Six Weeks of Troubleshooting...I think I found it!

[bandersen]

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[Chris K]

Does your unit display MHz values like this? What's the purpose of showing out to more than 3 decimal places?

[Chris K]

Did the steps exactly as you did. When I get through the sweep time and push auto sweep I get the too large span message. Same too large for single sweep and manual says it can't do it in continuous mode...obviously

[Chris K]

There's a special function I saw for wiping all saved setups clean. Maybe I'm in some saved mode that's stopping me from doing this...IDK

[bandersen]

So you press special then 112? I don't know what to tell you

[Chris K]

Yeah...I know. Here we go again with this crap.

[bandersen]

I started with auto, manual and single all off. Entered special 112, then center frequency, then span, then rate then turned auto on.

Can you post a photo showing your entire control panel?

[Chris K]

The widest sweep span it’ll do if I ask it to do 100ms sweeps is 50KHz. I pretty sure somewhere in the documentation for this it gave center frequency ranges in increments of 20MHz. I think it said from 16 to 30 or so MHz the fastest it would sweep is half a second. I have no idea why that would be the case. The fastest it would do a 1MHz sweep around a 21.25 CF was 1 per second. That’s as fast as it could go. If I lowered it below a second I got an error saying the sweep interval was too small for the frequency. Looks like my future lies in the older HP generator/marker and the effectiveness of my replacing the chip. If the beast can’t sweep it’s gone. My equipment winning streak continues!

[Chris K]

Originally Posted by bandersen

I started with auto, manual and single all off. Entered special 112, then center frequency, then span, then rate then turned auto on.

Can you post a photo showing your entire control panel?

Sure thing but I’ll need to do it tomorrow evening. The work week becons. Thanks for the help tonight!

[bandersen]

Originally Posted by Chris K

The widest sweep span it’ll do if I ask it to do 100ms sweeps is 50KHz. I pretty sure somewhere in the documentation for this it gave center frequency ranges in increments of 20MHz. I think it said from 16 to 30 or so MHz the fastest it would sweep is half a second. I have no idea why that would be the case. The fastest it would do a 1MHz sweep around a 21.25 CF was 1 per second. That’s as fast as it could go. If I lowered it below a second I got an error saying the sweep interval was too small for the frequency. Looks like my future lies in the older HP generator/marker and the effectiveness of my replacing the chip. If the beast can’t sweep it’s gone. My equipment winning streak continues!

You are describing the behavior in digital sweep mode. Phase continuous is a smooth linear sweep and recommended for IF work.
Also, the slower you sweep, the more accurate the results are. Is 0.5s really so bad?



Oh 1MHz sweep is too wide. Lower it to 0.625 MHz or less

[Chris K]

You are describing the behavior in digital sweep mode. Phase continuous is a smooth linear sweep and recommended for IF work.
Also, the slower you sweep, the more accurate the results are. Is 0.5s really so bad?

I guarantee you I am in phase cont. mode. Maybe I'm missing a solution with the wrong machine. My issue is not with the quality of the sweep but with what is visible, or should I say not visible, on the oscilloscope. I don't have a curve shape on the scope, just a cursor that traces the curve shape once or twice a second as per how fast the HP is sweeping. I'm trying to make adjustments in the TV IF transformers that alter and tweak the symmetry of the curve around 21.25MHz on the scope. With the previous 8600/8601 combo, I had a sweep rate that was so fast, I had a solid line on the scope out of the TV so I could make fine adjustments to the TV IF transformers that got the shape exactly right. Is there something I should be setting the scope for...some mode that will display a line instead of a slow moving cursor?

[bandersen]

You need to decrease your sweep width. You can't do 1MHz - 0.625MHz or less.
A slow moving cursor is all that you will get at 0.5s sweep rate.

No, this isn't the best generator to use for TV alignment. It's one of the finest RF generators ever made, but it was designed for communications work and cost a small fortune.
8662A would have been a better choice. Older, but has 5 markers and less restrictions on sweeping. I don't think it has a continuous mode though. Only discrete steps so not as nice in that regard.

[Chris K]

OK Bob. I’ll keep it for now for other uses but it seems Penthode is right. The 8600/8601 pair is the sweet spot for this era of TVs. Thank you for all the help and your time!

[bandersen]

Well at least try reducing the sweep width to 0.5Mhz to verify your generator is working properly.

[Chris K]

Okay will do.