Greetings! First post, long time user of Boss stomps and multi-processors. I picked up a CS-1 off eBay and it's in need of some restoration. The input/output jacks are lightly corroded and really do not grab the plugs. The footswitch needs replacement, you really have to stomp it hard a couple of times to turn it on/off. The effect seems to work fine, but I do notice a distinguishable loss of volume when it is on, more than just the fact it is compressing. I do not get that noticeable a signal loss with my CS-2. I don't want to mod it, but just restore it but I have no idea who to send it to that will put it back into factory spec. Any recommendations?
For the footswitch try a little electronic contact cleaner alongside the black (or transparent) pin. Pump it up and down a couple of times. This may work, otherwise you have to change the switch. The jacks can also be cleaned with the same solution and then try to retighten the contact pins. A bit of work with a fine sandpaper can also do wonders.
Edit: A little amount of contact cleaner needed...
If Goran's suggestions doesn't help you can get the replacement parts from Roland. The jacks can be replaced by generic ones but only Roland can supply the switch (I think, correct me if I'm wrong).
Other people has complained about the volume drop on the CS-1 too so that's probably normal.