OK..to correct a few things:
1. The ZIPP modules are fast memory, not chip. They are inserted in sets, and thereofre if you fill the boad with an incomplete set, you will receive an error. There are jumpers on the logic board that determind what kind of ZIPP modules you are using. These have to be set correctly as well. If even one pin on on ZIPP is not fully inserted, the system may fail to boot, or may act flakey.
2. Yellow is an error reported by the processor, not an error for the lack of. Generally I have found this to be a misconfiguration of either the ZIPP memory expansion on A3000 systems, or a misconfiguration of the processor jumpers. There are jumpers for the board clock, the system speed, the fpu ststus, and the cpu ststus that need to be set appropriately. If even one of these is off, the system may malfunction with a yellow or grey screen.
I really can't say much more without seeign the board. If you want to send it in we can diagnose it and repair it for you, but as it stands, withotu examining it personally, I really can't offer you much help. I suggest that you remove the ZIPPs, insert one complete set (make sure you skip the sockets so that you have one in, the skip three, one in, skip three, etc.)..make sure the jumpers are set for the right type of ZIPP too...
When inserting them, they should make a harsh feeling (metal on metal), not a mushy feeling. If they feel mushy, then there is a bent or misalligned pin.
If that fails, make sure that your jumpers are set correctly. (These are for using the internal 030 processor.)
J100, Quadrature Clock Phasing "QUAD CLK": Pins 1 and 2(INT).
J102, System Clock Source "BRD CLK": Pins 2 and 3 (INT)
J103, FPU CS/BERR "FPU ON/OFF/BRR": Pins 2 and 3(ON)
J104, CPU Clock Source "CPU CLK": Pins 1 and 2(INT)
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For the 040, use this configuration:
J100, Quadrature Clock Phasing "QUAD CLK": Pins 3 and 4(EXT).
J102, System Clock Source "BRD CLK": Pins 2 and 3 (INT)
J103, FPU CS/BERR "FPU ON/OFF/BRR": Pins 1 and 2(OFF)
J104, CPU Clock Source "CPU CLK": Pins 2 and 3(EXT)
Ram jumpers are J851 and J852:
J851, RAM Speed, "RAM SPD": Pins 2 and 3
J852, RAM Type, "RAM TYPE/4M 1M": Pins 2 and 3.
Please also note your DMAC version, and your RAMSEY version. If yoru DMAC is an -02 rev, an 040 card may not work well (or at all) if you persue that route. If you have a DMAC-04, you are a lucky b@stard.

Hope this helps.
Cheers,
//R//