New (broken) pedal day!

[laurie]

I can't find a 10uF tantalum capacitor anywhere on the schematic. The only one I can see is 0.1uF C130. Yeah, if that one is it then it would definitely sound wrong.

I had thought the "R" was a tolerance marking, but there is nothing in the literature that confirms that. What the "R" can sometimes represent on older gear is a decimal point ... so R10/35 would be 0.10uF at 35V. That would align with it being C130.

Can you see any other Tantalum caps on the schematic? (they are labeled with a "T").

[Pepe]

No, I have only spotted this one and it seems the one in this position as well. This should be C130. Too bad that the circuit board doesn't name the components. It would make things a bit easier.

If the tantalum still works a bit, then my multi tester should be able to tell me its specifications. I'm going to desolder it in the evening.

[laurie]

I agree that it should be C130. Not sure what the testing will show - be interested to see.

It has definitely failed. The board will need a careful cleaning to get rid of the electrolyte. A new 0.1uF cap should fix the tone.

[Pepe]

My multi tester confirms that the tantal has 0.1 µF ("99.6 nF").

At this point I'm more confused than before. Because my friend's CS9 has the same tantalum capacitor built in in the same direction. He wrote that it could be a typo on the circuit board. And the schematic says the following:

Screenshot 2024-07-15 at 20-08-30 IBANEZ CS9.jpg (143.55 KiB) Viewed 9557 times

The positive leg goes to the (negative) ground?! All the other electrolytic capacitors have the negative legs connected with the ground. Could there be some logical reason why the tantalum capacitor is reversed?

[Pepe]

Yep, sometimes it happens! I'm in the process of fixing for a friend a Voodoo Labs amp switcher. The factory put a 2N3906 transistor in the place where an LM317L voltage regulator should have gone (they look the same physically, and the every other 3-pin semiconductor in the pedal is a 2N3906). They just picked the wrong part when it was manufactured.

It must have sat in a cupboard for nearly 20 years. Took a bit of detective work to figure that one out - there is no schematic available.

In those cases you can only wonder how things like these pass the quality check. It has never worked, right?

[laurie]

My multi tester confirms that the tantal has 0.1 µF ("99.6 nF").

At this point I'm more confused than before. Because my friend's CS9 has the same tantalum capacitor built in in the same direction. He wrote that it could be a typo on the circuit board. And the schematic says the following:


Screenshot 2024-07-15 at 20-08-30 IBANEZ CS9.jpg

The positive leg goes to the (negative) ground?! All the other electrolytic capacitors have the negative legs connected with the ground. Could there be some logical reason why the tantalum capacitor is reversed?

The PCB may be mis-labeled. What side of the device connects to ground (zero Ohms to the pedal case)?

Not sure why it is "reversed". I'd need to analyse the circuit...

I stand by my assessment that it is leaking, even though it tests OK.

IF it isn't this capacitor making it sound weird, we will need to go hunting for the cause. What are the symptoms, exactly?

[Pepe]

The PCB may be mis-labeled. What side of the device connects to ground (zero Ohms to the pedal case)?

I double-checked everything. The unit is 100% negative ground. The negative side of the battery clip goes to ground (and pedal chassis) when a plug is inserted, as well as the tip of the DC input jack. I tested some of the electrolytic capacitors - their negative legs go to the ground. The spot where the tantalum capacitor was soldered in is correctly labelled. The "+"-side is NOT connected with the ground, the "non-+"-side IS directly connected with the ground.

The tantalum capacitor was definitely soldered in with the positive leg directly connected to the negative ground.

EDIT:
I just found a current auction with a Maxon CS9 Chorus and there the tantal is soldered in in the very same way as it was in my unit (that "T" labelling is also visible on the circuit board of my Ibanez model, I just looked it up):

Screenshot 2024-07-15 at 23-55-58 Maxon CS-9 STEREO CHO[...].png (37.65 KiB) Viewed 9533 times

But then again, here is a picture of a Maxon CS9 where the tantal seems to be connected with the negative leg to the ground!

Screenshot 2024-07-16 at 00-07-27 637fb6a0-c3b2-11e9-9a[...].png (245.78 KiB) Viewed 9526 times

IF it isn't this capacitor making it sound weird, we will need to go hunting for the cause. What are the symptoms, exactly?

The LFO doesn't sound like a sine or triangle waveform. Instead it sounds kind of like a deformed waveform, a mixture of sine and square. My idea is that this might be caused by malfunctioning capacitors that have problems with charging and discharging in the proper way.

There are some mini electrolytic capacitors. I have stumbled over quite a few of these from the early '80s that have become bad over time, especially those with 10 µF. Isn't that also a common fault in the DD-2 and MIJ DD-3 these days?

[zentropa]

Will just chime in here that while the CS9 is one of my favorite chorus pedals of all time, the vintage ones often have a lot of weird LFO noise (that the reissues do not suffer from).

[laurie]

The only capacitor that *might* have an effect is this one. 47uF
.

Picture1.jpg (247.07 KiB) Viewed 9507 times

[Pepe]

Thanks a lot for the information and especially for taking the time. Very, very much appreciated!

The tantalum capacitor is still a mystery to me. Would you ever consider putting the positive leg of a tantal to negative ground?