STK-0050 replacement for SX-780 and others

I do have considerable machining experience. There are several things that can come into play for a nice tight thread fit. The tap drill size, class of thread spec of tap, proper cutting fluid, and also the type thread (cut vs. rolled) on the screw used in the tapped hole.
 
rcs16 said:
5) A 4-40 tap and handle, drill bits.
6) #43 drill for the 4-40 tap into Al. A 3/32" drill will probably do it. Some lube or water to cool the tap.
Click to expand...

rcs16 said:
Practice makes perfect. I remember working as a motor re-winder tech as a summer job and the Jamaican master said " tricks in trade like match in box"
The #43 drill in my old Motorola design handbook, is I believe for tapping into hard steel. you could probably go down one or more sizes for Al ,Cu etc since they are much softer.
Click to expand...

petehall347 said:
use quality tools and always test in some scrap piece first . i would just use a number 1 tap for aluminium and an undersized drill bit .
Click to expand...

book says: 4-40 NC = tap 0.089 = #43 closest fractional 3/32 = 0.0938
3/32 is 0.0937 theoretical % of thread: 56.4%
#42 is 0.0935 theoretical % of thread: 57%
#43 is 0.089 theoretical % of thread: 70.8%
#44 is 0.086 theoretical % of thread: 80.1%
#45 is 0.082
#46 is 0.081
#47 is 0.785
5/64 is 0.0781
#48 is 0.076


this is a work in progress.
 
There are #1 taps? Presumably other numbers as well but I have not run into this in my limited machining experience. I looked up "#1 Tap" and found an article about how to kill someone with just one shot from an AK-47. Probably not quite the correct genre. :rflmao:
 
over here we generally get taps in one two and three . it is so you can start with number one then use the others to gradually get to the standard size . at least that is how i understand it to be . just had a though that it might be more for tapping blind holes .i knew i should have taken more notice in technical college ..
i just use number 1 taps and have a nice tight fitting thread . well its not really tight it is just right .
 
I've been inspired by this post and I wanted to try and build my own STK0050 module. I've got a JVC JA-S44 integrated amp that uses STK0050 packs. I was in the process of refurbishing this amp when I blew out on of the packs. I've grown tired of replacing these with either counterfeit packs, or used ones. So I ordered the parts, fabbed a chunk of aluminum and decided to just wire it up point to point. Since I've never done anything like this in a while and there was no model to follow, I just started wiring the parts together. It turned out looking pretty bad, like something I put together in high school electronics class. I made several mistakes and had to fix them. each change made the thing look worse. Anyway, I feel like I could really improve on this a second time having gone through the initial build.

IMG_0865.JPG

Ignore the bottom 2 large transistors, they are miswired in this picture. Also the toasted resistor, it still measures 75ohms

I'm in the process of testing this module and so far, it's performed perfectly. I can't tell any difference between the 2 channels (the other channel has the original STK pack still installed).

So, the question is, is this a worthy replacement? So far I'm please with it, it looks like crap, but it works.
 
assemble a few kits, add up your cost + labor + markup vs. market demand and you'll begin to understand why it's not taking off. I have offered a few to those who pm'd me, but had no takers so far.
 
HBrown said:
assemble a few kits, add up your cost + labor + markup vs. market demand and you'll begin to understand why it's not taking off. I have offered a few to those who pm'd me, but had no takers so far.
Click to expand...

well the chinese already did it:) they stuff in what ever they can find. IRF´s TIP´s....no just kidding shure the demand isn´t high enough. not many amps worth saving have theese chips and by that i mean the STK in general.
 
As RCS16 has mentioned, this circuit really should be considered an upgrade to an STK as the bias is user adjustable, made from modern components, is discrete and repairable, and the entire circuit is more robust.

It is well worth doing for a hobbiest who has an otherwise healthy unit that they want to upgrade and continue to enjoy. IMO, it would not be worth it to repair a unit to try and flip for profit.
 
HBrown said:
As RCS16 has mentioned, this circuit really should be considered an upgrade to an STK as the bias is user adjustable, made from modern components, is discrete and repairable, and the entire circuit is more robust.

It is well worth doing for a hobbiest who has an otherwise healthy unit that they want to upgrade and continue to enjoy. IMO, it would not be worth it to repair a unit to try and flip for profit.
Click to expand...
Yes, I think this is true. It took me several hours to build my model, granted I should be able to do it quicker, but it's still going to be $40 or $50 for my time per module including parts. Most will see the counterfeit module on ebay for $12 and go with that.
 
make a nice circuit board and maybe use smd components . nothing wrong with through hole though just takes up more time .
have the transistors hanging off the board to screw down to the plate . also Incorporated a row of pins to solder to amp board if indeed it is soldered in the first place .
once you made one it should be pretty quick to make lots in one day .
 
petehall347 said:
make a nice circuit board and maybe use smd components . nothing wrong with through hole though just takes up more time .
have the transistors hanging off the board to screw down to the plate . also Incorporated a row of pins to solder to amp board if indeed it is soldered in the first place .
once you made one it should be pretty quick to make lots in one day .
Click to expand...

or some sort of diy kit. a ziperbag with some components a etched pcb and a printed A4 with some instructions.
 
My personal experiences with installing SMD devices by hand (a repair here and there) have not really stuck in my mind as being a faster operation, but I suppose it could be with proper tools and experience. Hanging the power devices off a flat board with SMD passive components and maybe soldering the legs down flat to solder pads may have some merit here.
 
That is ironic- I HAVE a CA-880 that a module took a dump in just this last week that I'm looking into.
 
You must log in or register to reply here.

Similar threads

lebrun53
Pioneer SX-780 STK-0050 voltages
Replies
9
Views
2K
merlynski
merlynski
jcon109
Sx 780 stk 0050
Replies
13
Views
2K
boreas
boreas
C
SX-780 - Counterfeit Darlingtons?
2 3
Replies
43
Views
3K
merlynski
merlynski
W
SX-780 Right Channel Dead
Replies
0
Views
231
wmar
W
w1jim
SX-780 dead in one channel - no, it's not the STK-0050
Replies
18
Views
1K
zebulon1
zebulon1
Back
Top Bottom