700B blew one Right channel 5A supply fuse

[62vauxhall]

Was just on my way out the door and I remembered that relay board. Shouldn't that be put in before the board goes back in place?

It looks like there's holes to drill and I fasteners I need to get.

 

[laatsch55]

No. Not at this time.

 

[62vauxhall]

Home now and wires are all attached to the board.

 

[laatsch55]

Ok, let me ger dinner ate and we'll bring this puppy up. Get the DBT plugged in to the variac..

 

[62vauxhall]

Ok, let me ger dinner ate and we'll bring this puppy up. Get the DBT plugged in to the variac..

Thought I'd have a hot meal later myself for a change. Got a frozen pizza standing by.

 

[laatsch55]

Plug the aamp in to the DBT and with the variac AT 0%, turn on the variac, with the amp on also....

 

[laatsch55]

Haro?????

 

[62vauxhall]

Haro?????

Yes, had to "fix" the variac. Knob wasn't set right so had to set it so all the way down read zero.

Variac on, set to sero, DB plugged in and amp is on.

 

[laatsch55]

Stick the meter on the left channel to monitor bias....

 

[62vauxhall]

Stick the meter on the left channel to monitor bias....

If I remember how, it's 0.00V. One meter lead on rail and one on other side of that resistor? Red or black lead to rail?

 

[laatsch55]

Don't matter, now bring the variac up to 10%, bulb should brighten, then dim after a 10 seconds or so...

 

[laatsch55]

But if your picky, red to the rail, blak to the resistors...

 

[62vauxhall]

Don't matter, now bring the variac up to 10%, bulb should brighten, then dim after a 10 seconds or so...

Not a flicker. Variac working and bulb is OK.

DEIT: forgot to mention - meter at 35.5MV DC

 

[laatsch55]

Whats the meter say? Got fuses in? Got the bias trannies bolted back in???

 

[62vauxhall]

Whats the meter say? Got fuses in? Got the bias trannies bolted back in???

Meter @35.5MV - fuses in - bias t's are bolted on.

 

[laatsch55]

Come slowly up to 50%, eyeballing that bulb all the time, as you move up, make sure it dims before going further...

 

[62vauxhall]

Come slowly up to 50%, eyeballing that bulb all the time, as you move up, make sure it dims before going further...

At 50V on the variac, bulb just barely starts to glow but does not dim. .415 (point 415) volts on the meter.

 

[laatsch55]

Get both bias readings below 200 before we go any further, and after that check DC offset, PLEASE DON"T SHORT ANYTHING WITH THE PROBES>>>

 

[laatsch55]

The bulb should have dimmed when you lowered the bias a wee bit...

 

[62vauxhall]

Get both bias readings below 200 before we go any further, and after that check DC offset, PLEASE DON"T SHORT ANYTHING WITH THE PROBES>>>

Turning down the variac to 20V made 192MV left bias on the meter. Checked bias on right side and got -10V. Offset volts .806V on Right .780V on Left