Daewoo/Solar 450-III boom hydraulic issue

[baexcavating]

I have an issue on my 450 Daewoo, for some reason that I can't find, the book will hydraulically lock when trying to go down. Sometimes you can get it to work by moving the stick, but other times you have to take what appears to be a check valve out to get it to drop.
Hope someone has some info for me on this. Thanks

 

[uffex]

Good day ba
The check valve is normally opened by the same line that operates the main valve, if the main valve is functioning correctly the issue must be at the check valve release mechanism.
Kind regards
Uffex

 

[baexcavating]

Good day ba
The check valve is normally opened by the same line that operates the main valve, if the main valve is functioning correctly the issue must be at the check valve release mechanism.
Kind regards
Uffex

I swapped the check valve (assuming that's what it is) from the raise side into it and problem remains the same...

 

[uffex]

Good day again
Please see attached it may help, if you need more detail email me a picture of the valve and valve chest.
KR
Uffex

 

[baexcavating]

Good day again
Please see attached it may help, if you need more detail email me a picture of the valve and valve chest.
KR
Uffex

For some reason I can't open the file you sent.

 

[uffex]

Good day Ba
We have tried with differing PC's it opens OK but you need a PDF reader, these are free you can download from the web
KR
Uffex

 

[baexcavating]

I temporarily resolved the issue by removing the check valve on the boom lowering circuit. Not the right way to fix it, but works fine til I can pull it all apart and figure it out this winter

 

[uffex]

Good day Ba
Please post me a snap of the main valve chest and the main lines that connect the boom cylinders.
KR
Uffex