SOLVED Duocast

boji

Active member
Hi all,

I finished building the Duocast yesterday. I used IPA for the first time (I know, I know) and was quite proud of my cleanest build yet. But I must have made a mistake somewhere, because it doesn't work properly.

- I got sound in bypass and when I press on the right foot switch
- Pressing the left footswitch kills the sound
- Both LEDs light up as they should

What should I check first?
Thanks!
 

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JamieJ

Well-known member
I think so, flat side down (like shown on the build docs)
Ok cool. I couldnt see on my phone. Soldering looks good. It can be worth reflowing the joints to see if that works. My next steps would be to double check all components and values.

Is the germanium transistor socketed? It’s always worth double checking the pin out
 

boji

Active member
I don’t have one yet but I’ll build one. It seems that the audio probe is the DIY pedal maker’s best friend :)
 
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boji

Active member
Ok cool. I couldnt see on my phone. Soldering looks good. It can be worth reflowing the joints to see if that works. My next steps would be to double check all components and values.

Is the germanium transistor socketed? It’s always worth double checking the pin out
It’s not socketed but I made sure the little side tab matched the one on the pcb. Could my transistor’s pins not match (even though the tab does)?
 

almondcity

Well-known member
the build calls for BC549C I believe which has the opposite pinout of many other similar transistors

I used the orientation shown on the PCB (Rev 3 anyway) and it was correct
 
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boji

Active member
Try to find the data sheet for that exact transistor online.
I bought it as part of a kit, no information on the manufacturer whatsover. On the transistor, I can see, from top to bottom :
A « T » in a circle
y8
AC125 U

I’ll try to ask the seller (musikding) for some more info
 

zgrav

Well-known member
I socket all transistors and clipping diodes, so I don't know but everything I've read suggests you can't test it in circuit. JamieJ's suggestion and a visual inspection is probably the closest to in-circuit as possible. I could be wrong, I've been wrong once before.
I have always enjoyed this quote: "I thought I was wrong once, but I was mistaken.
 

fig

Village Idiot
I looked at their offerings, [E]BC for the solo 125s. I doubt they'd buy another brand for the kits. [] = tab

Looking at the schematic, I would wager that the Emitter goes to the A10 pot which would make the orientation you described (per silkscreen) correct.
 
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boji

Active member
Here are the schematics. I'm not sure of where to start and what path to take.
Do I start at D100 ? If so, I lose signal right away

Edit : Or more probably I should start at R12 and C1. It doesn't make much of a change. Apart from the tips of the jacks, I can't seem to get audio anywhere. 🤔
 

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fig

Village Idiot
D100 is going to be the protection diode. Since the power seems to be working but the audio isn't, you'll want to trace the audio path starting at [IN] - R12 and check the nodes along that path. When it splits, first try where it joins again. If the signal is still good, keep moving towards OUT. If not, let us know the point closest to the OUT you were able to find a signal.
Someone else may have a better method, but I've found most signal problems in this manner.
 

boji

Active member
D100 is going to be the protection diode. Since the power seems to be working but the audio isn't, you'll want to trace the audio path starting at [IN] - R12 and check the nodes along that path. When it splits, first try where it joins again. If the signal is still good, keep moving towards OUT. If not, let us know the point closest to the OUT you were able to find a signal.
Someone else may have a better method, but I've found most signal problems in this manner.
I think I was editing my message while you were writing yours. I figured I probably would have to start at R12. But I can’t even get audio there
 
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