Adding A Focus Pot To A B&K 1077B TV Analyst

[Tom9589]

While I was waiting for the latest shipment of parts to work on my B&K 1077B TV Analyst, I decided to add a focus pot. The 1077B just wasn't as sharp as my old 1076. The schematic said the focus should be between 0 and 300 VDC. I found the perfect spot under the chassis to add the control with 0 and 300 VDC on adjacent terminals on a terminal strip. I used a 1 Meg CTS 201 pot and connected the focus line (pin 6 on the CRT - blue wire) to the wiper on the pot.

Optimum focus was achieved at about 150 VDC.

[kf4rca]

Did that improve the sharpness? I was thinking about redesigning the pre-amp using an FET and putting in adjustable equalization.

[Tom9589]

Yes it did. Don't expect miracles. After all it is just a flying spot scanner. I did find a sweet spot at about half of the pot's rotation.

One thing I haven't adjusted yet is the beam current. It's supposed to be adjusted for 75 uA. I'll see if that has any improvement on the sharpness.

[kf4rca]

Easy to make slides for these.
1) Download you favorite test patterns off the web.
2) Using a graphics program resize to about 333x444. Exact size may depend on your printer.
3)Print the B&W image to your printer. Use a black majik marker to surround the image with black.
4)Take the sheet to Staples or Office Depot and get a transparency made. Tell them you want extra contrast. That will make the blacks really black.
They used to charge 50 cents for this but its probably more now. They use a laser printer. If you use an ink jet, the pattern will rub off. So check before you leave the store.
5) Cut the transparency to fit the slide holder in the B&K.