Boss Chorus Problem

[Pablomago]

I have an old Boss CE-2 Chorus from the '80's that I love the sound of but can't use because it flakes out. When you hit the switch it may or may not come on or it may come on at half volume or no volume. Or it may just work fine. It doesn't matter if it's powered by a battery or wall wart so that rules out power supply problems. I've cleaned the jacks and sprayed out the switch and it seemed to help for a little while. Could it be a faulty switch or a bad solder joint somewhere or ???? Any guess or experience with this kind of problem?

[MarkusBass]

The schematic is available here: http://www.mif.pg.gda.pl/homepages/tom/files/ce2.gif
You can easily verify whether the switch works correctly - it switches the LED either ON or OFF. The problem may be caused by VR3 trimmer - please check it.

Marek

[Mark Hammer]

The switching in a CE-2 consists of a single FET that is either turned ON to provide the delay signal in addition to the dry signal, or turned OFF to leave only the dry signal. Consequently, there would seem to be something wrong with that FET or with any of the components that result in it normally being turned on properly. For instance, the diode that feeds the gate of the FET.

There is really no reason to suspect that the delay chip itself is the source of the problem if it provides the same quality of delay/chorus sound even when the volume level changes.

If the issue is the overall volume of the whole pedal, whether in effect or bypass mode, then the chances are good the issue is found in the power lines. More specifically, you should replace C29 and C30 to be on the safe side. That shouldn't cost more than a dollar.

[cjlectronics]

I get these types of problems sent to me all of the time on many of the older guitar pedals and it doesn't matter the brand or the type of effect. Typically, the pedal is in need of TLC. I replace both input and output jacks as well as the momentary bypass switch. Keep in mind that Boss pedals use a metric thread on the input and output jacks and the clearance hole size for the jacks is not big enough for a switchcraft jack that is a standard English thread size.

Something else on the older Boss pedals (your CE2 would qualify) that I am starting to see is leaking electrolytic capacitors. Particularly in the miniature electrolytic caps. Look for a white crust around the bottom of the caps...or better yet, just replace them all with the same value.

CJL

[Mark Hammer]

CJ,

First, hi and hope the family is well.

Second, in the interest of clearing up any vagueries regarding capacitor age and need to replace, do you have any idea how old these pedals with the "crust" might be? I'm not challenging you at all. Rather, as cap manufacturing techniques change, and as the types of caps used changes, what counts as "old" can also be expected to change. presently, if a cap is 15 years old, I figure that unless there are clear visual indications that nothing is amiss, it is highly likely to be up to spec, and if it is 30 years old I should probably consider replacing it. While the cost of replacing caps is a mere pittance, skill in desoldering and removing components without damaging the PCB or adjacent components varies widely. Consequently, I think it is useful to be able to keep the amount of rampant cap replacement to a blessed minimum and appropriately targetted.

So, in your experience, how recent does a pedal need to be before your intuition says "No point in checking out the caps or replacing them as a precaution"?

[cjlectronics]

Hi Mark,
The family is doing great! Thank you for asking.

Based on your post I should clear up the details of my recommendation to Pablomago and other DIYers who are repairing their pedals.

I approach most all of my repairs with the intention of replacing as little as possible and leaving as much vintage as possible, especially on the analog based pedals mfg'ed between from the 60's up to the late 80's. What prompted my recommendation to replace the caps is the fact that I have seen on more than a half dozen occasions the 10uf/16v electro's in an 80's DD-3 (big chip version DD2/DD3) where these caps have white crust leaking at the bottom. Some are not easy to spot and require removal to see the leakage. Also, I've seen these caps in other Boss pedals of that same era and remember replacing those as well. Probably, these were a bad lot and got distributed in various Boss pedals during that time. So, in Pablomago's case I recommend replacing the electrolytic caps because of the CE-2's age and if the new jacks and switch do not solve the problem.

Of course, the 60's and early 70's fuzz pedals have a higher probability of bad capacitors and I recommend to all of my clients to replace the caps with same value electro's.

So, to answer your question, I don't replace caps without a good reason. On 60's and 70's pedals, most likely I would replace the electrolytics unless I get a request to leave everything as vintage as possible and the pedal sounds good (this is a whole different discussion). On 80's and 90's pedals, if the pedal is experiencing intermittent failure then I would suspect electrolytic cap problems. If bad caps were found then I would recommend replacing all of them.\

CJL

[Mark Hammer]

As they used to say on "Family Feud", "Good answer! Good answer!"

[Pablomago]

Thanks for the tips. I'm going to start with the switch, but when I have it open, I'll check out other components. It sounds great, it just doesn't want to work all the time.

[Pablomago]

I replaced the switch yesterday and it works like new. I looked at the circuit board and the caps look OK, but I might replace them at a later date. Thanks for the tips, all!