qqiao

For eha5, you may refer to this thread on erji.net, http://bbs.erji.net/forum.php?mod=viewthread&tid=2300120&extra=page%3D1

Hi Kevin and Justin, Thank you very much for the invaluable information. The power supply is made by myself and 62k is just from my inventory. With current setup, there is no noise from output, and Justin is correct, I tried some NOS tubes and the best one is JJ. With respect to adjustment, I think I need more study to do it.

@spritzer Hi Spritzer, Do you know the 12ax7 plate voltage and ecl86 grid bias voltage? Mine is 230v/-12v, not sure whether this is correct. Thank you.

Almost found the reason, the dc gnd and ac gnd doesn't have a connection, I put a 62k resistor and 0.1uf cap between them, almost no noise now. The pot case connects to dc gnd, I found it's better than ac gnd. Thank you guys.

Very straightforward, I will follow the suggestion and do some tracing, thank you.

I did more testings and keep current setting, there are two gnd on aristaeus, one connects to inlet gnd and chassis connects to this gnd, one connects to power pcb ground. By default, pot connects to inlet gnd, but the noise level is very high, left/right noise is not same, right is lowered than left(1.8v/3.4v), I assume the power gnd is not that clean. I tried to adding a resistor(64k) between chassis to inlet gnd, the noise lowered, but it's not enough, still buzzing noise from my l300. The second try is that disconnect chassis from inlet gnd and connects pot to pcb gnd. This time, left side is perfect, no noise at all, but right has higher noise level, I can hear small noise when pot turning up, but when it goes to a specific level and won't increase more with pot. But when I touch chassis, the noise level increases on right, left is good. How can I do further debugging? Thank you.

I tried different ground connections, it looks like right channel connects to power gnd and left doesn’t. So I removed power ground from amp chassis and connects pot to circuit ground, the ac level lowered about 2v and bg noise level is decreased accordingly. But when I touch the amp chassis, the noise level will be increased. Now I always set the volume to maximum, there is no noise at max, I don’t know the reason.

I have a 2nd hand headamp aristaeus, the background noise follows the volume pot. I measured ac between L+/L- and R+/R-, the left is 3.48v when volume pot is turn to max while right is 1.74v, I swapped ecl84 and 12ax7 but still same value. Also I tried to adjusted vr p1, p2+,p3- but it didn't help, same value. May I ask how can I solve the issue? Thank you in advance.

@spritzer Hi spritzer, one of my dac module is broken, it looks like transistor q2 is broken. I measured b-c which is shorted. But I don't understand the purpose of this pnp transistor, b-c-e are connected and I don't see any resistor around it. Could you give me some hints? Thank you.

understand, thanks very much for the explanation.

https://i.imgur.com/Dz9hxo6.png I found the schematic fo 007, the bias circuit should be similar as t1, actually I don't fully understand how it can get 580v voltage, the output from the transformer only provides 270v, it looks like a half wave rectifier circuit.

Hi Jamesmking, Thank you very much for the details. The t1w has an adjust resistor for one pro bias port, so it can give 3 different bias voltage, a very versatile amplifier.

Hi stax experts, I measured my t1w bias voltage, the pro bias port is 420v and normal bias is about 150v, is this normal or something needs to be replaced? Thank you.

I would like to ask a junior question for power supply, what's the purpose of d2(24v zener) and may I replace ccs and two resistors(1200,100) with a 47k resistor? Thanks.

Thank you for the help.