WOPL 700 series II build

[Dnspy007]

Cool, I was holding off continuing on. Since it's nothing major then. Moving on to 2nd row of transistors........

 

[Hexis22]

Hey Joe, It was the left channel UF_B- Fuse. I didn't check them. Dim bulb didn't stay lit. I figured everything was good. I know better now. I replaced the fuse, Fired it up 4 times rechecked each time, everything seems normal. Relays kicking in and 0V at the outputs. B+/B- 94v...What do you think caused it to blow?

Did you remember to reconnect the bus bar to chassis ground termination to the left upper backplane mount stud before placing the control board?

 

[Dnspy007]

OOPS....No Sir, I did not..... It's connected now.

 

[Hexis22]

OOPS....No Sir, I did not..... It's connected now.

That is likely the reason your backplane fuse opened.

That ground wire most likely touched the backplane board at some point blowing the fuse.

 

[mlucitt]

That is likely the reason your backplane fuse opened.

That ground wire most likely touched the backplane board at some point blowing the fuse.

And if a fuse was the only casualty, you are a lucky man.

 

[Dnspy007]

Thanks guys, I got a little excited after wiring up the control board. I guess I need to slow down, double check my moves. I believe I'm back on track now. Everything's going more gooder....

Set the Bias.....Left channel


Right channel

 

[Dnspy007]

Second row transistors in.....
No shorts DC ground or B+/B- rails and transistor cans to chassis
Reattached ground, powered up.... Relays working, proper voltage, no shorts or blown fuses, no smoke or smell
Rechecked the Bias Left 350, Right 348. Everything's looking good.
Thanks for looking

 

[Hexis22]

Disconnect the chassis ground wire at the bus bar so you can verify the TO-3 drivers are not shorting through the sil-pads after installation. Reattach after all outputs installed.

With chassis tied to ground, you end up measuring across the bulk caps preventing a robust measurement of output driver isolation.

 

[Dnspy007]

Disconnect the chassis ground wire at the bus bar so you can verify the TO-3 drivers are not shorting through the sil-pads after installation. Reattach after all outputs installed.

With chassis tied to ground, you end up measuring across the bulk caps preventing a robust measurement of output driver isolation.

Hey Eric, I do disconnect the DC ground when checking for shorts from the B+/B- rails and the transistors to the chassis. I reattach when powering up to check voltages. Am I doing wrong ?

 

[Hexis22]

You are fine.

It was not clear you were disconnecting the chassis ground wire when checking for shorts.

 

[laatsch55]

The "unfused b- fuse"............