Arthur Smith
Super Member
These are the same people that claim that a Crosley will destroy a record on the 5th play. Not the 2nd, not the 4th, but, the 5th. Internet mythology has a life all it's own.
HBrown
Active Member
If folks dont realize the problem with the sub-par knock-offs then they just havent had much dealings with them. There are pics on the forum from guys who had problems who cut the knock-offs and the original STK's open to expose the insides and posted pics and it is obvious that the knock-offs are inferior junk that is not up to the task at hand. If we COULD STILL GET original quality STK's reasonably, this whole issue would be avoided.
This whole effort by rcs16 and myself is to solve the problem with a suitably robust design from readily available modern components. It's a little more involved and expensive than just slapping a new STK in the unit, but It gives an individual who has a nice SX-780 (and other units) an option to improve the reliability and repairability of their unit and keep it running into the future.
This whole effort by rcs16 and myself is to solve the problem with a suitably robust design from readily available modern components. It's a little more involved and expensive than just slapping a new STK in the unit, but It gives an individual who has a nice SX-780 (and other units) an option to improve the reliability and repairability of their unit and keep it running into the future.
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The non sequitur for the day.
The module is to be considered more of an upgrade, since you add more cost.
The advantages are that you can now set the bias point, to where you want it ( the sweet spot as shown in the simulations) and the devices have much higher SOA (won't fail so easy). If it becomes the only viable replacement then you will just have to pay the price.
Sure, the added advantage is being able to keep a 780 or similar device alive regardless of STK-0050 availability.
So the list of gear using STK-0050 is,
Pioneer SX-780
Fisher RS-2004A
EW or anybody else, can you recommend a thermal insulator for the TO-3P devices
Is this one suitable 951-SPK10-006-00-105 for use with NJW3281G and NJW1302G ?
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Too lazy to check device and pad size, but if those are big enough for the trannies you got, they will do nicely. The K-10 pads are the best you can buy, period, and are superior to mica & grease.
You are correct, that was the initial reason for the design.
qprhooligan
Well-Known Member
They may not be time bombs as you say, but they aren't hard to kill if you do something wrong. I have received at least 5 SX-780 receivers in the last few years and 4 had bad STK modules. There is a great demand for STK-0050 modules, that isn't panic, it is a mater of fact.
If you are so confident your modules will last, why did you bother buying spares?
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Beatnik
What's this ?
I have a door stop 780 I repaired once for my daughter, STK modules. Wasn't long after that it was dead again, sits on the shelf collecting dust and was replaced with a 650. I don't know if it was crap replacement modules or ????, but I will eventually look into this build myself !
)
Arthur Smith
Super Member
Expect the unexpected with anything of this vintage. Until then, use them to enjoy them, and don't fret about things going wrong until they do so.
kramden, PM HBrown and ask him if he will help you out? As you are aware, it is a time consuming task, best done by doing it yourself. Maybe you do not have the means to cut/machine the Al plate, so maybe that and the pcb is all you need. You can order parts from Mouser and solder up yourself, not much to it.
You will need a DMM in order to set the bias.
You probably would want to replace both of them, so that the channels match.
You will need a DMM in order to set the bias.
You probably would want to replace both of them, so that the channels match.
punchback
Active Member
Attached is a pdf of a dimensioned drawing for the Aluminum Plate. I haven't actually made one so use it at your peril. The measurements came from a gerber viewer that gave measurements in millimeters so consequently the drawing is metric also. My intentions are to make another layer in the drawing and dimension again in inches. The three holes that go through the PCB line up great on a 1:1 printout. The holes were placed based off of the center hole. I only dimensioned the center and the left three as the right three are a mirror of the left three. I didn't look hard enough to find out what the 5 tapped holes should be. Based on the BOM from rcs16 they should probably be 4-40. As far as I could tell a STK050 had 3.6mm through holes for the mounting screws.
qprhooligan
Well-Known Member
Anyone wanna trade some pcb boards for aluminum plates?
qpr, are you not able to make your own plate?
It is a few tools,
You need some
1) 1/4" plate Aluminum from a building center, cut it to size,
2) might need the hack saw to cut, file to take off the sharp edges,
3) 360-400 emery cloth to polish up.
4) A hand drill will do it if you are careful. The idea is to get it as perfect to 90 degrees as possible but a little off center will work. Just make sure the frill does not wonder and make the hole too big. A drill press is the best to use if you have one. There have been suggestions for counter bore but that is precision depth drilling.
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.
7) Fine tip Ink marker, Hammer and center punch to mark drill locations.
use the pcb as your template guide to mark where to drill the holes. center puch locations.
Use the bjts as your guide, after you lead form them. The center pins, on the pcb are you guides in one plane. How far they stick out is up to you, but the lead bend should be on the thinnest part that it to be soldered in the pcb plated thru holes.
Feel free to help complete the build instructions.
It is a few tools,
You need some
1) 1/4" plate Aluminum from a building center, cut it to size,
2) might need the hack saw to cut, file to take off the sharp edges,
3) 360-400 emery cloth to polish up.
4) A hand drill will do it if you are careful. The idea is to get it as perfect to 90 degrees as possible but a little off center will work. Just make sure the frill does not wonder and make the hole too big. A drill press is the best to use if you have one. There have been suggestions for counter bore but that is precision depth drilling.
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.
7) Fine tip Ink marker, Hammer and center punch to mark drill locations.
use the pcb as your template guide to mark where to drill the holes. center puch locations.
Use the bjts as your guide, after you lead form them. The center pins, on the pcb are you guides in one plane. How far they stick out is up to you, but the lead bend should be on the thinnest part that it to be soldered in the pcb plated thru holes.
Feel free to help complete the build instructions.
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Try as I may, I have never gotten good fine threads (3mm, 6-32, 4-40) by hand - they are always loose and sloppy. sigh...
I'll chuck the tap in a drill press using the chuck as a handle. Makes for a perfect tapped hole. Remember to unplug the press. Only by hand. Grinding the tip of the tap, leaving a small portion of the starting taps will produce a nice deep threaded hole, as long as your drill press bed is true and plumb to the chucks drive shaft. Works best on aluminum stock.
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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.
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.
