O5R/W startup distortion (again)

[MichaelMcG]

I've had an O5R/W for about 9 years (I bought it used) and it worked fine when I first got it. Over time it started to have low, distorted sound at startup, with the sound rectifying itself after several minutes. I stopped gigging after an accident several years ago, and the module has just been sitting in its box since. I took it out a few days ago to have a listen to it and it wouldn't even turn on. I tried several 12v psu's and it wouldn't work with any of them. A friend suggested trying a regulated 9v psu, and it worked with the two I have here.

I stripped the module down to have a look to see if there was anything obviously wrong with it, but other than a brown-ish sticky residue over most of the underside of the main board, everything looks OK. I cleaned it up the best I could with isopropyl alcohol but it still only works with a 9v psu and is still distorted for several minutes after powering it up.

I have read on here that this module has problems with the caps leaking and needing replacing and that these tend to be at the output rather than power stage. Has anyone here had a go at trying to replace the faulty caps themselves? Is there a recommended list of which ones to replace? I have the engineers manual so I shouldn't have too big a problem locating the ones which need replacing, but they're quite small and would be extremely difficult to work with.

Sorry for this being so long winded, but I wanted to give as much detail about the problems as possible.

[T3owner]

[...]
I have read on here that this module has problems with the caps leaking and needing replacing and that these tend to be at the output rather than power stage. Has anyone here had a go at trying to replace the faulty caps themselves? Is there a recommended list of which ones to replace? I have the engineers manual so I shouldn't have too big a problem locating the ones which need replacing, but they're quite small and would be extremely difficult to work with.

I had to change several capacitors in my own 05R/W, and repair some printed circuit traces that were damaged from corrosion due to the electrolyte that leaked from those caps.

Surface mount electrolytic capacitors from the time period the 05R/W was manufactured are prone to failure. Leakage is common, but isn't the only cap failure mode. Since there's plenty of headroom above the pc board, I replaced the caps with radial lead type, with the leads cut relatively short and bent at right angles to the cap bodies.

If you don't have proper soldering equipment and some experience using it, you'll likely find the repair to be challenging - even more so if the electrolyte has attacked circuit traces or vias (connections from one side of the board to the other).

If you're interested in pursuing this further, I can provide a list of the ones I had to change. However, be aware that there's no guarantee your unit will require replacement of the same ones.