voltage measurement problems after output upgrade BeePre 2

[denteom]

I finally finished the upgrade but ran into some problem. I noticed immediately the D tube is dim compared to the C tube. Do I need to plug the D tube deeper and not getting enough contact? (It's a daunting task plugging these small (6CM7), feels like it might break. The 300B glow looks equal.  When I measured the voltages at terminal 45 I get 6.5 vdc.  But terminal 60 voltage went up to 7.8 vdc.  The LED on the output upgrade PCB all lighted up bright and equal intensity.

Also not sure how to measure kREG voltage. Is the black lead still connected to 4u and use the red lead to measure kREG? positive or negative terminal. Or do I remove the black lead at terminal 4U then measure kREG (-) with black terminal and kREG (+) with red terminal?  Not to sure about this.

The voltage at Terminal 46 is 175 vdc while terminal 51 showed 225 vdc.

[Paul Birkeland]

To measure Kreg you use the red probe just like all the rest of the measurements.

I would list the OA, OB, KregA, and KregB voltages on the new boards.  The glow intensity of the 6CM7 can change substantially from tube to tube, so that's not necessarily indicative of a problem.

[denteom]

Thanks, what about the voltage imbalance between the two halves? it's kinda wide difference, need to troubleshoot anything?

[Paul Birkeland]

It would be good to know the IA, IB, OA, OB, KregA, and KregB voltages on that upgrade board before being concerned about the other voltage difference.

[denteom]

Found the problem it is the Kreg B.  But what should I do?

Measuring voltage at
Terminal 45- 6.4 VDC
Terminal 60 - 7.2 VDC
Terminal 46 -  175
Terminal 51- 210 VDC
IA 220 VDC
IB 230 VDC
OA 175 VDC
OB 220 VDC
KregA 8.2 VDC
KregB 200 VDC

[Paul Birkeland]

The KregB tells me that the 431 regulator on that side is deceased.  You also either have a massive miswire on that side of the PC board, or possibly that the resistor on pin 8 on that 6CM7 socket isn't well connected to ground.

[denteom]

Finally I got it right it was just the black solid wire connecting -reg to bB one end went loose
The new measurement are now spot on:
voltage at
Terminal 45- 6.4 VDC
Terminal 60 - 6.4 VDC
Terminal 46 - 175 VDC
Terminal 51- 175 VDC
IA 215 VDC
IB 215 VDC
OA 175 VDC
OB 175 VDC
KregA 8.2 VDC
KregB 8.2 VDC
I'll give it a listen in a while

[denteom]

Having problem with sound.  The volume became very soft and muffled with either using RCA or XLR.  Before I was already okay with the third coarse notch.  There is also an audible crackling sound.  It is the same using a power amp to speakers, or to a headphone amp. I thought my problems are over. How do I trouble shoot this?

[denteom]

The left channel sounds slightly softer.  It sounds like a bad sounding radio.  kinda lost it's life,
.

[Doc B.]

Did your voltages change when you discovered this problem?

[denteom]

I did listening after the voltages were already correct. If you mean to check it again I have not taken it out from the audio chain. I will check it again later after work.  Just the voltage checks found on the output upgrade manual? No need for additional voltage checks?

[Paul Birkeland]

I would still measure OA and OB on the large C4S board installed with the attenuator upgrade.

[denteom]

I got almost the same values
Terminal 45- 6.2
Terminal 60- 6
Terminal 46 175
Terminal 51- 175
IA- 215
IB- 215
OA- 175
OB- 175
KregA- 8.2
KregB- 8

[Paul Birkeland]

Could you check OA and OB on the large C4S board with the heatsinks?

[denteom]

The  from the C4A board (BeeTwo Quiet)
OA 115
OB 115