I would like recomendatios for PSU filter caps in a Dynaco Mark VI amplifier. I am now using some Aerospace quality film caps But they are physically very large and I can only fit two in the chassis. My go to cap has always been the JJ line but I would like to know if there is another electrolytic altenative out there
Thanks, Kevin
Thanks, Kevin
Way less money at Mouser: ALS30A101DA500 KEMET | Mouser Canada
Cheaper still at Arrow: https://www.arrow.com/en/products/a...r&utm_content=inv_listing&utm_source=octopart
Or these Rubycons... rated for 12000 hours and way less money than the above! 500LXW100MEFR18X45 Rubycon | Capacitors | DigiKey
Cheaper still at Arrow: https://www.arrow.com/en/products/a...r&utm_content=inv_listing&utm_source=octopart
Or these Rubycons... rated for 12000 hours and way less money than the above! 500LXW100MEFR18X45 Rubycon | Capacitors | DigiKey
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Thanks everyone. Yes, Dynaco Mark VI (6). Thanks for the suggestions. I have four holes in the chassis to fill. And they are for 1 3/8" cans. The Kemets would be good but there is only one cap per can. Also, the amp runs 545 B+ so I need to parallel caps to get enough voltage capacity. It seems that so far the JJ's have the edge.
The amp originally had two first caps 50uf 300 volts and second 100uf 300 volts. So it seems barely enough. So with four JJ double 100 uf at 500 volts each I'll end up with 400 uf at 1000 volts total.
The amp originally had two first caps 50uf 300 volts and second 100uf 300 volts. So it seems barely enough. So with four JJ double 100 uf at 500 volts each I'll end up with 400 uf at 1000 volts total.
I used panasonic 450 v caps in my ST-70 from dynakit in 1961. OEM was allegedly a 525 v cap, but I think that was surge rating. I never read that for B+ when the amp was operating, and my wall plugs are 125 v, not 115. More like 380. My transformer is original.
Those E15 super expensive Kemet's merlin found had a 11000 hour service life rating. The $4 panasonics I used had 3000 hours I think.
I put them on cinch solder terminal strips under the chassis, under the holes. I covered the holes with metal mesh to keep the spiders out. Those cinch strips are hard to find, I was getting them from electronic surplus, apexsurplus, or tubesandmore.com I like the 5 terminal one with the grounded terminal on the end. I use #6 screws with elastic stop nuts to hold the strips to the chassis, since I don't want them to come unscrewed or have loose nuts rattling around in the chassis. If I was starting over I suppose I'd use 3 mm screws, US machine screws might disappear some day. I get the screws from mcmaster.com in packs of 50 or 100.
****, the digikey link for the rubicon cap gave me a black screen with a nice white border. I realize I'm asking for the canadian website which is wrong but I'd like to see it. At least merlin's link worked.
Those E15 super expensive Kemet's merlin found had a 11000 hour service life rating. The $4 panasonics I used had 3000 hours I think.
I put them on cinch solder terminal strips under the chassis, under the holes. I covered the holes with metal mesh to keep the spiders out. Those cinch strips are hard to find, I was getting them from electronic surplus, apexsurplus, or tubesandmore.com I like the 5 terminal one with the grounded terminal on the end. I use #6 screws with elastic stop nuts to hold the strips to the chassis, since I don't want them to come unscrewed or have loose nuts rattling around in the chassis. If I was starting over I suppose I'd use 3 mm screws, US machine screws might disappear some day. I get the screws from mcmaster.com in packs of 50 or 100.
****, the digikey link for the rubicon cap gave me a black screen with a nice white border. I realize I'm asking for the canadian website which is wrong but I'd like to see it. At least merlin's link worked.
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I found these; ALS70A471DB500 KEMET | Capacitors | DigiKey 470 uf at 500 volts and only 12.09 each. In two parallel pairs I would have 470uf at 1000 volts. Pretty much the same price and voltage as the JJ's but at more than twice the capacitance. If it possible to have too much capacitance? And would the two smaller JJ double 100' be faster than the Kemets?
Capacitors in series add the voltage (sort of, balancing is a problem) and halve the capacitance. capacitors in parallel add the capacitance and maintain the lowest voltage rating. If you are using original rectifier tubes, yes you can have too much capacitance. If you are using silicon diodes, you can buy 3 amp or 6 amp ones that will take the surge current at turn-on. I don't have the Mark IV schematic downloaded, but the ST-70 which was a few watts less per channel had 20-20-20-30 B+ capacitance. So don't overdo it without some engineering. BTW hammering the amp tubes with B+ milliseconds after turnon , some people say that causes cathode stripping. Others deny that. As expensive as tubes are these days, I still use a $13 5AR4 rectifier tube. There are other ways to delay the B+ until after the cathodes warm up, like NTC resistors in the transformer primary, or an amperite thermal time delay relay in the B+ line (ha, that was a joke, haven't seen one for sale in 40 years).
This a Mark VI with four KT88's. Originally it ran four 8417's for 120 watts. With the KT88's its more like 160? watts. It has some massive diodes that are good for 10 amps if I remember correctly and the B+ is held up before the outputs by an NTC thermistor. When I first rebuilt the amps I used some 380 uf 350 volt in parallel Spragues and they held up fine. Currently there are two 100uf 600 volt CE manufacturing film cans in there. The ESR of the CE's is like .00065 if I remember correctly?
I use Kemet PEH534 caps in almost every power supply I build. So far they are excellent with no failures... Here is a listing of the exact ones from the exact seller I use: 20PCS 470uF 450V PEH534 HQ Class A Tube Audio Capacitors 20pcs | eBay
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