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How do you drain stored energy on a yamaha cr2020

Thor1961

Thor1961

Member
I was wondering how I drain the stored energy on my cr2020 receiver so that I can attempt to work on it ? I read that you can discharge the unit by draining the capacitors ? It looks like there's 100's of them on the power board. Isn't there a less time consuming way to drain the stored power so that I don't get blasted while attempting to work on unit ?
 
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Thor1961 said:
I was wondering how I drain the stored energy on my cr2020 receiver so that I can attempt to work on it ? I read that you can discharge the unit by draining the capacitors ? It looks like there's 100's of them on the power board. Isn't there a less time consuming way to drain the stored power so that I don't get blasted while attempting to work on unit ?
Click to expand...


You really only need to drain the Large filter caps in the Power supply. This are usually 15000uf to 22000uf.

I use a 330 ohm 2 watt resister( just cause I had it handy) that I hold with a pair of pliers across the legs of the caps to be discharged. I also clip my Multimeter probes with mini grabbers and monitor the voltage drop till it hits the mV range.

Athanasios
 
Nashou66 said:
I use a 330 ohm 2 watt resister( just cause I had it handy) that I hold with a pair of pliers across the legs of the caps to be discharged.
Click to expand...
Really difficult to do on a CR-2020.. The big caps are buried. Need to find a remote spot topside.
 
Nashou66 said:
You really only need to drain the Large filter caps in the Power supply. This are usually 15000uf to 22000uf.

I use a 330 ohm 2 watt resister( just cause I had it handy) that I hold with a pair of pliers across the legs of the caps to be discharged. I also clip my Multimeter probes with mini grabbers and monitor the voltage drop till it hits the mV range.

Athanasios
Click to expand...

Thank you for the input.. appreciate the help
 
avionic said:
Really difficult to do on a CR-2020.. The big caps are buried. Need to find a remote spot topside.
Click to expand...


Thanks again for the help. The unit is acting crazy... most the day it would run for about 5 min. then shut down. Around 1:51 this afternoon, I turned it back on, it played for 5 hours straight. It again shut down, this time I left it on, changed the station, two minutes later it clicked and played again. Now it's been playing for about 48 minutes straight. It's probably possessed !
 
Thank you.. I was thinking that something wasn't too solid. So far, it's been running for another hour without shutting down... I ordered a small soldering station, so hopefully, I can get it up to specs without smoking my back side with current.
 
Thor1961 said:
without smoking my back side with current.
Click to expand...
There are two bleeder resistors across the two large caps . Two 4.7KΩ 2 watt resistors will bleed down the cap voltage when power is disconnected. You can monitor this voltage by measuring the voltage on the output transistor metal cases (collector) and chassis ground. The output transistors are mounted on the large aluminum heatsinks centered within the receiver.
You only need to monitor one channel.. Each channel shares the same power supply.

One of the outputs on each heatsink will have a negative voltage and the other one will have a positive voltage.

2N3771-NPN-Power-Transistor-Pinout.jpg
 
Last edited:
avionic said:
There are two bleeder resistors across the two large caps . Two 4.7KΩ 2 watt resistors will bleed down the cap voltage when power is disconnected. You can monitor this voltage by measuring the voltage on the output transistor metal cases (collector) and chassis ground. The output transistors are mounted on the large aluminum heatsinks centered within the receiver.

2N3771-NPN-Power-Transistor-Pinout.jpg
Click to expand...

Awesome ! Thank you so much. I was worrying about damaging the unit more than myself incase I grounded out ! You helped me out a ton, thank you.
 
Just put your black meter probe on that heatsink screw head ( chassis ground ) and your red probe on the transistor case.
 
Thor1961 said:
Thanks again for the help. The unit is acting crazy... most the day it would run for about 5 min. then shut down. Around 1:51 this afternoon, I turned it back on, it played for 5 hours straight. It again shut down, this time I left it on, changed the station, two minutes later it clicked and played again. Now it's been playing for about 48 minutes straight. It's probably possessed !
Click to expand...
A known cause of this issue is R801 and R802 as well as FR801 and FR802.. It is also covered in a service bulletin.. These parts run hot and eventually basically unsolder themselves.
 
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