SX-1010 won't Power On...
- Thread starter D.E.K
- Start date
Transistors are cheap (and more easily damaged) , but with care the caps will not be damaged (don't put them in backwards!!).
So I would get extra transistors, but not caps. (I have scads of transistors around - I hate waiting)
LWB
Well-Known Member
Protection Circuit modification?
This sounds like something I ought to do to my 1010, too. :yes:
If you'll walk D.E.K. through it, I'll watch, too, please & thanks!
This sounds like something I ought to do to my 1010, too. :yes:
If you'll walk D.E.K. through it, I'll watch, too, please & thanks!
D.E.K
Loader
I was thinking about the process last night and something kind of troubled me. Something that might have gone wrong or neglected along the process. When I applied (more like SMUDGED a big blob) the thermal compound for the first time onto the new transistors, a considerable amount might have gone into the sockets carried in by the transistor leads. Would that cause any inconductivty and cause the relay to disengage? Hence the volume fading out and coming back? Just a shot in the dark.
D.E.K
Loader
Practiced de-soldering and re-soldering. I think I fried the circuit board around where I re-soldered a bit. I might have held the iron tip for too long on the pad, I had to try with the vacuum pump several times to get the molten solder. The board was too small (1in. X 2in.) and it was standing on a switch attached to the pad so it was hard to keep it still. I think it will be a little easier with the desoldering braid.
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Not likely, conductive thermal paste would be something like arctic silver and if you got the stuff I specified, that's non-conductive electrically.
I sure hope that board isn't critical to something, but it doesn't look too bad.
The pictures ZeroJunk posted are excellent, you can see the extra diode on pins 9 & 10, and just below it the square zetex transistor... we will be doing one more square transistor - I have only seen one failure with it, but what the hey...
ZeroJunk, is that a Zetex I spy in the Q6 position?????!!!!!!!??????????!!!!! D.E.K. - yours should look JUST like this when you are done!!!
Yes. I actually got the parts list off of a thread you were responding to back in the summer. I noticed in this thread you had suggested doing Q6 also. Luckily I had ordered an extra.
DEK, you will notice I got careless and picked the trace up on the capacitor on the left side of the board. It's not the end of the world, you can scrape enough of the insulating material off the trace to bridge it, or you can jump it with a small piece of wire if you have to.
But, ideally you take your time.
D.E.K
Loader
http://www.mcmconnect.com/tenma/pro...s;jsessionid=62CDCB4CD5C77A2002A85DD61A440764
Would be nice to be able to afford to have something like that to reduce fussin' around.
Would be nice to be able to afford to have something like that to reduce fussin' around.
LWB
Well-Known Member
An alternative to solder-sucking
When removing components from a circuit board, I often prefer to use soldering braid instead of a solder sucker. I find that it takes a little more time, but the advantage of the braid is that it also acts as a heat sink, so you won't damage the traces or pads. If you are removing a component to test, the braid is good for this reason, too, because you don't want to overcook a component you might re-install. The braid is sold in small spools and in various sizes. I like to use a width just a little bit wider than the soldering tip I'm using on the iron. The braid, heated between the iron tip and the component lead, wicks up the molten solder. If you want to speed the process, you can use a flux pen on the braid, this makes it even thirstier.
Bear in mind that, quite often, when it looks like you've scorched the board, you may have just scorched the varnish or residual flux from manufacture. This will clean off with isopropyl alcohol. It's a good idea to clean off residual flux after working on a board, anyway. Flux is corrosive.
Some component data sheets provide heat exposure time limits for soldering. Of course, these assume you are using a temperature-controlled iron.
I found these URLs to be useful for soldering and de-soldering tips:
http://tangentsoft.net/audio/new-diyer.html
http://www.kpsec.freeuk.com/solder.htm
http://www.epemag.wimborne.co.uk/solderfaq.htm
When removing components from a circuit board, I often prefer to use soldering braid instead of a solder sucker. I find that it takes a little more time, but the advantage of the braid is that it also acts as a heat sink, so you won't damage the traces or pads. If you are removing a component to test, the braid is good for this reason, too, because you don't want to overcook a component you might re-install. The braid is sold in small spools and in various sizes. I like to use a width just a little bit wider than the soldering tip I'm using on the iron. The braid, heated between the iron tip and the component lead, wicks up the molten solder. If you want to speed the process, you can use a flux pen on the braid, this makes it even thirstier.
Bear in mind that, quite often, when it looks like you've scorched the board, you may have just scorched the varnish or residual flux from manufacture. This will clean off with isopropyl alcohol. It's a good idea to clean off residual flux after working on a board, anyway. Flux is corrosive.
Some component data sheets provide heat exposure time limits for soldering. Of course, these assume you are using a temperature-controlled iron.
I found these URLs to be useful for soldering and de-soldering tips:
http://tangentsoft.net/audio/new-diyer.html
http://www.kpsec.freeuk.com/solder.htm
http://www.epemag.wimborne.co.uk/solderfaq.htm
LWB
Well-Known Member
Not clear on why this mod
On 1010 Power Amp Board AWH-032-0, I'm wondering why you replaced diodes D7 & D8, which were each originally a single 1S1885 diode (rating: VRRM 100 Volt, IFSM 66 Amp) with two Fairchild UF4004 (rating: Repetitive peak reverse voltage 400 Volt, Peak one cycle surge forward current 30 Amp) in series. This seems like less protection rather than more in terms of the current capability of the replacements. Am I missing something?
I attach ccheath's illustration of the components from his earlier posting and a pic of my original unmodified board.
On 1010 Power Amp Board AWH-032-0, I'm wondering why you replaced diodes D7 & D8, which were each originally a single 1S1885 diode (rating: VRRM 100 Volt, IFSM 66 Amp) with two Fairchild UF4004 (rating: Repetitive peak reverse voltage 400 Volt, Peak one cycle surge forward current 30 Amp) in series. This seems like less protection rather than more in terms of the current capability of the replacements. Am I missing something?
I attach ccheath's illustration of the components from his earlier posting and a pic of my original unmodified board.
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Looks like you have an older version of the amp board AWH-032. You're the only person I see having that.
You'll see my entire board in pic below. You'll notice your board has 2 STV-3H diodes mounted on the small heatsink for those 2 driver transistors. DEK's and my boards had the diodes relocated at the factory. One on the driver heatsink and another attached to the output heatsink. You'll notice 2 missing wirings going from pins 21 and 22 to the STV-3H that is supposed to attach to the output heatsink. It wasn't attached at the time I took the pic but it is now. I should have taken another pic before I closed it up.Okay, to answer your question. The original diodes (D7 & D8) were STV-3 not 1S1885. DEK has the same thing in his SX-1010. I just replaced them for reliability because the one of the original was subjected to heat from the power resistor for a long time even though it still worked. I'd like to consider it a replacement rather than a mod even though it's a small mod. STV-3 is actually 3 diodes in series in one package. I can't remember which thread spoke of this but I do recall running into a thread speaking about those doides replacement. Markthefixer suggested the number UF4004 because it's ultrafast. Echowars had agreed to use fast diodes in that part of the circuit. He even suggest to use only 2 instead of 3. The reason having such diode in that particular area is to prevent the outputs from saturating at high volume. 2 diodes in series put added protection for someone who is heavy on volume. Pioneer has just put extra protection by using 3 diodes in series (namely STV-3). The diode delivers the voltage to the driver not the outputs. It does not require huge amount of current for the driver to drive the outputs. Certainly not 30 amps nor 66amps anyways. That's the outputs job to deliver much current.
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LWB
Well-Known Member
On replacement of the STV-3H varistors - or diodes?
In my unit, STV-3H (called Varistors in the Service Manual) are in positions D5 and D6, as per the SM, and are little U-shaped dohickies that attach with a single screw to each side of the heat sink beneath the Q9 & Q10 transistors. Your photo appears to show one of these mounted on the right side of the heat sink, but not on the left side. The service manual shows 1S1885 diodes in the D7 and D8 position, as in my unit (my serial # indicates Sept 74 mfr according to Strangelove's scheme). Are we referring to the same components? What are the components in positions D5 and D6 on your board? I wonder if the board traces are any different.
And, I wonder if I should make some changes? On the one hand, I know the former owner of this unit liked 'volume', and it hasn't failed yet. On the other, I'm interested in making sure it doesn't fail...
Last question - why 'high speed' diodes? The 1S1885 is a general purpose rectifier.
In my unit, STV-3H (called Varistors in the Service Manual) are in positions D5 and D6, as per the SM, and are little U-shaped dohickies that attach with a single screw to each side of the heat sink beneath the Q9 & Q10 transistors. Your photo appears to show one of these mounted on the right side of the heat sink, but not on the left side. The service manual shows 1S1885 diodes in the D7 and D8 position, as in my unit (my serial # indicates Sept 74 mfr according to Strangelove's scheme). Are we referring to the same components? What are the components in positions D5 and D6 on your board? I wonder if the board traces are any different.
And, I wonder if I should make some changes? On the one hand, I know the former owner of this unit liked 'volume', and it hasn't failed yet. On the other, I'm interested in making sure it doesn't fail...
Last question - why 'high speed' diodes? The 1S1885 is a general purpose rectifier.