Re-capping Nichicon FW "audio" caps with LD "long life" caps? - Page 1
Forum section: electronics / repair

author: armandhammer
author_rank: Contributor
timestamp: July 10, 2021, 01:53:16 am
content: I'm recapping the main PCB of my Yamaha A4000 Sampler (from 1999; I already recapped the PSU) and I noticed that almost all of the THT electrolytic caps are Nichicon FW type which are for audio use, and they're all part of the opamp circuits at the outputs and inputs. However I have a lot of Nichicon LD caps already which are "long life" developed to survive the heat of LED circuits, not specific for audio.Will using the LD series wreck the quality of the audio, or is it one of those "golden ears" types of things? I would use the exact same rating and diameter caps as the old FW ones.If LD is NOT okay, what should I be looking at in the specifications of LD vs FW that would tell me this? Other than capacitance, voltage, temperature, and lifespan I'm not really sure what sets apart all these different series of caps that Nichicon offers, other than some are "designed for audio".Also there are a handful of SMD electrolytics on the board, and I've never recapped SMD -- is there anything special to know when looking for new ones of those, other than the diameter/footprint and rating?

author: armandhammer
author_rank: Contributor
timestamp: July 10, 2021, 02:19:49 am
content: Here's the service manual on my Google Drive. I highlighted the FW caps on the main PCB schematic on p59, and the ones on the front panel JK board are on p60 (not highlighted, but it's all of the 47uf electros).https://drive.google.com/file/d/1iPbgT8hrKN_yNQk-eCSf8rlVUS21MFB4/view?usp=sharing(don't view it directly on Google Drive, save it to your PC, then view it -- else the highlights might not be in the right location)

author: armandhammer
author_rank: Contributor
timestamp: July 11, 2021, 11:53:31 pm
content: Nobody knows?

author: Smoky
author_rank: Frequent Contributor
timestamp: July 12, 2021, 02:22:37 am
content: I'd say that their specs look similar when it comes to leakage current after 2 minutes.Long-life would tilt the scale IMO.

author: David Hess
author_rank: Super Contributor
timestamp: July 12, 2021, 01:43:00 pm
content: In some coupling applications leakage can matter, but if this is comparable then I would expect no difference in performance.

author: Zero999
author_rank: Super Contributor
timestamp: July 12, 2021, 02:33:31 pm
content: Quote from: armandhammer on July 11, 2021, 11:53:31 pmJust one question: why?My advice is, if it's working, leave it alone.

author: TheMG
author_rank: Frequent Contributor
timestamp: July 12, 2021, 03:55:42 pm
content: Doubt there would be any measurable difference in audio performance between the two.But also consider if it does need recapping or not. Unlike power supplies, capacitors in signal (line) level audio circuits are under very little stress and heat. They will typically last a very very long time. Sample a few of them and if they measure within tolerance leave them alone, if it ain't broke don't fix it.

author: rsjsouza
author_rank: Super Contributor
timestamp: July 12, 2021, 05:57:31 pm
content: As others have said, capacitors in audio lines tend to last a long time unless the circuits have a very high difference in DC bias - in the diagram, this does not seem to be the case. If these are still working, I would leave them alone. Capacitors in my 1989 sampler (Roland W30) are still in tip top shape after all those years.One aspect, however, is that those capacitors do not have much electrolyte and it is very easy to miss when one is bad. Also, if they are assembled very close to the PCB, they may leak but almost nothing can be seen in a visual inspection.Good luck in your repair!

author: armandhammer
author_rank: Contributor
timestamp: July 12, 2021, 10:11:03 pm
content: Thanks everyone. I learned a lot from your replies. I thought all electrolytic capacitors are at risk of leaking after 20+ years, but I guess this is really only a big concern for power supplies. I’ll leave the audio caps alone until I actually have an issue. It’s easy enough to peek inside the case once a year for a visual inspection.

author: tooki
author_rank: Super Contributor
timestamp: July 13, 2021, 09:48:30 am
content: Quote from: armandhammer on July 12, 2021, 10:11:03 pmNo, I would not say it's a concern only for power supplies. For example, on classic Macs, which are all now >20 years old, cap leakage on motherboards is an issue, especially for some models from around 1990. On some models, a common problem is no audio output, precisely because the output coupling cap has failed and leaked.But I also agree that just replacing everything just in case isn't the best approach. I think an annual inspection is the best solution.