Phase Linear 400 issue help!

[enoyes12]

Are they the half moon shaped ones toward the bottom of the case?

 

[enoyes12]

See thats the problem I couldnt see them thru all the mold. What should the meter be set to?

 

[Gepetto]

See thats the problem I couldnt see them thru all the mold. What should the meter be set to?

Your meter should have a diode scale on it. The diode symbol will be printed on the meter case.

 

[Gepetto]

View attachment 12163

Bumping this photo to the top...

 

[Gepetto]

Bumping this photo to the top...

See the Red/Black/Brown wires on the back of the board? Those are your measure points.

Positive lead to the black wire and then the negative wire successively to the red and brown wire. What do you get? Tell us.

 

[enoyes12]

which probe goes where?

 

[enoyes12]

ok left side red wire 670, brown wire 670, right side red wire 578 brown wire 520

 

[Gepetto]

which probe goes where?

Red meter lead to black wire. Leave it there. Then put your black meter lead on the red wire, take a reading. Then move your black meter lead to the brown wire, take a reading.

Next put your black meter lead on the black wire. Leave it there. Then put your red meter lead on the red wire, take a reading. Then move your red meter lead to the brown wire, take a reading.

Tell us what you get.

 

[Gepetto]

ok right side red wire 670, brown wire 670 left side red wire 578 brown wire 520

Those look like good transistors...

 

[enoyes12]

Thank god you guys know how to do this and can communicate this so I can understand. Good thing is once I understand how I rarely forget.

 

[Gepetto]

Thank god you guys know how to do this and can communicate this so I can understand. Good thing is once I understand how I rarely forget.

That is because we stayed at a Holiday Inn Express last night ...

 

[enoyes12]

Now that was funny and just thought it was cause you were smart

 

[enoyes12]

What else would cause the bias to not adjust?

 

[NavLinear]

Nav, you need to do this more often, very methodical of you. I have a tendency to bounce around a bit which probably confuses the less knowledgeable (like me).. Very consise directions too. Nice Dennis...

Less knowledgeable? You've felt these girls out for quite some time and have an ass ton of knowledge with these honeys. I bow down to your inputs Lee. I'm just anal and have been around the electronic field for a few years.

 

[laatsch55]

Nav, if I knew ANYTHING I'd know what that new diode is for on Joe's new backplane board...

 

[laatsch55]

What else would cause the bias to not adjust?

Big E, all you've done with the diode test is prove that the transistor is not shorted out, whether it has gain or not is an entirely different question. To do a down and dirty test, buy some 2N5088's----a 10 cent transistor, desolder the red, black, and brown leads from the back of the boards, check to see you have no solder blobs connecting things they shouldn't. Print out the data sheet for the 2N3403 and the 2n5088. Solder the 2N5088 directly to the back of the board, then try adjusting bias. DO NOT PLAY THE AMP LIKE THAT, we're just checking the bias trannies. Without a heatsink and bolted to the backwall the 2N5088 will not track heatsink temp as it's supposed to. Where the red wire was is the COLLECTOR connection, where the BLACK wire was is the BASE connection, where the brown wire was is the EMITTER connection. If this does not solve the bias problem, the we have other stuff to check (duh, that was brilliant eh).. Let us know how that test works out...

Big E, transistors have to have gain to operate, if you know someone with an hfe meter or curve tracer, have it tested, otherwise Do the change out.

 

[laatsch55]

Now that was funny and just thought it was cause you were smart

He's both...

 

[enoyes12]

The place by me only carries NTE brand. Is there an equivalent or what are the parameters of the 2n5088's I can pick some up tonight. If I can adjust the bias with the 2n5088's What does that mean?

 

[laatsch55]

The 2N3403's are bad.

 

[laatsch55]

The place by me only carries NTE brand. Is there an equivalent or what are the parameters of the 2n5088's I can pick some up tonight. If I can adjust the bias with the 2n5088's What does that mean?

NTE's are ok for test purposes ut don't run ANY NTE for any lenght of time, very poor stuff. Have them crossreference the 5088's and have them give you a pinout.