Unwell Phase Linear 700 series II

[FredR]

Anne Francis

 

[WOPL Sniffer]

Anne Francis
View attachment 40159

HUH?????

 

[Michael F]

There seems to be a discrepancy between my control board and the manual. I have an extra wire (purple) on my board that doesn't correspond to what is on the manual. It`s right between the white/red striped wire and the input ground wires. That is the same on both Left and Right channels.

 

[grapplesaw]

There seems to be a discrepancy between my control board and the manual. I have an extra wire (purple) on my board that doesn't correspond to what is on the manual. It`s right between the white/red striped wire and the input ground wires. That is the same on both Left and Right channels.

Yes that is correct

the manual is for quasi complimentary
Attached is service doc

a new white wire goes to the old Violet and blue connection. The violet and blue reconnect to the transistor as on the attached

 

[grapplesaw]

There seems to be a discrepancy between my control board and the manual. I have an extra wire (purple) on my board that doesn't correspond to what is on the manual. It`s right between the white/red striped wire and the input ground wires. That is the same on both Left and Right channels.

Here is connection for the color wires.

 

[grapplesaw]

There seems to be a discrepancy between my control board and the manual. I have an extra wire (purple) on my board that doesn't correspond to what is on the manual. It`s right between the white/red striped wire and the input ground wires. That is the same on both Left and Right channels.

Here is connection for the color wires.

 

[Michael F]

Yes that is correct

the manual is for quasi complimentary
Attached is service doc

a new white wire goes to the old Violet and blue connection. The violet and blue reconnect to the transistor as on the attached

Thanks for that Grapplesaw
Now the only difference is the White/Red wires that I have and White only wire on the drawing, everything else seems ok.

 

[Michael F]

I`ve traced the wires that lead from the control board to the back planes; this is what I came up with going from left to right:

Left Channel

Black* B- fused

White/Red * NPN column output transistor Base buss

Red* Collector of bias transistor

Blue* Base of NPN column driver

Black* Base of Bias transistor

Brown* Emitter of bottom NPN column output transistor

Orange* Collector buss NPN column/fused B+

Grey* NPN and PNP output transistor common emitter point



Yellow* Emitter of bottom PNP output transistor

Brown* Emitter of bias transistor

White/Red * Collector buss of PNP column/Fused B-

Purple* Base of PNP column driver

Grey* Input ground

Black* Input signal



Right channel

Red* B+Fused

White/Red* Base buss NPN column

Red* Collector of Bias transistor

Blue* Base of NPN column driver transistor

Black* Base of Bias transistor

Brown* Emitter of bottom NPN transistor

Orange* Collector buss of NPN column/Fused B+

Grey* NPN and PNP output transistor common point

White* Chassis Ground

Yellow* Emitter of bottom PNP output transistor

Brown* Emitter of Bias transistor

White/Red* Collector buss of PNP column/fused B-

Purple* Base of PNP column driver

Grey* Input ground

Red* Input Signal

Does that seem right?

 

[grapplesaw]

I`ve traced the wires that lead from the control board to the back planes; this is what I came up with going from left to right:

Left Channel

Black* B- unfused

White/Red * NPN column output transistor Base buss

Red* Collector of bias transistor

Blue* Base of NPN column driver

Black* Base of Bias transistor

Brown* Emitter of bottom NPN column output transistor

Orange* Collector buss NPN column/fused B+

Grey* NPN and PNP output transistor common emitter point



Yellow* Emitter of bottom PNP output transistor

Brown* Emitter of bias transistor

White/Red * Collector buss of PNP column/Fused B-

Purple* Base of PNP column driver

Grey* Input ground

Black* Input signal



Right channel

Red* B+

White/Red* Base buss NPN column

Red* Collector of Bias transistor

Blue* Base of NPN column driver transistor

Black* Base of Bias transistor

Brown* Emitter of bottom NPN transistor

Orange* Collector buss of NPN column/Fused B+

Grey* NPN and PNP output transistor common point

White* Chassis Ground

Yellow* Emitter of bottom PNP output transistor

Brown* Emitter of Bias transistor

White/Red* Collector buss of PNP column/fused B-

Purple* Base of PNP column driver

Grey* Input ground

Red* Input Signal

Does that seem right?

I am tied up right now and my wife will let me go.
here are the connections on the back plane. I think you may have a couple labeled wrong.

 

[Michael F]

As per your request Glen.

 

[Michael F]

. I think you may have a couple labeled wrong.

I double checked everything and it`s good. Only the B- was labeled as un-fused but that has been since corrected.

 

[Michael F]

New control board installed (very nice btw). Backplane populated and all is good there, 0vdc offset both channels.
Left channel bias rock solid at 350mv however, I cant get more than .050v on the right channel board regardless of trimpot position.
Bias transistors were tested prior to being terminated on the new board.
Bias transistors were tested in-circuit and measure identically.
HELP!

 

[Michael F]

Problem solved:
I forgot to replace the 1 amp rail fuses following the control board and transistor installation and start up .... Those tests were conducted with the DBT and variac in line. When bypassed, the initial rush current must have popped the right channel B+ fuse.
Bias steady on both channels, DC offset immeasurable but the nice surprise is the power output, 421 wpc @ 8r (single channel driven)
Dare I try a 4 ohm load? Will the 5 amp rail fuses be up to the task I wonder.

 

[Gepetto]

Glad your unwell turned into well...

 

[Gepetto]

Before you wrap it up totally Mike, you should ditch those CP-5 wirewounds in the Zoebel network and move to metal oxide to reduce the inductance. Inductance is self defeating in a Zoebel network.

 

[laatsch55]

Problem solved:
I forgot to replace the 1 amp rail fuses following the control board and transistor installation and start up .... Those tests were conducted with the DBT and variac in line. When bypassed, the initial rush current must have popped the right channel B+ fuse.
Bias steady on both channels, DC offset immeasurable but the nice surprise is the power output, 421 wpc @ 8r (single channel driven)
Dare I try a 4 ohm load? Will the 5 amp rail fuses be up to the task I wonder.

No. The 5 amp rail fuses will blow at around 600 watts per channel at 4 ohms..

 

[Michael F]

No. The 5 amp rail fuses will blow at around 600 watts per channel at 4 ohms..

Will it be able to do 600wpc into 4 ohms?

 

[laatsch55]

Theoretically 770.

 

[Michael F]

Theoretically 770.

OMG. What kind of rail fuses would support that kind of power,8 amps?

 

[laatsch55]

Yep. And then you risk components when the high frequencies hit. 20 k at 770 watts at 4 ohms ain't happening..