A15Mk2, working but out of spec voltages

    Just finished building and testing the A15Mk2, everything appears to be working, It sounds pretty normal, but several of my voltage measurements were over 20% out of spec.

    This only seems to be some of the lower voltage lines that are incorrect, 17v measuring at 20v 16v measuring at 19.4 and some of the tube voltages from 2.8, 3, and 1.2 up to 3.4, 3.6 and 1.5 respectively, they only seem slightly out, but its over double the difference as stated in the manual as being in spec. This is only my second amp build so I am being super careful.

    Everything else seems to function correctly. Mains voltage is measuring at 245v, I am getting 255v AC at the input to the bridge rectifier and 7.28v on the heater circuit. Will any of these cause any issues?

    Hi and welcome to the forum. If the amp is working fine you shouldn't bother too much about the voltages with two exceptions:
    1) With a plate voltage of about 280V, the cathode voltage of V5 & V6 should be 35mV (which means about 10W when idle) to set the operating point of the power tubes correctly.
    2) Heater voltage shouldn't be way above 7V, a heater voltage >7V is out of specification of most tubes (6,3V +10%/-5%) and might reduce lifetime of your tubes.
    Is your mains voltage always >240V or maybe only at some time of the day? Upto 240V all voltages should be OK ;)
    Regards,
    Martin

Jetzt mitmachen!

Sie haben noch kein Benutzerkonto auf unserer Seite? Registrieren Sie sich kostenlos und nehmen Sie an unserer Community teil!

Benutzerkonto erstellen Anmelden