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Thank you very much Oz, David and Colin.

Sorry for such a late response just been dealing with health issues.

And thanks for the correction on the TO as I did not know what those letters stood for.

James

But that is the preselector that you are tuning.

-Chuck Harris

adil malik wrote:

The sticker is blank unfortunately. But I have opened it up to have a look and the YIG preselector is present and seems to be hooked correctly.

Ok thanks for that. I will try what John suggests but the preselector or its relays feel like the fault to me.

What options does the analyzer have? there is a sticker on the back
outlining that.

BR. Thomas.

tor. 1. aug. 2019 kl. 18:48 skrev adil malik <adilmalik_n@...>:

--
With Best regards, Thomas S. Knutsen.

Please avoid sending me Word or PowerPoint attachments.

The PEAK John was talking about is a knob that allows you to
tune the center frequency of the YIG Tuned Filter to peak at
the frequency of the YIG Tuned Oscillator. In other words, make
the two YIG's track each other more perfectly.

It is simply adjusted for maximum signal amplitude in the swept frequency
range of interest.

The PEAK/AVERAGE knob, if I recall correctly, divides the display
into an upper region, and a lower region. The signals displayed
above the dividing line are using a peak detector, and the signals
displayed below the dividing line are using an averaging detector.

It has nothing to do with what John was suggesting.

-Chuck Harris

adil malik wrote:

On Thu, Aug 1, 2019 at 06:48 PM, <twincam18@...> wrote:

I have checked the voltages that come into to the deflection amplifier/high
voltage board. There is a 200v+, 30v-, 30v+. 5v+ and they are all right on the
dot. I have done a quick visual inspection and esr readings on most the
capacitors and so far I am not seeing anything.

Any help or just ideas of what I should check would be greatly appreciated!

Unlike the 576 Test Fixtue the 577 Test Fixture (177) is not passive i.e it has a
pre amp. If the input FET get busted it will send the beam off screen. I've seen
this happen several times.

If my memory is correct this could happen due to arcing in the Looping Compensation
variable cap when the Collector Supply is set to its max (> 1600V) and the Vertical Current/div
is set to a low current.

So checking the output from the 177 would be a good place to start.

/H?kan

Hi John,

Thanks for your help.

Is there a section in the manual that explains what the peak/average knob does? Im not quite sure what I am testing with what you suggested above.

Thanks

The bottom readout line on my 7704A appears to be out of position and has gone up - it is located at
one third of the screen from the bottom. The one at the top is ok and well positioned. I tried to
use
the vertical separation pot but if I use it, then the top line goes up outside the CRT. I've
replaced the
tantalum capacitors on the readout board and the voltages appear to be spot on. do you know what I
could try to troubleshoot?

Apart from the occasional dead readout chip (which has much more obvious problems) I once had a
resistor on the readout board go open. Very odd since it looked like metal film - but worth checking
on yours.

Craig

Thierry,

Pull the vertical plug-ins out, power the scope on with known good horizontal time base(s). This will see if the vertical is centered inside. If not, remove the left side cover then adjust R4493 on the vertical board. This the main centering pot. When that is centered, turn off the scope, install a vertical plug-in with its left side panel removed on the left for easier adjusting. See if the readout is centered, not with what you say is happening now. If centered, adjust R3490 (vertical separation) to see if that causes the readout to expand to the top and bottom. If it works, then adjust the Character Scan R3457 for the character height desired. If it is still off, see if contact problems are causing the problem. This is common. Clean the pins with 91% alcohol using an artist brush that is small. Pull the devices, ics and transistors out first. Put the alcohol on the pins of each device and sockets, insert the device, pull up some then down several times while keeping the pins in the socket holes. A few mm of up and down with the device usually cleans the contact problem. Doing this to the coax ends inside the unit should also be done. The center wire will oxidize enough to cause problems even though it cannot always be seen. A bad transistor, ic or both can cause readout problems. I replaced the 1500 and 510 ohm resistors to Q3493 and Q3499 with 1/2W and 1W respectively because the originals are too small in wattage, 1/4W. I use only 1% types for the low drift due to temperature, 50ppm/deg. C. I used 47mfd 25V Nichicon ULD types for the decoupling in place of the original 1mfd tantalums. These give higher decoupling while having a very low ESR and long lives. Some 1mfd tantalums were replaced with 1mfd 63V film types. The left panel removal on the left side of a vertical plug-in is for internally adjusting the vertical centering inside of that type once the trace is centered on the vertical board. I hope this helps.

Mark

Perhaps you might check the socketed chips on the board located on the right side of the instrument. Carefully wiggle or reinsert the IC's in their sockets, the transistors are also removable as well so give them a careful moving around, maybe this might improve things if there is oxidation on the contacts. I recently had to replace a failing IC that was on the CRT horizontal driver. Also on this forum it was mentioned these 577's can have IC sockets that are prone to failing due to their design.

Here is some more information on the the horizontal and vertical display CRT driver IC's
U520 U530 Horizontal driver MC1456N 8 PIN DIP
U570 Vertical driver MC1456N 8 PIN DIP

Here is a quick test I did on a 577 you could perform
With the horizontal and vertical display controls centered, collector supply set to 6.5V, collector supply polarity set to AC, horizontal volts division set to 0.5V, if you adjust the variable collector supply with the beam finder button pushed do you notice the appearance of a emerging horizontal line on the screen? If so then I believe your horizontal circuit is somewhat working.

To start debugging, I inspected the 2nd LO used for the higher bands, and

it

correctly turns on in the appropriate bands despite not responding to any

input

signals. This tells me the 2nd LO circuit is operational.

Any ideas about how to proceed debugging?

I'd start by checking the preselector. Hit the blue-shift PEAK MENU button
and put it in KNOB mode, apply a strong signal at +10 dBm or so, and see if
you can find it by adjusting the MANUAL PEAK control back and forth slowly.


If you can peak it manually, you can either go through the tracking
calibration steps in the manual, or just use it in manual-peaking mode.
Worst-case, you can bypass the preselector and use the analyzer that way,
but the preselector itself seldom fails.

-- john, KE5FX

On Thu, Aug 1, 2019 at 11:48 AM, <twincam18@...> wrote:

Hello, this is my first post here. I hope I am placing this in the right spot.


I have a 577 Curve Tracer that I bought from school surplus. It had been
sitting in storage for many years. Upon power-up, I do not get a trace/dot on
the screen. However, if I press the 'beam finder' button it shows a dot in the
lower middle of the screen. Yet when I go to adjust the beam onto the screen
neither the horz or vert position knobs make any change. If I hold down the
find beam button and turn any of the scope settings there is no change on the
beam dot, it stays in the same place and a single small dot.

I have checked the voltages that come into to the deflection amplifier/high
voltage board. There is a 200v+, 30v-, 30v+. 5v+ and they are all right on the
dot. I have done a quick visual inspection and esr readings on most the
capacitors and so far I am not seeing anything.

Any help or just ideas of what I should check would be greatly appreciated!

I forgot to ask, how are the controls set up? You should have them set per the Operation Manual under “Preliminary settings”.

--
Michael Lynch
Dardanelle, AR

Hahaha-
Thanks for the offer, Bob; tempting, but I think I'll pass.? The tube stuff doesn't get used much since the garage has been almost completely taken over by machinery.??
-Dave

Mike,

I am currently troubleshooting Trace problems on my 465B Tektronix
Ocilloscope.

JR

Or possibly the deflection amplifier? see Sheet 6 and Sheet 7 of the schematic. Should be easy enough to verify voltages and/or waveforms through the circuit. Look for a common point that would affect both Horizontal and Vertical alike.
--
Michael Lynch
Dardanelle, AR

The 577 has something called “auto-position”, This circuit routes through the test fixture, possible something is amiss there? I have not worked on a 577, but that is where I would start.

--
Michael Lynch
Dardanelle, AR

You can buy my 1A2 if you want another step toward a complete collection.
Bob On Thursday, August 1, 2019, 01:33:50 PM PDT, Dave Seiter <d.seiter@...> wrote:

Certainly not the full set at all, but Tek only: 067-0521-00, 1A1, 1A4, 1A6, 1A7, 1A7A, 1L5, 1L20, 53/54C, 53/54G, B, CA, D, G, H, K, L, M, ML, O, Q, R, W, Z.
I think the mil versions (like the ML) are pretty elusive.?
-Dave

Certainly not the full set at all, but Tek only: 067-0521-00, 1A1, 1A4, 1A6, 1A7, 1A7A, 1L5, 1L20, 53/54C, 53/54G, B, CA, D, G, H, K, L, M, ML, O, Q, R, W, Z.
I think the mil versions (like the ML) are pretty elusive.?
-Dave

Years ago I got a SC502 for a song as "parts only"(but it had a trace), and while it worked, the vertical positioning was weird- both knobs affected both traces, in opposite directions.? I did reseat all the connectors back then, but must have missed the ones to the V amp... (it is a rather compact unit, after all!)? Today I started wondering if it might have the same issue as the 5111, and sure enough, not only was one wire loose, it was off the lead entirely.? No way it vibrated off unless someone didn't reinstall it correctly.??
-Dave