Sorry to hear you got caught using too tall ecaps that interfere with the big ones. I was warned by another member earlier of the issue. Lots of little details. I see a lot of nichicon parts on back order.
The scratches on the solder mask are okay, as long as no exposed metal is visible it is cosmetic. Leaning one ecap over to clear the others should be okay. Just looks odd. Once the cover is on know one will see.
My advise, to all constructors, please use what is exactly in the shopping carts/BOM, especially if this is your first rodeo. We spent hours getting it right for release, not wanting problems. You can have potential problems if you deviate from what has is specified and proven to work.
Once you get a unit running, then you can improve further, replace, upgrade the rest.
If something is back ordered, sometimes it is best to ask.
On those alternate heatsinks for the to-126 devices, the package is insulated, so it is best to use some thermal compound only and remove the silpad insulators. I will ask mouser if they can stock the hs i specd instead of having to go to digi-key just for them or improvising. I’ll look again, there is an assman second source. The heatsinks should not be touching other components because they do get fairly warm.
Okay good luck
The scratches on the solder mask are okay, as long as no exposed metal is visible it is cosmetic. Leaning one ecap over to clear the others should be okay. Just looks odd. Once the cover is on know one will see.
My advise, to all constructors, please use what is exactly in the shopping carts/BOM, especially if this is your first rodeo. We spent hours getting it right for release, not wanting problems. You can have potential problems if you deviate from what has is specified and proven to work.
Once you get a unit running, then you can improve further, replace, upgrade the rest.
If something is back ordered, sometimes it is best to ask.
On those alternate heatsinks for the to-126 devices, the package is insulated, so it is best to use some thermal compound only and remove the silpad insulators. I will ask mouser if they can stock the hs i specd instead of having to go to digi-key just for them or improvising. I’ll look again, there is an assman second source. The heatsinks should not be touching other components because they do get fairly warm.
Okay good luck
Thanks, Rick.
I know the deviation is entirely on me. That’s what I get for being eager and impatient. I got some more of those just desserts last night. I kept going too late trying to get the amp completed to test things. Dim bulb test worked, bright, then dim. Set the bias for the left channel fine. Then the right channel sparked at the heat sink and blew the mains fuse. I think I had poor insulation at one of the power mosfets and a loose star ground. They may be toast. I’m going to take them all out again, test the driver boards, find if anything else needs replacing, order some exicons (and the right caps), and be very diligent with heat sink isolation. Learned my lesson.
I know the deviation is entirely on me. That’s what I get for being eager and impatient. I got some more of those just desserts last night. I kept going too late trying to get the amp completed to test things. Dim bulb test worked, bright, then dim. Set the bias for the left channel fine. Then the right channel sparked at the heat sink and blew the mains fuse. I think I had poor insulation at one of the power mosfets and a loose star ground. They may be toast. I’m going to take them all out again, test the driver boards, find if anything else needs replacing, order some exicons (and the right caps), and be very diligent with heat sink isolation. Learned my lesson.
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Oh boy, I've been there 
Well at least you got one channel going
make sure the OPS flying ground wire is connected securely.
I do not want to preach what we wrote in the build guide as far as going slow and easy, check and check again, like a broken record
test those mosfets again since you know how to. You can test run with only stuffing one pair.
Back to square one on the right channel, practice makes perfect.
Good Luck
Well at least you got one channel going make sure the OPS flying ground wire is connected securely.
I do not want to preach what we wrote in the build guide as far as going slow and easy, check and check again, like a broken record
test those mosfets again since you know how to. You can test run with only stuffing one pair.
Back to square one on the right channel, practice makes perfect.
Good Luck
Hey guys, I was asked by a friend to repair a DH-200. It has the PC19c driver boards. One channel is dead. I measured the bias current for the dead channel @ 2mA. Would someone be willing to help me fix this? I didn't do any drain tests on the transistors but they seem to all measure good with the diode function on my DMM. Any help would be really appreciated.
While I’m waiting for fresh outputs from the UK (they will be here tomorrow), I ran the AFE tests again. Nearly everything checks out per the build instructions. My one discrepancy is with one channel’s VAS bias.
“Measure the voltage drop across either R29 or R44 (33-ohm). It should be in this range, 264-330-396mV. If it is outside this range, refer “VAS Bias Current” section in this document, “The DH-220C MOSFET Power Amplifier”
I get ~ 415mV on one channel. I read the corresponding section of the other document and am unsure of what to check next. The other channel measures fine ~ 350mV.
Any suggestions would be appreciated.
“Measure the voltage drop across either R29 or R44 (33-ohm). It should be in this range, 264-330-396mV. If it is outside this range, refer “VAS Bias Current” section in this document, “The DH-220C MOSFET Power Amplifier”
I get ~ 415mV on one channel. I read the corresponding section of the other document and am unsure of what to check next. The other channel measures fine ~ 350mV.
Any suggestions would be appreciated.
Good news,
Interesting and I tested them Just slightly out of range.
Of course, you first adjusted RV1 for the 4mA IPS, measure across either R13 or R25 (180 ohm) for 360mV?
Bob's trick is to swap devices in the package, rotate one of them, lsk489 or lsj689, 180 degrees and see what you get.
You have 4 combinations to try Everytime the IPS has to be re-adjusted.
Interesting and I tested them
Just slightly out of range.Of course, you first adjusted RV1 for the 4mA IPS, measure across either R13 or R25 (180 ohm) for 360mV?
Bob's trick is to swap devices in the package, rotate one of them, lsk489 or lsj689, 180 degrees and see what you get.
You have 4 combinations to try
Everytime the IPS has to be re-adjusted.
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All but one. I remember looking at the jfets underneath and making sure I matched up where the “dot” was supposed to go according to the PCB underside image. Turned that one around and am now starting the adjustment again.
Got them in the right arrangement. Ended up with the dots facing each other. Unless I need to get the measurement very close to one of those three values. One channel ~350mV, the other ~310mV.
Got them in the right arrangement. Ended up with the dots facing each other. Unless I need to get the measurement very close to one of those three values. One channel ~350mV, the other ~310mV.
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It’s alive!!!!
New Exicon outputs are in, bias set without a problem, dim bulb test passed, and played music through expendable speakers.
I AM THRILLED.
It sounds great, so far. I will try it out in the main rig tomorrow. I will also replace the AFE tall caps once the appropriate ones arrive.
Thanks to Bob and Rick for their generosity with this design and patience with circuit dullards like myself.
New Exicon outputs are in, bias set without a problem, dim bulb test passed, and played music through expendable speakers.
I AM THRILLED.
It sounds great, so far. I will try it out in the main rig tomorrow. I will also replace the AFE tall caps once the appropriate ones arrive.
Thanks to Bob and Rick for their generosity with this design and patience with circuit dullards like myself.
Attachments
The dots on the DIP adapter PCBs were already there, as purchased.Two of the orientation options didn’t result in appropriate VAS bias. The third arrangement worked, with the dots facing each other.
The other channel measured fine with the expected orientation, dots in the direction of R24.
I’ve completely forgotten how these dots relate to the dots on the actual devices.
The other channel measured fine with the expected orientation, dots in the direction of R24.
I’ve completely forgotten how these dots relate to the dots on the actual devices.
Attachments
I’ve been listening to the completed amp for about 8 hours now. It’s just great. I think it provides considerably more “fullness” of the source material than what I have become accustomed to with the admittedly great Aiyima TP2351 amp (with OPA1656). I think this must be what people call bass authority, or speaker control. There is no apparent lack of detail, either.
I’m throwing a whole heap of subjective bias into this assessment, yet I don’t care. This is my first significant amp build and I am enthralled with it. My dog appreciates the high bias for class A operation.
I do not want to stop listening to music. That is what this is all about.
I’m throwing a whole heap of subjective bias into this assessment, yet I don’t care. This is my first significant amp build and I am enthralled with it. My dog appreciates the high bias for class A operation.
I do not want to stop listening to music. That is what this is all about.
Attachments
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Dead channel
All measurements are in VDC. Looks like the dead channel is sitting slightly more negative.
All measurements are in VDC. Looks like the dead channel is sitting slightly more negative.
