I'd recommend ordering replacements for all op-amps, the two regulators (LM337T and LM317T are the part numbers), the capacitor and the 10 ohm resistors. Order extras of each component in case there is a problem that causes the newly replaced components to fail. You won't reconnect the preamp board until you have the main board working properly (as was done on the 7801 repair).
ok my parts arrived from mouser today and i installed both power regulators and the 2 op-amps. i am getting 15 volt at the omp amp but after about 30 seconds i cooked the op-amp again. is it possible to install them upside down? all i did was lined up the letters the same direction from the pieces i pulled out . i am also getting a humming noise from the board that i never had before.
After removing the defective op-amp, confirm that the voltage on pin 4 is approximately negative 15v. Also confirm that the voltage on pin 8 is approximately positive 15v.
If the markings were orientated the same as the other IC, it was likely installed properly. There is a white dot near pin 1 on the board. There is either a dimple or a cutout on the end of the op-amp nearest pin 1.
If the markings were orientated the same as the other IC, it was likely installed properly. There is a white dot near pin 1 on the board. There is either a dimple or a cutout on the end of the op-amp nearest pin 1.
here is a picture. but my one op-amp starts smoking as soon as i put power to it. is it possible they are defective right from the manufacturer? should i change this out now or look for other problems first?
im still uncertain how to verify oreintation of the chips i cant see the dimple or a cut out
im still uncertain how to verify oreintation of the chips i cant see the dimple or a cut out
Attachments
i replaced the 072c that was smoking and i think i must have crewed up the install because it seems to be working now. but now the 2nd op-amp that i replaced is getting hot (595-NE5532D) i am getting +- 15v on the 4 and 8 legs, i cant leave the power to it very long because it gets really hot. its not smoking but im sure it will if i let it be.
i am getting a lot of static or white noise when i hook up a speaker.
i also replaced the 2 large power regulators and i have +-49 volt at either transistor.
i replaced 2 op-amps there is a picture of both on the previous page.
i am getting a lot of static or white noise when i hook up a speaker.
i also replaced the 2 large power regulators and i have +-49 volt at either transistor.
i replaced 2 op-amps there is a picture of both on the previous page.
The second op-amp (driving the class D amplifier) may run hot if the amp is in protect but it shouldn't run too hot to touch. If it's getting really hot, it's probably defective also.
You won't get any audio without either the preamp board or the jumpers in place on the connector that goes to the preamp board. The preamp board likely has defective op-amps so you shouldn't plug it in yet.
Is R106 marked 1002?
You won't get any audio without either the preamp board or the jumpers in place on the connector that goes to the preamp board. The preamp board likely has defective op-amps so you shouldn't plug it in yet.
Is R106 marked 1002?
If I'm not mistaken, R106 and 3 other resistors set the rail voltage. With the resistors I see, ±50v is approximately the correct rail voltage.
Looking back at the datasheet for the regulators, they are rated for 40v but that's the supply voltage minus the output voltage so 50v of rail is OK.
Measure the DC voltage on the 4 pins on the end of the black connector (nearest the heatsink). If all are essentially at 0v, connect jumpers across them (as was done for the 7801 repair) to see if you can get audio from the amplifier. I'm not sure if this preamp board is wired the same as the other amps I've done this on so there is some risk.
http://bcae1.com/temp/IMG_3477jumpers01.jpg
Looking back at the datasheet for the regulators, they are rated for 40v but that's the supply voltage minus the output voltage so 50v of rail is OK.
Measure the DC voltage on the 4 pins on the end of the black connector (nearest the heatsink). If all are essentially at 0v, connect jumpers across them (as was done for the 7801 repair) to see if you can get audio from the amplifier. I'm not sure if this preamp board is wired the same as the other amps I've done this on so there is some risk.
http://bcae1.com/temp/IMG_3477jumpers01.jpg
well i changed out both op amps. and i put resisted power to it and smoked both the op amps. now i need to order some more i only ordered 2 of each. so im out of parts for the time being.
i bought 2 identical broken amps at the same time because i figured it would be easier to learn this way. i have a perfectly fime preamp board i can swap in for the time being.
while im waiting on parts to arrive can i start soldering the preamp board? do i need to replace all 14 legged "074c" on the preamp board? i have 4 of them and one 8 legged 072c (ill have to wait for that one)
i bought 2 identical broken amps at the same time because i figured it would be easier to learn this way. i have a perfectly fime preamp board i can swap in for the time being.
while im waiting on parts to arrive can i start soldering the preamp board? do i need to replace all 14 legged "074c" on the preamp board? i have 4 of them and one 8 legged 072c (ill have to wait for that one)
If the voltage isn't excessive, there's no reason for the op-amps to fail (particularly the one near the RCA jacks).
Is it taking longer than 10-15 seconds total (time iron is on op-amp) to solder the op-amps to the board?
If it's taking longer...
Remove the defective op-amps.
Desolder all pads with braid so that they have essentially no solder on them. If the braid doesn't wick the solder well, use flux. The stuff from Radio Shack (64-022) works well enough (not sure if RS is still operating in Canada).
Apply new solder to one corner pad (the corner pad with the most copper if possible).
Tack the op-amp in place by soldering the leg to the board where you applied solder to the corner pad.
Apply flux to the rest of the legs.
On the side where no legs are soldered, apply solder to the corner pin (opposite the one that's soldered down) and pull the tip of the iron from that pin across the rest of the pins on that side. With the flux, solder should flow readily to the other legs and to the board. If you bridge some of the legs together, Use the braid to wick off the excess solder.
Repeat for the other side.
Clean up the excess flux with acetone and a cotton swab an inspect the solder connections.
If the tip on your iron won't tin well, use the tip cleaner from Radio Shack (64-020).
Is it taking longer than 10-15 seconds total (time iron is on op-amp) to solder the op-amps to the board?
If it's taking longer...
Remove the defective op-amps.
Desolder all pads with braid so that they have essentially no solder on them. If the braid doesn't wick the solder well, use flux. The stuff from Radio Shack (64-022) works well enough (not sure if RS is still operating in Canada).
Apply new solder to one corner pad (the corner pad with the most copper if possible).
Tack the op-amp in place by soldering the leg to the board where you applied solder to the corner pad.
Apply flux to the rest of the legs.
On the side where no legs are soldered, apply solder to the corner pin (opposite the one that's soldered down) and pull the tip of the iron from that pin across the rest of the pins on that side. With the flux, solder should flow readily to the other legs and to the board. If you bridge some of the legs together, Use the braid to wick off the excess solder.
Repeat for the other side.
Clean up the excess flux with acetone and a cotton swab an inspect the solder connections.
If the tip on your iron won't tin well, use the tip cleaner from Radio Shack (64-020).
i checked the pre amp board near the 074c's and found this...
i will order the 100 ohm resistors but does it mean that i need to change the 074c aswell?
this and the little cap that blew seem to be all i can find wrong with this board, i will change the 072c aswell though. is there anything else i am missing?
when i am ordering new parts like the 100 ohm resistor. how do i know which part number is correct? or what to search for? all i have to go on is that it says 1000 on it and its a resistor. do i phsically measure it?
i will order the 100 ohm resistors but does it mean that i need to change the 074c aswell?
this and the little cap that blew seem to be all i can find wrong with this board, i will change the 072c aswell though. is there anything else i am missing?
when i am ordering new parts like the 100 ohm resistor. how do i know which part number is correct? or what to search for? all i have to go on is that it says 1000 on it and its a resistor. do i phsically measure it?
Attachments
The 074 is probably damaged so it will probably need to be replaced.
I'm not sure what those resistors are for, R205 on the other end of the op-amp appears to be burned. It's likely a 10 ohm.
The resistors appear to be 0805 (size). The one on the right in the image below is an 0805. The one on the left is a 1206. Use the pin spacing of the op-amp to determine the size of your resistors. If you have a dial caliper, you can use it to measure the resistor.
http://www.bcae1.com/temp/ttIMG_7796b.jpg
I don't know where you're buying parts but searching with the following keywords should narrow it down.
SMD resistor 0805 100ohms 1%
I'm not sure what those resistors are for, R205 on the other end of the op-amp appears to be burned. It's likely a 10 ohm.
The resistors appear to be 0805 (size). The one on the right in the image below is an 0805. The one on the left is a 1206. Use the pin spacing of the op-amp to determine the size of your resistors. If you have a dial caliper, you can use it to measure the resistor.
http://www.bcae1.com/temp/ttIMG_7796b.jpg
I don't know where you're buying parts but searching with the following keywords should narrow it down.
SMD resistor 0805 100ohms 1%
i got a new op-amp in the mail today and the one near the rca inputs seems perfectly fine. i can apply un-resisted power to the board and no problem. the other op-amp (N5532) on the corner of the board is getting super hot. its way too hot to touch.
i can leave full power to the board for 20 mins and nothing is smoking or exploding and im still +-15v at both op-amps.
im not sure if its normal for one of these to get this hot.
thank you for the soldering tip i didnt know i could use flux with the copper wick
i can leave full power to the board for 20 mins and nothing is smoking or exploding and im still +-15v at both op-amps.
im not sure if its normal for one of these to get this hot.
thank you for the soldering tip i didnt know i could use flux with the copper wick
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