I have a Sigma SG-50B and my machine will not allow the Dollar Bill Validator to accept any paper if the credits are over 100. Must be 99 or less. That is per the manual. The only way I see to get a lot of credits is to put a big bill in. My machine is set up ( I haven't figured out why, yet!) to give 20 credits per $1. With a $.25 machine, that's like putting in $5. I only have 1 $5 and a whole lot of singles. I put $1, $1, $1, $1. That gets me to 80 credits, then I add my$5 and it adds another 100, so now it's at 180 credits. What DBV system are you using? I have a list of heads and different versions of the programs on the Eproms. I just checked the Manual and did not see any reference to changing the DBV credit limit. I am looking for some old $20's or $50's. That way I can add a lot of credits and not have to keep dropping quarters into it...