php?page=view_products&category_id=5&sub_category_id=27 Erik I have no clue why your so surprised. I haven't purchased from Euro tubes in about 2 years and as far as I can see he has the only information on this "new" 560V cap from JJ. Heck its not even on the JJ website yet. Must be fairly new. But it sure is a great option. I myself will keep running caps in series for amps with near 500V present. I like having a few hundred volts of safety in my power supply. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 5, 2006 Share Posted November 5, 2006 Thanks all for the comments thus far. I guess one of our american manufactures of tube amp equipment cut the "capacitor class" during engineering school. I was checking a tube amp that had a very faint, but audible hum. The main power supply capacitor was rated at 450 volts with a 525 volt max surge value. Power supply voltage was 496 volts. The faint hum went away when I dropped the line voltage from 125 volts down to 105 volts which resulted in a 452 volt power sullpy voltage. So I am on the hunt for 550 volt or above caps. Second choice, putting lower voltage caps in series. Fritz, Are we talking about the amps you purchased not long ago? Are they built on a circuit board? How many of these 450V caps in each amp? Are you sure they are not already run in series? I'm surprised the manufacturer in question would use a cap running almost 50V above its rating. By the way dropping the wall voltage does not absolutely mean the hum is caused by the power supply cap. It could very well be the problem hard to say without checking the ripple on a scope. Craig Quote Link to comment Share on other sites More sharing options...
Guest " " Posted November 5, 2006 Share Posted November 5, 2006 ssl.eurotubes.com seems to be a good source. i have the schematic's for the amp inbound so I'll stay with the manufacturer's uf values and just address the voltage ratings. thanks all Quote Link to comment Share on other sites More sharing options...
Guest " " Posted November 5, 2006 Share Posted November 5, 2006 NOSValves schematics in bound. I have plenty of room in the case. I'll keep the resistor requirements in mind. That should get me going. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 5, 2006 Share Posted November 5, 2006 Make that 60uf. More to it then that.......... http://www.triodeel.com/5ar4_p1.gif Maximum Ratings ( DESIGN CENTER VALUES) Maximum Peak Inverse Voltage 1500 volts Maximum Peak Current (per plate) 750mA A. C. Supply (plate to plate) Voltage (rms) 1100 volts Maximum D.C. output current 250mA Maximum capacity (condensor input filter) 60uf All 4 above ratings have to be taken into effect. Design center values isn't listed for nothing!! Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 5, 2006 Share Posted November 5, 2006 I have many books with enormous amounts of information regarding power supply design. Thanks, though. If you wanted to post this for others, I'm sure it will be helpful. Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 5, 2006 Share Posted November 5, 2006 Speakerfritz: Can you tell if this hum is very low 60cycle hum or 120? If this is a vintage amp and your AC supply is running as high as you mentioned, it may also influence the heater supply secondary winding, which are more critical than those for plate (B+). It would be possible to install a thermistor on the AC into the amp, which once settled down to a lower resistance after warmup, will help lower things a bit, and perhaps put your heater supply very close to original spec for the amp. This is one area restorations may neglect, but it's an important one. You may have a leaky cap, as well as some other possibilities. Grounding of the high voltage center tap is one area to look at, as well. Despite the fact that it goes to common like the rest of the grounded connections, its actual connection point can be inportant in terms of unwanted noise. Be careful working around those charged caps, and be sure to properly discharge them before working in the amp. This doesn't mean simply shorting the positive to ground; there is a better and safer way of doing it. If the power supply has a bleeder circuit on the output, it should do that job for you. Just check to make sure before you work on stuff. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 5, 2006 Share Posted November 5, 2006 These are not vintage 60's era amps. 80's or 90's SS rectified PP amps from a very popular high end tube audio company. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted November 5, 2006 Share Posted November 5, 2006 "Can you tell if this hum is very low 60cycle hum or 120? " It's a very very faint hum, I can't tell the frequency.....it does go away when I drop the line voltage enough to bring the power supply voltage below the rated voltage of the main power supply capacitors. Example, if I drop the line voltage from 125 volts to 105 volts, the power supply voltage drops from 496 volts to 456 volts, and the hum goes away. I can lower the AC line voltage pretty easilly usng a toroidal balanced isolation transformer which has numerous wiring options. I have a few of them, there rated at 1500 watts each. The power supply capacitors are inexpensive, so I'm going to replace them. These may not be the original capacitors. 450 volt / 525 max surge capacitors seem under rated for a 496 volt power supply. I'll know for sure when I recieve the schematics that I ordered. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted November 5, 2006 Share Posted November 5, 2006 "80's or 90's SS rectified PP amps from a very popular high end tube audio company" I think they were manufactured in 1989. I am also thinking the caps are not original. Will know for sure when the schematics show up. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted November 5, 2006 Share Posted November 5, 2006 Ah, these are the Cary amps, right? When you get the schematic, that will be a help. Good luck, Erik Quote Link to comment Share on other sites More sharing options...
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