Danelectro Cool Cat Chorus w/ Low Volume

yazooligan

yazooligan

Active member
I picked up one of these seafoam green 18v models used and it's got an issue. Volume is really low, whether the pedal is on or in bypass. I've opened it up but I'm not sure what I should be looking for unless there's a trim pot in there somewhere. Does anyone have any ideas on this one? It’s definitely getting 18v. Thanks so much!


 

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Mcknib said:
I'm wondering if it might be a problem with the switching set up because you get low volume in both effects and bypass mode

Unfortunately I've no idea how the switching works maybe someone knows how the 4013 is used so you could check input and output

All that flip flop logic stuff is beyond me
Click to expand...

I think the 1N4148 I pulled might be part of the switching system. Added the photos to the OP too.
 
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yazooligan said:
Also, never hurts to give someone new to the thread all the evidence up front, since some of us don’t care to read the entire thread before deciding whether to weigh in.
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True that, it had crossed my mind of course after I posted my question.

Right now I can't get off my mind what IPAs you've been using, ehr, consuming. 🍺
 
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Mcknib said:
Let us know what happens when you replace it

It might be a clamping diode does it connect to the transistor next to it
Click to expand...

While the diode was out, I plugged in and got the same low volume in bypass and no sound at all when engaged. Put in a new N4148 and I'm back to where I started. It does look like it connects to the transistor next to it though.

I made an audio probe and probed around the main board and the I/O board. I could only get signal to come through in a few spots. On the bottom IC (HA17741) it sounded really loud and overdriven/distorted. In other spots closer to the jacks there was a lot of buzz with the clean signal audible in the background. I'll make a video to demonstrate where they are and add it to the OP.
 
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I used to think with components coming from power or ground and not being part of the audio path you would get no audio at those points

You can in fact get distorted audio for example on op amp power pin 8 as I discovered with a trouble shoot a while back but it's still not part of the audio path and with your effect signal sounding good in your video I'd think it may just be that
 
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Mcknib said:
I used to think with components coming from power or ground and not being part of the audio path you would get no audio at those points

You can in fact get distorted audio for example on op amp power pin 8 as I discovered with a trouble shoot a while back but it's still not part of the audio path and with your effect signal sounding good in your video I'd think it may just be that
Click to expand...
 
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Try probing the 4013 pins

I'm not sure if you'd get audio I don't know what it does possibly acting to toggle signal from the input to 1 or the other outputs

You know it works with low volume in both effect and bypass mode so it's perhaps something common to both

I'd check that and use datasheets to check outputs on the ICs and transistors see if you can find where it goes in at a good volume but comes out lower
 
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yazooligan said:
Oof. I’m just about ready to throw this thing in the fucking trash. I’m pulling my hair out over it. That said, it was fun building my first probe.
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Set it aside and come back to it later, if need be, but it sounds too good to give up entirely on it.



Here's a link to a thread where the OP wants to mod the mix ratio, but there's some good info there that might be relevant or at least give you a better understanding of the overall circuit:

Cool Cat schematic

Cool Cat schematic
www.diystompboxes.com

Same guy, same desire, different thread, yet clues to your puzzle seems unlikely in this thread — but it's short and you never know what may wind up being useful:

mixing stereo outputs of an 18v danelectro cool cat chorus. Formula?

mixing stereo outputs of an 18v danelectro cool cat chorus. Formula?
www.diystompboxes.com


Various Chorus schematics (alas no CC DC-1, but a great resource nonetheless):



Sometimes I get lucky searching online in another language, but apparently no Russians nor Japanese have traced the DC-1. I'll try a few other languages later...
 
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Mcknib said:
You know it works with low volume in both effect and bypass mode so it's perhaps something common to both

I'd check that and use datasheets to check outputs on the ICs and transistors see if you can find where it goes in at a good volume but comes out lower
Click to expand...
I thought this was a transistor, but it's an IC. MC78L12CP

According to the CS-505 schematic I think it's the last IC in the chain. There's a 1N4001 diode right next to it.

ibb.co

1683-CF61-ABEB-463-B-8-CFF-0086-B6-B06-E8-E hosted at ImgBB

Image 1683-CF61-ABEB-463-B-8-CFF-0086-B6-B06-E8-E hosted in ImgBB
ibb.co ibb.co
 
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That's the voltage regulator.
Common to find that style of regulator in Chorus/Flanger/Delay/Reverb builds.

If you look at the lower left of the schematic, or at the block diagram, in the CS-505 service manual that Mcknib gave the link to, you'll see the regulator comes shortly after the 18V power input, and knocks it down to 12Vcc and Vref 6v, if I understand it correctly.

I suppose if the regulator's fried/faulty and not giving enough juice that could explain the low volume. It makes me wonder though, I'd think it's okay 'cause the 4013 and the 3102 will both demand a steady solid source of power — if not your bypass (4103) would be wonky and the chorus might not happen if the clock (3102) isn't getting its due. I'm taking stabs in the dark here.

EDIT: Is the 78L12 getting unusually hot when the pedal's powered up?
 
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I tried the audio probe again, this time focusing on all the transistors. On most of them I could hear some of my clean signal very faintly. A few of them gave me nothing.
 
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Some transistors will be being used as switches

You're probably best just starting at the in pad through the buffer which is probably a transistor looking at the CE2 and CS505 schematics

All you can really do is continuity check to see what connects and probe each section and hopefully find where volume drops out

Each section will be similar to most analog choruses in that you'll have a buffer, filtering, a mixer, bbd circuit, LFO etc
 
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yazooligan said:
Not sure how to tell. Do I just touch it with my finger? It’s kind of hard to get to sandwiched between the two PCB’s.
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You don't need to touch it; just put a finger near it — it's normal to be warm, all electronics get warm, but if it's radiating enough heat to make you wary of touching it or the parts near it (since it's hard to access) ... 🌡️♨️ 🔥.
 
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