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SX-1010 won't Power On...

Yeah I have soldered before. Not more than a dozen times though and none of them on a circuit board. I replaced the power lamps for both my SA-9500 II and SA-8500 II. Oh and that bridge where I put the fuse in the middle today. And a few more tiny jobs here and there that's all. I am not an expert but am not totally a stranger to it. I do have a soldering iron and solder. However, I don't have a de-soldering iron or a pump.
 
We are now at a dilemma, the most info can be obtained if the unit were turned on with just two output transistors of opposite polarity installed, and the dead ones removed, BUT with the transistor sockets loose, there is a severe danger of shorting things and causing more damage.

With the main fuse blowing I HAD wanted to see if any of the fuses on the pc board had blown, pointing us to other possible problems, the FIRST step of systematic troubleshooting. Instead you two got VERY lucky that none HAD blown, and THEN the ONLY way to get the power BACK on without blowing fuses was to find what was shorting out the ONLY winding of the transformer that didn't have a fuse on it, the winding that powered the output transistors.

So, D.E.K. , did you mark which transistors came from where, and can you put back the four good transistors, two to a channel?

YOU HAVE to make sure that none of the leads or screws in each transistor mount are NOT shorted to the heatsink, if they short, there will be damage, possibly fireworks. They can be very touchy as there are small ridges that align things, and if tightened with the wrong alignment, the sockets can be broken.

You MUST not power up the unit until we have discussed more things, including the construction and use of a dim bulb tester using a 100 watt incandescent bulb to try to prevent damage in case of a fault. It will also prevent the blowing of fuses.

With two transistors of opposite polarity in each channel (and the empty sockets insulated) and a dim bulb tester, the unit can be powered up and if lucky (again) the protection will engage and music heard, just not to over 1/3 (for safety) power.

If successful, that will mean that all is needed are the new output transistors.

Otherwise we start taking voltage readings inside, and desoldering transistors and other components for removal for testing.
 
Yes, I know which transistor came out of what socket as I placed the transistors in front of the heat sinks in order as they came out. I also took some pictures and marked the shorted transistors. No problem there. I also can put 2 to a channel, no sweat. I just need to know which ones. Apparently not the shorted ones which leaves me with 2 good ones on the left and 4 good ones on the right. You're telling me to put 2 on each side assuming I only have 4 good ones left instead of 6. Or... OR I really have to put 2 on each side and leave out 2 bad and 2 good ones which will leave me with 2 good ones per side in order to maintain some kind of balance. I don't know what balance, but a balance of some sort. As for the 100W incandescent, I am totally in the dark. I don't know what kind of rig you want me to set up.
 
Correcting my previous message: I have 5 good transistors NOT 6. I have three 2SA679's and two 2SC1079. If you refer to the pictures I attached on page 2 of this forum, there are two 2SC1079 and two 2SA679 per side. I am assuming the SA's are PNP and SC's are NPN. Am I right? If I am, you want me to put one of each per side (one 2SC1079 and one 2SA679 per side) please confirm? Also, does it matter which sockets, of course assuming the SA and SC go into designated sockets. For instance say we number the sockets on the left side 1-4 going from left to right. I am going to have to use Socket #2 for 2SC1079 and Socket #4 for 2SA679. As for right side, number the sockets 1-4 from right to left. I am going to use Socket #2 for 2SC1079 and Socket #4 for 2SA679 as a mirror image of the left side. Does everything sound right so far?
 
D.E.K said:
If you refer to the pictures I attached on page 2 of this forum, there are two 2SC1079 and two 2SA679 per side. I am assuming the SA's are PNP and SC's are NPN. Am I right? If I am, you want me to put one of each per side (one 2SC1079 and one 2SA67 per side) please confirm?
Click to expand...

Yes, exactly.

edit: hmmm:
D.E.K said:
Correcting my previous message: I have 5 good transistors NOT 6. I have three 2SA679's and two 2SC1079. If you refer to the pictures I attached on page 2 of this forum, there are two 2SC1079 and two 2SA679 per side. I am assuming the SA's are PNP and SC's are NPN. Am I right? If I am, you want me to put one of each per side (one 2SC1079 and one 2SA679 per side) please confirm? Also, does it matter which sockets, of course assuming the SA and SC go into designated sockets. For instance say we number the sockets on the left side 1-4 going from left to right. I am going to have to use Socket #2 for 2SC1079 and Socket #4 for 2SA679. As for right side, number the sockets 1-4 from right to left. I am going to use Socket #2 for 2SC1079 and Socket #4 for 2SA679 as a mirror image of the left side. Does everything sound right so far?
Click to expand...

Use the four transistors from the side where they ALL tested good.

In this model the 2sc1079's share the same collector and base connections, and both emitter resistors connect to the same place, so it does NOT matter which of the two positions on THAT heat sink the one 2sc1079 is installed in. That also goes for the 2sa679. As a BACKUP check, the wire color to the collectors of the 2sa and 2sc transistors will be different, I believe the 2sa will be orange (-64v) and 2sc will be red (+54v) if the color codes hold true, although white could be used instead of orange.



When there are two of the same type, it doubles the power handling capacity.

re:dim bulb

The light bulb goes in series with the plug, like a fuse. There are several threads on AK about making the dim bulb tester.

What happens is, if the unit pulls too much current, like if it were to blow a fuse, the bulb would light brightly instead, absorbing the power and starving out the unit. If the unit pulls only a little current, the bulb will glow dimly and the unit will get enough power to work - but like it's in a brownout.

The bulb WILL glow brightly for a second or so after the unit is turned on, because of the initial surge that charges the capacitors. But then it will dim down if everything is ok.

A second or so after the power is turned on and the capacitors charge, the first relay click will happen. About 5 seconds later the second click should happen. That's the protection circuit deciding it is safe to connect the speakers. That means the amplifiers have no major faults that would endanger the speakers.
 
markthefixer said:
Yes, exactly.

edit: hmmm:



The light bulb goes in series with the plug, like a fuse. There are several threads on AK about making the dim bulb tester.

What happens is, if the unit pulls too much current, like if it were to blow a fuse, the bulb would light brightly instead, absorbing the power and starving out the unit. If the unit pulls only a little current, the bulb will glow dimly and the unit will get enough power to work - but like it's in a brownout.

The bulb WILL glow brightly for a second or so after the unit is turned on, because of the initial surge that charges the capacitors. But then it will dim down if everything is ok.

A second or so after the power is turned on and the capacitors charge, the first relay click will happen. About 5 seconds later the second click should happen. That's the protection circuit deciding it is safe to connect the speakers. That means the amplifiers have no major faults that would endanger the speakers.
Click to expand...


Something like that little hole on the inside top of the sinks as a backup drainage in case the main drain is clogged.
 
Mark, upon your confirmation, I am installing 2 good transistors on each side as shown in the attached pictures.
 
D.E.K said:
Mark, upon your confirmation, I am installing 2 good transistors on each side as shown in the attached pictures.
Click to expand...


Looks good from here,

please please please - - - insulate the empty sockets thoroughly.

Are those sockets that would be used on the END or the MIDDLE of each of the four cables with two sockets each? If it were me, I would install the transistor in the socket that most easily allows me to get the OTHER empty socket to hang unmolested in midair, and then insulate that socket in midair.

remember:
The two pins are NOT centered, they are closer to one end (screw hole) than the other

The socket has little protrusions that fit into recesses in the two pin holes (maybe the screw holes) it's a FEEL thing - try it first WITHOUT the transistor to complicate things, use just the socket and no screws.

Once the transistor is in place, use an ohmmeter to test all the pins for a short to the heatsink.

It's getting late for me, I'll not be up much longer....
 
D.E.K said:
For me also, just before you leave, tell me how to insulate the empty sockets.
Click to expand...

If they are sticking up out of the chassis, I would put a sandwich bag over each, and use a rubber band to hold it in place, alternately an easily removable tape (masking tape - not duct or packing) covering all the metal. Fold a sheet of paper around each one?

That's why the "sticking up" part, easier to insulate.
 
Okay, all 4 transistors are put back though the little horseshoes made me a wee bit nervous. Pins tested for shorts to the heat sinks, good to go. Sandwich bags...Check! Time to build a dim bulb tester.
 
I couldn't find a bulb socket so I decided to operate on one of my old lamps that I don't use. Here are the pictures of my dim bulb tester. First time I am making one of those (first time I ever even heard about them, for that matter) so bare with me.
 
Done. Before hooking up the receiver I thought it would be a better idea to test the DBT with another end table lamp. I didn't want to plug in the receiver to a non-functional DBT. All seems well.
 
Hands are shaking, receiver plugged in. I am using a long screwdriver to flick the Power swicth to "ON" position.. In case I get a fireworks frenzy.
 
Now the ultimate test, hooking up the speakers and trying a CD player in AUX. Do I dare? Darn right I do!!
 
I am really anxious so I grab my daughter's little radio/CD Player which is right next door. Hook it up, turn on the receiver, press PLAY. I tell you, "Mary Had A Little Lamb" never sounded so good!! :lmao: I am reluctant to turn up the volume past 2 though. I'll build up my courage eventually. Most important of all, we got the beauty working. You guys are GENIUSES. I don't know how to thank you but for what it's worth, I am greatful. Thank you.
 
I just discovered something. When the receiver is in FM mode and when I find a station, I hear chirping noise, like a cricket, coming from somewhere around the two circuit boards in front of the heat sinks. I am not liking it.
 
Bad news, I lost the volume. Even at 3-3.5 volume, it is very low and faint. When I turn off the receiver and turn it back on after 15-20 secs, the volume comes back for about 5 secs then dies out. I am not planning on turning up the volume because that is exactly how she blew the fuse the first time.
 
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