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Chip Amps Amplifiers based on integrated circuits

When STK4241V burn...
When STK4241V burn...
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Old 9th May 2016, 10:46 AM   #1
galinvayov is offline galinvayov  Bulgaria
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Default When STK4241V burn...

First, sorry for my bad english.
One friend of mine bring to me Sharp SX-8000H(GY) for repairing. Left channel not working. Relatively quickly I discovered why. STK is burn out. Аlso it is not original.I buy a new one from e-store, it was described as a original SANIO but it was exactly the same, fake.
I try to repair the burned one. I removed all parts and replaced them with new ones. Complete waste of time and money.
A little and finally
I must build a new module, based on the internal schematic of STK and fully compatible electrical and mechanical.
Here is the result. Currently running the latest checks. Working steadily and I think that is a good alternative.
Attached Images
File Type: jpg stk 004.jpg (817.9 KB, 241 views)
File Type: jpg stk 008.jpg (984.8 KB, 233 views)
File Type: jpg stk 014.jpg (802.9 KB, 229 views)
File Type: jpg stk 016.jpg (831.6 KB, 224 views)
File Type: jpg stk 017.jpg (558.7 KB, 224 views)
Attached Files
File Type: pdf stk4241vgv2.pdf (257.9 KB, 72 views)

Last edited by galinvayov; 9th May 2016 at 02:03 PM.
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Old 9th May 2016, 12:33 PM   #2
adason is offline adason  United States
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Great work man!
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Old 9th May 2016, 10:14 PM   #3
basi is offline basi  Croatia
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Fantastic work a lot of enthusiasm!!! Well done!!
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Less is more!!!
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Old 12th May 2016, 07:08 PM   #4
Mooly is offline Mooly  United Kingdom
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When STK4241V burn...
Only just seen this. Yes, well done very impressive indeed.
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Old 5th July 2016, 08:54 AM   #5
galinvayov is offline galinvayov  Bulgaria
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The first revision works well. Of course, there is always something to improve.
There should be offset controll.
Should be able to use trimpots with a horizontal and a vertical adjusts.
...
And here's the second revision.
Attached Images
File Type: jpg stk 021.jpg (1.00 MB, 109 views)
File Type: jpg stk 022.jpg (1,017.2 KB, 93 views)
Attached Files
File Type: pdf stk4241gv_sch_pcb.pdf (255.1 KB, 26 views)
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Old 5th July 2016, 10:15 AM   #6
Mooly is offline Mooly  United Kingdom
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When STK4241V burn...
That's great and the boards look terrific.
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Old 5th July 2016, 11:09 AM   #7
voltwide is offline voltwide  Ireland
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These STKs are known to burn sometime with no obvious reason for decades. There must be a reason for this - so I would be sceptical copying their design.
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Old 5th July 2016, 11:33 AM   #8
galinvayov is offline galinvayov  Bulgaria
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They burn due the limitations imposed by production technology. There is little reserves of power. Not tolerate to overloading. Furthermore, widely sold substituents with unknown parameters.
This development is not an exact copy of STK4241. It is based on it but there are many differences. The components are of great reserves of power and voltage. The output stage is different. Heat is transferred directly from the output transistors to the heatsink. The other components are not stressed thermally.
And so on...

PS One example. In this Sharp SX-8000H (GY) has an external current generators to pins 7 and 17. Current is about 10mA. The supply voltage is 70 volts. This means that in TR3 and TR4 will dissipated 700mW. 700mW in SOT-23 case? WTF

Last edited by galinvayov; 5th July 2016 at 11:57 AM.
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Old 10th July 2017, 06:37 AM   #9
galinvayov is offline galinvayov  Bulgaria
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Hello. At the request of a user, I apply the Gerber files and the assembly scheme of version 02.05/16.
By the way, I continue with the improvement of this module. The third version introduces SOA protection. An additional board is provided which allows the addition of parallel output transistors.
Here is a description of the protection scheme (in Bulgarian).
Attached Images
File Type: jpg stk_load.jpg (114.0 KB, 37 views)
File Type: jpg pcb.jpg (265.0 KB, 29 views)
File Type: jpg ptr_board_slim.jpg (154.4 KB, 29 views)
Attached Files
File Type: pdf stk4241gv_sch_pcb.pdf (255.1 KB, 18 views)
File Type: zip stk020516.zip (595.2 KB, 16 views)
File Type: pdf stk4241v_soa_prot.pdf (246.9 KB, 15 views)
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Old 10th July 2017, 07:48 AM   #10
thejohn is offline thejohn  South Africa
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Very cool! Thanks for that...

John
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