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 Post subject: Heath 100-203-31 oscope clock conversion
PostPosted: Apr Wed 04, 2018 2:45 pm 
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I have a Heath 100-203-31 oscope that I installed an oscilloscope clock in a few years back.

Decided to replace the clock because the RTC stopped working properly around a year or two ago and noticed that I got no trace.

Checking around showed R208 a 470K resistor open with a burn near one end.

Replaced the resistor with four 100K resistors and one 75K resistor then powered it up noticed a buzzing and saw the resistors start to smoke.

Figuring that C203 a .1uF 1600V cap was bad I replaced it with no change in operation.

Here's a link to the schematic.

http://www.bunkerofdoom.com/lit/belland ... index.html

Any ideas as to where the problem is?


Last edited by Tube Radio on Apr Mon 30, 2018 8:18 pm, edited 2 times in total.

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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Wed 04, 2018 3:50 pm 
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I must be missing something. The R204 I found is a 100K. ?

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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Wed 04, 2018 4:56 pm 
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Correction:

R208


Think I may have found the problem.

Since there is buzzing I decided to bring a 10X scope probe close to see if I could see any AC and sure enough there was an oscillation that got greater as I moved the probe near Q202.

When I tested Q202 using the diode check on my DMM it checked ok.

Now either the oscillation is just arcing inside the transistor or it is an actual oscillation due to a failed component somewhere.


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Wed 04, 2018 7:29 pm 
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This is a puzzler. I noticed IC201 is an opto-isolator. It probably functions as a feedback signal to a voltage regulator circuit. I don't know whether or not there should be oscillations in the signal. The pulsing would be filtered out of the final (Probably high voltage) if it is supposed to oscillate.
What does the signal (or dc voltage) look like at terminal H ?

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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Wed 04, 2018 8:08 pm 
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Well, given the obvious overload condition of the HV supply, and assuming you have verified the HV doubler components (diodes and caps) as ok, I'd start disconnecting loads to isolate the issue. Unplug the CRT socket to eliminate a shorted CRT as any possible culprit. Also consider that given the HV nature of this circuit, you could have a device testing OK with your DMM, but failing once HV is applied to it. There aren't many components here ... might be a lot quicker just to replace the two transistors and handful of diodes if "load shedding" doesn't isolate it for you

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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Thu 05, 2018 12:27 am 
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Notimetolooz wrote:
This is a puzzler. I noticed IC201 is an opto-isolator. It probably functions as a feedback signal to a voltage regulator circuit. I don't know whether or not there should be oscillations in the signal. The pulsing would be filtered out of the final (Probably high voltage) if it is supposed to oscillate.
What does the signal (or dc voltage) look like at terminal H ?


The opto isolator is part of the retrace blanking circuit.

It's a weird circuit for sure. More complicated in my opinion than it needs to be.

I do have another board from another of the same scopes that is for parts. I could try the transistor from it.


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Thu 05, 2018 1:35 am 
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Ah, I see. Was the signal you were picking up from the blanking?
It doesn't look to me that the transistors have much voltage across them.
Maybe a control has developed a short to ground. Isolating the possible loads is a good idea.

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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Thu 05, 2018 6:56 pm 
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Not sure it was the blanking I was picking up.


I did find the other scope that I have for parts, but it did not have the power supply/HV board in it, although the vertical and horizontal baords do use MPSU10 transistors for the deflection plate drivers so I will just use one of those and see if it now works.

One sugegstion was to remove components one at a time until I found the colprit, but the problem with that is the PC board isn't necessarily of the highest quality and it's quite easy to pull a trace plus I don't want to pull one component and it allow a higher voltage on another component and damage it.

I don't quite understand the retrace blanking circuit.

Looks like there's two control lines for it.

One that feeds the opto-isolator.

One that feeds Q203.

The one that feeds the opto-isolator might be something to just turn the beam on and off so that when the trigger mode is set to normal and there's not enough signal to trigger the scope the beam is not shown.

The other which is capacitively coupled to G1 might be the actual retrace blanking.

Here's a solid state CRT driver and it does support a 5UP1 albeit with a dim picture.

http://www.electronixandmore.com/projec ... index.html

Would be better as the original circuit in this scope isn't necessarily the best given it was a kit scope.

I am contacting the designer to see if the circuit can be modded to use the higher B+ necessary for the 5UP1 CRT.

If I use that circuit I gotta decide if I want to restore the working scope to original and use the parts scope for the clock or use the working scope and gut all of the circuitry not needed.

Thing is given this is a kit scope and I have other much better scopes this will never see any use as an actual oscope.

If the solid state circuit works well I could modify the parts scope with that circuit given it is mostly complete.

The issue is finding 1 meg panel mount controls that can handle the HV.

That said do I really need 1.6KV on the 5UP1 or will the peak unloaded rectified DC voltage of 1.131KV from the 800 volt winding be enough?


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Fri 06, 2018 1:34 am 
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Why not just try to isolate the problem by disconnecting different circuit sections at the wire connections. I don't think unplugging the CRT will cause a problem.
Why do you suspect a transistor, could be a number of things.

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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Fri 06, 2018 3:30 am 
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I suspect the transistor because that's where the strongest oscillations are from which was checked by moving the 10X probe near the components on the power supply board and is one place arcing can occur quite easily.

Plus I have three good transistors from the parts scope and that is an easy change.

I can rule out the CRT socket because I replaced the original with a new ceramic socket when I restored the scope.

I did notice that the 3.3 meg resistor in the focus circuit does read a little over 4 megs which could explain why the focus control has to be turned father CW than normal for proper focus.


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Fri 06, 2018 1:44 pm 
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Things I've tried that did not work.

1. Replaced Q202
2. Unplugged CRT
3. Verified 800 volt winding is good.
4. Verified resistors in spec.

Now what's interesting is this.

I get oscillations on terminal H of the power supply board which is the blue wire and goes to the opto-isolator.

I had previously cut the wire in two in an attempt to get an intensitity modulation input, but soldered the wire back together.

If I unsolder that joint I still get oscillation coming from the horizontal board and the same oscillation on the other end of the blue wire attached to the power supply board as long as the CRT popwer supply has voltage.

The voltage on the other end of the 470K resistor is 135Vdc and it isn't stable due to the oscillation.

Now if C201 were to go bad would that cause the transistor to start oscillating?


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Fri 06, 2018 1:50 pm 
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methinks thou hast doneth too mucheth ..... but ... what do you mean by "oscillating" ?? Can you see this on a scope? What approx frequency?

I'm guessing that what you describe might be HV going into some kind of protective shutdown. As far as scope HV circuitry goes, this scope has a pretty simple approach and should be relatively straightforward to resolve. Might try stepping away from it for a few days and revisiting it .. I know that sometimes I get stuck like this, and when I come back a few days later the issue is obvious...I'd been seeing the same problem over and over so much I overlooked it completely.

lotsa luck :)

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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Fri 06, 2018 2:32 pm 
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It's a pulse and I am not sure of the frequency.

Seems like the transistor is oscillating.

I did swap C201 and C208 to see if C208 was bad and unless C201 is also bad there was no change in operation at all.

Pretty sure the intensity control is not shorting to ground unless the plastic used to mount it in the front panel hole has gone conductive.



EDIT:

Unfortunately I found the problem.

Decided to do an ohms check across C203 and got 1K. I got to looking and there is a wire from there to the intensity control and also to one side of the CRT heater.

I came across either C204 or C205 (forgot to discharge them) got a shock and now I get 42 ohms.

Disconnected the wire to the intensity control no change.

Disconnected the wire to one heater pin and got well into the megohms resistance.

So there is a short to ground of the CRT heater winding in the power transformer or one of the leads.

Going to remove the transformer from the shielded box it is in and look at it to be sure there's no easily repaired fault with the wires.

If it can't be fixed I will pull the power transformer from the parts scope and install it.


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Fri 06, 2018 5:00 pm 
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The transformer was on my list of suspects, but I didn't want to jinx it. Tin whiskers in the pots was
another.

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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Fri 06, 2018 5:27 pm 
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I did a check between the CRT heater winding and all other windings. I got 255.5 ohms between the CRT heater winding and the 6.3Vac winding I used to power the clock.

Given one side of that winding is grounded here's what I think happened.

Those two windings might be wound close together and with one side grounded the HV DC might have eventually gotten to the point where it would jump over to the other winding.

Now is it safe to use that transformer or should I use the other one and just find another way to power the clock?


EDIT:

Success.

Put it back together and it works except I cannot control the intensity as it is full brightness no matter what I do.

The parts scope was like that and I never found the problem.

I checked voltages on Q202 as I varied the intensity control and the voltages did vary a good bit although I don't know what the voltages should be.

Any ideas as to what the new problem is?

Also I tried powering the clock from the LV power supply which is 33Vdc before any regulation using a 500 ohm series resistor.

Seemed to work, although I tested that with the old clock as I was not gonna experiment like that with the clock I just built.

From what I saw when powering the new clock from the power supply i have at work it draws around 50mA. Will that be ok on the LV transformer winding or will I need some other method of powering the clock?

EDIT 2:

I'll try troubleshooting Monday and see where I get.

At this point it might be better to go with that other circuit.

It's much simpler and doesn't produce near as much heat.

Also with that circuit dpending on the hv I might be able to get away with using regular uninsulated pots for the intensity and focus controls.

I ordered three of those boards as I have two of the heath scopes and plan on making a 3" clock for work.

Will still troubleshoot this one until the boards arrive and I get them built.


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Mon 09, 2018 2:13 pm 
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Got the intensity control problem fixed. Turns out one terminal on the CRT socket was touching another.

I used a 475K resistor after the first one to form a voltage divider and I can get a usable display on -816Vdc to the CRT. Won't go full brightness and focus is a little off though.



As much as I hate to I may use the original CRT power supply. In a way that simplifies things because the CRT circuitry is on the main power supply board so I will already have the properly rectified DC voltages for the CRT driver circuit and the clock circuit. I can just remove from the board what components I don't need.

That said I will build the circuit as is and try the CRT on the circuit just to see how dim it really is.

Interestingly enough the original focus control is 1 meg which is what the driver circuit calls out for the focus control so I can leave that in place.

Now if I 1/2 wave rectify the 800 volt winding I would get an unloaded V+ of 1.131.2KVdc. I can test if that will be enough by using a 1 meg resistor for the divider which will give me 1.106KV.

If that is bright enough I can leave out the 1uF cap on the driver board which supplies the AC voltage to the voltage doubler and omit one diode and filter cap.

For the clock I found that a 250 ohm resistor fed B+ from the 45 volt transformer winding works great and gives me a B+ of 16Vdc to the clock circuit.

Think the main B+ there is 35Vdc, which includes the load of the rest of the scope that does not receive any high voltage so when just the clock is running on that B+ line I may need a different resistor depending on how much B+ is increased if it takes B+ over 25Vdc given that's what the caps on the board are rated at.

Now while doing a test I accidentally touched a grounded lead to one of the wires for that 6.3vac winding and did get a spark so there is indeed DC leakage to that winding from the CRT heater winding.

EDIT:

So I did a test using a 1 meg resistor which was made up of two 1 meg in parallel in series with two 1 meg in parallel and I get these voltages. Had to take the voltage across one resistor and double it since my meter will not go over 1KVdc

Intensity control full CCW -1.142KVdc
Intensity control full CW -1.110KVdc

Nice bright display.

Focus not quite as good as it should be, but that's because of the out of tolerance 3.3 meg resistor in series with the focus control.

Now given the HV will a standard panel mount variable resistor be ok for the intensity control or will I need one of those that is insulated from the front panel?

The resistance load that will be seen by the HV circuit is 970K and at a B- of 1.132KV that will give me a load of 1.132mA.

Now I've stumbled upon a problem.

I measured the B- current across R208 the 470K resistor and the current is only 420uA which given the voltage doubler would be 840uA.

The problem is I don't know the current rating of the 800 volt winding so I don't know that I can use the 800 volt winding. It would take a voltage quadripler on the 210 volt winding in order to get the necessary B- for the CRT.

That basically means I will have to use the power supply board.

Now to show how inefficient the scope is it uses a 10K 10 watt resistor fed from the 180 volt source ( derived from a 1K 7W resistor in series with the B+ which feeds the horizontal deflection output transistors as well) followed by a zener to ground for the sole purpose of providing a regulated 68Vdc for the retrace blanking transistor.

EDIT 2:

Found out that the opto-isolator does indeed blank the trace and it's an on or off type of control.

That is controlled by a front panel knob called stability.

Also the transistor that does the retrace blanking I tried to use it for the scope clock by putting a 10K variable resistor in series with it and the ZINV output.

I could get it adjusted to where it looked good for the clock face, but the menu didn't look so good.

The new clock board apparently uses less B+ current because I only needed the 500 ohm resistor to provide around 10Vdc B+ to the clock.

Another benefit to using this circuit is it eliminates all the power resistors in the power supply so there's a good deal less heat inside the scope.

The plan is to use panel mount pots so I have all the adjustments on the front panel aside from the astigmatism adjustment.

Will keep the original knobs so I'll need D shaft controls.


EDIT 3:

So the plan is this.

Given I have another of these scopes that is complete minus the power supply board and the other clock board (sparkfun version of dutchtronix clock) fully works aside for the Z axis output and RTC I will leave the fully working scope alone for now and use the other scope and scope clock to experiment with the CRT driver board and once I get it right I will most likely leave that circuit in that scope and buy another of the current Dutchtronix clock boards.


EDIT 4:

Noticed something when adjusting the scope for the best display.

The 100 volt adjust (vertical linearity) affects the focus on the left side of the CRT and I can set the astig control to where either the 9 is focused decently the 12 is sharply focused and the 9 is out of focus or to where the whole display is decently focused.

Not sure if it is a CRT issue or just the scope circuitry, but I am betting it is the scope circuitry.

Also found out the opto isolator was causing the intensity to vary and drop for low intensity control settings so I just removed it from its socket. After doing that the issue of the CRT having a dimmer display for about a minute when the scope is first turned on seems to be gone.

Don't know if this was intentional or was done to keep costs low, but while the red power LED on the clock board lights up a normal brightness for a modern red LED, the green flashing LED lights up obnoxiously bright.

Had I known that I could have put the red LED mounted to the top of the cabinet in series with it and not needed the reistor in series with the red LED which is in parallel with the green LED.

I did notice that the clock does get a little off slightly which is partly due to the XTAL for the RTC and I'm sure the heat in the scope is part of the issue as well. I do have an OCXO i got for use with the other clock board as I had thought the XTAL was bad so I may use that with this clock and figure a way to install a 5 volt always on supply to power it.

This is the TCXO I plan on using.

https://datasheets.maximintegrated.com/ ... 32KHZS.pdf

Looks like instead of a separate power supply running the TCXO I can just use a battery connected to the proper terminal so that it operates properly when the scope is turned off.

OR

I could remove a diode in series with the battery and remove the battery on the scope clock board and replace the battery with a 1F or larger 5.5 volt capacitor which would power both the RTC and TCXO and keep them powered when the scope is turned off. It won't last as long as a battery though.

Noticed the display decreasing in size around once a second in the menu mode and traced that to the B+ dropping some.

I felt the filter cap for the 30Vdc supply and it was hot. I used a good quality Sprague Atom because I knew the power resistors near it would heat up the cap some.

Found a 10K 10 watt resistor was the hottest one in the scope and it just so happened to be the one for the retrace blanking transistor :shock: So I promptly removed that resistor since I am not using the retrace blanking. That increased the deflection circuit B+ to 230Vdc from 200Vdc, but didn't affect the deflection at all.

That's just how dumb some of the original scope circuitry is and is exactly why I am testing the CRT driver board so once it is perfected in the other scope I can ditch the original circuitry in this scope and install the driver circuit.

I know it was only a kit scope possibly designed as cheaply as reasonably achievable with the commonly available components of the day so I don't really fault it as it did what it was designed to which was to allow a person to build their very own oscope and learn how one operates.


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Wed 11, 2018 3:07 am 
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Now for the other scope like this one I am thinking of installing a red LED in place of the neon lamp and connecting it to the clock board,s power indicator LED through a resistor that will make it light at 1/4-1/2 brightness then I will connect through a resistor the same LED to the flashing LED on the clock board so it is full brightness. I will use a diode in series with each resistor so that the PC board connections are isolated from each other or maybe I will use one of my RGB LEDs and just use the red and green which when flashing will give me yellow or I can use red and blue for purple when flashing or blue and green for blue green when flashing or I could use some sort of switch arrangement to select which LED color is used for what. It all depends on how the original red lens does the colors though or I could use a LED grommet and ditch the original neon bulb lens.

For this scope I had drilled a hole in the top of the scope for a red LED so that I could see the status of the clock (flashes at .5Hz) without opening up the scope which is important when for instance putting the clock in programming mode for uploading new firmware.

I figured with the other one I needed a power indicator light anyways and the LED was a perfect suggestion as it could do both functions and I wouldn't have to be drilling any extra holes in the case.

Also if I can find two pushbuttons to either fit where the banana jacks go or where two controls go I will have to drill no holes aside from the rear of the scope where the serial port will be.



EDIT:

Got the TCXO installed and running off the same power point as the RTC so that it is powered at nearly 5Vdc when the scope is on and 2.9Vdc when the scope is powered off.

What I shoudl do is remove the diode in series with the battery and test how much current is being drawn, although I'm sure it is in the microamps based on the datasheets for the RTC and TCXO.

After running several hours this morning the clock is still 2 seconds faster than the clock I used to set it around 8 AM.



Also found a 270 ohm 2 watt carbon comp resistor reading around 330 ohms that was quite warm to the touch.

I promptly replaced it with a 270 ohm wirewound resistor.

Why try to replace parts on the original scope circuitry when I'm just going to replace it soon?

Because I want this one operating properly and safely until I get the CRT driver perfected at which point I will either swap the circuitry into this scope if the Dutchtronix clock is still sold out or if the Dutchtronix clock is available again I will buy another and install it in the other scope then buy the parts for the second CRT driver board.


EDIT 2:

Installed some new rubber feet on the scope bottom.

Also another reason for ditching the scope circuitry is that upon cold startup the vertical for the most part and to some extent the horizontal is out of position with the top and right of the clock display slightly off screen for a few minutes as the circuitry warms up and the clock face will gradually move to the correct position.

What I would like to do if I can find them is get some multi turn panel mount pots with a D shaft for the vertical and horizontal size and position controls. That way I have more of a fine control.

Also having reset the clock to the official NIST time it is two seconds fast, but I cannot remember if that was due to the delay after setting gthe time or if I didn't set it exactly on the minute or if it is just the XTAL aging which for the first year is +/- 1PPM. Also for temperatures between 32-104F the variance in frequency is -2 to +2 PPM.

That's another reason for ditching the original circuit. Less heat generation which will be better for the TCXO.


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Sat 21, 2018 2:12 am 
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A couple nights ago I had the clock running while i was looking for something and came back to thr display expanded as though I turned up the vertical and horizontal gain a good bit and the intensity was lower.

When I reduced the vertical and horizontal gain the display was very unstable changing size on its own.

Not sure what the issue is, but I do believe I'm going to use this scope to try the CRT driver circuit in since the original scope circuit seems to keep developing problems and I'm not gonna keep troubleshooting it when I'm just gonna replace the circuitry soon anyways.

Going to first try the voltage doubler on the board, but I will build it using the HV components I ordered in case I do need to use the 800 volt winding. All I have to then do is remove the 1uF cap coupling the winding used for the deflection supply to the voltage doubler and connect the 800 volt winding. If I need a lower B+ i could sub the cap with the 800 volt winding wired out of phase which will reduce the voltage going to the doubler by around 200 volts.

I'll first check to see if it is a voltage issue on the HV winding. If so and it is present with the HV winding disconnected then the transformer is no good and I'll use the one from the other scope.


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Mon 23, 2018 11:57 pm 
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Well I started building the CRT driver and I removed all of the original scope circuitry I didn't need.

I pulled the necessary controls from the other scope and had enough to where I didn't need the 1 Meg and 100K controls I ordered given I have decided not to use the other scope for a clock.

I decided to try using the 800 volt and the other HV winding in series opposing to lower the 800 volt winding, but I was only getting 52Vdc out of the voltage doubler.

I decided to check and I am getting 250 ohms from the side of the 800 volt winding that is normally grounded in the stock scope circuit and when power is applied I am getting 2Vac between that winding and ground.

So I believe that transformer is no longer any good and maybe that is what was wrong with the intensity doing like it was.

Now the other power transformer is good at least it was when I got the scope and was trying to troubleshoot why the intensity was full on all the time so I will replace it.

Good thing is now I will have a good 6.3Vac winding to power the + and - OP-AMP supplies on the CRT driver board and maybe the clock board without having to use the 42 volt winding.

Also while testing the board with just the focus and intensity pots connected the 800Vac winding dropped to 798Vac so it should be able to handle the load.

The 1 meg pots were originally the focus controls in both scopes and they both have a plastic shaft. At nearly 1.6KV I did not hear any arcing to the chassis from the controls so I really won't need to drop the HV down any.

Makes me wonder if the other transformer will suffer the same issue.

Also makes me wonder if using the unused 6.3Vac winding caused the issue with the transformer.

Of course I could still use the original power transformer, but I don't know how long it will last before finally giving up the ghost.

Also there's around 72Vac ripple on the B+ of the CRT supply which is due to the smaller value caps I used in order to get to 1.6KV voltage handling since the two 2.2uF caps intended for the circuit are only 450Vdc each. Never dealt with that high of a voltage so I don't know if the ripple is too high or if it is fine.

If necessary I can mod the circuit somehow to include a 470K resistor and another filter cap which will drop the B+ down some and provide better filtering.


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 Post subject: Re: Heath 100-203-31 oscope problem
PostPosted: Apr Thu 26, 2018 9:46 pm 
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A little preface.

The designer of the CRT driver board did tell me I should keep the original CRT power supply and intensity and focus control circuitry which I promptly ignored not wanting any of the original scope circuitry at all and thinking I can make the driver board power the CRT properly.




Well I've been experimenting with the board and CRT trying to get it to work good.

I found out why I could not add any resistance after the voltage doubler. It was due to where G1 was receiving its voltage which was from the board itself. I disconnected the 47K resistor from the board and connected it to the end of the controls that receive the B- voltage. I then installed a 470K resistor between the last filter cap and the controls then put a .1uF cap to ground to provide better filtering.

That seemed to work ok, although it worked fine without the resistor which placed a higher B- voltage on the CRT with one caveat which is there isn't enough drive from the deflection transistors as the left side horizontal will not expand fully to the left when displaying the clock.

One problem I have is getting the focus just right.

I've had to experiment and nothing I do can get the focus exactly correct.

I ditched the on board astigmatism pot in favor of the one the scope had and connected it in the same spot.

I can get the focus close at low intensity levels, but nothing like what it was with the original scope circuitry.

I can maybe post some measurements tomorrow if I have time, but if not then it will be Monday before I can do anything with it.

Also the geometry of the clock display is off with some of the letters and numbers not being exactly right.

I think that I have a ground loop issue though of some sort as I moved the ground for the clock board to where the main ground is (used to be connected to where the signal ground was in the original scope circuit) and the display was a little better.

Perhaps that's the issue with the geometry as well.

I did notice that when I soldered the deflection plate wires (300 ohm twin lead originally which I kept) to the board instead of using clip leads the display looked a little better.



I'm going to need some help from those who know electrostatically deflected CRTs specifically the 5UP1.


https://frank.pocnet.net/sheets/049/5/5UP1.pdf



EDIT:

Well I re-drew the original crt power supply and control circuitry and I understand better how it works and how I should mod the current CRT driver HV section. Or at least what I should try far as getting the correct voltages.

Only thing I don't have is voltage measurements of the original circuit unless the scope's asembly manual has the voltages listed.

If I knew the voltages I could calculate the current drawn and could figure out the necessary resistors to get the proper voltages.


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