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Class D Switching Power Amplifiers and Power D/A conversion

iraud200 short story
iraud200 short story
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Old 6th January 2016, 06:29 PM   #21
Buehgemeiste is offline Buehgemeiste
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Join Date: Oct 2013
Quote:
Originally Posted by mgshightech View Post
... To make the list complete though, I am going to list all of the problem of the board including those already mentioned. ...

So, this is the intro. page .. as days progress, I'll get to work making all of this information more visual and understandable.
Thank you mgshightech.
It is still a wall of text and i cannot make a personal list of priorities for myself to mod this board.
Maybe it is absolutely pointless without a osci.
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Old 6th January 2016, 10:23 PM   #22
mgshightech is offline mgshightech
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look at the parts list and the images. Every important mod is on the list and the images.

priority #1 get a heat sink on the irs2092 chip and make sure the transistors are heat sink greased and solidly mounted before you even dare power this up or all the fun will not last ... also .. I would not try doing this without 7 amp fuses on each incoming power line. If something goes wrong, those fuses will likely save you.
priority#2 mod the feedback loop (the 200k resistor .. there's only one on the board) as shown on the image
it's close quarters, so testing with your meter will help you to know what's dangerous. That resistor labelled 512 has one end that can be allowed to accidentally attach to the end of the 200k resistor (not the 150 pf cap) because it's already connected in the circuit layout. The tiny hole right next to that connection however is absolutely off limits. One tiny thread of solder to that hole and you'll have trouble .. I think you'll burn the fuse cause it will instigate exclusive positive feedback. One of the transistors will turn on solid. All of this detail is visible on the image that shows the feedback loop mod.

When you get the board, the 200k resistor connects the transistor outputs straight to the rest of the feedback circuitry. De-solder it and very carefully put it on an angle so you can connect the 1k resistor to the connection closest the main transistors that you just took the 200k resistor off of. The 200k resistor remains connected at the end closest to the rest of the feedback circuitry. Angle the two resistors so that they meet each other and solder them together at that meeting .. then connect the 150 pf cap to that junction and point it towards the little ground pole. It won't reach the ground pole, so you have to add some solder or a little wire and some solder to get it there .. Check carefully for stray connections and errors this is the hardest part of the mods cause those tiny parts wiggle all over..

priority#3 swap the output filter cap for 0.27 uf as on the parts list and add the dampener circuits as shown on the images. One of the dampeners is 0.1 uf with around 3 ohms in series from top pole to bottom pole .. the important one is 0.22 uf with 4.7 ohm, 5 or 10 watt in series from speaker output to ground .. also 0.33uf with 4 ohm 10 watts is what I moved to .. both options work. Least important dampeners .. 2 small .01uf caps, each from one of the power poles to ground.

at this point I believe you'll have a functional board, but #5 may also be required for this.


priority #4 add heat sinks also .. one to the output inductor and one to the main heat sink

priority #5 add additional 10 uf 50v ceramic caps to the floating power supply so that it stores plenty of charge.

use heat sink plaster to attach heat sink to irs2092 chip
use heat sink grease to attach heat sink to inductor until you're satisfied everything is aok .. then remove heat sink grease and plaster it on. I would not use heat sink plaster to attach an additional large main heat sink .. in stead I would use screws or .. in my case, I'm going to use heat sink grease and a string and some springs for the final setup .. for the test setup, I just set the heat sink on top, with heat sink grease. For a fabulous set of heat sinks, go to ebay and look up "antminer s1"

Last edited by mgshightech; 6th January 2016 at 10:51 PM.
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Old 6th January 2016, 11:00 PM   #23
mgshightech is offline mgshightech
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also .. keep forgetting for the parts list ... ferrite beads if you want more than one board on a single 0 volt power supply reference and heat sink plaster from ebay for some of the heat sinks.
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Old 6th January 2016, 11:10 PM   #24
mgshightech is offline mgshightech
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original vs new for the feedback loop mod .. the required 1k resistor and 150 pf capacitor are on the parts list .. order from Mouser
Attached Images
File Type: jpg origb2s.jpg (24.1 KB, 271 views)
File Type: jpg modb2s.jpg (18.5 KB, 266 views)
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Old 6th January 2016, 11:13 PM   #25
mgshightech is offline mgshightech
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the output filter cap needs replacing .. original one is 1uf 100v .. change to 0.27 uf 275v as listed on the parts list The new cap has to be angled to fit, and the ground leg won't fit in its hole, so scrape the ground plane with a razor and solder straight to the ground plane
Attached Images
File Type: jpg badcap.jpg (20.3 KB, 264 views)
File Type: jpg NewOFCapS.JPG (30.5 KB, 262 views)
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Old 6th January 2016, 11:19 PM   #26
mgshightech is offline mgshightech
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the dampener circuits shouldn't need pre-post images .. the images are already shown .. they are the glued-on looking capacitors and resistors some to the underside of the board some to the speaker output. These dampeners kill the parasite. Also, the post image for the feedback loop mod shows additional 10uf 50v ceramic caps soldered to the pre-existing floating power supply caps.
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Old 8th January 2016, 11:47 PM   #27
mgshightech is offline mgshightech
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there is some data on the ljm l30D here on this site: L30D IRS2092 IRFB 4227 IRAUDAMP9 MYDIY looks like it's running hot, and it does not have the overtemp protection component that the iraud200 has ... don't mean to be rude, but at this point, I would choose the iraud200 Plus mods ... over the L30D (iraudamp9 knockoff) .. This modded board is running flawlessly .. it runs cool at quiescence.
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Old 9th January 2016, 12:25 AM   #28
Greg32 is offline Greg32  Australia
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Some great info here. i will reread over the weekend. you have given me hope. Greg
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Old 13th January 2016, 02:18 AM   #29
Lo_Tse is offline Lo_Tse  Canada
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Quote:
Originally Posted by mgshightech View Post
the output filter cap needs replacing .. original one is 1uf 100v .. change to 0.27 uf 275v as listed on the parts list The new cap has to be angled to fit, and the ground leg won't fit in its hole, so scrape the ground plane with a razor and solder straight to the ground plane
Sorry I cannot extract any info regarding the board that you are working with. Is it the L30D board that LJM sells? Or it is one of the EBAY ones? Did you actually tried the LJM L30D? I neither have the time and knowledge to do what you have done. Just would like to get something that will work right out of the box. Thanks!

Regards,
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Old 13th January 2016, 09:42 AM   #30
mgshightech is offline mgshightech
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ljm_ljm keeps claiming the L30D works great ... this is not the L30D, but the iraud200 that you can find in a lot of places. Try ebay for example. Others have not been satisfied with the L30D .. Looking it over ... the L30D is missing the overtemp protection and has a smaller heat sink ... I don't think it's as good of a board, I don't know for sure whether it will or won't work out of the box for you. I have not tried the L30D .. might be willing to mod an iraud200 for someone else at a price .. I don't know what to expect from an L30D. I would love to see some more comments on the L30D thread here on DIY audio, but not enough info. there to be convinced of anything. Someone else claimed it didn't work for him. ljm_ljm claims that the L30D works great at +/-75 volts, but has problems at significantly lower voltages. ljm_ljm I believe designed and markets the board, so people really need more opinions than his. I didn't design and haven't marketed the iraud200, so the information here and in the other iraud200 thread has no monetary motivation.

Last edited by mgshightech; 13th January 2016 at 09:58 AM.
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