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Post by Michael on Sept 3, 2013 12:09:33 GMT -5
Picked up some parts from local store and had to order 2SA1492 and 2SC3856 from Digikey. I ordered two 2SA1492 since Q19A's screw is also look discolored and does not look good, even though it does not show any shorts I think it might not be a bad idea to replace it while I have the board out. What are your thoughts? I should be getting them by the week-end.
Questions;
1- Bought q301 and going to replace Q301 as well. Does it matter which way 3 legs will be installed in the board?
2- Should I remove the jumper on the relay now?
3- On D301 which side the flow arrow the Cathode band should be on? Pointed side?
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Post by mastertech on Sept 3, 2013 14:59:08 GMT -5
Picked up some parts from local store and had to order 2SA1492 and 2SC3856 from Digikey. I ordered two 2SA1492 since Q19A's screw is also look discolored and does not look good, even though it does not show any shorts I think it might not be a bad idea to replace it while I have the board out. What are your thoughts? Sure you can replace it if you wish. Questions; 1- Bought q301 and going to replace Q301 as well. Does it matter which way 3 legs will be installed in the board? Yes it matters. The board is marked for the direction it is to be installed. The lettering faces the relay. What is the part number of the replacement part you got?2- Should I remove the jumper on the relay now? Yes.3- On D301 which side the flow arrow the Cathode band should be on? Pointed side? Again, board is marked on both front and back I believe. The stripe goes to the left when looking at the end of the relay towards the D301 ink lettering. |
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Post by Michael on Sept 3, 2013 16:25:38 GMT -5
Update;
Installed Q301 (originally removed part with the lettering facing the relay) and D301. Removed the jumper from relay and plugged in the unit. No display light came on however, when I pressed the power button, a very low buzzing sound could be heard from the relay. Installed the jumper back in again and display lighted up after hitting the power button and went out about two seconds later. Do you think I could have damaged the relay here? Is it better to get that relay replaced as well?
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Post by mastertech on Sept 3, 2013 19:15:09 GMT -5
The buzzing could be the relay. But to verify the relay you can just take a 9 volt battery and connect a wire to each contact the then hold them on the replay and see if the relay still buzzes or a nice click. Of course the receive is not plugged in when you do this. Positive of battery goes to the side which the diode has the stripe.
If the relay clicks nice and firm with the battery then you will have to do some voltage testing again. Let me know what you get with the battery test.
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Post by Michael on Sept 4, 2013 0:09:45 GMT -5
Nice, firm click on the battery test.
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Post by mastertech on Sept 4, 2013 8:59:34 GMT -5
Check that S12 voltage again. DMM on DC. Then using MG for ground again test the pin in between the S12 and MG pins. It should be PRY. Your looking for around +5v. The voltage may only be there when you hit the power button and while the display is lit. Try to get the best voltage reading you can before it shuts off.
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Post by Michael on Sept 4, 2013 10:16:32 GMT -5
On MG - PRY I get 1.9xx V to 2.1xx V only when I hit the power button. Still have 16.5 V on MG - S12.
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Post by mastertech on Sept 4, 2013 10:19:47 GMT -5
Ok, This could also be why it does not stay on. It may get a little trickier now to test. Are you up for it? LOL.
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Post by Michael on Sept 4, 2013 10:24:13 GMT -5
Try me!! Lol! I hope I don't disappoint you!
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Post by mastertech on Sept 4, 2013 11:11:40 GMT -5
Ok. You are now going to do some tests on the function board. This is the long, upright board with the audio inputs at the rear. There are a bunch of ribbon cables connected to the top edge of the board. Locate the ribbon cable nearest the front of the board.
Set DMM to DC voltage and connect negative probe to the chassis again for ground. Plug in receiver but it does not have to be turn on. Now on that front connector you can see the metal contacts right where the ribbon enters the connector. Touch the positive probe to the second from the front metal contact and see if you have +5v.
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Post by Michael on Sept 4, 2013 12:03:11 GMT -5
4.81 V
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Post by mastertech on Sept 4, 2013 13:14:13 GMT -5
Looking at the component side of that board below the 4th ribbon front the front edge down about a inch or so you will see 2 diodes, D520 and D521. Now look at the back side of that board for the 4 pins of those 2 diodes. Stand the receiver on its side with the transformer down so you are looking right at those 4 pins. Plug in receiver, set DMM to DC voltage, neg probe in chassis gnd and give me the voltage of each pin.
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Post by Michael on Sept 4, 2013 13:41:48 GMT -5
D520= 5.35 V and 4.82 V
D521= 5.49V and 4.80 V
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Post by mastertech on Sept 4, 2013 14:07:38 GMT -5
This next one is very trickey so be careful your probe doesn't slip. Receiver still standing up on its side. Receiver plugged in, DMM on DC voltage and neg probe in chassis gnd. Look for the 4th ribbon from the front and notice the pins sticking through the back of the board. They are staggered. Count to the 4th pin in from the front, it would be the 2nd on the second row. Put your positive probe on that pin and make sure you hold it steady and do not slip. Then hit the power button and see what the voltage goes up to. If it will turn on again after it turns off, try it a couple times to see what the voltage is on average.
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Post by Michael on Sept 4, 2013 14:24:04 GMT -5
It's 0.3 mv turns to 0.4 mv when i hit the power button. Does not turn on again by itself. If I hit the power button, it turns on and repeats the readings.
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