Catalinbread Sabbra Cadabra Mirosol Layout Trouble

[lvluffster]

I've just built the Catalinbread Sabbra Cadabra via Mirosol's layout and I can't get any sound out of it except for a "hiss". The Gain, Presence, and Volume/Output all have the proper effect on the hiss when turned, but the range knob affects nothing. This makes me think that the problem is somewhere in the Range part of the circuit, with nothing getting through, and I am affecting the post-range noise/hiss with the other three knobs.

Any ideas? I've already checked for solder bridges/continuity/etc. with a multimeter and I've also double-checked my component placement with the layout. Used the exact BC184/MPF4393 Trannies as called for on the layout, and also used exactly correct values for all other components including pots.

[lvluffster]

Two pics of my work, and the layout link is here:

http://tagboardeffects.blogspot.com/2015/03/catalinbread-sabbra-cadabra.html

[Zanius]

Hey, welcome!

From a quick look, your placement looks good. My bet by experience and by your solder side looks, is on a bridge. Checking with a multimeter is a good way to go, but I've stopped doing so for bridge checking. What I do now is pass a stanley knife across every row. If I hit a bump, I make sure to give a good scraping between the lines and move on. Bridge may be something less-than-hair thin, and multimeter may measure it as big resistance instead of continuity (as least mine seems to do so). Finally some good blowing and brushing with an old toothbrush. Never had a bridge problem since I've been doing that.  

Since the overall system sounds like it's working, I suppose your input doesn't ever reach the circuit. But that's just a guess.

About the tantalum caps, I don't know how you decided to use them (I never used any unless the schematic specifically asks for them), Are you sure they are in the right direction? Notice that on normal electrolytics, the side marked is cathode. But on tantalums the side marked is anode (at least on those I use).

[lvluffster]

Hey Zanius, thanks so much for the detailed reply man! I'll try scoring the whole board again and check my tantalum orientation. I didn't have enough electros or I would have used all electolytic, had the right values in polarized tantalum though. If I recall correctly, I just used a few of the same tantalums successfully in a rat build and the short leg was negative as normal. These all came from Tayda.

Will report back later, thanks again!

[lvluffster]

Scored every track by running a dremel cutoff in-between each row then scoring with a knife...still nothing. Also double-checked tantalum polarity and it was ok. Bout ready to pull my hair out on this one.

[Zanius]

In your place I would now reflow solder on my board. Look really close for suspicious connections and try making them better with some extra solder or by passing the iron along them to flow solder better.

If that also fails, next step is also a lesson. It's best to use sockets for trannies than soldering them directly to the board. One of them may be bad, some may got fried in the soldering process, or who knows what. If you had them on sockets, that would be a 2 min test. Now it's a unpleasant trip :)  

[Emil]

Following up on what Zanius said here, posting your transistor voltages could help give an indication what might be wrong.

[lvluffster]

Thanks again for the suggestions guys, it's very possible that I overheated them. The MPF4393 and the BC184 were quite hot to the touch when I soldered them in. It would be great if I could just replace and socket the trannies to get things working, even though the MPF4393 were a bit difficult to find and had to special order from China.

I reflowed a few spots with no dice. Anyway, will check transistor voltage and report back, hopefully that's the problem.