Believe it or not I obtained one ! However it is from another scope so I am kinda back where I started becasue two scopes are better than one.

Turns out the first specimen had been modified but I didn't really notice it. Beside my eyesight going to the bats (not dogs), I was totally unfamiliar with the unit and the modification was under the aluminum plate on which the vertical output amp lives.

The first one had option 034, which is alot more useful to us than the option 101 on the parts donor. Don't look it up, 034 is the multimeter on top and 101 is an interface for a data acquisition unit.

So, upon installing the IC along with the whole board because I figured there would be the least amount of alignment needed that way, plus who knows what else they did to it, it worked, but not quite fine. Here's what channel A looked like on the internal calibrator with a 1X probe :

https://dl.dropboxusercontent.com/u/...725/shch01.jpg

At first I thought the output amp was all whacked out for some reason, can the plate capacity be that damn different ? Nope, this is channel B :

https://dl.dropboxusercontent.com/u/...725/shch02.jpg

Turns out the brainiac who came up with the modification decided to tamper with the vertical preamp instead of what had been changed. I am a mad modifier from way back so I know better. I also know what DC coupling is, unlike that guy, who came up with this :

https://dl.dropboxusercontent.com/u/.../wingnut01.jpg

All nicely put on a perf (which is OK actually) :

https://dl.dropboxusercontent.com/u/...725/this01.jpg

And mounted well : (or is that mounted, well ?)

https://dl.dropboxusercontent.com/u/.../1725/aa01.jpg

And totally disfunctional. It had no vertical deflection except in chop mode where you could see a haze of a waveform when you adjust the position. Not quite the accuracy I was looking for...

So someone here turned me on to a Romanian website with a possible modification thus :

https://dl.dropboxusercontent.com/u/...725/romo01.jpg

Looked pretty good. The MOSFETs probably didn't exist when the thing was built, and it saves components. So I used it on specimen number two. Of course it was supposed to be this :

https://dl.dropboxusercontent.com/u/...725/orig01.jpg

After looking around, I found a local supplier with some surplus VN88AFs laying around. Looked like pretty low capacitance so I took them.

At this point, other than the usual other problems like it won't trigger half the time and the sweep time knob takes a pipe wrench to turn, the amplitude is low. About 33% low. It is the same on both channels. I am pretty sure I can adjust it there, but I would rather get the gain where it is supposed to be, especially since the position controls just barely take the trace off screen. It should have a bit more range than that.

On this unit, the 1Khz calibrator signal looks pretty good. However a 1Mhz square wave, even though I can't get it to lock right now, appears to have a hell of alot of ringing in it. Also in chop mode, you can see a bit too much that you are not supposed to see.

I figure I should tackle the gain problem first because without that the thing is a toy. What I am thinking at this point is to change the 1,000 ohm resistors to about 1,500. Or should I go higher ?

In the orginal IC, the two 500 ohms add up to 1K, that constitutes the feedback obviously. I find it hard to believe the gain is lower using that MOSFET. I do realize that it takes more voltage to turn it on, but that doesn't necessarily cause that.

Also, the Romanians have their 47 ohm to ground, I tried that and the plate voltages were too low. I tied it to the original land for the IC pin on the amp board and it is alot closer. The print calls for 40 volts and I got 38 and change. Of course I tried jumping out the resistor but as expected it did nothing for the differential gain, just lowered both plate voltages some.

So at this point I have set it aside and figured I'd see if anyone has any ideas. I'll find the right resistors sometime later and see about getting that gain up. Then I want to do something about the ringing but first mayb I'll get it to trigger. I suspect that as I've read on a bunch of these units, the switches are just dirty. I'll give them a good bath of course. Hopefully that does it.

There is another problem that might be best fielded by someone familiar with these units. I have my little board under the aluminum, which is right where part of option 101 goes. I have no room for both. I could try to make the thing smaller so it can go on the top, but since the original was on the heatsink, I figure the modification should be as well. It would be damn tough to get these parts to fit down there.

So since I have no need for option 101, any ideas on how I can remove it and have the thing still work ? It would do nothing without it connected. Not just not a trace, not even a dot at the left side of the screen.

Any ideas, thanks. If you want to comment and tell me I am crazy, fine. I'll just go back on my meds - Budweiser. (probably do that anyway...)

On Monday, April 7, 2014 3:03:26 PM UTC-4, wrote:
Believe it or not I obtained one ! However it is from another scope so I am kinda back where I started becasue two scopes are better than one.



Turns out the first specimen had been modified but I didn't really notice it. Beside my eyesight going to the bats (not dogs), I was totally unfamiliar with the unit and the modification was under the aluminum plate on which the vertical output amp lives.



The first one had option 034, which is alot more useful to us than the option 101 on the parts donor. Don't look it up, 034 is the multimeter on top and 101 is an interface for a data acquisition unit.



So, upon installing the IC along with the whole board because I figured there would be the least amount of alignment needed that way, plus who knows what else they did to it, it worked, but not quite fine. Here's what channel A looked like on the internal calibrator with a 1X probe :



https://dl.dropboxusercontent.com/u/...725/shch01.jpg



At first I thought the output amp was all whacked out for some reason, can the plate capacity be that damn different ? Nope, this is channel B :



https://dl.dropboxusercontent.com/u/...725/shch02.jpg



Turns out the brainiac who came up with the modification decided to tamper with the vertical preamp instead of what had been changed. I am a mad modifier from way back so I know better. I also know what DC coupling is, unlike that guy, who came up with this :



https://dl.dropboxusercontent.com/u/.../wingnut01.jpg



All nicely put on a perf (which is OK actually) :



https://dl.dropboxusercontent.com/u/...725/this01.jpg



And mounted well : (or is that mounted, well ?)



https://dl.dropboxusercontent.com/u/.../1725/aa01.jpg



And totally disfunctional. It had no vertical deflection except in chop mode where you could see a haze of a waveform when you adjust the position. Not quite the accuracy I was looking for...



So someone here turned me on to a Romanian website with a possible modification thus :



https://dl.dropboxusercontent.com/u/...725/romo01.jpg



Looked pretty good. The MOSFETs probably didn't exist when the thing was built, and it saves components. So I used it on specimen number two. Of course it was supposed to be this :



https://dl.dropboxusercontent.com/u/...725/orig01.jpg



After looking around, I found a local supplier with some surplus VN88AFs laying around. Looked like pretty low capacitance so I took them.



At this point, other than the usual other problems like it won't trigger half the time and the sweep time knob takes a pipe wrench to turn, the amplitude is low. About 33% low. It is the same on both channels. I am pretty sure I can adjust it there, but I would rather get the gain where it is supposed to be, especially since the position controls just barely take the trace off screen. It should have a bit more range than that.



On this unit, the 1Khz calibrator signal looks pretty good. However a 1Mhz square wave, even though I can't get it to lock right now, appears to have a hell of alot of ringing in it. Also in chop mode, you can see a bit too much that you are not supposed to see.



I figure I should tackle the gain problem first because without that the thing is a toy. What I am thinking at this point is to change the 1,000 ohm resistors to about 1,500. Or should I go higher ?



In the orginal IC, the two 500 ohms add up to 1K, that constitutes the feedback obviously. I find it hard to believe the gain is lower using that MOSFET. I do realize that it takes more voltage to turn it on, but that doesn't necessarily cause that.



Also, the Romanians have their 47 ohm to ground, I tried that and the plate voltages were too low. I tied it to the original land for the IC pin on the amp board and it is alot closer. The print calls for 40 volts and I got 38 and change. Of course I tried jumping out the resistor but as expected it did nothing for the differential gain, just lowered both plate voltages some.



So at this point I have set it aside and figured I'd see if anyone has any ideas. I'll find the right resistors sometime later and see about getting that gain up. Then I want to do something about the ringing but first mayb I'll get it to trigger. I suspect that as I've read on a bunch of these units, the switches are just dirty. I'll give them a good bath of course. Hopefully that does it.



There is another problem that might be best fielded by someone familiar with these units. I have my little board under the aluminum, which is right where part of option 101 goes. I have no room for both. I could try to make the thing smaller so it can go on the top, but since the original was on the heatsink, I figure the modification should be as well. It would be damn tough to get these parts to fit down there.



So since I have no need for option 101, any ideas on how I can remove it and have the thing still work ? It would do nothing without it connected. Not just not a trace, not even a dot at the left side of the screen.



Any ideas, thanks. If you want to comment and tell me I am crazy, fine. I'll just go back on my meds - Budweiser. (probably do that anyway...)

I have a suggestion Jurb. If I recall your original post you had determined that the HP hybrid was defective. Now you said that you obtained a good replacement from the organ donor scope. Instead of ****ing around with all these modifications why not use that good hybrid and just return the circuit to what it was when the scope left the factory? I mean you know that it worked, once. If it was my scope I think that's what I would try first. You would be starting from scratch, but with no variables. And you can take your meds whatever you decide. BTW how old is this scope? If it's as old as my computers, maybe I'll have one with you. Lenny.

Actually I did that. That scope is now working. I am now dealing with the donor scope. Maybe I didn't word it right.

My pardner wanted the one with the meter built on it, he has that now. I am trying to put together this humpty dumpty now for a second one.

I doubt I can really get it to do 275Mhz like this, but hell, I would be happy with half that.

On Monday, April 7, 2014 3:03:26 PM UTC-4, wrote:
Believe it or not I obtained one ! However it is from another scope so I am kinda back where I started becasue two scopes are better than one.



Turns out the first specimen had been modified but I didn't really notice it. Beside my eyesight going to the bats (not dogs), I was totally unfamiliar with the unit and the modification was under the aluminum plate on which the vertical output amp lives.



The first one had option 034, which is alot more useful to us than the option 101 on the parts donor. Don't look it up, 034 is the multimeter on top and 101 is an interface for a data acquisition unit.



So, upon installing the IC along with the whole board because I figured there would be the least amount of alignment needed that way, plus who knows what else they did to it, it worked, but not quite fine. Here's what channel A looked like on the internal calibrator with a 1X probe :



https://dl.dropboxusercontent.com/u/...725/shch01.jpg



At first I thought the output amp was all whacked out for some reason, can the plate capacity be that damn different ? Nope, this is channel B :



https://dl.dropboxusercontent.com/u/...725/shch02.jpg



Turns out the brainiac who came up with the modification decided to tamper with the vertical preamp instead of what had been changed. I am a mad modifier from way back so I know better. I also know what DC coupling is, unlike that guy, who came up with this :



https://dl.dropboxusercontent.com/u/.../wingnut01.jpg



All nicely put on a perf (which is OK actually) :



https://dl.dropboxusercontent.com/u/...725/this01.jpg



And mounted well : (or is that mounted, well ?)



https://dl.dropboxusercontent.com/u/.../1725/aa01.jpg



And totally disfunctional. It had no vertical deflection except in chop mode where you could see a haze of a waveform when you adjust the position. Not quite the accuracy I was looking for...



So someone here turned me on to a Romanian website with a possible modification thus :



https://dl.dropboxusercontent.com/u/...725/romo01.jpg



Looked pretty good. The MOSFETs probably didn't exist when the thing was built, and it saves components. So I used it on specimen number two. Of course it was supposed to be this :



https://dl.dropboxusercontent.com/u/...725/orig01.jpg



After looking around, I found a local supplier with some surplus VN88AFs laying around. Looked like pretty low capacitance so I took them.



At this point, other than the usual other problems like it won't trigger half the time and the sweep time knob takes a pipe wrench to turn, the amplitude is low. About 33% low. It is the same on both channels. I am pretty sure I can adjust it there, but I would rather get the gain where it is supposed to be, especially since the position controls just barely take the trace off screen. It should have a bit more range than that.



On this unit, the 1Khz calibrator signal looks pretty good. However a 1Mhz square wave, even though I can't get it to lock right now, appears to have a hell of alot of ringing in it. Also in chop mode, you can see a bit too much that you are not supposed to see.



I figure I should tackle the gain problem first because without that the thing is a toy. What I am thinking at this point is to change the 1,000 ohm resistors to about 1,500. Or should I go higher ?



In the orginal IC, the two 500 ohms add up to 1K, that constitutes the feedback obviously. I find it hard to believe the gain is lower using that MOSFET. I do realize that it takes more voltage to turn it on, but that doesn't necessarily cause that.



Also, the Romanians have their 47 ohm to ground, I tried that and the plate voltages were too low. I tied it to the original land for the IC pin on the amp board and it is alot closer. The print calls for 40 volts and I got 38 and change. Of course I tried jumping out the resistor but as expected it did nothing for the differential gain, just lowered both plate voltages some.



So at this point I have set it aside and figured I'd see if anyone has any ideas. I'll find the right resistors sometime later and see about getting that gain up. Then I want to do something about the ringing but first mayb I'll get it to trigger. I suspect that as I've read on a bunch of these units, the switches are just dirty. I'll give them a good bath of course. Hopefully that does it.



There is another problem that might be best fielded by someone familiar with these units. I have my little board under the aluminum, which is right where part of option 101 goes. I have no room for both. I could try to make the thing smaller so it can go on the top, but since the original was on the heatsink, I figure the modification should be as well. It would be damn tough to get these parts to fit down there.



So since I have no need for option 101, any ideas on how I can remove it and have the thing still work ? It would do nothing without it connected. Not just not a trace, not even a dot at the left side of the screen.



Any ideas, thanks. If you want to comment and tell me I am crazy, fine. I'll just go back on my meds - Budweiser. (probably do that anyway...)

Sometimes you can't beat going back to basics. Lenny

Let's not take that too far th0ugh. I meant to ask you about thart cassette deal. Any moves on that ? Did you consider the 1 Khz square wave method I said ?

Anyway, I finally gave this HP a bath. It's like a new nmachine. Now remember there is the good one, and ?I thought it was all ****ed up, but not I see that we had ****ty probes. Long story, but these babiers are working better thaan I thought. I had a ****load of pictures of 1Mhz square waves and ****, but the camera ****ed up and they are lost. I willget more.

I decided fukit, see if I can get the gain right. No good, the end of the range of the vcontrol is not even close. I see how they design, and I do not like it. The gain seems like they are shunting the signal, it is all one sided. I could design better than that. Of course that is all over the place.. My assocoiate just got stumped checking bias and **** on an old vintage unit, what it was it that the bias control had too much range, and it don't go below zero. Of course that is why I am here.

I have stuck the thing to the aluminum for now. In fact now that...

Oh. I have solved the option 101 problem. I disconnected all kinds of thigs and now know what must remain connected. I have the board off to the side now and it won't be bothering anyone. However I now know that I must increase the values of those resistors, and I THINK I should bump them from 1,000 to 1,500 ohms. Now that I see how this thing is, I am thinking of going even a bit higher. Extra gain is usually easier to handke than the lack thereof.

I did do something though. I got this buzzbox welder, or I did. I loaned it to a buddy of mine and he still has it, I don't care. But the rollaround stand fits this HP really nice so now I got that, the Fluke 8050A on top of it (option 035 ?) and the Wavetek 111 on the shelf underneath (option ZZZ).

It's looking pretty good actualy. And my dude brung me the 422.

/sending befroe this becomes the new bible

On Monday, April 7, 2014 3:03:26 PM UTC-4, wrote:
Believe it or not I obtained one ! However it is from another scope so I am kinda back where I started becasue two scopes are better than one.



Turns out the first specimen had been modified but I didn't really notice it. Beside my eyesight going to the bats (not dogs), I was totally unfamiliar with the unit and the modification was under the aluminum plate on which the vertical output amp lives.



The first one had option 034, which is alot more useful to us than the option 101 on the parts donor. Don't look it up, 034 is the multimeter on top and 101 is an interface for a data acquisition unit.



So, upon installing the IC along with the whole board because I figured there would be the least amount of alignment needed that way, plus who knows what else they did to it, it worked, but not quite fine. Here's what channel A looked like on the internal calibrator with a 1X probe :



https://dl.dropboxusercontent.com/u/...725/shch01.jpg



At first I thought the output amp was all whacked out for some reason, can the plate capacity be that damn different ? Nope, this is channel B :



https://dl.dropboxusercontent.com/u/...725/shch02.jpg



Turns out the brainiac who came up with the modification decided to tamper with the vertical preamp instead of what had been changed. I am a mad modifier from way back so I know better. I also know what DC coupling is, unlike that guy, who came up with this :



https://dl.dropboxusercontent.com/u/.../wingnut01.jpg



All nicely put on a perf (which is OK actually) :



https://dl.dropboxusercontent.com/u/...725/this01.jpg



And mounted well : (or is that mounted, well ?)



https://dl.dropboxusercontent.com/u/.../1725/aa01.jpg



And totally disfunctional. It had no vertical deflection except in chop mode where you could see a haze of a waveform when you adjust the position. Not quite the accuracy I was looking for...



So someone here turned me on to a Romanian website with a possible modification thus :



https://dl.dropboxusercontent.com/u/...725/romo01.jpg



Looked pretty good. The MOSFETs probably didn't exist when the thing was built, and it saves components. So I used it on specimen number two. Of course it was supposed to be this :



https://dl.dropboxusercontent.com/u/...725/orig01.jpg



After looking around, I found a local supplier with some surplus VN88AFs laying around. Looked like pretty low capacitance so I took them.



At this point, other than the usual other problems like it won't trigger half the time and the sweep time knob takes a pipe wrench to turn, the amplitude is low. About 33% low. It is the same on both channels. I am pretty sure I can adjust it there, but I would rather get the gain where it is supposed to be, especially since the position controls just barely take the trace off screen. It should have a bit more range than that.



On this unit, the 1Khz calibrator signal looks pretty good. However a 1Mhz square wave, even though I can't get it to lock right now, appears to have a hell of alot of ringing in it. Also in chop mode, you can see a bit too much that you are not supposed to see.



I figure I should tackle the gain problem first because without that the thing is a toy. What I am thinking at this point is to change the 1,000 ohm resistors to about 1,500. Or should I go higher ?



In the orginal IC, the two 500 ohms add up to 1K, that constitutes the feedback obviously. I find it hard to believe the gain is lower using that MOSFET. I do realize that it takes more voltage to turn it on, but that doesn't necessarily cause that.



Also, the Romanians have their 47 ohm to ground, I tried that and the plate voltages were too low. I tied it to the original land for the IC pin on the amp board and it is alot closer. The print calls for 40 volts and I got 38 and change. Of course I tried jumping out the resistor but as expected it did nothing for the differential gain, just lowered both plate voltages some.



So at this point I have set it aside and figured I'd see if anyone has any ideas. I'll find the right resistors sometime later and see about getting that gain up. Then I want to do something about the ringing but first mayb I'll get it to trigger. I suspect that as I've read on a bunch of these units, the switches are just dirty. I'll give them a good bath of course. Hopefully that does it.



There is another problem that might be best fielded by someone familiar with these units. I have my little board under the aluminum, which is right where part of option 101 goes. I have no room for both. I could try to make the thing smaller so it can go on the top, but since the original was on the heatsink, I figure the modification should be as well. It would be damn tough to get these parts to fit down there.



So since I have no need for option 101, any ideas on how I can remove it and have the thing still work ? It would do nothing without it connected. Not just not a trace, not even a dot at the left side of the screen.



Any ideas, thanks. If you want to comment and tell me I am crazy, fine. I'll just go back on my meds - Budweiser. (probably do that anyway...)


I did like the square wave idea and was thinking about trying it but suddenly work got very busy, so as long as duty calls I have to leave this for a Saturday afternoon. Lenny.

The HP is backburnered for now. Actually my associate says he might find a third, if so and it doesn't need the same thing, fine.

I modified it by adding 680 ohms to tha 1 Ks. I saw those 680s and said "sElf, those are perfect". Problem is that when I fired it up then it owuldn't trigger. I DID give the thing a nice bath in LPS2 and it did seem to improvr things. I was going to say OK, I'll just set the gain and be done with it for now, but the gain onb the preamp wouldn't go high enough. I wasn't too crazy about doing it thart wqay anyway.

I had a bunch of pivcutre sI thought but the card got corrpupted somehow. I had a fairly decent 1Mhz square wavw on it, one I wiggled and juggled enough to get all the old comnections connectioning.

The other "good" HP ike this might need some help. ZSeems like I get better response on this one than on that one. Next time I am going to hok it up with clip leads, screw the probes. I have to look see about that Wavetek 111 I got, how it reacts to a 50 ohm load, and align it with that. Maybe put the whole damn front end from this is there, because as much as I tried, the thing just didn't seem to come out right. ringing and all this,. even in the 1Khz square wave.

I got an old 422 on a lend/lease type of deal, a Hameg and a B&K. They all work. And now we might be getting a 7633. Not sure about that though.

Anyway, got ta get a few things out of here myself. the profit potential in the HP is not great really. I know it is among the fastest analogs out there, but so what. I don't need to carefully exmine the eye pattern on a CD player or whatever, hell even scoping the Ysus in a plasma is no problem for the old 422, or even the B&K which no matter how ****ty it is, still works.. When it didn't it was some bad connections in the vertical output. Didn't need a single component.

More later. I am not co,mpletely throwing it out, butit is getting on my nerves. Why the hell would it stop triggering ?