BeePre Resistance Check-Some Are Off

[taffet]

Hi-I am building a BeePre as my first Bottlehead kit.  I am posting all my resistance values here, as some are off, and I dare not plug it in until I am certain it is safe to do so.  Readings with a “*” are fluctuating. Readings with “**” are w 300B in either Socket A or B (other socket empty). I used an AstroAI DT132A Multimeter. I have bolded the readings that I found questionable. I included all the readings in case they provide clues. I have inspected for miswiring and bad joints. I must be missing something(s). I appreciate your help!!!!! Thanks much, Michael

Terminal   Resistance (Ohms)

1      4.2
2      4.4M
3      0
4      4.8**/Unstable
5      0
6      145K
7      468K
8      0
9      0
10      400K and dropping (starts high, drops)
11      145K
12      472K
13      0
14      0
15      900K and dropping (starts high, drops)
16      4.1
17      >4M
18      0
19      5**/Unstable
20      0
21      0
22      >100K
23      0
24      0
25      >225K
26      0
27      0
28      0
29      *
30      *
31      *
32      0
33      0
34      *
35      *
36      *
37      0
38      0
39      0
40      OL
41      0
42      0
43      OL
44      0
45      0
46      >100K
47      NA
48      603
49      0
50      NA
51      607
A1      4.9**/1,054
A2      4.53M
A3      22K   
A4      4.1**/4.2
B1      8.1**/4.2
B2      OL
B3      45K
B4      8.9**/3.9M
C1, D1      NA
C2, D2      217, 215
C3, D3      OL, OL
C4, D4      >4K, >1.6K
C5, D5      >4K, 24K
C6, D6      NA
C7, D7      145K, 145K
C8, D8      NA
C9, D9      145K, 145K

[Paul Birkeland]

What's important about 10 and 15 is to see high resistance there.  You have that.  Your meter is behaving a little differently than the one we used, that's all.

B1 attaches to 16L with a piece of wire.  You can't have 4 ohms at 16, 8 ohms at B1, and a well connected piece of wire.  You could have a loose joint where the 8 ohm resistors connect together, and that could give you a resistance reading that wanders a bit as the loose connection does and doesn't make contact.

[taffet]

Paul-

I re-melted all the joints you mentioned and I now have 4.1 at both 16L and B1. Are my other bolded readings ok? Some are beyond the 10-15% tolerance. The readings at A1 with and without the 300B plugged into B seem strange.  I also re-melted and got B4 down to 4.9 with the 300B plugged in.

Thanks much, Michael

[Paul Birkeland]

A1 and B4 should show the same behavior with your meter.  I would check them again. 

[taffet]

Paul-

I have checked wiring for all nearby connections to A1 and B4 and have re-soldered. At A1 I get 4.8 ohms w 300B in socket (1056 w 300B out). At B4 I get 4.9 ohms w 300B in (3.2M out).  Is this similar behavior? What should I check next please if there are still issues in my resistance readings (other readings I posed previously too?

Thanks much!

[Paul Birkeland]

Are you sure the 1056 isn't 1.056M? 

You can power the amp up like this, it's just weird that your meter reads such a huge difference between two caps that are otherwise the same.

[taffet]

Hi- The 1056 ohms is real-very strange for sure!  I plugged it in and the small tubes glow-not sure if the 300Bs are, Turned it off after noting that the two B side LEDs closest to the front were not glowing. I guess I have to check the wiring to those. Is there a safe way to discharge the caps prior to touching the BeePre? I am guardedly optimistic as I was expecting to blow the fuse. Thanks! Happy Friday!

[Paul Birkeland]

The caps will discharge themselves through the LED strings.

You need to turn the BeePre back on and take voltage measurements.  LEDs that don't glow are rarely the LEDs themselves, but more often you'll find that something else in the circuit isn't working properly.

If you go in and start applying tons of solder to the LEDs themselves, it's likely you'll damage them and make an additional problem that will need its own troubleshooting effort.

[taffet]

Hi Paul-The 300B in the B socket and the two B-side LEDs closest to the front are not glowing. Are the low mV readings that should be O acceptable?  I bolded the readings that are way off.

Thanks much, Michael

Here are the data:
Terminal   Voltage  (V)

1      4.9
2      88
3      0
4      9.9
5      65 mV
6      144
7      0
8      0
9      0
10      190
11      164
12      0
13      0
14      0
15      193
16      0.9
17      163
18      0
19      1.15
20      1.2 mV
21      0
22      217
23      6.5 mV
24      6.5 mV
25      217
26      0
27      0
28      10 mV
29      8
30      8
31      16
32      0
33      0
34      14
35      7
36      7
37      42 mV
38      0
39      0
40      219
41      2.4 mV
42      2.4 mV
43      219
44      0
45      0
46      219
47      NA
48      0
49      0
50      NA
51      0

A2      88.4
A3      0   
B2      163
B3      0

C2, D2      6.2 mV, 1.8 mV
C3, D3      4, 2
C7, D7      144, 163
C9, D9      144, 163

















      

[Paul Birkeland]

Is one of the 10,000uF caps mounted by the 4 pin sockets in backwards?  Can you post a bunch of build photos?

Both sides of your build have issues.  On one side, the 300B is operating correctly but the high voltage regulator is not.  On the other side, nothing is really working properly.

[taffet]

Hi Paul-I believe the 10,000 uF caps are installed with the correct polarities. Please let me know if you need some other views. Thanks so much for your time and essential help! Michael

[taffet]

Two more photos......

[Deke609]

Hey Michael - What soldering iron are you using? What wattage is it?

I ask b/c you have A LOT of cold and flaky solder joints.

Subject to what PB says, I think your fastest route to a working and reliable amp is to pop all the boards off and reheat/resolder every solder joint. It won;t take as long as you think.  Use more heat on everything except the little red LEDs.  And make sure the soldering iron tip contacts both the wire and the terminal/lug at the same time, give it a second or two to heat up and then zap it with some solder - applying the solder to a contact point between wire and terminal/lug (not the soldering iron tip).  For terminals with multiple wires, I usually need to come at the same joint multiple times from different angles to make sure all wires/leads get heated directly.

Although this sounds like it will take forever - you'll be done in an hour or two. Trying to chase the problem a la "Maybe it's this wire, or this terminal, etc." could take days and possibly a lot longer.

Not what you wanted to hear, I'm sure. But I really think this is the simplest solution.

cheers and good luck, derek

[Paul Birkeland]

In the very first picture on the bottom of the PC board you have flipped up, I see multiple joints with no solder at all and no leads trimmed.  I also see a broken white wire between one of the power supply boards and a 9 pin socket.

[taffet]

Paul and Derek-I am using an X-TRONIC 3020 at a temp of about 740F. I will up the temperature a bit and re-solder all joints (except LEDs), including the ones on the bottoms of the boards. This will hopefully improve contact and keep all wires connected to the boards. I will also trim all the leads, including those from the transistors. After all looks good, I will measure voltages again and report back. Thank you both for your patience and time!