Zenith Color Roundie Alignment with B&K 415

[old_tv_nut]

Hard to tell, but maybe you have the scope sweep set way too fast? The sweep generator should be sweeping about 60 times per second, so the scope sweep should be around 1 or 2 msec/div. Best is not to use the internal horizontal sweep of the scope, but set up for X-Y operation, with the "too scope horizontal input" of the sweep generator for X.

[bhegges]

old_tv_nut, thanks for the quick reply and suggestion. This leads to more questions. My apologies for the very basic questions, I am in completely uncharted territory.

• Next step try connecting the B&K 415 output labeled "To Scope Horz Input" to the Oscilloscope "CH1 or X"
• I assume I can connect the scope probe to the B&K 415 cable as shown below, note this measures as a simple straight through cable
• I currently have just a single 10x scope probe, model 4904-2RA, specs here: https://store-9x7452d.mybigcommerce....ta%20Sheet.pdf
• I assume I need a second scope probe to connect "CH2 or Y" to the TV chassis test point C1
• Looking at the B&K 415 connection diagram it also shows connecting the "To Scope Vert Input", when would this be used, I would think this connects to the scope "CH2 or Y" input, this is confusing, don't I need to be measuring TV chassis signals?

[bhegges]

Watching Shango work on TV alignment with a B&K 415 and it looks like he has the "To Scope Horz Input" connected to the A Trigger scope input via a simple dual banana to bnc connector. Video here: https://www.youtube.com/watch?v=CmEyYAjjsn0&t=992s. Here is maybe a connector adaptor I could use: https://www.pasternack.com/banana-ja...-pe9011-p.aspx

I'm still not sure when I would then also use the "To Scope Vert Input" coming out of the B&K 415.

[zeno]

First what ever you do is FLAG you alignment tool with a piece
of tape so you can go back to the start !!!! Write down the turns
CW or CCW as you go. It shouldnt take much, like <1/2 turn.
Traps can be adj with an OTA signal ( 41.25, 4.5 etc)

Now the dirty truth. I was in the TV biz from 1970 til the end of CRT's
I never did an alignment. Only one tech I knew in the area did one
just to say he did. I may have seen ten sets ever that needed it.
A few had a damaged transformer & got eye balled. A few more
got tweaked but not by a tech. A few others were real Emersons
built in the mid - late 60's. Total toilet sets !

good luck
Zeno
LFOD !

[jr_tech]

Originally Posted by bhegges

Watching Shango work on TV alignment with a B&K 415 and it looks like he has the "To Scope Horz Input" connected to the A Trigger scope input via a simple dual banana to bnc connector.

He is using an older scope (453?), which uses the trigger input for external horizontal input. Your newer scope uses channel 1&2 for x-y display.

jr

[bhegges]

The problems were operator error, Jr was correct, I had never noticed the the very last time division setting was for X Y. With the scope maybe(?) now setup correct I am ready to go.

Note the first section of the scope output seems to be dead, regardless of the scope setting or the sweep settings. The first pic is while measuring the TV, the second pic is just from the B&K 415 and TV not connected:







On to the alignment, step 1 - 41.25 Trap Alignment:

• Set tuner in-between two channels, I also have the antenna disconnected
• Ground test points B, F, E
• Connect from the "Direct" output to test point C, note the direct cable has an in-line 10K resistor
• Connect from the "RF-IF-Video" output to test point G and set the function to IF and the probe to 75 ohm, also note I am not using the capacitor/resistor network as described in the Zenith service manual
• Connect from the "To Scope Horz Input" and "To Scope Vert Input" to the X and Y (CH1 & CH2) on the scope and set the Sec/Div to XY mode
• Alignment instruction state to center frequency at 43.5 mc which is not easy to see, with all of the markers shown in the service manual turned on I set the center frequency where the full wave form was visible
• Alignment instruction state to set the sweep at 6 mc, there are no markings for this, the manual states the IF range is less than 1 MHz to over 10 Mhz), I left the sweep width at max, note from about 3/4 to max there is little affect, below 3/4 and I start to loose the waveform
• Alignment instruction state to adjust the bottom slug on L4 to minimize the 41.25 mc response and then to adjust the top slug on L4 to further minimize the 41.25 mc response

Turns out I don't have the the right adjustment stick, mine is either worn or undersized, a 3/32 allen wrench fits perfect which is just under 0.1", I have order a plastic adjustment stick and will report back soon. Edit: adjustments sticks arrived, no adjustment was needed for L4.