HP1725a Trace Anomoly

There is a haze on the screen sort of. I have removed the clear blue plastic over it and that is not the problem. It seems the haze is magnified compared to the trace. See pics :

https://dl.dropboxusercontent.com/u/29948706/hpsi01.jpg

https://dl.dropboxusercontent.com/u/29948706/hpsq01.jpg

I notice the CRT has an internal mesh. It's not for storage, it seems likely it is to protect the phosphor from the intensification need for the writing speed. Could that be it ?

I notice all it gets is +53 volts on one element and -15 on the other.

It is a function of intensity, it is practically gone when you turn it down, but then when it is in the intensify mode, it is quite visible. (delayed sweep is another issue for another thread)

By the way, it is for sale. Looking at Teks which I think are a better scope.

 

[Baron]

jurb6006@gmail.com scribbled thus:

There is a haze on the screen sort of. I have removed the clear blue
plastic over it and that is not the problem. It seems the haze is
magnified compared to the trace. See pics :

https://dl.dropboxusercontent.com/u/29948706/hpsi01.jpg

https://dl.dropboxusercontent.com/u/29948706/hpsq01.jpg

I notice the CRT has an internal mesh. It's not for storage, it seems
likely it is to protect the phosphor from the intensification need for
the writing speed. Could that be it ?

I notice all it gets is +53 volts on one element and -15 on the other.

It is a function of intensity, it is practically gone when you turn it
down, but then when it is in the intensify mode, it is quite visible.
(delayed sweep is another issue for another thread)

By the way, it is for sale. Looking at Teks which I think are a better
scope.

My 1735A doesn't do that ! I think the voltages may be wrong.

--
Best Regards:
Baron.

 

On Friday, June 6, 2014 6:35:47 PM UTC-4, jurb...@gmail.com wrote:

There is a haze on the screen sort of. I have removed the clear blue plastic over it and that is not the problem. It seems the haze is magnified compared to the trace. See pics :



https://dl.dropboxusercontent.com/u/29948706/hpsi01.jpg



https://dl.dropboxusercontent.com/u/29948706/hpsq01.jpg



I notice the CRT has an internal mesh. It's not for storage, it seems likely it is to protect the phosphor from the intensification need for the writing speed. Could that be it ?



I notice all it gets is +53 volts on one element and -15 on the other.



It is a function of intensity, it is practically gone when you turn it down, but then when it is in the intensify mode, it is quite visible. (delayed sweep is another issue for another thread)



By the way, it is for sale. Looking at Teks which I think are a better scope.

Jurb
Can you reverse the deflection plates wiring and see if the problem moves?

I worked for a cal lab/rental company in the early 80's. I remember when we got a load of those brand new HP 1700 series scopes in for rental. They actually weren't bad scopes, and from a service standpoint, compared to a 400 series Tek, working on them was a walk in the park.

The problem was that most Techs who grew up playing with Teks were not willing to switch. As illogical as this was I have to include myself in this group. This really hurt HP. Like many other guys, I was and still am a die hard Tek man.

I still have my 561B which I pulled out of a snow covered scrap pile outside of a GE plant. It had been junked for poor phosphor storage performance. Well phosphor storage always sucked anyway and the scope, in standard display mode was just fine.

The old girl treated me well for many years. I've since upgraded to a 453 but the old horse still sits in a corner of the shop still with it's little roll of silver solder inside. I just can't seem to part with it. Lenny

 

[Jeff Liebermann]

On Fri, 6 Jun 2014 15:35:47 -0700 (PDT), jurb6006@gmail.com wrote:

There is a haze on the screen sort of. I have removed the clear blue plastic over it and that is not the problem. It seems the haze is magnified compared to the trace. See pics :

https://dl.dropboxusercontent.com/u/29948706/hpsi01.jpg
https://dl.dropboxusercontent.com/u/29948706/hpsq01.jpg

You chopped off the right side of the scope front panel, so I can't
see the position of the sweep controls. My guess(tm) is that you have
it setup for delayed trigger, with identical sweep times for both the
sweep and the intensified delayed sweep. In that position, the entire
trace is intensified. Try turning off delayed sweep and/or trigger.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

>"You chopped off the right side of the scope front panel, so I can't ..."

I know how to use a scope. This abberation eeiss a all scales, time or voltage.

It is as if it is projected onto a sendary sreen beyond the phosphor. I have been in alot of CRT technology in my life and never seen this. It is as if the beam can project something through ana angle.

Very coincidentlly, I notice a video in which a guy cut teeel, THICK STEEL with a torch, ON AN ANGLE. That means using the torch like a mitre saw.

Within a year, we shopuld be able to cut you something.

 

Damn I fucked that up.

Anyway, the sweep was set to main.

That's the way we usuually use them...

T

 

First of all I do appreciate all your reponses, especialy from such a group..

>"My 1735A doesn't do that ! I think the voltages may be wrong. "

Those voltages are only routed through the gate board, not modified at all, as far as the print is concerned.

>"Can you reverse the deflection plates wiring and see if the problem moves? "

Yes Mon Cpaitain, but... It might not prove anyhting. I can reverse the H plates but not the V plates.

The reason for this is because the V plates are consideed a wavguide. (this answers a question posed here in another thread)HP runs the output of the collectors into one end of the plates, and feeds their bias to the other ends. Apparently they had to do this to achieve 275 Mhz bandwidth.

I guess I undersatand why, when trying to control a stream of electrons in a vecuum, it might be different than riding a bike.

There is also that delay sweep problem...