Derek92994's 700 Ser II White Oak conversion

[derek92994]

Here ya go...

Nice! Heavy Duty.

 

[laatsch55]

Yeppers!

 

[mlucitt]

Here ya go...

I like those Pomona clips. they come in every color of the resistor color code rainbow from Mouser.

 

[derek92994]

No Half Bias going on here!

 

[Gepetto]

VR1:
C pin: 20.2 (the relays engaged for 2 power ups just now, previously this voltage was 7.6)
C pin 2nd test: relays did not engage, you get 7.6 volts when this happens, meters peg 30 seconds after power down then go down slowly
A pin: 0v
R pin: 2.5v

VR2:
C pin: 0v
A pin: -20.5
R pin: -17.9

Hello Darcy, seems you have an intermittency going on of some form. The regulator VR1 is the misbehaving circuit. As a first step, I would be inclined to lift one end of the 30V zener diode D80 as a test to see if this has any bearing on the results.

Make sure that things are fully powered down and fully discharged before any solder operations are attempted.

 

[laatsch55]

Darc is still at work Joe, he'll get on it when he gets home..

 

[derek92994]

Hello Darcy, seems you have an intermittency going on of some form. The regulator VR1 is the misbehaving circuit. As a first step, I would be inclined to lift one end of the 30V zener diode D80 as a test to see if this has any bearing on the results.

Make sure that things are fully powered down and fully discharged before any solder operations are attempted.

Thank you Joe. I will look into this tonight and reply.

 

[Gepetto]

Thank you Joe. I will look into this tonight and reply.

Also look around for cold solder joint, broken solder joint etc. around R85 (20.5K ohm 1/2W) and Q1 (MJE15032)

The fact that this regulator sometimes comes up properly with proper voltages makes an intermittent seem quite possible.

 

[laatsch55]

Here ya go Darc, this will help you identify the components ..

 

[derek92994]

Also look around for cold solder joint, broken solder joint etc. around R85 (20.5K ohm 1/2W) and Q1 (MJE15032)

The fact that this regulator sometimes comes up properly with proper voltages makes an intermittent seem quite possible.

Here ya go Darc, this will help you identify the components ..

Cheers Guys, Just got home 13 hour shift. Straight to bed and have a maintenance run to do early in the morning. If they dont call overtime tomorrow, I will be home at a reasonable hour and can dive into this Amp.

 

[laatsch55]

10-4 Darc..

 

[derek92994]

Still pulling 13 hour shifts.....

 

[laatsch55]

You workin class hero you!!

 

[derek92994]

You workin class hero you!!

Burn out is for pussys

 

[derek92994]

So keen to dive into the wopl, I will be cheering if its a dry joint. Might resolder the whole board just for shits and giggles.

i owe i owe, so off to work i go!

 

[derek92994]

Resoldered the control board, I did not remove the old solder, as I have always fixed dry joints this way, not sure if its the correct procedure. I do have a solder sucker so can remove and re-do if required.
Now the left channel meter pegs instantly when powered on. Can you guys please have a look at this pic and tell me if I have shorted something.

 

[derek92994]

Will check fuses and do those checks that you asked Joe. I should have done those first, was hoping it was a dry joint.

 

[mlucitt]

Why are pin three's of the Backplane Boards not connected to Pin three's of the Control Board?

 

[derek92994]

Why are pin three's of the Backplane Boards not connected to Pin three's of the Control Board?

That would be a Lee or Joe Question. This amp has been running perfectly for 6.5 years.

 

[BlueCrab]

I would clean the board with brush & alcohol. Looks like there is a fair amount of residue flux. Great way to both inspect the board and remove any solder balls.