Sansui AU-5900 power light question

The 1 watt is better. The resistor calculator recommended around 0.75 watt. That resistor is perfect. Have you used it to replace R601?

- Pete
 
The 1 watt is better. The resistor calculator recommended around 0.75 watt. That resistor is perfect. Have you used it to replace R601?

- Pete
Hey Pete,

Yes, I replaced the R601. It seems that the LED goes off when the amplifier is working for a minute or so.
 
I don't see anything in that circuit that would turn it off. It should be on when the power switch is on and off when power is off. Put your red meter probes on pin 13 and the black probe on the metal chassis. What are the measurements before and after the LED turns off?

- Pete
 
As I did what you said, the LED went off and on and stayed on while my red probe was on pin 13 ! I think that the red wire on pin 13 was loose and that the probe stabilized it. Now, it's been on for 5 minutes and it did'nt go off ! Keeping my fingers crossed here !

Thank you so, so much Pete ! You saved the day !
 
I don't see anything in that circuit that would turn it off. It should be on when the power switch is on and off when power is off. Put your red meter probes on pin 13 and the black probe on the metal chassis. What are the measurements before and after the LED turns off?

- Pete
Me again ! The red wire on the connector in pin 13 is loose, it's the reason of the LED shutting down. How can I repair this ? Do I have to change the whole connector ? For now, the light is on, sometimes it goes off, I play with the red wire and it comes back on.
 
Where is it loose, the circuit board side or the connector that attaches to the LED? If it's the circuit board side, you can probably just reflow the solder. If it is the connector at the LED you have some choices. First, try the original LED again to be sure it's dead.

Ideally you don't want to modify or damage the connector. The leads on the replacement LED may be a different diameter than the original LED. I'd try to find some solid wire (not stranded) that is slightly larger than the original LED leads. You can test the size by just sliding wire samples into the connector and feeling the tension on the connector pins. Solder pieces of that wire to the LED leads and you should be good to go. Be sure to insulate any exposed wire.

It just occurred to me that you may have spread the pins in the connector with your meter probes. Did you ever force the probes into the LED side of the connector? If so, you may have to replace the connector or at least the connector pins.

- Pete
 
Where is it loose, the circuit board side or the connector that attaches to the LED? If it's the circuit board side, you can probably just reflow the solder. If it is the connector at the LED you have some choices. First, try the original LED again to be sure it's dead.

Ideally you don't want to modify or damage the connector. The leads on the replacement LED may be a different diameter than the original LED. I'd try to find some solid wire (not stranded) that is slightly larger than the original LED leads. You can test the size by just sliding wire samples into the connector and feeling the tension on the connector pins. Solder pieces of that wire to the LED leads and you should be good to go. Be sure to insulate any exposed wire.

It just occurred to me that you may have spread the pins in the connector with your meter probes. Did you ever force the probes into the LED side of the connector? If so, you may have to replace the connector or at least the connector pins.

- Pete
It's the connector to the pins on the board. I don't think I forced the probe, but I might have press too hard without knowing it. If I pull a little bit on the red wire while it's connected to the LED, the LED stays on. If I let it go, it goes off, then back on. The new LED and his connectors are not loose, they're the same size as the old one. How do you call those kind of connectors if I want to change it ? Should I try soldering it before doing so ?

Thank you Pete.
 
You can always solder it but that will make future service more difficult. The pins can usually be removed from the connector shell but it can be tricky to do without damaging them. There should be a "tang" that holds the pin in place. The tang may be part of the pin or part of the shell. Use a small tool to push the tang out of the way and the pin will slide out. Then you may be able to squeeze the pin with pliers to make it hold the LED better.

Here is an example. Your connector will be a little different but the concept is the same.

Connector tang.jpg

- Pete
 
Well Pete, this time, I think I repaired it for real ! Thank you again so much for your kindness and your time ! Keep on the good work !
 
Whoa, this forum is so great. After fully renovating my sansui au7900 I got this exact problem. After reading this thread I learned that the big connector to the lamp is loose on the solder side.
This saved me a lot of time. Many thanks and may the vintage gear live forever
 
Hi, exactly how did you fix this? Was it the connector? My amp has exactly the same issue. Thanks.

Hi, so figure - most likely you have the same problem with a loose connector to the power supply/power amp board (where the LED) gets power from. Probably reflowing the solder will fix it.
 
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