Assistance regarding troubleshooting a new BeePre build [resolved]

[Audionorth]

Despite my best efforts I need some assistance with my Beepre with BeeQuiet build (assembled at the same time).  . . . thanks in advance for the support!

Resistances were good.  A few voltages are faulty. I included the correct voltage in parentheses only for questionable voltages, the rest are assumed correct. If there is a better way to present needed information I'm clearly open to providing it. . . my amp doesn't sound that great sitting up side down on my work bench . . .;-/

Terminal
1  5v
2  .15vdc (should be 90-110v)
3  0v
4  9.8vdc
5  0v
6  145vdc
7  0v
8  0v
9  0v
10 186vdc (Should be 188v)
11 158vdc (should be 146v)
12 0v
13 0v
14 0v
15 170vdc (should be 186v)
16 4.9vdc
17 93vdc
18 0v
19 9.9vdc
20 0v
21 0v
22 213vdc
23 0v
24 0v
25 213vdc
26 0v
27 0v
28 0v
29 6.8vdc
30 6.8vdc
31 13.6vdc
32 0v
33 0v
34 13.6vdc
35 6.8vdc
36 6.8vdc
37 0v
38 0v
39 0v
40 206vdc (should be 213v)
41 0v
42 0v
43 205vdc (should be 213v)
44 0v
45 0v
46 205vdc (should be 213v)
47 n/a
48 0v
49 0v
50 n/a
51 0v
A1 - A4; B1-B4 voltages all good

C3 5.3vdc (should be 3.5v-4.5v)
D3 1.9vdc (should be 3.5v-4.5v)
C9 145vdc (should be 147v)
D9 156vdc (should be 147v)

"A" side amp
A leds both on
B leds both off

"B" side amp
A leds both off
B leds both on

Best regards,
Mike
(Anchorage, Alaska)

 

[Paul Birkeland]

Despite my best efforts I need some assistance with my Beepre with BeeQuiet build (assembled at the same time).

It is fairly frequent that you will end up needing to pull the upgrades to get the stock kit working first.  We aren't necessarily there yet, but it's something to keep in mind.

2  .15vdc (should be 90-110v)
A1 - A4; B1-B4 voltages all good

Your A2 voltage can't be good.  A2 wires to terminal 2, and you have no DC voltage at terminal 2.

C3 5.3vdc (should be 3.5v-4.5v)
D3 1.9vdc (should be 3.5v-4.5v)
C9 145vdc (should be 147v)
D9 156vdc (should be 147v)

"A" side amp
A leds both on
B leds both off

"B" side amp
A leds both off
B leds both on

Pictures of this build will be very helpful.  There have to be multiple errors to get all of the deviant voltages that you have.  Some common problems that create these issues, ranked by how often they pop up:

1.  Jumper wires on the high current C4S boards between OA and IB not installed between OA and IB.
2.  MJE5731A transistors not adequately soldered to the PC board.  You should heat them until the solder flows to the opposite side of the board.  You will not damage these transistors from excessive heat.
3.  R1 resistors on the C4S boards not in the correct places.
4.  TL431 regulators mixed up with PN2907 transistors.
5.  TL431 regulators installed backwards.

Your low voltage supplies are working, and your 300B tubes and their sockets are properly mounted, as is shown by the voltages you have, so that is helpful to know. 

 

[Audionorth]

Thanks for your response.

I realized part of the issue with A2 and Terminal 2 is the problem is intermittent. . .  I fired it up after reading your response and all 4 leds lit up (Side A) and the voltage was 96v at Term 2.  Turned it off and then back on awhile later and back to .015v. . . not good 

Attached are a few pics of the build.  I counted up and realized this is my 13th audio kit build (numerous AN kits, BH SEX used as a headphone amp, Audio Creative DDDAC, WAD monoblocks, Transcendent tube analyzer and OTL amp, AKSA solid state amp, others) plus 2 Nixie clocks.  Clearly I don't really know shinola or I wouldn't need the help but I'm not exactly a newbie either.  At least I thought I knew how to solder . . . I guess I mention this because I thought with how much attention to detail has gone into the build documentation with BH projects and previous project experience it would be a breeze. . . what could go wrong?  :

I didn't realize that building the Beepre and the BeeQuiet at the same time was pushing the envelope . . .

Before my original post I disconnected both regulators and C4S boards and re-soldered every connection.  I also re-soldered the transformer connections/diodes, terminal strips, etc with the regulators removed and the same with the 300B sockets and connections with the C4S removed. 

The obvious changes I made were fitting the caps that are the same specs but bigger physical size (K75-10B  10uf 250v connected to terminal 2, 7 and 12, 17; and the AN 10,000uf 16v connected to terminal 4, 5 and 19, 20); finally using Shinkoh resistors for the BeeQuiet . . . 

The jumper wires on the high current C4S boards between OA and IB were checked
MJE5731A transistors look adequately soldered to the PC board
I measured the R1 resistors on the C4S boards for accuracy
The TL431 regulators are in their correct locations and installed correctly
The PN2907 transistors are in the correct locations

Regards,

 

[Doc B]

Check for a wire that has broken just inside the insulation. Sometimes the wire stripper will nick the wire and it will fracture just inside the jacket where you can't see it.

 

[Paul Birkeland]

It's hard to see much in those photos, the resolution is really low. 

An intermittent voltage issue like you're describing does sound a lot like a loose or broken wire.

-PB

 

[Audionorth]

Thanks Dan and Paul,

Unfortunately 3 hours of sleuthing tonight only resulted in an increasing sense of incompetence . . . experience tells me persistence will pay off . . .

Regarding the resolution of the pics - lesson learned.

Regarding a wire broken inside the insulation - I didn't find any (which of course doesn't mean it's not present).  I used a slightly more robust wire for that reason in a few parts of the build having experienced this before . . .

Terminal 2 continues to fluctuate between about 75v to 95v over time with the unit powered on continuously.  Term 17 steady at 94v. 

C3 6.4vdc  D3  1.9vdc

I'm not sure why I'm reaping bad karma for previous transgressions now but I suppose some things cant be known. . .

Trying to get good pics is a bit challenging but hopefully these are better. . .

Thanks in advance for the support!

 

[Paul Birkeland]

Terminal 2 continues to fluctuate between about 75v to 95v over time with the unit powered on continuously.  Term 17 steady at 94v. 

This is a far cry from the 0V that you reported initially...

C3 6.4vdc  D3  1.9vdc

Swap EL84 tubes between sides.  I suspect this won't make a difference.  When I see 1.9V at Kreg, that makes me suspect a saturated regulator (300B not drawing any plate current) or a dead TL431.

 

[kgoss]

Nice work on the build!  Paul will help you resolve your problems.
Just a note in the third picture (PS board) it looks like POS OUT could use some more solder and NEG OUT looks like it might need to be re-flowed.

 

[Doc B]

My general sense is that you could maybe use a bit more solder and a bit more heat on quite a few joints. I see what look like joints where maybe the solder flowed well onto the pad but not that well onto the wire that is through the pad.

 

[Audionorth]

Paul,
As you expected the 6BQ5 tube swap didn't change anything. . . 

Side B reg: Is the 1.9v measured on the "K" leg of the TL431 (and associated Kreg) a symptom or the problem? (Do I need to change out the shunt reg on that side?)

"saturated regulator". . .?

T2 still vacillates (with associated flickering leds on the "B" side of the A side C4S.)  . . . it seems to stay at the correct voltage the longer the amp is on. I realize the flickering leds is a symptom.  Any thoughts on whether this is likely coming from the C4S board or a connection to it?

Dan,
I re-soldered all the terminal connections and also where wires connect to the PC boards. I turned up the iron a bit and was more generous with the solder. . . 

Ken,
Thanks for the feedback.  I re-soldered POS and NEG Out.

Regards,
M-

 

[Paul Birkeland]

The flickering and vacillating voltage at T2 needs to be remedied before you worry about the 431 regulator.    Flickering is always something loose, and the only cause you wouldn't have control over would be a weird 300B, which you can check by swapping them between channels.

 

[Audionorth]

Hi PB,

The 300Bs have been swapped with no change. . . 

The TL431 issue is on the "A" side of the amp (Left channel) and the flickering leds on the "B" side of the amp (Right channel) so I assumed they are two independent problems???

 

[Paul Birkeland]

Hopefully independent, yes, but digging around to find the cause of the flickering may lead you to firm up other connections in the BeePre, which seems like a prudent course of action prior to replacing the 431 regulator.

 

[Audionorth]

After repeatedly re-soldering connections didn't solve my build issues I started over. . . I had the needed terminal strips and a few other parts on hand so I removed all the power supply parts including the 9 pin sockets.  I re-soldered the wires on the C4S boards, inspected and re-soldered all the PCB regulator components, and replaced the TL431 regulator on the "B" side of the amp. . .

A side checks out.

B side of amp:
term 11  157v (should be 146v)
term 15  170v (should be 186v)
term 40  205v (should be 213v)
term 43  205v (should be 213v)
term 46  205v (should be 213v)
D3 1.9v
D9 156v
"B" side of amp:  "A" side diodes not lit

Thanks for any thoughts to help me resolve this. . .
Mike

 

[Paul Birkeland]

Your EL84 is attempting to suck down all the available B+ current, while your 300B draws none.  What's your OB voltage?

147V on the plate and 1.9V on the cathode of an EL84 triode strapped means about 60mA of current is being sucked down by the EL84 (implying that the 300B isn't drawing any current at all).

If your POS OUT on the B side is approximately correct (9.5-10V DC), and the grid is grounded (pin 3 on that 4 pin socket shows 0V DC during operation), then the only thing you have left is a C4S board that is not passing adequate current on the B side, or that is miswired. 

 

[Audionorth]

The POS out is correct and Pin 3 shows 0v so the C4S must be the problem. . .

Any thoughts on what is likely the culprit . . . I re-soldered all the connections and the wires on the bottom board of C4S.  It is wired correctly . . . replace various parts?

Thanks!
M-

 

[Paul Birkeland]

You can swap the C4S boards side to side to be 100% sure.

The issues I see with C4S board usually revolve around poor soldering on the MJE5731A.  Miswired jumpers are a close second.

 

[Audionorth]

Thanks for your patience. . .

I switched the C4S boards and the fault followed the board. Good news . . .

Bad news . . . I replaced the PN2907 transistor and then an MJE5731A "OA/IA end" (because I didn't know what else to try). . . neither corrected the problem. 

The jumpers are correct and solidly soldered so what ever the fault is it's obscure (at least to me) . . .

Regards,
M-

 

[Paul Birkeland]

You could inquire about ordering up a replacement board from replacementparts(at)bottlehead(dot)com. 

 

[jjvornov]

Just to second Paul's suggestion, I had a BeePre problem child. It had intermittent problems, I destroyed one of the boards trying to resolder, it went in for repair then started up again.

I finally replaced the flaky board (and one of the 300b sockets which was loose in one of the contacts) and now I have a perfectly functioning BeePre. Definite was worth just starting over with the bad board.