Beiträge von oetzi1977

  • Doubts on the A15Mk2 documentation

    Don't worry: no one is going to answer you... I've asked many times. Martin Adams tell me about "additional instructions", if you ask musikding they don't answer you... So you just have to be faithful...
    funny thing: I've discovered that the topics about it have been deleted...

  • BIAS Voltage on Pin 8 of V5-V6 (A15MK2)

    Hi Martin, I've finished the assembly of the A15MK2 And everything seems to work fine.

    Voltages are "in the window", maybe a little higher but I think it may depends to the voltage in my house... For example: heater voltage is 6.9/7 V Wich I know is a "limit" value, but it's in the 5% tolerance, is it right?

    The main doubt is about the BIAS voltage of the 2 6V6.

    As described in the manual I've set the bias of V5 measuring on pin 8 at 34,5mV, but if I measure the bias on the same pin of the other 6V6 it gives me 14,7mV, is that difference too high? Or is it normal?

    The only problem I Got on the second test with the amp was the volume raising low until it disappear. V5 Turned off and no more voltage on pin8. So I've made again two solders that not convinced me a lot and swap the two 6V6, and re-made the bias regulation.

    The difference is the same: 34,5mV on pin 8 of V5 and 14,7mV on Pin 8 of V6.

    At the moment the amp is turned on from 40 minutes and everything seems ok...

    UPDATE: one of the tube was probably damaged... it's working no more. During a test it stopped working then it turns on again, but now it's gone... I've tried swapping and the "right" one turns on, but the other is gone. It was probably damaged during the shipping, the only shield was a paper box in an envelope with really poor padding... Quite unhappy...