Thank you, trag, for your response. You may be familiar with the IIci, in which header W1 at (roughly) H7 is marked ROM SELECT. Because there is/never was a ROM SIMM for the IIci, the jumper must be in place permanently to use the soldered-in ROM. There is room to suspect that one of the headers in the IIfx does the converse, by selecting the ROM SIMM, given that there is no onboard ROM. However, that could be entirely spurious reasoning.
The IIfx that I have came in immaculate condition, as if it had been recently cleaned as well as having been carefully maintained during its active life in the mid-90s. It is just conceivable, although none of the jumpers is marked as such, that the ROM-activating jumper was misplaced during/after cleaning. Even the certainty of that, however, would not explain the functions of the other two headers.
This IIfx behaves just as a IIci without its ROM-select jumper does. No PSU activity. No other startup activity of any kind. No voltages appear at the PSU/MLB connector, and especially not a 5V TRKL. Yet the PSU fuses are intact.
de
The IIfx that I have came in immaculate condition, as if it had been recently cleaned as well as having been carefully maintained during its active life in the mid-90s. It is just conceivable, although none of the jumpers is marked as such, that the ROM-activating jumper was misplaced during/after cleaning. Even the certainty of that, however, would not explain the functions of the other two headers.
This IIfx behaves just as a IIci without its ROM-select jumper does. No PSU activity. No other startup activity of any kind. No voltages appear at the PSU/MLB connector, and especially not a 5V TRKL. Yet the PSU fuses are intact.
de