Mark Hammer ce-2 question

[jimbob]

Mark- I can see there are many threads that youve addresed concerning the boss ce-2 chorus in the past and had a question- this pedal i bought - i can hear a chorus sound present and decent - but there is also some distinctive distortion in there as well. So can i assume the bbd is still good and 2) would anything associated with that have anything to do with the led not working? Im wondering if i should try i ask for some money back and fix it myself  or just return the item for full refund. It doesnt seem like it would be in expensive  or even difficult fix. Or am I wrong there?

Very much thanks

jim

[puretube]

Sorry to interfere prematurely, here, Mark:
if you bought it new, on a regular base (in opposition to your usual "finds"...): get back your money,
if the distortion is really beyond acceptable, and if the LED problem is not related to using a wrong power supply;

If it`s a "find & fix"-case, check for a trimpot inside (circuit-wise at the input of the BBD), which sets the bias for the BBD - it can be the cause (if "mis-aligned", as my friend Howard Davis would call it...) for distortion;
(of course there are other possible distortion causes...)

[jimbob]

I bought it off ebay and was supposed to be w out a problem. Work like new it said. I tried the trim pot and no difference. As far as the good deals go.. my guy sd business slow til mid jan and come back then. Im seeing if the guy wants to refund some dough since it dont work right or send it back for all the money.

[puretube]

fresh battery? (sorry - I had to ask...)

[jimbob]

used power adapter and a fresh battery- gotta ask.

[puretube]

OK - we`ll have to wait for Mark...

[Fret Wire]

Could have an electro going bad. Does it show any signs of soldering repair/modding? Check wiring to jacks and pots. Very small adjustments can make a big difference trimpot wise.

[jrc4558]

Hey, I'm no Mark and I ain't got a schem in front of me. But...
1) Loose solder joints on the components in the gain setting places, like feedback loops of op-amps (i had a case like this with Ibanez Bi-phaser).
2) Electrolytic capacitors, as was noted.
3) Damaged FETs, usually if they are used as buffers, or sometimes even in the bypass application can cause audible distortion in the BOSS/IBANEZ bypass cirquit.
As I've said, I ain't got a schem, but just from the previous experiences...
2cents...

[george]

3) sounds the most likely,  it sounds as if there is some kind of problem with the switching circuitry, if the LED isn't going on ...

I'd check out Q8 and Q9 and everything in between ...

[Mark Hammer]

Two things are going on here which may or may not be related.

As some folks have quite naturally suggested, a distorted sound and dysfunctional LED *would*direct one's attention to the battery.  From your comments, though, that option can be excluded.  You said that you tinkered with the trimpot, but to no avail.

For me that now directs my attention to the switching.  Call up your CE-2 schem and walk through this with me.

Note that just about every Boss effect uses a pretty standard (you can find it in circuit collection books from 40 years ago) 2-transistor flip-flip circuit.  Hit the momentary switch and one output goes high.  Hit it again and the other output goes high, with the first now going low.  In some Boss effects that need to turn one thing off and another thing on to change over from effect to bypass, each of the two transistor outputs (measurable at the collectors, which this link -  http://220.130.99.70/pdf/2sc945.pdf  - says will be the middle pin) is tied to its own switching FET/s.  In the case of the CE-2, the BF-2, the VB-2, the PH-2, etc., the "cancellation" of the effect only involves a single FET and essentially only one side of the flip-flop.  It doesn't really matter which "side" of the flip-flop - you could actually reroute R48 from the collector of Q7 to the collector of Q6 without changing a thing in the functioning of the pedal.

What the actual voltage reading is on the collector of each of those 2SC945 transistors, I could not tell you, and perhaps this is where you get to find out something useful for yourself and everyone else here by popping the hood in a Boss pedal of yours that you KNOW to be in 100% working order and measuring the collector voltages there when the switch is stepped on repeatedly.  Alternatively, if someone ELSE already knows that info, or is in a position as they read this to provide it, it would be good if they could volunteer it.

Okay, now that you know what is supposed to be going on with the flip-flop, the question to be asked and answered is this one:  Is the FET that connects the BBD output to the mixing stage, and the LED that is simultaneously turned on to indicate effect engagement, being ADEQUATELY DRIVEN by the flip-flop?

There is the possibility of the FET itself being busted somehow, but the coexistence of the LED problem suggests a common source of difficulty.

Note that since the input signal is always tied to the utput in the case of the CE-2, misfunctioning of the switching system will have NO effect on the signal quality of the non-effect signal.  Were this a distortion pedal or some other pedal where both sides of the flip-flop and multiple FETs were used, that might not be the case; a misfunction of the switching system that, for example, resulted in less than a suitable switching voltage being routed to either FET might conceivably produce a poor quality effect sound AND poor quality bypass sound.

[dubs]

Are you using a 9v power supply? I say this because some early versions of ce-2 had a diode/ resistor combo to reduce the voltage to the circuit to around 9v as early boss adaptors were 12 volt.
Hence if you place a 9 volt adaptor the led won't function as I discovered when modding someones ce-2. You can remove the resistor and diode or use a germanium diode.

[george]

Are you using a 9v power supply? I say this because some early versions of ce-2 had a diode/ resistor combo to reduce the voltage to the circuit to around 9v as early boss adaptors were 12 volt.
Hence if you place a 9 volt adaptor the led won't function as I discovered when modding someones ce-2. You can remove the resistor and diode or use a germanium diode.

good point but jimbob gets the same result with a battery ...