As suggested by ClaveFremen, I'm posting my questions to this thread.
Anyways
I just finished soldering up my MyRef and hooked it up for testing. When I turned it on, I heard a pop and saw sparks. It seems like I blew DR1 and DR2. Any theories for what happened? Can it be saved?
My other channel worked fine, but I didn't hook up the heatsink this time. Do you think the heatsink could have caused DR1 and DR2 to blow on the first channel?
Thanks!!
Edit: My other channel just blew too, DR3 and DR4. This time. It happened right when I plug the power cord in. (I didn't use a power switch.)
Anyways
I just finished soldering up my MyRef and hooked it up for testing. When I turned it on, I heard a pop and saw sparks. It seems like I blew DR1 and DR2. Any theories for what happened? Can it be saved?
My other channel worked fine, but I didn't hook up the heatsink this time. Do you think the heatsink could have caused DR1 and DR2 to blow on the first channel?
Thanks!!
Edit: My other channel just blew too, DR3 and DR4. This time. It happened right when I plug the power cord in. (I didn't use a power switch.)
I sure hope it can.
This is my first build with an unpopulated pcb.Here's the pic. I just desoldered DR1 and DR2.
An externally hosted image should be here but it was not working when we last tested it.
At a first look, unless you bridged some pads on the bottom side it seems correctly assembled.
From the picture R11 seems burnt, which is pretty normal when something goes wrong.
I'm starting to think you, maybe, wired transofrmer secondaries the wrong way...
Did you try to measure AC-PGND-AC before connecting the transformer to the PCB?
Did you used my tutorial?
You can find it attached to this post (the BOM is outdated but the tutorial is current)
It is for TP boards but can be used also for Siva's ones and has a section on how to wire the transformer.
From the picture R11 seems burnt, which is pretty normal when something goes wrong.
I'm starting to think you, maybe, wired transofrmer secondaries the wrong way...
Did you try to measure AC-PGND-AC before connecting the transformer to the PCB?
Did you used my tutorial?
You can find it attached to this post (the BOM is outdated but the tutorial is current)
It is for TP boards but can be used also for Siva's ones and has a section on how to wire the transformer.
Yes, R11 is burnt on both boards. I didn't even notice it until you pointed it out.
I measured the transformer at 25.X volt before wiring it on. I don't "think" I wired it the wrong way. I couldn't have done it twice right?
I forgot about the tutorial until I was almost done. But I did use it for the transformer wiring
I measured the transformer at 25.X volt before wiring it on. I don't "think" I wired it the wrong way. I couldn't have done it twice right?
I forgot about the tutorial until I was almost done.
But I did use it for the transformer wiring
What I mean about wiring correctly and measure it's:
Look at the transformer you should have a table like this (for a double secondary):
25V secondary: Brown/Yellow
25V secondary: White/Green
Brown should be AC1
Yellow and White tied together should be PGND
Green should be AC2
Then power on the transformer and you shoud measure, referenced to PGND, on both AC1 and AC2 25V AC.
(pay attention that wires don't short... )
It's so?
OK
Then let's check how you branched those wires to the PCB.
The faston nearer to smoothing caps should be PGND
The other two are AC1 and AC2.
I'm insisting on this because I've also fried TWO modules branching AC1 to PGND
Even if it was the 50th time I was branching them...
Look at the transformer you should have a table like this (for a double secondary):
25V secondary: Brown/Yellow
25V secondary: White/Green
Brown should be AC1
Yellow and White tied together should be PGND
Green should be AC2
Then power on the transformer and you shoud measure, referenced to PGND, on both AC1 and AC2 25V AC.
(pay attention that wires don't short...
)It's so?
OK
Then let's check how you branched those wires to the PCB.
The faston nearer to smoothing caps should be PGND
The other two are AC1 and AC2.
I'm insisting on this because I've also fried TWO modules branching AC1 to PGND
Even if it was the 50th time I was branching them...
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I have an Antek transformer. The secondaries are Blue/Green, Blue/Green
I wired Blue AC1, Green/Blue as PGND, and Green AC2.
AC1 to PGND and AC2 to PGND measure 25.x V
I don't think I wired the PCB wrong. I was very tempted to switch AC1 and PGND too (it just feels natural LOL) but I remember double checking before plugging it in.
I wired Blue AC1, Green/Blue as PGND, and Green AC2.
AC1 to PGND and AC2 to PGND measure 25.x V
I don't think I wired the PCB wrong. I was very tempted to switch AC1 and PGND too (it just feels natural LOL) but I remember double checking before plugging it in.
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Wow! My best bet for sparkles was on transformer and or wiring...
I imagine that sparkles came suddenly, not after some time, right?
At his point I would check that each component is the right one for each position.
Sorry, here are 4.00AM so I'm going to sleep now.
Tomorrow I'll check the thread again
Good luck!
Yes, it happened right when I plugged in.
If input signal and ground got shorted, would it cause any issues? (Not sure if it happened, but so far that's the only possibility I can think of going wrong in terms of wiring)
Hey, thanks for helping! I hope we can figure this out. Do you think I should replace the rectifiers and resistor and try again?
If input signal and ground got shorted, would it cause any issues? (Not sure if it happened, but so far that's the only possibility I can think of going wrong in terms of wiring)
Hey, thanks for helping! I hope we can figure this out. Do you think I should replace the rectifiers and resistor and try again?
I think the only thing that will happen from shorting input to ground is silence. I don't think it will damage the amp.
You mentioned this is your first bare board build. Did you check actual value of each component before mounting? All 'lytic caps and zeners are properly oriented?
If you blew both boards, then you made the same mistake twice and it should be easier to find. It's probably not a construction error or defective part, but an incorrect component location or direction, or a power wiring mistake.
I suggest initial power up through the light bulb tester (do a search). And always use a heatsink. Once you get them to not blow up, first output connection should be to a junk speaker in case there's something still wrong.
Peace,
Tom E
You mentioned this is your first bare board build. Did you check actual value of each component before mounting? All 'lytic caps and zeners are properly oriented?
If you blew both boards, then you made the same mistake twice and it should be easier to find. It's probably not a construction error or defective part, but an incorrect component location or direction, or a power wiring mistake.
I suggest initial power up through the light bulb tester (do a search). And always use a heatsink. Once you get them to not blow up, first output connection should be to a junk speaker in case there's something still wrong.
Peace,
Tom E
The only thing that looks out of place (it's not clear in the pic, but could be a problem) is
that SPKR OUT seems to be bridged to a pad of C17 and then further to the speaker.
If so, that will short the output to one of rails (V+, from memory), which could have
destroyed the LM3886TF chipamp, and then the rectifiers as well as R11.
Before removing the chipamp, check carefully for rail-to-ground and rail-to-rail shorts as well.
R3 is slightly crooked (probably because its leads are 9 mm apart, while the
pad pitch on V1.3 is only 5 mm, for the Caddock MP8xx/9xx), but this should
not be a problem unless a lead of R3 comes into contact with V+.
The solder pad for SPKR OUT (in addition to the two mounting holes for the male
faston connector) is actually next to one end of R4. That's also a slightly unsafe
location, and that has been shifted a bit to the left in V1.4, IIRC.
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I measured the resistors but lacked the means to measure the caps.
It's weird that one of the boards worked for the first two plug ins before failing on the third. Would it have worked at all if it was a location/direction issue? The other board failed on the first plugin. I will pick up some MUR820 and R11 and try the light bulb test. Do you think anything else was damaged?
The SPKR OUT wire is an optical illusion. A slight bend makes it appear to be bridged to C17 but it's totally separate.
How do I check for rail-to-ground and rail-to-rail shorts?
Thanks for the replies guys!
It's weird that one of the boards worked for the first two plug ins before failing on the third. Would it have worked at all if it was a location/direction issue? The other board failed on the first plugin. I will pick up some MUR820 and R11 and try the light bulb test. Do you think anything else was damaged?
The SPKR OUT wire is an optical illusion. A slight bend makes it appear to be bridged to C17 but it's totally separate.
How do I check for rail-to-ground and rail-to-rail shorts?
Thanks for the replies guys!
For shorts, just disconnect the board completely and measure the rail-to-ground and rail-to-rail resistances with the lowest range on a DMM. Any value of an ohm or less is most probably a short.
The secondary AC voltage measured correctly as 25 VAC per winding, right? If it's much higher than that (say 32 VAC), it will probably exceed the max rail voltage rating for the LM3886TF (+/- 42V), which could cause it to fail shorted and take out the rectifiers and R11.
As Dario mentioned, check and double-check all the trafo connections to the PCB AC1, GND and AC2. I've also interchanged a pair in the past, and luckily lost only R11.
The secondary AC voltage measured correctly as 25 VAC per winding, right? If it's much higher than that (say 32 VAC), it will probably exceed the max rail voltage rating for the LM3886TF (+/- 42V), which could cause it to fail shorted and take out the rectifiers and R11.
As Dario mentioned, check and double-check all the trafo connections to the PCB AC1, GND and AC2. I've also interchanged a pair in the past, and luckily lost only R11.
Does it matter that I pulled some of the rectifiers? It's definitely greater than 1 ohm, but it jumps around in one of the higher ranges.
Yes the secondary AC measured ~25 VAC. I don't know if it was at 25 once it was hooked up or during power on though as I only measured it when it was not hooked up to anything. Once I verified it was okay, I shut it down and hooked up the MyRef.
Yes the secondary AC measured ~25 VAC. I don't know if it was at 25 once it was hooked up or during power on though as I only measured it when it was not hooked up to anything. Once I verified it was okay, I shut it down and hooked up the MyRef.
Once again, more information on that "light bulb tester".
http://www.diyaudio.com/forums/power-supplies/167579-light-bulb-tester.html
http://www.diyaudio.com/forums/power-supplies/167579-light-bulb-tester.html
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