STK-0050 replacement for SX-780 and others

rcs, I have a question, on your Mouser BOM you have R2 listed as a 75ohm 1/2 watt resistor, but in your PDF from page 1 you have R2 listed as a 1K ohm 1/2 watt resistor. which is the correct resistor?
See post #8
I have also put this project back to read only to stop people from editing it. If you want to alter quantities or add substitutions, you will have to place an order based on the BOM and make your changes in the order not in the BOM. If you want me to make changes to the BOM, just ask and I will review the changes first b4 editing the BOM.
 
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I finished populating my replacement board and mated it with some 22AWG wire and when I went to power it up I blew the fuse between points 3 and 4.

I thought I could use the 22AWG just to test the circuit. It seems the recommended wire gauge is 20.

Thoughts?
 
Can you post an image of the install?
Of course!

I have checked continuity between all six pins (wires) going to the board and I have no shorts.
gU9BoXq.jpg


I left the leads on the BJTs for now just encase I made a mistake and have to feed them through again. They all have solic connections on the backside of the board, I know it looks like a handful aren't soldered but the solder just didn't come through the other side.

Is there a standard way for myself to check the module in and of itself for correct operation?
 
Is Q5 installed correctly?
Double check the TO-220 placements. Q3 should be a NPN, an MJE15032 or equivalent. Q2 a PNP.
Other than that It looks good.
The smaller wires should work, certainly on the DBT. But might be an issue at full power with volume?
 
Is Q5 installed correctly?
Double check the TO-220 placements. Q3 should be a NPN, an MJE15032 or equivalent. Q2 a PNP.
Other than that It looks good.
The smaller wires should work, certainly on the DBT. But might be an issue at full power with volume?

Q2 is the PNP (MJE15031G) and Q3 is the NPN (MJE15030G). Is that what you mean when you say check the TO-220 placements or are you referencing something other than the PNP/NPN placements being correct (as in, correct board spot).

I believe Q5 is installed correctly, the exposed body part is touching the insulation which is touching the aluminum heat sink.

I picked up some 20AWG from a different lab that had it so I am going to desolder and resolder the board and see if it will power on again with a new fuse. I think what may have caused it was that I plugged it into the wall-plug with the switch accidentally in the on-position, but I don't know. I have a second board I was going to populate and replace the other darlington pack with once I got the first one working, part of me wants to populate that one and test it but I think it would be better form to get this one working first.

I can't seem to find any information in the service manual scan I found with information about what the fuse I blew implies. Anyone happen to know? I could probably do some searching on the forum and find some info.
 
At some point in time I think that we should work on a proper set of documentation, to hopefully avoid obvious mistakes and bundle up all the pieces of important info scattered about.
I looked over the ebay info and it looks good, I did see that it specs M3 screws and the Mouser BOM calls out 4-40. Why M3? when the BOM calls out screws of correct length (Know one has told me that they are wrong so far). The idea is to make things easier not have to chop down screws to length? 22AWG is fine imo. Could even use a smaller gauge and it can act as a fuse :)

Always check that the live TO-220 bjt mounting tab (collector) is isolated from the Al plate! Did you use the shoulder washer?

Fuses, p23 in the SM
 
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At some point in time I think that we should work on a proper set of documentation, to hopefully avoid obvious mistakes and bundle up all the pieces of important info scattered about.
I looked over the ebay info and it looks good, I did see that it specs M3 screws and the Mouser BOM calls out 4-40. Why M3? when the BOM calls out screws of correct length. The idea is to make things easier not have to chop down screws to length? 22AWG is fine imo. Could even use a smaller gauge and it can act as a fuse :)
Noted.

I found a thread that seems to confirm the consensus is that the 4A 125V fuse (3-4 node fuse) is associated with the darlington power packs. This makes me think I did something wrong on my PCB populating that caused it. I'm going to remove the heat sink and take some photos of my soldering work and double check all of my components are correct. Once I get a replacement fuse, which hopefully doesn't blow with the daughter board out of the equation, I'm going to confirm the previously working darlington power pack is still working, hopefully I don't have two dead darlington power packs now.

And yes, I noticed the screw lengths are a bit too long for the heat sink. I'll have to take them into the machine shop to shorten them.

Do you have any testing protocol for your board to ensure everything is working properly on the daughter board? I'm sure I've done something wrong on my end as it seems very few people populate the board and then run into issues after that.
 
Minimal documentation, sorry, want to start to write it up :) People have varying degrees of experience, so good docs are in order to make the project easier to follow for all.
Doing some rudimentary continuity/ohms testing before power is applied is a good idea. Verifying that comp placement matches known good is crucial to success.
Obviously a DBT is the best to use in order to prevent fuses blowing,.
 
At some point in time I think that we should work on a proper set of documentation, to hopefully avoid obvious mistakes and bundle up all the pieces of important info scattered about.
I looked over the ebay info and it looks good, I did see that it specs M3 screws and the Mouser BOM calls out 4-40. Why M3? when the BOM calls out screws of correct length (Know one has told me that they are wrong so far). The idea is to make things easier not have to chop down screws to length? 22AWG is fine imo. Could even use a smaller gauge and it can act as a fuse :)

Always check that the live TO-220 bjt mounting tab (collector) is isolated from the Al plate! Did you use the shoulder washer?

Fuses, p23 in the SM

I used the washers when screwing on the board to the aluminum plate. I placed them above the actual BJT packaging before screwing them in, is that correct? Or were they supposed to be under the BJTs (i.e. touching the thermal insert between the BJT and the aluminum plate).

@ info about fuses, thank you!

I took images of my soldering work (album here: https://imgur.com/a/cOyTX ), I checked all resistances and they are correct/as expected. Checked for continuity to make sure no accidental shorts. What exactly do you mean by "known good" comp placement?

I appreciate you troubleshooting with me greatly!
 
The nylon shoulder washers are used first,only needed on the TO-220 devices, required to isolate the mounting screw threads from the live voltage on the device metal package, so it is, nylon washer, flat washer, screw in this order.
Make sure that the shoulder washer seats correctly in the TO-220 mounting flange(tab) hole and the shoulder is not damaged which could make it off centre.
Look at figure 5 in attached pdf. No nut required as the al plate is tapped thus acts as the nut.
In this thread, there are a few images of an assembled module and
http://www.ebay.ca/itm/STK-0050-Module-W-Power-to-operate-sets-up-to-100-Watts-Open-Source/122649581190?ssPageName=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649

good luck
Rick
 

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I tapped the heatsinks for the M3 threads.
This was due to all the spare metric hardware I have from donors and thought others might have. The M3 hardware can be easily cut to length.
I'll contact Mouser and see if they can accommodate the M3 hardware we need. Or include them in the PCB/Plate order.
 
The nylon shoulder washers are used first,only needed on the TO-220 devices, required to isolate the mounting screw threads from the live voltage on the device metal package, so it is, nylon washer, flat washer, screw in this order.
Make sure that the shoulder washer seats correctly in the TO-220 mounting flange(tab) hole and the shoulder is not damaged which could make it off centre.
Look at figure 5 in attached pdf. No nut required as the al plate is tapped thus acts as the nut.
In this thread, there are a few images of an assembled module and
http://www.ebay.ca/itm/STK-0050-Module-W-Power-to-operate-sets-up-to-100-Watts-Open-Source/122649581190?ssPageName=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649

good luck
Rick
Thanks for those images and that resource! That was how I originally screwed it in.

When you say "shoulder" are you talking about the body portion's hole/screw terminal of the TO-220 package? They don't appear damage from when I first tried to mount them.

I'll continue to troubleshoot with what I can/what I have right now. I know I've seen a few different references to testing out other modules of the board with the power pack gone so I may look into those and double check there isn't something before the power pack going on causing the issue.
 
I mean the smaller diameter of the shoulder washer can get crushed if it is not inserted into the tab flange hole correctly b4 the flat washer and screw are used. Note the mounting torque on the screw, some people over torque the screw thinking that it has to be very tight which is not the case. You do not want to squash the insulator pad too much, just make it snug.

cutting screws = PITA, I like to make things simple, I guess I am a simple Simon :) iirc Mouser and many other US suppliers have a limited supply of metric hardware since the US has yet to convert to metric standardization, like the rest of the world has done years ago. Even the Brit's abolished their own imperial measuring system.
 
McMaster-Carr carries both SAE and Metric in every style you can think of.
Yes of course, the idea is to get all the parts from one supplier, if possible, to minimize costs

As far as initial check out, it is a another idea to measure with an ohmmeter in diode test mode the module b4 it is installed
1) path from pin 10 to 8, red (+) lead on pin 10
2) path from pin 1 to 3, red (+) lead on pin 3
This checks that the bjts are installed correctly. Both paths should read close to the same, basically 2 diode drops plus the small value resistors
 
I will include the proper screws with the order.
2 M3X0.5X6 for the TO-220's
3 M3X0.5X8 For the SOT-32-3 and the two TO-3P-3.

I took "IIwhtt" advice and ordered from McMaster Carr. The pricing for the bulk orders can't be beat when it comes to the hardware.
It worked out to .03 cents apiece for the metric steel Phillips head screws. And I'm not stuck with a thousand screws. I was able to order in packs of 100.
 
Yes of course, the idea is to get all the parts from one supplier, if possible, to minimize costs

As far as initial check out, it is a another idea to measure with an ohmmeter in diode test mode the module b4 it is installed
1) path from pin 10 to 8, red (+) lead on pin 10
2) path from pin 1 to 3, red (+) lead on pin 3
This checks that the bjts are installed correctly. Both paths should read close to the same, basically 2 diode drops plus the small value resistors

My pin 1 to 3(+) is 1.111V and my pin 8 to 10(+) is 1.162V when in diode test mode. Do those sound like allowable values? I've always remember diode drops in the range of .5 to .7 or so, seems close to expected from my mind.
 
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