LEDs not lighting Help Please (solved) New C4S Board

[thdewitt]

OK, so I finally got around to finishing my Bee Pre.  I built pretty much all of the kits.  This one was definitely the most involved.  Everything on the resistance seems to check out fine but the voltages do not.  I am not getting the bottom two LED's to light on the right side CS4.  :'(

I have looked through the instructions and compared to the other side and can't locate the problem.  Any ideas on what I can test to narrow the problem down.

Thanks
Tom

 

[Grainger49]

Post the voltages that are off.  Also post the expected voltage.

 

[thdewitt]

OK, sorry it took so long I have been out for the weekend.  So I am going to just post the voltages that are off since there are so many.

terminal        Correct
10  178.7    186
11  182.5      146
16  0            5
17  181        90-110
22  205        213
25  205        213
29  8.1          6.8
30  8.2          6.8
31  16.3        13.6
34  12.8        13.6
40  209          213
b2  181          90-110
d3  1.9          3.5-4.5
d7  182        147
d9  180        147

Any help would be appreciated.  There is something wrong with the power supply on the right side just can't seem to see it.

Thanks,
Tom

 

[Paul Birkeland]

The 300B on that side isn't drawing any filament current, as can be seen by having 0V on terminal 16.  If you have 10V or so at POS OUT on that side, then you should have 10V going into the 300B, passing through the 300B filament, then traveling through the paralleled 8 Ohm resistors.

This could be an issue of an improperly oriented 4 pin socket, or no voltage at POS out.  (Go ahead and measure it)

-PB

 

[thdewitt]

I am getting zero at the positive out.

Tom

 

[Paul Birkeland]

How about at positive in?

 

[thdewitt]

OK, I found a broken wire on the positive in.  I replaced that as somehow it had a cut.  Anyway.  The voltages have changed but still no light on the diodes.  Here are the voltages out of whack now.

Terminal    Reading  Correct
10          173          186
15            175          186
17            127          90-100
22            201          213
25            202          213
40            202          213
43            202          213
46            202          213
b2            132          90-110
d3            7.0          3.5-4.5

 

[Paul Birkeland]

What voltage do you have at POS OUT now?  It looks like that 300B still isn't conducting all the way.

-PB

 

[thdewitt]

9.79 Volts.

 

[Paul Birkeland]

Alright, that's spot on.  Can I get the IA, OA, and OB voltages on the offending channel?

 

[thdewitt]

IA 174.7
OA 130.4
OB 121.8

Thanks so much Tom

 

[Paul Birkeland]

Can you switch both the EL84 and the 300B between channels (do them both at once).

Your 300B isn't drawing current, and the shunt regulator is also not regulating properly. 

 

[thdewitt]

Pretty much stayed the same

IA 174
OA 127.1
OB 121.8


Tom

 

[thdewitt]

I wrote the OB wrong.  IT was 119.5

 

[Paul Birkeland]

The next thing I would do is to recheck the IA, OA, and OB voltages with no EL84 plugged into that channel.

-PB

 

[thdewitt]

OK, here are the readings without the EL84 plugged in.
IA 180, OA 127, OB 120.  So they really did not change.  Is that strange?  What does that mean?  What does the EL84 do?

Thanks,
Tom

 

[Paul Birkeland]

Can you confirm that the R1 resistors are the correct values?


Unplugging the EL84 removes the high voltage regulator from functioning in the circuit, which just leaves us with a couple of C4S's and the 300B.  For whatever reason, your 300B on that side is not drawing proper plate current, and I believe we have it narrowed down to an issue on that C4S board.

-PB

 

[thdewitt]

They seem to be fine.  Should i take them out to measure.  The numbers are good and I usually measure when installing them.

 

[Paul Birkeland]

I'd have a long look at the jumper and solder joints on the bottom side of the board, as well as around the 4 pin socket.  You may also want to be sure that pin 3 of that 4 pin socket shows 0V when the BeePre is on.

-PB

 

[thdewitt]

OK, now I am really frustrated.  I took the CS4.  Put in new jumpers following the directions in the manual.  While it was out, I carefully inspected the manual pages and the 4 pin to make sure it is right.  I did notice that the wires on pin A1 and B4 are the only ones that are not symmetrical but that is the same as the manual.  I reflowed all the joints on the 4 pin and surrounding connections.  I reflowed the CS4 again.  I then put it back together and there was no change.  The LED's are still not lighting.  I am stuck.  Are there any readings I can take to further check the board to find if one of the components are faulty.

Tom