Repairing/Improving Alesis M1 MK2's

[james2k2]

I'm not sure if it's been talked about here before, but I also know Dave's love for bad caps, and guess what - these units are filled with bad caps.

Basically, the power supplies on these are prone to failure and highly susceptible to surges/spikes. The great thing is that they are an easy fix.

I'm recapping both the problematic caps, and the large AC filter caps (JunFu brand). I'm also replacing a couple of power resistors with metal film instead of carbon film that they are now due to heat (my research suggests these would be better for handling higher temperatures).

I've attached some photos of my intentions. My only problem is sourcing replacements for those big AC caps. Currently, they are 200V 390uF 105deg. I have found some Samwha, but at £5.30 (Around $8) a piece I can't justify replacing working caps for the sake of it. So, as I understand the voltage doesn't matter as long as it's equal or greater? But what about the capacitance? Any suggestions for a good replacement cap for these? I'm willing to spend about £1 per cap ($2 ish).

In the photos:
1 - 100Ohm 1W 5% (To be replaced with a 100Ohm 2W 1%) - Cracked and discoloured due to heat build up
2 - 390uF 200V 105deg (Need help with these) - no problems yet, but would like to replace
3 - 2x 47K 2W 5% (To be replaced with 47K 2W 1%) - these build up heat causing the cap in 4 to dry up
4 - 220uF 35V 105deg (To be replaced with a Panasonic 220uF 50V where its 105deg rating will actually be true!). I will also use some heatshrink around the legs and raise it from the board slightly for extra protection.

[SeanB]

Use 470uF 200V units, same size and within the +50% tolerance. Samwa is only marginally better than JunkWoe cap in any case, you will be replacing again in under 5 years.