Need a little help- BK 1077

[leadlike]

I drug out the old BK 1077 tonight to see that I had pulled one of the twin triode tubes at some point. Now worries-I'll just pull out the service info and find out what "V5" is....turning to that page reveals that BK did not ID their tubes at all! It simply states what the two halves of the tube do in the circuit.

So, can anyone do me a favor, lift the lid of their Television Analysts and tell me what 12a?7 series of tube is used in the V5 socket? Many thanks in advance.

[bandersen]

It's a 12AU7. I have the schematic and parts list if you're interested

[leadlike]

I might like that at some point. I've never had any luck in getting it to generate a video signal, although the crt "lights up" the vertical is still compressed. I replaced all of the lytics, but those green capacitors look fishy to me. I need something to generate at least some tv audio to continue digging into this neverending GE 802 project.

Thanks for the tip, Banderson. I had my money on it being a 12AT7-glad I asked.

[bandersen]

I would have guessed that too since V12 & V13 are 12AT7s. I have a couple of these guys. One is about 85% working the other is dead. I'll probably dig into restoring the working one properly soon.

What I'd like to know is how do you go about calibrating one of these? There is an adjustment for vertical linearity for example. Should it be hooked up to a known good TV and do it visually

[old_tv_nut]

Originally Posted by bandersen

I would have guessed that too since V12 & V13 are 12AT7s. I have a couple of these guys. One is about 85% working the other is dead. I'll probably dig into restoring the working one properly soon.

What I'd like to know is how do you go about calibrating one of these? There is an adjustment for vertical linearity for example. Should it be hooked up to a known good TV and do it visually

You could do that. Another way would be to use a cross-hatch slide and check the timing of the horiz lines with a scope (if your scope is linear )

[bandersen]

Good to know. My HP scope is the most accurate piece of equipment I have.

[leadlike]

Hey, I got a little bit of a surprise when I put in the 12au7-the B&K works! I always thought that the purple raster would have filled the screen, so I thought I had some serious sweep problems, but once I fiddled with the horizontal sync control, I pulled in a nice picture on my Motorola 7" set. I only ever had this thing generating audio before, I guess I never tried it after that last round I recapping I did to it. This has been a pleasant surprise.

[old_tv_nut]

hey, good deal! - how about some pix?

[bandersen]

How did you go about recapping your 1077 ? Mine has several circuit boards deep in the cabinet that are hard-wired in. Kinda like a Predicta TV. What a pain!

[bgadow]

I ran into that myself; mine has a bad cap somewhere that prevents the vert lin from being correct. Hard to believe that a company catering to the service industry would make something so difficult to service.

[leadlike]

To recap, I just snipped off the leads close to the old cap bodies, which left enough of a tail of wire still sticking up from the circuit board that I could solder the new cap to that. I would never do this to an old tv, but for a piece of gear that I will only use a half dozen times? Then absolutely.