Replacing old multisection cap with modern equivalents - Page 1
Forum section: electronics / beginners

author: JHAnd
author_rank: Contributor
timestamp: October 30, 2023, 10:27:20 pm
content: I'm recapping an old tube amp...The filter cap is a multisection one with 30,30,30,10 uF pins and a ground rated at 475V 85C. I can't seem to source such a specialty cap here in Sweden so was thinking of replacing with individual caps.I found these:33uF 450V 20%https://www.elfa.se/sv/elektrolytkondensator-33uf-450v-20-a33045016040/p/1670479410uF 450V -10...30%https://www.elfa.se/sv/elektrolytkondensator-10uf-450v-31ua-10-30-kemet-peg124yf2100ql1/p/16769145Can I replace the older caps rated at 475V with modern caps rated at 450V?Also will the extra 3uF per 33uF cap make a difference in a power filter section? Or should I go more exact by using two 15uF caps in parallel instead of the one 33uF?Schematic:http://bentonelectronics.com/wp-content/uploads/2011/12/leslie147.gifI will have to get some kind of terminal to solder the caps and make them stay in place. Do you have any recommendation on how to do this... I don't want to print a PCB just some simple cheap or DIY solution. Would be nice to know a solution for both radial and axial components.

author: Nusa
author_rank: Super Contributor
timestamp: October 30, 2023, 10:57:19 pm
content: Quote from: JHAnd on October 30, 2023, 10:27:20 pmLooks like circuit voltage is only 420V, so 450V caps should be ok.I wouldn't worry about an extra 10% on a 20% tolerance part. You can always bin them yourself to find ones closest to 30 if you want.Modern caps are typically smaller than the originals, so space shouldn't be a factor. I'd suggest opening the can and installing the replacements in there to get the original look and wiring.

author: floobydust
author_rank: Super Contributor
timestamp: October 30, 2023, 11:07:53 pm
content: Problem is the Leslie 147 uses a solid-state rectifier, so on power-up B+ will skyrocket until the tubes warm up. There's no HV load (I would add bleeder resistors) with cold tubes.I'd expect the electrolytics to see more than 450V for that short time.It's OK to round up to EIA values like 33uF.

author: srb1954
author_rank: Super Contributor
timestamp: October 30, 2023, 11:59:02 pm
content: Quote from: floobydust on October 30, 2023, 11:07:53 pmSome brands of HV electros specify a short term surge voltage rating, typically 110% of nominal voltage rating, to allow for the higher voltage before the tubes start conducting.It might be advisable to look for some caps that have a suitable surge rating otherwise using 450V rated caps in this circuit might be marginal without adding a suitable bleeder resistor or Zener clamp to keep the voltage under 450V.

author: MarkF
author_rank: Super Contributor
timestamp: October 31, 2023, 12:28:17 am
content: I have an idea:Use 500V rated capacitors.Digikey has eight flavors in stock.https://www.digikey.com/en/products/filter/aluminum-electrolytic-capacitors/58?s=N4IgjCBcoEwAwBYCcVQGMoDMCGAbAzgKYA0IA9lANogDMNABAK0BiIpNcTrAuqQA4AXKCACqAOwCWAgPKYAsoWz4ArgCdCIAL6l4AdhTQQGSDgIlyVEAFY4nAGoheIQcPFTZCpWo3aQAWhhUIygBVWVzCkhqK0dNX0Coo2w%2BbDQpMlV8WKAThey can't be the only supplier...

author: JHAnd
author_rank: Contributor
timestamp: October 31, 2023, 05:42:56 pm
content: Thanks for your insights!I found some 500V electrolytic caps at RS components.Film caps seem to be easier to find in high voltage ratings. They go up to kV range. But I heard something about electrolytics distorting in a way that we are used to in musical amplifiers.

author: floobydust
author_rank: Super Contributor
timestamp: October 31, 2023, 06:22:54 pm
content: The 4-section (30uFx3, 10uFx1) and 200uF 50V electrolytics are not in the signal path and can't do anything for sound character or distortion. Just do not change the grounding of those parts. I think film caps would be quite large in size and work as well. If it were me, I would use 500V parts and maybe add a bleeder resistor.Some people take the old multi-section can apart and stuff in (4) new caps (they are much smaller) to keep the look. Using the old can.The 200uF 50V I would go with 220uF 50V or 63V. It is critical, if it shorts it will roast the output tubes.The Woodstock mod (as I call it) popular in the psychedelic era was an extra footswitch or modifying the console Tremolo? switch to turn the motor on or off. As the motor spins up or down, the Leslie sound was really a sensational effect, you could slow it down too by toggling the switch on and off. So some Hammonds out in the wild are modified by hippies lol.Once I had a buzzing rattling Leslie treble horn and it was due to a dead moth fell down in there.

author: JHAnd
author_rank: Contributor
timestamp: October 31, 2023, 08:31:27 pm
content: I like the idea of using the old canister. But I don't want the caps to rattle around in there...could I fill it with packaging foam or something? Will they get hot in there?

author: floobydust
author_rank: Super Contributor
timestamp: October 31, 2023, 08:58:33 pm
content: There are many articles and videos on replacing multisection can electrolytics by putting new parts inside. Just use silicone to mount them. The hardest part is getting the old can apart.There are also adapter PC boards, or just put the replacement caps inside chassis. It really depends on your level of restoration you want to do.Yes they get hot, the can gets heat radiated from the tubes but reflects a lot of it with shiny aluminum.https://www.tdpri.com/threads/restuffing-multi-section-can-capacitors.404905/https://www.nmr.mgh.harvard.edu/~reese/electrolytics/

author: Nusa
author_rank: Super Contributor
timestamp: October 31, 2023, 11:19:29 pm
content: Or if you just want to throw money at it, the parts appear to be available:Can by itself:https://classichammonds.net/store/Leslie-Electrolytic-Can-Capacitor/prod_20.htmlFull kit:https://classichammonds.net/store/Leslie-147-Component-Kit/prod_420.html

author: GLouie
author_rank: Regular Contributor
timestamp: November 01, 2023, 03:24:42 pm
content: As Nusa says, you can buy a new version made by CE in the USA. They use the original Mallory tooling, they say.https://www.cedist.com/products/capacitor-ce-mfg-475v-30303010-f-electrolytichttps://www.cemfg.com/I am not certain if the 2 CE companies are the same or not, but they seem popular with the guitar amp repair crowd. I have not purchased from them personally.

author: Nusa
author_rank: Super Contributor
timestamp: November 01, 2023, 06:35:02 pm
content: Cheaper than the Hammond link. Higher voltage too.https://www.tubesandmore.com/products/capacitor-ce-mfg-525v-30303010uf-electrolytic

author: JHAnd
author_rank: Contributor
timestamp: November 01, 2023, 09:24:25 pm
content: Price+shipping cost/time and import duties is prohibitive for my situation... if I was in the US perhaps...So for now I think I'll want to do an under chassis job because I think it will be easier. I'll keep the can for looks.I was thinking of using padboard/prototype board or terminal strips for the supply filter caps and for the crossover filter which I'm also recapping.With the terminal strips the crossover would look something like this:https://imgur.com/a/Vi2HzfYFor the supply caps I haven't decided what to use... either the same kind of terminal strips or something like this:Prototyping Board FR4 Epoxy ResinThen I can cut off an appropriate size piece and screw it to the chassis. But I'm not sure of how I should fasten the board to the chassis. I would need some kind of standoff so the underside of the board doesn't touch metal... I'm very new to this...what kind of standoffs should I use?There is this kind but I'm not sure how to use them:https://www.elfa.se/en/standoff-8mm-m2-brass-wuerth-elektronik-971080154/p/30263629?cq_src=google_ads&cq_cmp=20280557228&cq_con=157172941104&cq_term=&cq_med=pla&cq_plac=&cq_net=g&cq_pos=&cq_plt=gp&gclid=CjwKCAjw7oeqBhBwEiwALyHLM2dGwZm9DiYaX-De1eZ76qXYb4PyMdE1oQGVwE_Q1fJDHORDcjZ6_xoCPbIQAvD_BwE&gclsrc=aw.dsThen there is the plastic kind with self adhesive, but how long will they last?https://www.elfa.se/en/self-adhesive-pcb-support-5mm-polyamide-pack-of-50-pieces-rnd-components-rnd-610-00140/p/30100896?ext_cid=shgooaqsesv-Shopping-PerformanceMax-CSS&cq_src=google_ads&cq_cmp=18208288444&cq_con=&cq_term=&cq_med=pla&cq_plac=&cq_net=x&cq_pos=&cq_plt=gp&gclid=CjwKCAjw7oeqBhBwEiwALyHLM0jkfi-yZd8jDP5_rVmXRwe3VJhNXg9cLGMRzaEvT1VxxfD0r0kTBRoC9vcQAvD_BwE&gclsrc=aw.dsand yet another one with plastic threads...should they go into the metal chassishttps://www.elfa.se/en/locking-circuit-board-support-38-8mm-polyamide-pack-of-50-pieces-rnd-components-rnd-610-00883/p/30388573?cq_src=google_ads&cq_cmp=20280557228&cq_con=157172941104&cq_term=&cq_med=pla&cq_plac=&cq_net=g&cq_pos=&cq_plt=gp&gclid=CjwKCAjw7oeqBhBwEiwALyHLM5xR6r7AHBgCKccPTH5J8HyS5fo--Ip68qCdFSv81b_3dqg41n9kYRoCAT4QAvD_BwE&gclsrc=aw.dsI'm sure there are other types...Any ideas on what to use?

author: alligatorblues
author_rank: Regular Contributor
timestamp: November 02, 2023, 01:05:02 am
content: They're called bolt spacers. The nylon ones are durable and nonconductive.

author: JHAnd
author_rank: Contributor
timestamp: November 02, 2023, 07:06:10 pm
content: Quote from: floobydust on October 30, 2023, 11:07:53 pmWhere would I put a bleed resistor?