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PostPosted: Wed Dec 09, 2020 2:26 pm 
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Hello again,

I have just completed my Super8 build and started testing functions. The issue is that loops 4-8 turn on as soon as power is applied and cannot be shut off. Everything else functions properly including the switches assigned to those loops. Those switches still will flash the green light on their respective loops. I can hear the relays switch when power is applied and removed. This may be something simple I am overlooking, but I cannot figure it out myself. To me it is a short, but I don’t know where the short would likely be found.

Any information is very much appreciated! I can provide photos is needed.


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PostPosted: Thu Dec 10, 2020 12:53 pm 
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Do the #4 and #8 red LEDs turn on and off as expected? Everything functions as expect, it's just that the 4 and 8 relays are stuck in "send" when power is on? Do 4 and 8 go into bypass when you remove power?

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PostPosted: Thu Dec 10, 2020 1:15 pm 
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No they do not.

Loops 4, 5,6,7,8 all turn on when power is plugged in, including the red lights. The switch will not turn them off (lights or send) but will flash the green light when held. I can hear the relays switch when power is plugged in and then unplugged. Loops 1,2,3 all work properly.


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PostPosted: Fri Dec 11, 2020 11:54 am 
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Remove the 40pin chip and plug in power. Do the red lights still come on and relays change to send?

Just to be clear, are all relays in bypass when there is no power applied? You should be able to plug a guitar into non-buffered input and amp into output and signal should pass.

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PostPosted: Fri Dec 11, 2020 12:36 pm 
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Yes the relays are in bypass when there is no power. I tested and signal does pass with no power. When power is applied with the chip removed the red lights still turn on and the relays switch to send.


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PostPosted: Sat Dec 12, 2020 10:57 am 
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This means you have physical shorts at all the points that are turning on when they shouldn’t be. Can we please see pics?

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PostPosted: Sat Dec 12, 2020 11:25 am 
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I hope this link will work. It worked for my last question. I appreciate the help. I thought it was shorted, but I can’t see where. Thank you!

https://www.dropbox.com/sh/juykcfecnzia ... 6Vm2a?dl=0


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PostPosted: Sat Dec 12, 2020 12:12 pm 
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Based on the behavior, my first guess would be that you’ve gots shorts between the base and collector of the transistor that corresponds to each channel with problems. This would cause the respective relays to send and the corresponding red LEDs to light. It looks like you might have used too much solder and have some unwanted flow out on the topside of the PCB. You also have some unusual flux spatter. You might want to get some isopropyl alcohol and clean that up.

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PostPosted: Sat Dec 12, 2020 4:43 pm 
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I tried desoldering and then soldering the transistor for loop 8 with no change. I could very well be doing something wrong as I am a beginner. I didn’t even know flux is conductive. I will give it another go soon. Thanks again!


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PostPosted: Mon Dec 14, 2020 1:38 pm 
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CollinJiron wrote:
I tried desoldering and then soldering the transistor for loop 8 with no change. I could very well be doing something wrong as I am a beginner. I didn’t even know flux is conductive. I will give it another go soon. Thanks again!


Please be patient and don't start replacing parts just yet. Do you have a digital multimeter? If so, do you know how to test for continuity?

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PostPosted: Mon Dec 14, 2020 2:34 pm 
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I will definitely remain patient. I don’t want to make anything worse. I do have access to a multimeter, and I can have someone assist me with it soon. Where should I start testing?


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PostPosted: Mon Dec 14, 2020 3:12 pm 
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CollinJiron wrote:
I will definitely remain patient. I don’t want to make anything worse. I do have access to a multimeter, and I can have someone assist me with it soon. Where should I start testing?

Check for continuity between the middle legs of all the transistors of all the loops in question. Then take a voltage reading of middle legs of all the transistors in question. If they all have continuity, you only need to measure the voltage on the middle leg of 1 transistor.

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PostPosted: Mon Dec 14, 2020 3:35 pm 
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byoc wrote:
Check for continuity between the middle legs of all the transistors of all the loops in question. Then take a voltage reading of middle legs of all the transistors in question. If they all have continuity, you only need to measure the voltage on the middle leg of 1 transistor.

Per Keith's guidance and what Collin has described, these would be the points to be tested:

Attachment:
S8_stuck_channel_trannies.jpg
S8_stuck_channel_trannies.jpg [ 238.94 KiB | Viewed 8024 times ]

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PostPosted: Sun Jan 03, 2021 8:22 pm 
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Alright, it took me a while to get to it, because I wanted to make sure that I had someone who knew how to use a multimeter properly present. When we ran the checks that were suggested we found that when you touched the middle leg of a good loop (no issues) to the middle leg of a bad loop (issue) it read ~5 volts. When we touched any two middle legs of bad loops there is no voltage. However there is continuity between the bad loops and no continuity between the good loops and bad loops. I have pictures showing the lights being activated when touching bad loops. I also had the person assisting me take a look at the PCB for shorts. They did not see anything that looked like it was touching.

Let me know where to go from here. I appreciate the help!

https://www.dropbox.com/sh/6y0sq6vs3hqt ... pFxqa?dl=0


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PostPosted: Mon Jan 04, 2021 11:59 am 
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If you have continuity between the middle legs of the transistors that correspond to the bad loops, then that means that there is a short somewhere.

You didn't actually test for voltage on the middle leg of one of the bad loops. You need to touch the red probe to the middle leg. Then you need to touch the black probe to ground. There are a lot of places that are ground. The middle leg of the 78M05 or the negative eyelet on the far left side of the PCB would probably be easy probe points. Please test the voltage of the middle leg of each of the transistors and report.

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PostPosted: Mon Jan 04, 2021 10:07 pm 
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I have now tested using the points suggested. I do get the same reading of 3.9V on each bad loop and none on good loops. I also accidentally touched the probe to two legs on the 78M05 and it did shut off the relays and then they turned back on when I stopped. Let me know where to look next.

Thank you!


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PostPosted: Tue Jan 05, 2021 4:16 pm 
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What voltage are you reading on the output of the 78M05 (the leg closest to the bottom edge of the PCB)?

And just to reiterate, this is all being done with the 16F887 out of the socket, right?

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PostPosted: Tue Jan 05, 2021 4:24 pm 
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That reads 4.9v

And yes that is still out of the socket.


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PostPosted: Tue Jan 05, 2021 4:36 pm 
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CollinJiron wrote:
That reads 4.9v

And yes that is still out of the socket.



Hmmm. Well...your problem is definitely that you have a short somewhere. The head scratcher is where are those traces touching and why are they only getting 3.9V? I think the most likely place this could occur is underneath the 40 pin socket.

You don't need to remove the entire socket...unless you have a pneumatic desolder station or you enjoy desoldering. You only need to desolder the 8 bottom rightmost pins (or bottom leftmost if you're looking at the solder side of the PCB).

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PostPosted: Fri Jan 08, 2021 11:12 am 
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Someone else had a problem identical to yours. We traced the problem down to defective transistors. The transistors in the non-functioning loops are shorting out between their respective base and collector pins. So it was a short, just not where I thought it was. Anyhow...you'll need to replace those transistors. Please contact sales@buildyourownclone.com and we'll send them to you.

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PostPosted: Fri Jan 08, 2021 9:07 pm 
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Thank you for the update. I am also glad I’m not alone. I did resolver those 8 pins and that did not correct the issue. I will contact them right away. Which type of transistor do I request?

It lists the following in the instructions and I didn’t know if it matters for this Rev 1.1 board?

‘ 2N3904, 2N5088, 2N2222 or other similar transistor with EBC pinout.’


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PostPosted: Mon Jan 11, 2021 11:48 am 
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CollinJiron wrote:
Thank you for the update. I am also glad I’m not alone. I did resolver those 8 pins and that did not correct the issue. I will contact them right away. Which type of transistor do I request?

It lists the following in the instructions and I didn’t know if it matters for this Rev 1.1 board?

‘ 2N3904, 2N5088, 2N2222 or other similar transistor with EBC pinout.’


Just let sales know your order info so we know who you are and that you need replacement transistors for the super8. It doesn't matter what revision PCB you have. It makes very little difference what kind of transistor you use here. They are being uses as on/off switches, so it's not like a fuzz face where you get different tones with different transistors. The pinout is the most important aspect, but FWIW, you'll be sent 2N3904.

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PostPosted: Wed Jan 13, 2021 7:09 pm 
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I have (or rather had) a very similar situation. Finished the build, went to testing, and had a mashup of various loops being stuck on. I do a lot of electronics building and repairs, and was fairly confident that I hadn't missed anything else, my solders were all good, and the symptoms were identical to what's in this thread. I had noticed while building that my kit came with 3 different kinds of transistors, none of them being the specified 3904's, which was kind of vexing but a quick look at the schematic showed that they were just being used as switches so I didn't think much of it. I didn't make notes of which (bad) transistors were in the problem channels - I just removed them all, and replaced them all with 3904s. And now everything works as it should.

I guess the moral of the story is: not all transistors work the same, even for mundane jobs like this. Let's stick with 3904s in these kits.


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PostPosted: Sat Jan 16, 2021 7:49 pm 
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sduck wrote:
I have (or rather had) a very similar situation. Finished the build, went to testing, and had a mashup of various loops being stuck on. I do a lot of electronics building and repairs, and was fairly confident that I hadn't missed anything else, my solders were all good, and the symptoms were identical to what's in this thread. I had noticed while building that my kit came with 3 different kinds of transistors, none of them being the specified 3904's, which was kind of vexing but a quick look at the schematic showed that they were just being used as switches so I didn't think much of it. I didn't make notes of which (bad) transistors were in the problem channels - I just removed them all, and replaced them all with 3904s. And now everything works as it should.

I guess the moral of the story is: not all transistors work the same, even for mundane jobs like this. Let's stick with 3904s in these kits.

I'm guessing that the loops that didn't work had 2N5458 transistors, which got mixed in with the 3904's in a vendor order. Those are JFET's, which function very differently than the BJT's that should be use for this switching duty. Any other general purpose NPN BJT (2N2222, 2N5088 and many more) will work there, assuming they're not defective in some way. See this thread: viewtopic.php?f=52&t=59169

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PostPosted: Mon Jan 18, 2021 5:34 pm 
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I am happy to report that after getting the new transistors and replacing the bad loops my problem has been resolved. Thank you again for the support!


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