RYO Penta issues - help me troubleshoot?

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OB1
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Post by OB1 » Fri Apr 13, 2018 9:50 am

Thanks both! More things to check this evening...

@csaban your issue sounds very much the same as mine, so will certainly look at the things you suggest. I think I can rule out the reset jack as the issue exists without that board connected, but R9/Q1 could definitely be culprits.

I've not really done any continuity testing before, so I'll probably check some youtubes before I have a go at that!

Thanks again.

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OB1
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Post by OB1 » Fri Apr 13, 2018 12:28 pm

OK, as suspected, pin 13 on the 40106 reads 0v.

I've located the switch header and I can't see any short to the ground pin next to it. Both joints are very neat and I've checked under a magnifier. The only way there's a short there is if it's hiding under the plastic on the front of the board, but that seems unlikely. Is there a way I can rule out a short using a multimeter?

I also had a look at Q1 - that all looks OK as well in terms of the soldering, but I also tested the continuity across the source/drain and I got continuity in both directions as well...

I also don't know if this is right or wrong!!

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Post by mcop » Fri Apr 13, 2018 1:11 pm

Sounds like you could have a duff Transistor there. Just checked the transistors on my build with the diode test function on my multimeter and only get a reading in one direction as I'd expect to.

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Post by OB1 » Fri Apr 13, 2018 1:40 pm

Yeah, I think you're right. I checked the other 6 transistors on the other board and I get nothing (1) in one direction and some reading between 400-800 in the other direction. With Q1 it beeps (0 or 0ish) in both directions.

Seems odd that csaban would have the exact same issue with the same transistor, but I guess if there was an issue with the board, there'd be a whole lot more people piping up!

Anyway, I guess I'll replace Q1 and see if that sorts it!

The only transistors I have to hand are 2N3904s - could I use one of those in place of the 2N7000 at Q1? Or does it need to be another 2N7000? If so I'll order some in...

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Post by csaban » Fri Apr 13, 2018 2:08 pm

I'm afraid 2N3904 won't substitute the 2N7000...

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Post by OB1 » Fri Apr 13, 2018 2:13 pm

That’s what I figured. I was reading something that suggested it might work in some applications with the addition of a resistor, but I figured a couple more days won’t hurt and ordered some 2N7000s!

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Post by OB1 » Fri Apr 13, 2018 4:31 pm

Confirmed - I desoldered the 2N7000 from Q1 and tested it again for continuity, which it has in both directions across source/drain. Double checked the board as well and there's no short between those pads.

Thanks everyone for your help tracking this down - you've taught me a lot!

I'll let you know if the replacement transistor gets it all moving ;-)

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Post by OB1 » Wed Apr 18, 2018 1:46 pm

Well, the replacement transistor got it stepping again!

However, this thing still has some similar issues to those described in my original post:
Step 1 - less range than the good steps
Step 2 - good
Step 3 - good
Step 4 - less range than the good steps, and even less than step 1. LED does not light fully, instead the LEDs for steps 1, 4 and 5 are dimly lit.
Step 5 - good

Also 3 step mode is not resetting after 3 steps, it plays all 5.

I can’t see any shorts on either board and I’ve spent a long time looking (any tips on how to spot/check for shorts would be great).

I’ve replaced both the 4017 and 40106 ICs in case either had an issue.

To be honest I’m not really sure where I should be looking next...

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Post by csaban » Wed Apr 18, 2018 3:37 pm

I'm glad to hear you got the steps back OB1! I hope you've ordered more than one 2N7000 replacement... (Please bear in mind, I'm not an EE, just trying to trace the symptoms on the schematic)

LED problem: the LEDs are controlled by the other 2N7000s (Q2-Q6). I would try to replace Q5.

Range problem: The outputs (3,2,4,7,10) on the 4017 provide 5V which is divided by the potentiometers. So first, I would check if pot1 lets all 5V through when turned all the way clockwise. If it doesn't then check pin 3 of the 4017 for 5V else check R10 which should be a 100k.
According to the mods page http://ljunggrenaudio.com/products/penta%20modifications.html R17 controls the output range: 0-5V needs a 100k.

3 step mode: In order for the 4017 to reset after step 3, step 4 is connected to the reset pin via the switch. So step 4 has to work perfectly to have the module reset after step 3. If replacing Q5 doesn't improve step 4, my other candidate is to replace Q7. But I would ignore this for now and try to solve the range problem with step 4.

Let me know how you get on.

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Post by OB1 » Wed Apr 18, 2018 4:22 pm

Thanks, that’s very helpful and all makes sense.

I ordered in a bunch of the 2N7000s so all good. Gonna give this all a go shortly.

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Post by OB1 » Wed Apr 18, 2018 5:40 pm

Well, this is great news!!

Switching out Q5 has completely resolved all problems related to step 4 and its LED, including the 3 step issue.

Step 1 still has slightly less range than the other 4 steps but right now I don't care, I just want to play with it!!

Thanks so much for your help, csaban. Your suggestions were bang on and your explanations helped to me to understand why.

:yay:

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No LED lights

Post by ray » Wed Sep 26, 2018 7:16 am

Hi, I have also an issue with the Ryo Penta, mine works fine except no led lights up. Any hints on where I have to look?

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Post by csaban » Wed Sep 26, 2018 4:08 pm

My first guess would be LED orientation... :)

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Post by ray » Thu Sep 27, 2018 8:25 am

csaban wrote:My first guess would be LED orientation... :)
Checked that, long leg to the square is right?

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Post by csaban » Thu Sep 27, 2018 1:06 pm

If I recall correctly, the one I had issues with (isn't mine, helped a friend fixing it) had to have all the 2N7000 replaced as they were all DOA.

If you have a spare, you could try replacing one of Q2, Q3, Q4, Q5 or Q6 and see if that fixes it.

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