So the Line6 Spider HD100 Bognor tube head issue appears to be well documented online & is therefore a common fault. The amps front end is all digital DSP & as the issue resides on the main DSP board explains why no signal reaches the tube power section. Checked all test point voltages post dual rail 12v power supply, 5vdc & 3v3 are present, so is the 10v fb voltage stated on the drawings.
This board was superceded by a mkii version, not backwards compatible, probably due to the addition of extra amp models not included on the panel facia & altered effects algorithms too.
Line6 website forum hints at reflow work as a solution suggesting faulty amps are returned for this process.
Think we will just dig a little deeper 🤔
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