Ken Nelson's Phase Linear 3300 ser II Pre-amp

[laatsch55]

R3 gets very hot. Can a ceramic short??

 

[Gepetto]

Let me pull up the schematic and see if I can see anything you might check out Lee.

 

[Gepetto]

Hi Lee
R3 is the series feed resistor for VEE2 which powers Z104-4 and Z102-4 with -V. What do you have in those locations? Are they socketed so you can remove them to see if the problem goes away.

R3 is also the source for C8, 470uF 25V. Check for correct polarity.

What voltage do you measure at C8 - if you can pull the Z102 and Z104 devices?

 

[laatsch55]

Already did that Joe. Pulled C8 already last night and no change, all IC's pulled but the phono section. Tis-97's and 93's ok. 5087 and MPSA 16's ok.

 

[laatsch55]

C8 shares a common node with R3, R5. I thought it might be the SS output relay section, but everything there checks out OK too. Checked for broken traces, solder bridges, out of spec resistors(R3 was 174, instead of 120, so I changed it). At the ommon node of C8, R3, R5 MINUS 1.314 volts DC. Just on the other side of R3 16.71 MINUS volts DC>

 

[laatsch55]

Pulled one end of the Jumper just to the left of the power switch, got MINUS 20.45 volts DC now at the common node. On the assembly diagram it would be the top, 1.8 inch insulated jumper. I'll install it back and pull the last jumper going to the phono section. Those are listed as 3.7 inch insulated.

 

[laatsch55]

pROBLEM IS ISOLATED TO THE PHONO SECTION. Shit what the heck could be wrong there, I didn't change much!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! That's some funny shit right there. I'm getting this sinking feeling those were Polar caps, cause I certainly didn't check, assuming they were Bi-polar...... The CAP BANK of 6 10UF.

 

[laatsch55]

Nope, they were film caps...NOT polarized..

 

[laatsch55]

Removed the phono op-amp, no change, removed "cap stack" no change. Found cold solder jt on cap stack assembly. Was reading 20uf instead of 30. With both cap stack and op-amp out, no change, still dragging voltage down.

 

[laatsch55]

D3, D6 are now suspect...

 

[laatsch55]

D1,D2,D3,D4 D6 are just fine.

 

[laatsch55]

Yes, this is kicking my ass...................

 

[derek92994]

You can do it master. Just keep all hammers out of the room and no pulling any hair out ok?

 

[NavLinear]

You can do it master. Just keep all hammers out of the room and no pulling any hair out ok?

Derek - a little hint here. Lee doesn't have any hair to pull out so no worries there mate. I do think he has something much bigger than a hammer though.

 

[derek92994]

Haha, well that problem is solved. Sometimes you just have to walk away and come back to these things. He'll get it eventually and maybe learn about another trick/trap of electronics.

 

[NavLinear]

Chasing electrons can kick your ass - been there myself more than once.

 

[laatsch55]

Yep, had to get away from it. One thing about changing so many components, makes it hard to chase a problem.

 

[laatsch55]

Headed to work for a few hous, later.

 

[laatsch55]

To thpose of you who have attempted to fix a 3300, the trace between R7 and ground IS SUPPOSED TO BE CUT, JESUS!!!!! Here I thought it was another case of the 3300's sorry ass traces giving up the ghost. Well live and learn. The AP is warming up./...

 

[Gepetto]

Hi Lee
Now that you found the gremlin, what are the VEE and VCC voltages?