So here’s a fun one (AD-100 clone woes)

[Mr_bibbles]

The amp's designer is still in touch with the owner- He texted the guy recently saying that he thinks the PT is under-rated for the amperage supply, specifically what's consumed by the (8!) KT88's. He proposed a possibly installation of a filament transformer.

The voltage from each secondary is 3.15 according to the spec sheet, so combined should provide each tube with 6.3VAC, yes? Measuring at the 'start' and 'end' of our supply chain proves the voltage is sufficient.

But how do we determine if the KT88's current draw is acceptable for the Transformer without an idea of supplied AC current? Is this a silly question to begin with?

[g1]

2 ways that can show if the xfrmr is under-rated for the heater current.
#1, voltage drops below tolerance (your testing shows this is not an issue, unless longer time period required)
#2, transformer overheats.

[Helmholtz]

[QUOTE=Mr_bibbles;n909403]The amp's designer is still in touch with the owner- He texted the guy recently saying that he thinks the PT is under-rated for the amperage supply, specifically what's consumed by the (8!) KT88's. He proposed a possibly installation of a filament transformer.
[QUOTE]

If the amp builder sold the amp with an underrated PT, he is liable and should offer to replace the PT at his cost.
An underrated PT is a potential safety (fire) hazard.

You might want to contact Heyboer and ask them if the PT is suitable for the amp in question. Also ask what mains fuse they recommend.

But a weak PT will not damage tubes.