Issue With DR-MQ5 Toroidal Transformer Wiring

[Slime_Lord]

Hi All,

I'm somewhat new to hooking up toroidal transformers, the only capacity that I've worked with them in the past was rebuilding/recapping my console power supply and had no issues hooking it back up after I was complete.

A few months ago, I purchased the DR-MQ5 Sontec clone kit from DIY-Racked and quickly gathered the parts and put it together.  Once complete, I followed the instructions in the wiring document (attached screenshot) for the toroidal transformer, fired it up, and.....nothing.  I'm not getting any measurable AC or DC current and have tried a few different fuses, IEC inlets, etc. with no success.

I emailed DIY-Racked and they believe that the transformer is faulty/needs to be replaced but after looking up how to test it with a multi-meter, I confirmed that it's in good shape.

I have the feeling that something isn't wired correctly but can't seem to figure out what it might be.  I've attached a screenshot of the wiring diagram and a few photos of the IEC/Toroid/Switch that it's attached to.  Let me know if the pictures in the PDF aren't large enough or if additional pictures are needed.

Any help is greatly appreciated, I've already purchased Elma switches to put in after I've measured the test points and really don't want to start assembling them until I can check the test points.

 

[rock soderstrom]

Hi, I do not know this project/kit but your switch looks very weak, maybe it cannot withstand the mains voltage and has burnt down. Tested?

 

[FarisElek]

There is no way that switch is rated for mains.

 

[Slime_Lord]

I had a feeling that the switch seemed too small.  I’ll double check the BOM but I believe that’s the same switch I’ve seen on other DR-MQ5 builds. 

I have some larger switches lying around from another project, I’ll swap out today and report back.

Thank you both for taking a look!

 

[rock soderstrom]

I took a look at the BOM, the manufacturer actually specifies such a switch. Max 120V, 5A.

https://de.farnell.com/multicomp/1ms1t1b5m1qe/switch-spdt-ein-ein/dp/9473378

Since you are in a 110V country it would be enough, here in Germany it would not be enough. I wouldn't take it, too small for my taste.

Just bypass the switch, then you can see if he is the problem.

 

[FarisElek]

I've had to replace switches a few times on units for using switches too closely rated. I get buy the largest switches i can for power. If the torroid works and is wired correctly, then its either that you've got no fuse in place, the fuse blew or your switch blew.

 

[rock soderstrom]

I've had to replace switches a few times on units for using switches too closely rated. I get buy the largest switches i can for power. If the torroid works and is wired correctly, then its either that you've got no fuse in place, the fuse blew or your switch blew.

+1

 

[Harpo]

I followed the instructions in the wiring document...

the wiring document is for 115VAC. What is YOUR local mains voltage? (please update your profile)
If you followed the text, connecting both secondary blue wires to X4 shorts out this secondary winding.
If connecting one secondary red wire to probably as well typo X3 will work, is depending on schematic or pcb layout.

for the toroidal transformer

that would have a name and type number or some rating data in order to get the correct fuse rating.

I'm not getting any measurable AC or DC current

AC voltage. Measured between which wire ends ? (FI ground is not involved in this measurement) and you removed the sometimes hard to see varnish attached to the transformer wires, that would prevent a safe contact.
The mains switch shown on the wiring document should have L connecting to an outer switch terminal and the transformers primary winding end connect to the switches center pin instead in order to avoid mains voltage at the free switch terminal when switched to off position.
Your SPDT toggle switch is easyly broken by too much heat from soldering.
+1 this switch might not meet the rating needed.

 

[Slime_Lord]

I'm in the United States, so the wiring document is the correct one.

Fuse has been in as well, I need to see if it's blown though.  It's entirely possible that the switch was over soldered as well, luckily I've got extra switches that are higher rated.

The fuse that's currently in is 315 mA as specified on the BOM.

Harpo, which text are you referring to?  I just checked the document again and am not seeing any text that mentions connecting wires together. 

EDIT:  Interesting, I see that the text mentions connecting red secondary 1 to X1 and red secondary 2 to X3 and both blue secondaries going into X4, which contradicts the drawing in the document.  I'm going to see if I can locate some pictures of finished units to see if they are shorting wires together in their pictures.  Did not notice this, thanks for pointing this out.

As far as the Toroid goes, I'm unable to find the manufacturer or any kind of model number on it.  I've attached a picture of it as well.

 

[abbey road d enfer]

Fuse has been in as well, I need to see if it's blown though.

I strongly suspect a blown fuse. You need a soft-start protector, you know, the thing with an incandescent light bulb in series. Or a variac.

 

[Harpo]

The fuse that's currently in is 315 mA as specified on the BOM.

For a toroidal transformer you want a /t fusing characteristic and not knowing your transformers VA rating, the 315mA rating might be the parts value for 230VAC mains that would need doubling up for 115VAC mains, so 630mA/t.

 

[Slime_Lord]

Appreciate everyone's insight into this - I tested the fuse that was in place the last time I tried to power it on and it was blown.  I'm checking to see if I have a 630mA 250V slow-blow fuse and will report back if that worked.

 

[Slime_Lord]

It's on! 

It was def a combination of the switch and fuse size.  I now know not to blindly trust a bill of materials and also learned how to calculate correct fuse sizes.

I really appreciate everyone's assistance with this, every build is a learning experience.

Now to put together the switches  .

 

[rock soderstrom]

It's on!