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scar
Joined: 02 Jul 2015
Posts: 34
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 Posted: Tue Aug 25, 2015 3:36 am Post subject: |
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| jts1957 wrote: | | R531 you're reading r529 plus r531 = 1502.2 ohms |
ok when i measured r531 i got about 1507-1508 and internal resistance of 2-3 so thats about 1505 so r529 is probably ok right? i can't seem to find r529 right now to desolder it.
received the two power transistors in the mail and they test out fine, 4 highs and 2 lows. i have some thermal grease for a CPU in a computer, its ok to use that right? |
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scar
Joined: 02 Jul 2015
Posts: 34
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| Posted: Tue Aug 25, 2015 3:51 am Post subject: |
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ok finally found r529 lol it looks like r528 on the diagram but its right next to r531. anyway i measured it to be 3.8, −1.6 internal resistance = 2.2 exactly
just waiting to hear back on the thermal grease then i will try to reassemble everything! |
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jts1957
Joined: 24 Nov 2008
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Location: Far, Far Away
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| Posted: Tue Aug 25, 2015 5:31 am Post subject: |
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Thermal silicone grease is O.K. CPU grease if you feel extravagant.
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scar
Joined: 02 Jul 2015
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| Posted: Wed Aug 26, 2015 7:58 pm Post subject: |
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well upon further inspection of the heat sink, it appears there is a thin plastic between the grease and the transistor. it looks as if the grease was put on the heat sink and then these thin plastic pieces were put on the grease, but there is also grease on top of the plastic, around the border of the transistors. i don't want the transistors to burn out, after all of this work, so i want to make sure i do this right. am i suppose to just leave it as is, and let the transistor sit on the plastic? or should i add grease on top of the plastic? or maybe just try and remove the plastic completely and just have some grease between the sink and the transistors?
heres a pic of the heatsink... the two positions on the left i haven't cleaned yet and you can see the outline of the transistor with the grease sitting at the border. the grease is underneath the plastic too but more concentrated around the edges and less concentrated in the center where the transistor actually rests... it seems i can move the grease around underneath the plastic and spread it out with my fingernail....
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scar
Joined: 02 Jul 2015
Posts: 34
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| Posted: Wed Aug 26, 2015 8:03 pm Post subject: |
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| looks like they actually show this part in the diagram, #28, SHEET AEE1014 (insulating sheet) |
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jts1957
Joined: 24 Nov 2008
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| Posted: Wed Aug 26, 2015 9:31 pm Post subject: |
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Collectors of transistors are at plus AND minus ~60 volts - NOT a good idea if they were to be connected to ground.
Insulators can be either plastic or mica and can be removed, and if undamaged reused. Wipe off old compound and apply fresh compound to BOTH sides (or to one side of insulator and also to heat sink. Use and spread enough realizing that pressure from the screw WILL help distribute.
Too little compound is the only way to mess up. Too much compound will make a mess, with just right amount somewhere in the middle.
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scar
Joined: 02 Jul 2015
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| Posted: Thu Aug 27, 2015 8:17 pm Post subject: |
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yes!! it works! it's staying on and i hear music!! 
nearly 2 months later...
i'd give you a big hug jts! and i definitely owe you some beers!
you are incredibly knowledgeable and an asset to this site, thank you so much!! |
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jts1957
Joined: 24 Nov 2008
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| Posted: Thu Aug 27, 2015 10:14 pm Post subject: |
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 Glad to 'hear' it.
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scar
Joined: 02 Jul 2015
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| Posted: Fri Aug 28, 2015 4:19 am Post subject: |
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| there is one other issue though! maybe its easy to fix... i have a pair of speakers plugged into the A channel, and they will short out depending on the movement of the B speakers button. this is a problem the receiver was having before. we usually have to lodge an object underneath the B button to push it up in order to get both speakers working. same problem happens if i plug the speakers into the B channel... so something is up with this "B speakers" button that is affecting the sound whether the speakers are plugged into the A or B channel. thought i might try fixing that if possible, before i give it back |
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jts1957
Joined: 24 Nov 2008
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| Posted: Fri Aug 28, 2015 9:29 am Post subject: |
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Only three possibilities:
1) Either end of J5/J6 connectors or any pin(s) of S570 could have bad solder connections. All of these are on the speaker switch board. The main board ends of J5/J6 hopefully were inspected earlier, plus the having to wedge the button point more towards the switch itself.
2) The contact surfaces inside of S570 are filthy and need cleaning (both the 'fixed' - that mount the switch to the speaker switch board and 'slide' - the metal shorting clip that moves from the outside and center contacts to the center and inside contacts as the plunger is moved forward or back).
3) The contact surfaces inside of S570 are actually worn through (more commonly associated with power switch applications, and normally only repairable by switch replacement).
Since the second option is the most likely, can you post a picture of switch so that the best method of getting a chemical cleaning fluid or preferably foam into same can be determined?
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