Hi there,
I have this problem with a15mk1...
When I measure tension at the secondary of the power transformer I have 23,7 V (pins 11 - 12)
Then when I measure the bias tension on pin 2 and 3 on the power supply board I have -17,1 V (range is -19V , -24V) (the bias pot is completely open) and If I rotate the bias potentiometer I have -0.4 V. Do you think that there is some mistake or is my tension acceptable?
Other tension (i.e. At the rectifier (+), output of the power supply board, Heater voltage are ok).
Thanks a lot.
Krusty
a15mk1 bias voltage
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Re: a15mk1 bias voltage
I have a problem with the bias too.. I can't have more than 30mV even with the bias pot maxed.. I first suposed that is a ground problem (I'm a newbie on this this) so I have checked, but evything seems to be OK.. any help for us?
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Re: a15mk1 bias voltage
Okay guys so first david, if youre voltage is allright at the biaspot, you should check the voltages around the two 6V6....
So if the voltages on G1 aren´t allright, you should check..
- the voltage before the diode
- the voltage behind the diode
- the voltage behind R62
- the voltage behind the pot...and then we´ll see
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Re: a15mk1 bias voltage
the problem is solved... I found a ground problem in the outputs (output of the OT).. then i've put another ground wire (a new one) and the bias amplitude is correct now..
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Re: a15mk1 bias voltage
i have the excact same problem as krusty
0 - 17 volts on the bias tensionany updates on this problem?
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Re: a15mk1 bias voltage
found the problem, stupid.
measured between pin 1 and pin 2-3 of the bias pot (dont ask why)now i measured from pin 2-3 to the ground
I get between -21,23v and - 27,43v
are this good values ?
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Re: a15mk1 bias voltage
Hi bastin,
this should be appropriate. If you need a lower bias voltage, you can enhance R62 to 3k3.
Regards,
Martin
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