Zero Point SDX issue - RESOLVED

[wstimson]

Hello.. I'm working on my ZPSDX and have run into an issue. 

(1) Project Name: Zero Point SDX

(2) General description of the problem
Basic problem is that the delay isn't working.  The clean signal passes through fine (with Mix and Feedback down all the way), but if you try to add in any delay, it instead makes horrible screeching sounds. 

Also, the 78L05 gets super hot when the effect is given power.  But only with the 2399s installed.
With the 2399s out, it does not get warm and the voltages are as expected (9.27 on one side, 5.01 on the other).  With the 2399s in, it's more like 7 on one side and 2.5 on the other and like I said, the regulator gets very warm.

(3) Steps that you have taken to try to resolve the issue
I've tested the 2399 chips in a working neptune delay, and they all work fine.
Reflowed solder joints, double checked component values, triple checked IC orientation.  Tried different ICs.

One thing I'm not sure about... I ran out of sockets so I just soldiered the BC550s in place.  They are labeled BC550B.  Looking at the data sheet Tayda has, they are 1. Collector, 2. Base, 3. Emitter.  I looked up BC550 datasheets on google and it seems that some of them are 1. Emitter, 2. base, 3. Collector.  And I'm not sure which pinout the silkscreen on the ZPSDX is for.  Any ideas?  If these were backwards, might that explain the behavior I'm seeing?  I don't want to desoldier them to try flipping without more info on whether or not that could be the issue.

(4) List any substitutions you used for parts/values
No subs...

Thanks for any help.  I can take some photos if you'd like, but I'm mostly after suggestions about the transistor pin outs and any other ideas about why that regulator is getting so damn hot. 

Thanks again!

-Bill

[wstimson]

Well, I went ahead and removed the BC550s and put in sockets.

Leaving the sockets empty makes the regulator stop heating up. 
It also has no delay effect or noise or anything.  Just clean signal. 

Putting them in the other way around... I'm not sure.  I lost one leg on each of them pulling them out.  I tried to rebuild those legs with leads, but that didn't seem to work.  I put them in and the regular heated up, didn't bother trying to hear what it sounded like.  Gonna score some new BC550s before moving forward.

So... any suggestions?  Overheating like that seems like maybe something is shorting to ground.  But I really don't know what to check.

[madbean]

Is your regulator putting out 5v as it should?

The pinout should be EBC. You don't have to use BC550, though. You can try 2n3904, or probably even 2n5088/89. Those are CBE, though, so make sure you flip them the right way.

[wstimson]

Is your regulator putting out 5v as it should?

The pinout should be EBC. You don't have to use BC550, though. You can try 2n3904, or probably even 2n5088/89. Those are CBE, though, so make sure you flip them the right way.

Cool, I'll check and see if I have any of those laying around and test it out.

The regulator puts out a solid 5v... as long as the 2399s are not in the sockets. 
With them in, it gets hot and reads about 2.5... but not very steady. 

[fendman]

Check you haven't put D1 the 1N4001 diode in back to front.... that will give you a hot 78L05.

[wstimson]

Yep, must've been the transistors.  Put some 2N3904s in there today and it's working! 
Yay!  Sounds pretty damn good.

What do those do?  Should I get some more BC550s instead?  Does it matter?

The only other thing is I feel like I'm hitting oscillation pretty quickly.  Like less than half way on the feedback pot.  Is that normal?