Duocast having problems.

[Ivantheterrier]

So I just finished up a Duocast build. Only to find out it has a rather wierd quirk. I think the problem centers around the germanium transistor.

Anyways here’s the deal. If I set the low cut to 0. I get no sound. More low cut = more volume. The gain control doesn’t seem to do much right now and it seems the transistor may be gating a bit. also changing the voltage selector in either direction causes a momentary massive boost in volume. Tried pulling the 1054 chip. No change.

I’ve checked the values in the low cut filter and everything seems up to spec. Tried re touching the solder joints as well. Also in a last ditch effort. Tried swapping the transistor around 180 degrees. And even tried a spare metal can instead of a red dot oc75. And it seems to behave the same in either direction….

ive previously built a simulcast. And own a dual foot switch broadcast. So I have a pretty good idea something is very wrong. Any ideas where to go from here? Haven’t pulled the board from the case as it’s quite late and I was hoping a retouch of solder would fix this thing…

 

[Ivantheterrier]

So some more digging (sorry I cant get pictures to post. Too large from my phone and the computer is tied up)
The more I test. The more I think it has to be something surrounding the bass cut control. I wonder if it’s bias related. As I disconnected the transistor Q2. And jumpered pins 2 and 3. Massive volume boost. The bass cut. As expected does nothing in this configuration.
For testing purposes I switched to a PnP silicon transistor. And it sounds the same flipped either way around. Could the transistor be incorrectly biased? All the values in the power supply resistors seem to be correct…. Needless to say this one has me stumped

 

[Feral Feline]

When I upload photos from my phone to this forum, there's an option for choosing small medium large — maybe try your phone again and see if that pops up for you.