The Phase Linear 400 Guinea Pig

[orange]

If you've lost faith in the Spec 2 I will gladly love it and care for it the rest of my life...

 

[laatsch55]

DC on the right speaker posts...+ dc on the right speaker post, Q7 way hot way quick, no short between C,B, E of any outputs to ground, between AC in on bridge rectifier to ground .......point 4 ohms.. can't find a direct path to ground on any board points..

 

[Elite-ist]

I've been following intently, so I hope it's something not too life threatening that caused you to abort the PL power-up, Lee.

Nando.

 

[laatsch55]

Me too Nando. Something simple. Just haven't tracked it down yet.

 

[Gepetto]

DC on the right speaker posts...+ dc on the right speaker post, Q7 way hot way quick, no short between C,B, E of any outputs to ground, between AC in on bridge rectifier to ground .......point 4 ohms.. can't find a direct path to ground on any board points..

You remembered to double check your lead trim on BP boards right Lee?

Were you running on the DBT?

 

[laatsch55]

Yes to both Joe.

 

[Gepetto]

Out of 1 ohmers, so, Joe, I'm gonna put some 2 ohmers in R34,35, any problem with that?

Yeah big problem with putting a 1 ohmer in the R34 position Lee. That is a DO NOT POPULATE location on the Full Comp board!!!!

 

[Gepetto]

Yeah big problem with putting a 1 ohmer in the R34 position Lee. That is a DO NOT POPULATE location on the Full Comp board!!!!

By populating that location, you were asking that poor little Q7 to do the job that the bottom half normally does

 

[laatsch55]

RTFM!!!!

 

[Gepetto]

RTFM!!!!

Yup, but wasn't gonna go there Lee. Make sure you read the Do Not Populate list on the backplane boards too. Double check.

 

[laatsch55]

Pulling R34, makes the bias hotter, and Q7 doesn't test bad, but it's probably toast. Coud not find a bad diode.

 

[Gepetto]

Botte of Memory Pills on their way to Gillette WY...

 

[laatsch55]

Betwee B % E of the outputs above the drivers they are .0015. Both channels. Both ways .

 

[Gepetto]

1. IF AND ONLY IF you are running the PL400 Backplane Board RevA in full complementary mode with PL14_20 RevD Control Board, the changes are as follows:</SPAN></SPAN>
   1. Change list for PL14_20 RevD Control Board:</SPAN></SPAN>
      1. R78L/R and R79L/R are 44.2 ohms, 1/4W, 1%</SPAN></SPAN>
      2. R35L/R are 1 ohm, 1/4W, 1%</SPAN></SPAN>
      3. R34L/R is not populated</SPAN></SPAN>
      4. D13L/R is not populated</SPAN></SPAN>
      5. C18L/R is not populated</SPAN></SPAN>
      6. R62L/R is 1.87K, 1/4W, 1%</SPAN></SPAN>
   2. Change list for back wall transistors:</SPAN></SPAN>
      1. Q11, 13, 15 and 17 are NPN MJ21196</SPAN></SPAN>
      2. Q12, 14, 16 and 18 are PNP MJ21195</SPAN></SPAN>
   3. Change list for PL400 Backplane RevA Board:</SPAN></SPAN>
      1. R6L/R is 1 ohm, 1/4W, 1%</SPAN></SPAN>
      2. R5L/R is NOT POPULATED</SPAN></SPAN>
      3. Comp [C] jumpers (20AWG bus wire formed on 0.5†centers) installed as follows:</SPAN></SPAN>
         1. J14 to J15</SPAN></SPAN></SPAN>
         2. J4 to J5</SPAN></SPAN></SPAN>
         3. J17 to J18</SPAN></SPAN></SPAN>
         4. J1 to J2</SPAN></SPAN></SPAN>
         5. J7 to J8</SPAN></SPAN></SPAN>
         6. J20 to J21</SPAN></SPAN></SPAN>
         7. J10 to J11</SPAN></SPAN></SPAN>
         8. J23 to J24</SPAN></SPAN></SPAN>
      4. Jumpers (20AWG bus wire formed on 0.9†centers) installed in R42 locations instead of 0.22 ohm resistors</SPAN></SPAN>

 

[laatsch55]

Rechecked all that , affirmitive on all that.

 

[Gepetto]

Betwee B % E of the outputs above the drivers they are .0015. Both channels. Both ways .

Which reference designators are reading like that Lee? XQ???

 

[laatsch55]

Yes. Also, when checking the AC sec going ihto the bridge rectifier I'm getting 0 volts referenced to ground. I think I have a bad BR.

 

[Gepetto]

Betwee B % E of the outputs above the drivers they are .0015. Both channels. Both ways .

If you remove the one chassis wire connection provided with this back plane kit, you should be able to quickly confirm that there are no component to chassis shorts anywhere. This is a neat trouble shooting trick.

You should read infinite everywhere. If you don't you have issues.

 

[Gepetto]

Yes. Also, when checking the AC sec going ihto the bridge rectifier I'm getting 0 volts referenced to ground. I think I have a bad BR.

You should be able to open the 2 connect points to the cap screws to prove that Lee.

 

[laatsch55]

The star point ground from the boards.