oscilloscope image partial collapse

snipped-for-privacy@gmail.com wrote: ===========================

** Schem:

Try checking all the resistors in the horizontal circuits - after the scope has been off for 15 mins. One might have gone high or open.

..... Phil

If I'm reading the schematic right, there's two tubes that do the horizontal drive, V5 (2BS8) and V6 (12BH7) as well as a pair of pullup resistors, R50 and R48, each 22k ohms, 2W. Start checking those.

the right side, the image is collapsed to the center.. a trace will only g o from the left to the center, then its gone. you can see the right side im age is collapsed in a vertical line, as its more intense . the trace from l eft to center is fine. it has vacuum tubes. all the tubes have heater glow. there are 2 pair of the same tubes, i swapped the positions to see if the problem moved. It didn't. I have a schematic pdf, not sure how to attach it . id like to get it going, but if its the crt, its pointless. where to from here? thanks

Why do you call this an Auto Ignition Oscilloscope? It is just a typical ho bby grade scope from 1960. A manual is on the BAMA site. This is not a binaries newsgroup, so it doesn't accept attachments. Check the plate voltage on both halves of the Horizontal driver tube. It lo oks like pin 10 of the CRT is the right side deflection plate.

the right side, the image is collapsed to the center.. a trace will only g o from the left to the center, then its gone. you can see the right side im age is collapsed in a vertical line, as its more intense . the trace from l eft to center is fine. it has vacuum tubes. all the tubes have heater glow. there are 2 pair of the same tubes, i swapped the positions to see if the problem moved. it didnt. i have a schematic pdf, not sure how to attach it. id like to get it going, but if its the crt, its pointless. where to from here? thanks

The Heathkit IO-20 was an Ignition Analyzer. It used a 12AX7 for the Horizo ntal drive. The plate resistors are 470K They are fed from a 350 VDC source and the CRT is a common 5UP1. It came with the clip on probe for the spark plug wire.

** You sure about that model number ? ** He does't know what it is. ** Think it is a lot better than " hobby grade".

Being fully calibrated, DC coupled with mag shielded CRT and regulated HT rails put in the " service / lab" category. Sure, 200kHz vertical BW is not great but still very usable for most service jobs and for students doing science / engineering classes.

...... Phil

rails put in the " service / lab" category.

ice jobs and for students doing science / engineering classes.

I considered anything under 5 MHz to be hobby grade, since I worked in vide o. My current scope is a Tektronix 2465A I have two of the 2465 as well. I also have two of the Tektronix P6201 900MHz FET Probe 010-6201-00 to xamine crystal oscillators and tuned circuits, with minimal loading.

the 470k resistors are good, and i have the 350v at the rail. still stumped.

Check R39, 40, 48, 50 all 22K each and check R45 and 47, 100 ohms each. The 12BH7 could be bad.

e:

rote:

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ter to the right side,

e left to the center,

erticle line, as its more intense .

tubes have heater glow.

if the problem moved.

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scope has been off for 15 mins.

mped.

he 12BH7 could be bad. i checked every resistor, all check good. i checked the pots, all good. i c hecked the voltage to a and b terminals on the crt, close to whats listed o n the schematic. whats makes this different than a bench scope is it has n o internal trigger. it is only triggered externally by an inductive pick up . same for the vertical , another pick up. one problem is i dont know how to induce anything to get it do do something on the bench other than a dot. however, if i turn it on, you can see the dot dive bomb to the right, and then come back from right to center. seems to me that indicates the crt is working ok. i posted a video on youtube.

still , when hooked to an 8 cyl engine, i get a normal image from left to c enter. from center to right it appears to be collapsed or squished toward the center. where the pattern ends at the center, the line is fairly thick and intense, like a partial collapse of a cga crt.monitor. thanks for an y input.

=======================

** Why did you tell us you had an IO-10 ???

.... Phil

it was either a typo or lack of sleep. not from this problem though. sorry bout that

snipped-for-privacy@gmail.com wrote: ======================= >

** Start again - the io-20 is a COMPLETELY different animal !!!

If all the tubes are OK and the voltage too - not much is left but the CRT.

Two possibilities:

1. Because of being used around cars, it is likely to have fallen onto a hard surface once or twice.

1. The steel case is magnetised - deflecting the trace.

See if removing the cover makes a difference.

BTW I could not find any internal pic on the net.

... Phil

i considered it may have been dropped. did you look at the video? im thinking if one of the defectors was damaged, the trace wouldnt move the way it does when it starts up, but maybe im off on that.

snipped-for-privacy@gmail.com wrote: =====================

** I see nothing unusual for a tube scope start up in your vid.

What you claimed in you OP and now is false. The dot quickly centers then moves off to the left slowly. Perfect.

..... Phil

Heathkit used aluminum for most of their cabinets. The CRT has a MuMetal shield.

Do you have a schematic and a real oscilloscope?

I see a NE2 neon and a diode used in previous stages that could affect linearity, but I don't have a parts list. There is a pot off the Neon lap marked 'Right Adjust'.

Fair Radio still has some unused 5UP1 CRTs

There is currently another IO-20 on Ebay, less the probes.

** So what ? This one may not be part of that "most". CRT scopes with Aluminium cases are rare as hell. ** How do you know that ? Another inspired guess ? ** Huh ?

** The OP is clueless and posting contradictory, total nonsense. So are you.

..... Phil

=

e CRT.

o a hard surface once or twice.

Maybe in Oz. HP and Tektronix used a lot of aluminum for their oscilloscope cabinets. Those aren't rare, among engineers or real techs.

From the photos that I linked to.

linearity, but I don't have a parts list.

Sigh, you are the queen of posting nonsense.

Look at the photos in the Ebay link that I posted and see inside the IO-20 for yourself. I've repaired a lot of Heathkit equipment, and most of it use d aluminum, except for some stereo equipment. They sold wood cabinets to c over a bare steel chassis, or you could build them into custom cabinets.

I built my first Heathkit about 55 years ago. I built dozens for myself, an d others.

I also used a Heathkit color bar generator to transmit a color station ID f rom a black and white TV station. I genlocked it to our master Sync Generat or, then used the monochrome video keyer to add color to a B&W 35mm slide. The information was displayed on the AFRTS page of the US DOD website for a bout a decade, before they purged all the shared emails.

The other links included a schematic for the OP and a source for a new CRT, if needed.

A working scope is quite handy when repairing an ailing scope.