Kaiju Failing Driver Testing [resolved]

[Roamconstant]

The A Board measures as follows:
IA= 512 VDC (fine)
OA= 298.7 VDC (fine)
Terminal 32U = 4.15 VDC- 8.99 VDC (depending adjustment of potentiometer).  (VERY LOW READING)

The D Board Measures as follows:
IA= 510 VDC (fine)
OA= 355.4 VDC (VERY HIGH READING)
Terminal 46U= 175.2 VDC (adjusted w/ potentiometer correctly).

One discrepancy I note from the instructions vs the parts list is the 0.1uf 630v metallized capacitors.  The parts list included 4 of these.
The manual calls for 0.1uf 400v film capacitors to be used on page 59, but these weren't included in the kit.  I used the 630v capacitors on the board instead, assuming this was the intent.

Anyone's eyes see my error here? 

 

[Roamconstant]

Images

 

[Roamconstant]

more images

 

[Roamconstant]

Update: the low reading on 32 seems to be a bad connection.  Tilting the board corrects that problem.  I’ll find the weak spot there. 

However the oa reading of 354v is perplexing me.

 

[Paul Joppa]

The 350v at OA is the Zener diode string, protecting the C4S from excessive voltages.

(The MJE5731A is rated 375v maximum. The Zener string has no other function, and is out of the circuit in normal operation.)

 

[Roamconstant]

Paul,

Thank you for the reply.

I've got the left side driver worked out.  Bits of wire from A2 to A3 were touching and causing the 32A reading to be low.  I clipped the overlap and can adjust the potentiometer to read 175 volts.  Whew!

Back to the 350v at OA:  The manual specifies 300VDC as the desired figure.  Do I have more troubleshooting to do, or should I move on and accept 350VDC @ 0A on the D board?  The A board does read 300VDC.

Regards,
Frank

 

[Paul Birkeland]

OA needs to be far closer to 300V.  What's the Kreg voltage on the B side of that board?

 

[Roamconstant]

On the b side of the d board, the Kreg voltage is 12.67vdc. 

On the b side of the a board (which measures correctly), voltage is 7.2vdc.

 

[Paul Birkeland]

12V on that Kreg and 350V on OA/IB means the regulator half of the 5670 isn't being allowed to draw any current.  This kind of thing happens from miswires with jumpers on the PC board, connecting the PC board improperly in terms of where the wires go into the circuit, or possibly the resistor that goes from either pin 7 or pin 2 on the 9 pin socket to the ground on the center of the 5 pin terminal strip with all the black zener diodes mounted to it.  Also if the R1 resistors are swapped on the PC board you could end up with this problem and everything else could be perfect.

If all else fails, you can post a bunch of pictures here and we might be able to point you in the right direction. 

 

[Roamconstant]

I think I've spotted the error. 

The 330kohm 3W resistor (R2 a side) is swapped with the 147kohm 1/2W resistor (R2 b side).  It appears I have cooked the 147kohm resistor-- I'm glad the thing didn't do worse!

Of course I'll use a new resistor instead of this damaged one, but anything else down chain I should remove as well?  I guess we'll find out.

https://www.mouser.com/ProductDetail/Vishay-Dale/CCF55147KFKE36?qs=rMX6kfwPG0oYC92HGmoCtA%3D%3D
Should I get this one on the way-- or is there a better source for a matching part? 

Thanks for the attention Paul.

 

[Paul Birkeland]

Yeah, that would do it.  If the resistor still reads 147K, you can keep using it.  The part number I would recommend using is MF1/2CC1473F.  The CCF will work fine but look quite a bit different.

 

[Roamconstant]

The 1/2 watt resistor measures 149kohm resistance while still soldered onto the board.
Close enough to assume it will still work?

 

[Paul Birkeland]

Yes, you could swap them and likely everything will pop into alignment.

 

[Roamconstant]

Sure enough!  I’m so happy everything’s reading correctly.  Thank you.