What is wrong with new S9j's?
The price is far too high.
I know you are not in USA but I can not stress more then if you go s9 of any kind used is better.
200 used with a psu vs 400 new with a psu
pretend you have the power to run 20 of them
so 30 x 200 = 6000 USD
and
20 x 400 = 8000 USD
So from the start you are 2000 USD ahead.
run the 30 units at slow speed you use 30 x 800 = 24000 watts you do about 30 x 9.5 th = 285 th
run the new units at medium speed you use 20 x 1200 = 2400 watts you do about 20 x 13 th = 260 th
so you are 2000 ahead with the old ones
you are 25th ahead with the old ones
you use the same amount of power.
yes the old ones will break faster so one breaks in a month you lose 800 watts and 9.5th
just set two to higher speed they use that missing 800 watts and they add 7th which is a drop to 282.5th
you still using same power and are at 282.5 vs 260
you end up tied in power once 10 used ones break down but I can bet it would take many months for that to happen.
and you are still the original 2000 Usd ahead by buying used gear along with all the months you had more hash power since used starts at 285th and new starts with 260 th.
I just made you about 2 grand Plus maybe 6 months of 12.5th hashpower which is 300 more .
so used 30 used s9s at 200 is about 2300 better then 20 new s9s at 400 after a six month time period.
but you need a broker or a source for the gear.
I am just giving you simple math here.
I mine with a lot of used s9's paid 150 to 250 with psu's included doing it since dec and around 3 or 4 of 24 have worked poorly (still work but poorly).
while 20 or 21 work well.