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Build STK8050 equivalent
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Old 19th June 2018, 04:40 PM   #81
Depaj is offline Depaj  France
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The stk-0050 replacement kit.
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Old 20th June 2018, 07:01 AM   #82
chregu is offline chregu  Switzerland
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Have you been able to keep the bass and treble adjustment? I'd be happy if you could provide a wiring diagram for this kit in the V4A.
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Old 20th June 2018, 01:12 PM   #83
SVI2004A is offline SVI2004A  New Zealand
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Build STK8050 equivalent
I have one I’m yet to do up... I am going to use either STK2058IV or SVI2004A
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Old 22nd June 2018, 12:34 PM   #84
chregu is offline chregu  Switzerland
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Hello Depaj


I tried to draw, what I think you did.


- It looks like you added emitter resistors 0.22 ohms
- It looks like you removed all components connected to pins 6-13 and pin 15
- It looks like you also removed the capacitor between pin 14 and 16


Am I right?


What's the setting of you potentiometer?
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File Type: jpg STK Schema.JPG (73.0 KB, 159 views)
File Type: jpg V4A Schema.JPG (143.1 KB, 140 views)
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Old 27th June 2018, 04:02 PM   #85
Depaj is offline Depaj  France
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Sorry Chregu, I didn't see your last post. Yes I was able to keep the tone controls without any modifications.

That looks about right yes.
Those are all the components used in the synchro bias circuit so they aren't needed any longer.
The kit doesn't have any emitter resistors as the sx-780 has them on the main board, I added them on the kit but you can just as well put them on the main PCB.
You can keep TP302 and 307 to connect your meter for bias adjustment.
I removed the cap on the main pcb because c2 on the kit has the same purpose (it won't harm if you leave it though).
I don't really remember where the pot was set in the end but if I remember correctly I started fully counter clockwise and went step by step from there. You can always do a test with your dim bulb connected, if the bias is to high that should limit things, you can do your tests with it connected but be sure to remove before final adjustments.

Good luck
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Old 28th June 2018, 05:28 PM   #86
horias is offline horias  Romania
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Hi everybody, sorry for barging in .

I bought a Technics SU-V4A a while ago (actually my step into these kinds of equipments). Ever since then I've been studying more about this era and obviously started to worry about the STK8050 ICs and how long they might last.
Yesterday I've been looking inside a bit through the top grills and noticed that those ICs are not really present, and that some work has been done in that area. I opened up the amp today and they have indeed been replaced with something else.

Now, I'm not an electrical engineer at all, far from it (just sort of tech savvy). But this is what I found (doesn't look very pretty), and I want to share it with you guys, maybe it's going to help someone. Parts are <<SANKEN B1647 & D2560>>.

BTW: Does anybody know anything about the setup I have there? Is it good? Is it bad ?
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File Type: jpg IMG_20180628_195640.jpg (1.01 MB, 83 views)
File Type: jpg IMG_20180628_195648.jpg (416.5 KB, 77 views)
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Old 2nd July 2018, 11:30 AM   #87
chregu is offline chregu  Switzerland
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This looks like a low-cost solution but probably some kind of works too. There seem to be only 2 power transistors per channel with added emitter resistors. There's also no possability to set bias current. The other components around the STK have been removed.
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Old 10th July 2018, 10:13 AM   #88
horias is offline horias  Romania
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Thanks. One more question if I may, do you happen to know how much power these might be putting out?

https://www.semicon.sanken-ele.co.jp...1647_ds_en.pdf
https://www.semicon.sanken-ele.co.jp...2560_ds_en.pdf

Not sure if these are the exact specsheets but it's the closest thing I found. It says they consume 130W. Does it sound resonable to assume that they will have a slightly higher output power than the old STKs, maybe closer to 80-90W?

Thanks again.
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Old 10th July 2018, 10:25 AM   #89
jaycee is offline jaycee  United Kingdom
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They will only "put out" whatever power is available to them. The power rating is that they can handle 130W at 25c. They should be adequately rated
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