HELP! - MPC4000 and TB303 connected via TR-707

I have MPC4000 and TB303 connected via TR-707. This is to sync TB-303 and MPC (MIDI and DINSYNC, TR-707 works as tempo master...) Well, it does kind of work and can sync these two if I turn on my MPC4000's SYNC IN ACTIVE and adjust to the external tempo. But the problem occurs in the MPC's sequence a bit. This set up is changing the sound level or something on MPC4000's sequence somehow. Why is this happening? Anyone can tell me the solution? Or is there any better way to sync these 2 machines perfectly? (Without paying 500 bucks for another converter.) Please help!!!

first off when you press start on 707 the 3030 will start correct?
but when you start the MPC does it also start the chain of events thus turning on the 303??
If so then your lucky actually..
Your problem lies in the fact that very few drum machines and sequencer emit a 1 volt per octave pulse which the 3030 needs to sync with
You need a Korg KMS 30 or a Kenton box or a logic micro sync 24 box
Then you hook sync out to the sync in on 3030 and the midi OUT from MPC to Midi in on the sync device
Im quite sure a 707 will only work if it CONTROLS everything
you want the MPC to be master NOT 707
good luck