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 Post subject: 1077B schematic?
PostPosted: Feb Fri 21, 2020 5:16 am 
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Does anyone have a schematic for a B&K 1077B? Looks like the horizontal oscillator on mine is kaput and I only have a 1077 schematic, which apparently differs from the 1077B significantly in that area.

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 Post subject: Re: 1077B schematic?
PostPosted: Feb Fri 21, 2020 5:25 am 
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Found this one online. It looks closer, but it shows a 6FQ7, mine has a 8FQ7...

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 Post subject: Fixing a B&K 1077B
PostPosted: Feb Fri 21, 2020 3:23 pm 
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That schematic helped a lot, I was confused by one of the input waveforms to the 8FQ7. Checking the output of that and the vertical deflection tube, they look OK, if slightly low in amplitude.

The story here is that the display on the internal CRT was OK-ish - it was distorted but it covered the full tube. I changed the input filter electrolytics and now the display isn't OK (see image below). I have double-checked that I didn't mess that up, going by the markings on the original can, and everything seems OK. Anyway, more poking around to do:

Attachment:
IMG_4730.JPG
IMG_4730.JPG [ 858 KiB | Viewed 1584 times ]

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 Post subject: Re: 1077B schematic?
PostPosted: Feb Wed 26, 2020 11:02 pm 
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It looks like my 1077B, I never could get it going correctly.


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 Post subject: Re: 1077B schematic?
PostPosted: Mar Mon 02, 2020 10:31 pm 
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Location: Phoenix, Arizona
There are two version of the 1077B and the schematic you show is the later version (I believe).

You will see the four flip-flops shown in the horizontal circuit, which is a divide by 12 using logic. Before this they locked the horizontal oscillator to 189 KHZ directly. This is a crystal controlled oscillator for the color bar grating generator The horizontal was quirky to lock so with the divide by 12 you get 15750 Hz as crystal controlled horizontal frequency'

I had both version which looked exactly the same except tor the sweep board.

You appear to have horizontal sweep but no vertical sweep. Vertical is triggered from the 60 Hz line frequency from filament voltage.

I would get the brightness down as you could burn a line in the screen.

Vertical should be easier to fix. They take the 6.3 volt AC filament supply and drive a couple of transistors to form the vertical sawtooth and then drive the output tube.

I have the non divide by 12 schematic and if you PM me I will hunt for the drawings. I believe I scanned the entire manual.

I did a page on this and if you search the forum you will find my pictures.

The Flip-Flops are CMOS and run on a separate 20 something volt power supply.

I re-solder the entire underside of all the boards as solder connections fail and you can't see the damage. This is easy to do as you can reach the entire underside.

I had both versions and liked the /12 version better and gave away the other.

Jim


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 Post subject: Re: 1077B schematic?
PostPosted: Mar Tue 03, 2020 3:39 am 
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Hi Jim,

The sawtooth is being generated, but many of the voltages are too low. For example, point 17 which is supposed to be 300V p2p, is actually 250V p2p. Basically anything that relies in Decoup Boost is low. All of the input voltages are fine, except that B-13 drops to around 7.6V when the power switch is set to 'on' instead of 'stndby'. So I am trying to find someone who has the same J/K flip-flop circuit that can measure B-13 when the switch is 'on'.

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 Post subject: Re: 1077B schematic?
PostPosted: Mar Tue 03, 2020 4:51 pm 
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Judge

I have the same style 1077B as you.

I can take a measurement but not until saturday 3/7 when I get another day off.

In a quick look at the schematic, it appears the minus 8 - 13 volts is obtained from the un-switched B- side of the B supply noting the Plus side is switched on / off by the Standby switch.

Are you thinking the horizontal frequency is wrong ? It should be 15750 Hz which could be eisily measured at the H-drive port with a freq counter. I would suppose the Boost voltage could go off if it is the wrong frequency, but due to the full width horizontal scan line I can't believe it is far off.

The culprit could well be one of the chips has failed and thoses were redially available last time I checked.

The Vertical sweep output B+ is +225 from the switched B+ supply. If there is any vertical drive coming from the two transistors I would expect to see some vertical sweep however I see no vertical at all.

If that 8 - 13 is too low the posibility is no low voltage for the vertical drive transistors (hence no vertical sweep). Some of the 189 KHz is gettig through to the Horizontal oscillator which would probably free-run without the trigger from the Flip-Flops

When I switch my 1077B from Standby to on, sometimes the raster doesen't come up, so I check under the hood for the purple glow.

My manual only had the schematic tor the non Flip-Flop version so thanks for posting the schematic.

Jim


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 Post subject: Re: 1077B schematic?
PostPosted: Mar Tue 03, 2020 7:34 pm 
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jimmc wrote:
Judge

I have the same style 1077B as you.

I can take a measurement but not until saturday 3/7 when I get another day off.

In a quick look at the schematic, it appears the minus 8 - 13 volts is obtained from the un-switched B- side of the B supply noting the Plus side is switched on / off by the Standby switch.

Are you thinking the horizontal frequency is wrong ? It should be 15750 Hz which could be eisily measured at the H-drive port with a freq counter. I would suppose the Boost voltage could go off if it is the wrong frequency, but due to the full width horizontal scan line I can't believe it is far off.

The culprit could well be one of the chips has failed and thoses were redially available last time I checked.

The Vertical sweep output B+ is +225 from the switched B+ supply. If there is any vertical drive coming from the two transistors I would expect to see some vertical sweep however I see no vertical at all.
If that 8 - 13 is too low the possibility is no low voltage for the vertical drive transistors (hence no vertical sweep). Some of the 189 KHz is getting through to the Horizontal oscillator which would probably free-run without the trigger from the Flip-Flops

When I switch my 1077B from Standby to on, sometimes the raster doesen't come up, so I check under the hood for the purple glow.

My manual only had the schematic tor the non Flip-Flop version so thanks for posting the schematic.

Jim

Hi Jim,

The horizontal frequency is fine. All the waveforms are fine, except the high voltage ones are all low - note that all the B+ voltages are fine though. I've checked just about every resistor and cap in the horizontal and vertical sections. I have tried new vertical and horizontal tubes. I have measured the resistance of the vertical deflection coils - they are about 4 ohms if memory serves me right. I haven't taken the yoke apart yet, but I don't see why that would cause the voltages to be low. I even tried replacing Q4, my theory being that the input from V6B to the base was causing that section to drag B-13 low. I will wait on replacing the flip-flops until I hear what your B-13 is with the power switch set to on.

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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 12:20 am 
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Where is the test point B-13? am I looking for a waveform or a voltage? can I get to it under the lid?

I recall the photo-multiplier tube gets close to 1000 volts from the decoupled boost. as I don't have more than the sch in front of me here at work

I recall the square boxes are waveforms. Normally boost would be maybe 500 - 600 volts (to ground). Decoupled boost could be high impeadance and a meter could load it down.

Since you are missing vertical. that low voltage would be suspect to me. It worked before you re-capped.

I have three of these things wihch include a model 1000, 1076, and the 1077B. My manual covers the non-Flip-Flop.

If you email me a pic I may be able to check tonight. check you messags.



Jim


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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 3:03 am 
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The waveform at point 17 being 250 volts instead of 300 volts may not be enough of a change to be important.
If the horizontal frequency is correct than the flip-flops are working correctly.
The -13 volts being low could be the problem. Looking at the waveforms at points 1, 2, 3, 4 & 5 would tell you if there is enough voltage to make
transistors Q-1 and Q-2 work correctly.

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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 5:09 am 
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Jim, I just measured B-13 at any point on the board that is labeled B-13 on the schematic. For example where R111 meets C64.

Tom, the waveforms all have the right shape, just lower peak-to-peak than they should have.

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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 4:54 pm 
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OK, Tonight (Wednesday) I will take some measurements.

It appears to me that all the transistor circuits run on that minus 13 volts (B-13, I thought it said 8 -13). I assume the two chips use that for VCC, I looked that chip up and they can run on up to something like 30 volts.

When I look at your picure I see no sign of any vertical sweep. You say it did work to some degree before you re-capped it? maybe a wrong value cap or infant mortallity. C-4, 5, 7 could load down the boost and kill the vertical drive to the V output tube.

It is common to use the boost voltage on the vertical sawtooth tube to get a nice high voltage drive to the V output, if you have some boost voltage you should have some vertical sweep.

I had both versions of this 1077 and the Flip-Flop version was the better of the two so I gave away the other one.

Jim


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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 5:19 pm 
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This appears to be a very interesting piece of TV test equipment. Some
ebay listings (pictured below) which gave me a good look inside.
So why does it have what appears to be a flying spot scanner with the photomultiplier tube. Was this to allow the tech to insert his own test pattern or picture ?


Attachments:
xUntitled.jpg
xUntitled.jpg [ 551.47 KiB | Viewed 1230 times ]

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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 5:39 pm 
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Back-in-the-day, which would be late 1940's, there was no TV signal on the air to receive until usually 5:30 PM, and maybe only one channel.

When I was a kid Kukla Fran and Ollie which was a really stupid puppet show came on local TV at 5:30, I was 8 years old.

The first unit was the model 1000 under the DynaScan name. It could go out with the installer and provide a signal so a new TV set could be adjusted. The name later became B&K I don't know the history

There is indeed a Flying Spot Scanner in the unit and you can find and print antique test patterns to display on your old TV.

Now in the year 2020; what we called the future, there is no analog Television on the air broadcasting.

There were several models of these things starting with 1000. The 1076, and 1077 were more for use on the repair bench and they provide color test signals as well as audio. They have output ports for horizontal drive, vertical drive as well as output on several TV channels including UHF.

They make a quick way to troubleshoot.

Jim


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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 6:08 pm 
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Thanks jimmc, now that does bring back some memories of this test equipment. Really could impress customers when after repair you could generate a test pattern with your own advertising picture.

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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 6:47 pm 
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They had fairly strong RF output so some large hotel/convention centers would print slides with event info and use analysts to pipe them down the antenna system..

Part of me wonders about turning one into an agile modulator...


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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 8:59 pm 
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As I recall the PM tube puts out 1 volt of video no sync.

I would suppose it would be easy to jeep it.

Jim


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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 10:15 pm 
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Quote:
As I recall the PM tube puts out 1 volt of video no sync.

Wouldn't the PM video have some semblance of sync during retrace and blanking periods ?. Of course proper sync levels can be added down stream.

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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 10:57 pm 
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judge wrote:
Tom, the waveforms all have the right shape, just lower peak-to-peak than they should have.

The height control should be able to compensate for that.
I wonder if the foil connecting the brown lead from the vertical part of the yoke back to the B+ could be severed.
That might be something that could have happened when you replaced the filter cap.
I am assuming that you did check for signal at the plate of V1B.

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 Post subject: Re: 1077B schematic?
PostPosted: Mar Wed 04, 2020 11:46 pm 
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Tom Schulz wrote:
judge wrote:
Tom, the waveforms all have the right shape, just lower peak-to-peak than they should have.

The height control should be able to compensate for that.
I wonder if the foil connecting the brown lead from the vertical part of the yoke back to the B+ could be severed.
That might be something that could have happened when you replaced the filter cap.
I am assuming that you did check for signal at the plate of V1B.


The height control makes a difference, but not much. There is maybe a quarter inch of deflection.

Foil eh? I'll have to have a look.

I probably checked the signal at the plate of V1B. I certainly checked the signal at the grid and I'm pretty sure I checked the voltage at the plate because I was wondering about T-1. And I've tried a new tube here.

Something I should be more careful of is checking that these signals get to where they're supposed to be going.

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