OK don't beat me up for this! The thread probably belongs in the "Diagnostic Equipment" category but the issue with my 1077 has to do with the picture I get on the CRT. It's supposed to be an ultraviolet color but on first power up and after recapping, cleaning and messing with the vertical controls, there is no change and the screen looks like the mess in the picture.

Someone has been in here because a number of resistors have been changed including 2 that are listed at 1 meg in the schematic (R-52 and R-53) replaced with much lower value resistors...in the 47 kohm range.

I have a lot of troubleshooting to do but I can use some advice on where to start. I think this is a vertical issue correct? Has anyone else had this problem? From what I've been able to see, most of these work straight away and only need some caps and adjustments. I guess I'm just so lucky eh?

Thanks

Did you replace the main filter caps? If that severe distortion of the raster wasn't locked to powerline freq, it would be a "crawling hourglass" caused by B+ ripple.

Main filter cap(s) shot, causing that severe distortion of the raster. It would be a "crawling hourglass" if the vert sweep wasn't locked to powerline freq.

Thank you but I've changed the main filter caps...a 4 part can that I used an Adapt-A-Cap base on and 4 new Nichicon capacitors. I also changed the 2 elecrtolytics on the sweep board. The caps you see in the picture have not been changed but I don't think they have anything to do with main filtering.

Looks like the horizontal freequency is off. Have you tried making any adjustments?

Looks like the horizontal freequency is off. Have you tried making any adjustments?

Not to the horizontal, I've just moved the vertical size and vertical linearity pots. I think the horizontal frequency is supposed to be 15.75 Khz.

HORIZ FREQ—Adjust for 15,750 Hz. This can be done by connecting an oscilloscope adjusted to 7875 Hz. horiz sweep to point M on the sweep printed circuit board, adjust R54 for 12 pulses. Refer to Fig. 16 waveform chart.

This is what is in the service manual but unfortunately it does not have the waveforms it refers to. I'm not sure I understand the instructions anyway...when I use my scope to measure a frequency, I just hook on the probe and press auto!!!

What I do to set horizontal frequency on TV (should also apply here) is hook my scope to the composite output of a DVD player or DTV box adjust the horizontal time scale control of the scope for 2-4 cycles of the H sync pulse on screen, count how many graticule marks are between the leading edges of 2 adjacent peaks....Once I have done this I don't touch the horizontal control of the scope or auto scale...Then I connect the scope to the horizontal osc in the TV, adjust the vertical scale of the scope to compensate for the amplitude difference, and adjust the TVs osc adjustment so the peaks of the osc have the same spacing on the graticule as measured earlier with composite video from a digital reference source. Most TVs I do this with are dead nuts in sync from warm up with no further adjustment.

What I do to set horizontal frequency on TV (should also apply here) is hook my scope to the composite output of a DVD player or DTV box adjust the horizontal time scale control of the scope for 2-4 cycles of the H sync pulse on screen, count how many graticule marks are between the leading edges of 2 adjacent peaks....Once I have done this I don't touch the horizontal control of the scope or auto scale...Then I connect the scope to the horizontal osc in the TV, adjust the vertical scale of the scope to compensate for the amplitude difference, and adjust the TVs osc adjustment so the peaks of the osc have the same spacing on the graticule as measured earlier with composite video from a digital reference source. Most TVs I do this with are dead nuts in sync from warm up with no further adjustment.

Thanks Tom…that’s graduate school stuff for me but your instructions are very detailed so I might be able to do this. I’ll give it a shot later tonight. In the meantime keep them comments comin’!!!

HORIZ FREQ—Adjust for 15,750 Hz. This can be done by connecting an oscilloscope adjusted to 7875 Hz. horiz sweep to point M on the sweep printed circuit board, adjust R54 for 12 pulses. Refer to Fig. 16 waveform chart.

This is what is in the service manual but unfortunately it does not have the waveforms it refers to. I'm not sure I understand the instructions anyway...when I use my scope to measure a frequency, I just hook on the probe and press auto!!!


Early scopes had the horizontal sweep “calibrated” in frequency instead of time. With a more modern scope, you would measure about 63.5 microseconds for one complete horizontal cycle. The “12 pulses” might be a miss print, I think it should be “2 pulses” :scratch2:

What scope do you have?

jr

Early scopes had the horizontal sweep “calibrated” in frequency instead of time. With a more modern scope, you would measure about 63.5 microseconds for one complete horizontal cycle. The “12 pulses” might be a miss print, I think it should be “2 pulses” :scratch2:

What scope do you have?

jr

The one I have from the 1077 era is an HP 54600B 100MHz

The one I have from the 1077 era is an HP 54600B 100MHz

I’m thinking that the scope is at least 10 years newer than the B&K. Horizontal sweep is expressed in time rather than frequency.

If you set the scope sweep time to 20 microseconds per division and connect the vertical input to point “M” on the B&K, how many complete waveforms do you observe?

jr

Yeah the scope is from the late 1990s. Sorry about that and I can vary the sweep time.

But I think full disclosure is necessary here. If I'm a novice with electronics, I'm even more rudimentarily acquainted with the oscilloscope. The extent of my abilities and to understand instruction are limited to looking at discrete frequency waveforms and that's about it. Having shopped for a sweep generator for TV alignment, I know what that does...sweeping through a frequency range over and over again as it generates a signal but I don't know anything about oscilloscope "sweeping" looking for signals. I guess I need to do more remedial reading and study.

MOST of the time......
Waveforms in manuals show 2 complete cycles. Some newer scopes
@1975 + have a setting for it like the Sencore. It may be called
line & field or TV hoz & TV vert on the time base SW.
Wave forms are pretty generic. If you can look at them on a running set
with manual it would help you a lot. Then write down the time base.
And dont forget the isolation transformer !

73 Zeno:smoke:
LFOD !

Yes the B&K and the HP Scope are on separate isolation transformers.

Yes, many earlier sources of service data assumed you would be using the older type of scope that had a horizontal (time) drive that was based on the frequency of a free running oscillator. That would often quote a scope sweep of 7875 for the scope horizontal signal. I suppose for convenience they also assumed that you would want two cycles of the monitored signal on the screen.
Maybe those scope often had distortion at the start and end of a horizontal sweep. This causes confusion today with modern scopes.

Another complication you should be aware of is that the exact TV horizontal frequency standard was changed in about 1954 when the color standard came out. The color system used a color carrier reference of 3.58 some MHz. The vertical and horizontal TV frequencies were slightly changed so that they would be obtained from dividing down the color carrier frequency. So the vertical frequency became slightly less that 60Hz and the horizontal frequency became a bit lower than 15750. From that time even Black and White TV broadcasting used the newer frequencies. The only place this makes any difference is color TV AND modern sources of video. You couldn't see the difference in frequency on an (analog) oscilloscope.
I'm not sure about the 1077 (there were at least two versions) but earlier B&K model generators of this type had a vertical frequency derived from the 60Hz power.

Here is a good video introductions to oscilloscopes.
https://www.youtube.com/watch?v=KYEMPm0c9kY

Well try as I might, the 1077 is still the same way it was when I first powered it up. I bought another one same model so maybe between the two I can make a functional one. Thanks everyone for your advice and suggestions. Stand by for more

Good luck, my 1077B has a vertical height problem and if I encounter a similar issue, I will post it here.

I went back and too a fresh look at your photo. The color is right and there won't be anything on the screen. It should just be a purple box.
The only issue I see is you have some diagonal lines. That's why I was thinking the horizontal freq might be off.

Should look like this

https://live.staticflickr.com/65535/53197268775_2a95a4ce48_c.jpg (https://flic.kr/p/2p3RUDe)


While you have this. Have you tried installing a slide and displaying the output on a TV?

http://www.videokarma.org/attachment.php?attachmentid=206064&d=1694521711

No I have not yet hooked it up to a TV and tried it. I will. Thank you for defining what the screen should look like. I was going for a full screen. Shango did a 1076 a couple of weeks ago and it looked like he had a full screen but, of course, that could have been camera artifact.

I had access to one of them in the 90s when I was working in a TV repair shop, and I remember being impressed at what it could do, I sort of remember it having a full screen raster, but I'm not 100% sure, it's been a while since I have seen one.
https://www.radiomuseum.org/images/radio/dynascan_corporation/television_analyst_1077b_897561.jpg

random pic found when searching.
But yeah, good idea, hook it up to a good TV, see what you get! :P

Don't worry about the size of the screen - that's not really important to it functioning.

Do you really have banding/folding/twisting as it appears in your photo? That's a bigger issue.

The “keystone” shape of the raster may be caused by a bad yoke... perhaps you could swap the yoke from the second unit to see if the shape of the raster changes.:scratch2:

jr

Subbing the yoke looks like quite a hassle. My very first thought on seeing the image http://www.videokarma.org/attachment.php?attachmentid=206064&d=1694521711 was a very large ripple(hum) on the main B+ line. Even if the main filter caps have been replaced, possibly a miswire(?) could be allowing a large ripple (since the vert sweep is locked to the powerline freq., a ripple would be stationary instead of a "crawling hourglass". Before doing a yoke swap, I would first want to verify that the main B+ is clean. Do you have a schematic for the unit?

Duh. Just found the schematic. Main B+ goes to pin 2 (damper) of the 33GY7. You could jumper an electrolytic from there to ground and see if it affects the distorted raster any. 47 mf or thereabouts.
https://antiqueradio.org/art/BK1077BSchematic2.jpg
https://antiqueradio.org/art/BK1077BSchematic1.jpg

I don't think that it is keystone shaped, rather a distorted raster which some have addressed above. Instead of changing the yoke, you might want to try to find out what is going on with that raster.

I have had some suspicions about the yoke but I agree, it's something I would change as a last resort. I think I'll try the jump to ground with the electrolytic from the 33GY7 to ground.

Duh. Just found the schematic. Main B+ goes to pin 2 (damper) of the 33GY7. You could jumper an electrolytic from there to ground and see if it affects the distorted raster any. 47 mf or thereabouts.
https://antiqueradio.org/art/BK1077BSchematic2.jpg
https://antiqueradio.org/art/BK1077BSchematic1.jpg

Thank you for the links to the schematic!

I went back and too a fresh look at your photo. The color is right and there won't be anything on the screen. It should just be a purple box.
The only issue I see is you have some diagonal lines. That's why I was thinking the horizontal freq might be off.

Should look like this

https://live.staticflickr.com/65535/53197268775_2a95a4ce48_c.jpg (https://flic.kr/p/2p3RUDe)


While you have this. Have you tried installing a slide and displaying the output on a TV?

http://www.videokarma.org/attachment.php?attachmentid=206064&d=1694521711

Wanted to try the operational test last night but I was finishing (finally!) a monstrous week long task of installing a 26KW standby generator for our house. I never want to work with 1/2" cable again. I'll try it tonight.

I don't think it's yoke. I picked up a really nasty 1076 once. It was out in the weather behind a tv shop that closed in a shopping center. The yoke was OK. After cleaning it up, I did have to change some electrolytics and 2M resistors.

Its easy to make slides for these.
Download your favorite test pattern or image, It should be about 333x444 in size but you can resize it in your paint program.
Print that image to an ink-jet printer in B&W. It should be about the size you want for the B&K.
Take that print to Staples or Office Depot and have them print it to a transparency. Ask for extra contrast if necessary.
They will print it on a laser printer to the transparency film. The last one I had done cost about 60 cents. Cut down to fit.
If you print to transparency film on an ink-jet printer, the image will rub off.

Its easy to make slides for these.
Download your favorite test pattern or image, It should be about 333x444 in size but you can resize it in your paint program.
Print that image to an ink-jet printer in B&W. It should be about the size you want for the B&K.
Take that print to Staples or Office Depot and have them print it to a transparency. Ask for extra contrast if necessary.
They will print it on a laser printer to the transparency film. The last one I had done cost about 60 cents. Cut down to fit.
If you print to transparency film on an ink-jet printer, the image will rub off.

Got it...thank you so much! Mine came with a set of transparancies but some of them are not optimal even after cleaning. I will try your suggestion...after I get it to work :D:D:D

I had the yoke fail on mine-the cement used to secure the windings corroded through and caused an open circuit. I was able to strip away the bad outer windings and got it working. The hardest part was getting it apart. You should be able to use your wiring diagram to ring out the individual coils in your yoke without removing anything. I rang mine out from wiring tie points on the underside of the 1077b chassis.