Boss DS-1 just died

[stoneattic]

Any suggestions would be greatly appreciated.

I have a modded Boss DS-1 that just died.  This is not one of those I tried to mod it and I killed it questions.  I did these mods a few years ago and it's worked great for many practices and gigs.

I did the Monte Allums Tri-Gain Rectifier mod and then true bypassed it using a 3PDT switch and removing and jumpering around Q6 and Q7 and removing Q8.  Schematic here:(http://stoneattic.homelinux.com/public/DS-1_SERVICE_NOTES.pdf) , it's the DS-1A.

So yesterday I stop getting any signal through when the effect is engaged.  Bypass works fine and I have continuity from the input, through the switch and through R1.  I don't know how to test below C1.  I also have continuity from the PCB point 11 to the output.  So it's not the switch or switch wiring.  I had the original IC so I put that back in with no change.  I replaced D1 with no change.

Nothing appears burnt, etc.  I don't really know how to check much beyond what I've already checked.  My next move will likely be remove and replace starting with the transistors.

Any thoughts?

[mistahead]

Check out the debugging page for how to check all that stuff after the thing you didn't.

Audio probe the circuit for a start...

[Henry89789]

Or don't waste your time with it. Find another one on CL for $20.00 and do the same mods to it.  Every time I found a cheap one I'd buy it. I have six DS-1 pedals and have done every DS-1 mod in the Wampler How To book. I always though they were the best pedals to mod because they are so cheap and the mods really improve them.  I found a couple of really cheap ones that didn't work and both times it was a diode near the power in that had to be replaced to get them working.

[R.G.]

The trick of using a shunt diode on the power supply for reverse polarity protection can be quite fragile. Even a few seconds of being plugged into a 9Vac power supply can kill them. In fact it's so common that I suspect an AC power supply whenever I hear about a diode being fried. I think that most people really don't know they're doing this, and plug in a 9Vac supply from one of the digital pedals on their board, it doesn't work, then the swap the power supplies around, only to find that their pedal has mysteriously died.

@OP.

First, go read the debugging page (what to do when it doesn't work), and get out your voltmeter. Find out whether you are getting power to the PCB, and if so, what the voltage is. A dead "protection" diode may be holding the whole thing off. If not, knowing the DC voltages on the pins of all semiconductors is the right starting point for debugging.

... that is, if you want to spend the time on such a pedal, as noted.

[stoneattic]

I used an audio probe to test and I have audio at the base of Q1 and I have +9V at the collector.  But I have no audio at the emitter, but do have +9V.  I'm pretty novice about transistors other than to blindly replace them.  Unfortunately I don't have a spare here to replace it with right now.  Is that what should be happening with Q1 or does that sound dead?

[stoneattic]

UPDATE:

It's working, and there might have not been anything wrong in the first place, kinda...

I figured out that the chassis and power grounds were not connected.  When I connected them it started working.  The only thing I can think of is that I never tried it on its own since doing the true bypass.  I'm thinking it was making the chassis to power ground connection through the other pedals on my board.

Does this make sense?

Thanks for the help.  Making an audio and the lesson learned was worth the time and headache!

[mistahead]

Makes sense - to me (a novice also).

I hate being the "read debugging" guy - but the audio probe is priceless and the "engineers approach" is something a lot of us DIY types need to revisit occasionally!

Good stuff on the win mate.