I am working on 2 Tektronix function generators. An FG 507 and a FG 502 both 2 Mhz. The 507 is on the bench currently and I am having a weird issue with the frequency selectors. Everything above 100X it working normally anything below 100X is mostly not working and at 10 I am getting an oscillation of 10 – 12 Mhz depending on what 2 opamps I have installed in the sockets. I have value check the main timing cap and it checks fine. I have also replaced the TI sockets and the Op amps thinking one was damaged and the TI sockets were bad. The power rails going in to the op amps are a little low at 13.5V so I am doing to keep digging I am just wondering if anyone knows what might be causing this? Also below 10 there is no oscillation at all. I have checked the timing resisters and all seem to be in order. There is nothing to make me think that the timing caps are bad but I have not measured them yet.

If it's those gold PCB mount flat spring contacts used in the cam switches, the Tek approved way of cleaning them is with plain white paper.
You don't want any residue left on them at all or you'll attract dust etc, so I wouldn't use deoxit here.
Flush them with isopropyl alcohol to wash yhem then after removing the cam assembly, carefully(!) slip some plain white paper between the switch leaf and the PCB and depress the leaf with your finger.
Withdraw the paper and the gentle abrasiveness of the paper will clean the contacts.

If it's those gold PCB mount flat spring contacts used in the cam

You don't want any residue left on them at all or you'll attract dust etc,

Flush them with isopropyl alcohol to wash yhem then after removing the cam

Withdraw the paper and the gentle abrasiveness of the paper will clean the

Thanks for the kick in the right direction. It did ended up being the switch
contacts. I tried the tek cleaning procedure and that got me to where I was.
I was much more aggressive at cleaning the switches and it seems to have
worked very well. Qtip and iso with some elbow grease. All the ranges are
working even the slowest at 50 Seconds/div on the scope I cant even get a
full cycle on the screen. Any one know why something would need to run this
SLOW? 0.002 Hz?

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Tom Lee
Sent: Sunday, January 24, 2021 12:18 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] A problem filled FG507

Yes that is absolutely the "right" procedure, but for a 2MHz instrument it
is overkill. Deoxit works very well and does not appear to leave a residue
of any significance here. I've used it for dozens of FG50x function gens
with no problems at all.

Tom

Sent from an iThing; please excuse the terseness and typos

On Jan 23, 2021, at 21:02, "Jared Cabot via groups.io"
<jaredcabot=protonmail.com@groups.io> wrote:

If it's those gold PCB mount flat spring contacts used in the cam

switches, the Tek approved way of cleaning them is with plain white paper.

You don't want any residue left on them at all or you'll attract dust etc,

so I wouldn't use deoxit here.

Flush them with isopropyl alcohol to wash yhem then after removing the cam

assembly, carefully(!) slip some plain white paper between the switch leaf
and the PCB and depress the leaf with your finger.

Withdraw the paper and the gentle abrasiveness of the paper will clean the

contacts.

Thanks for the kick in the right direction. It did ended up being the
switch contacts. I tried the tek cleaning procedure and that got me to where I was.
I was much more aggressive at cleaning the switches and it seems to
have worked very well. Qtip and iso with some elbow grease. All the
ranges are working even the slowest at 50 Seconds/div on the scope I
cant even get a full cycle on the screen. Any one know why something
would need to run this SLOW? 0.002 Hz?

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Tom Lee
Sent: Sunday, January 24, 2021 12:18 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] A problem filled FG507

Yes that is absolutely the "right" procedure, but for a 2MHz
instrument it is overkill. Deoxit works very well and does not appear
to leave a residue of any significance here. I've used it for dozens
of FG50x function gens with no problems at all.

Tom

Sent from an iThing; please excuse the terseness and typos

On Jan 23, 2021, at 21:02, "Jared Cabot via groups.io"
<jaredcabot=protonmail.com@groups.io> wrote:

If it's those gold PCB mount flat spring contacts used in the cam

switches, the Tek approved way of cleaning them is with plain white paper.

You don't want any residue left on them at all or you'll attract dust
etc,

so I wouldn't use deoxit here.

Flush them with isopropyl alcohol to wash yhem then after removing
the cam

assembly, carefully(!) slip some plain white paper between the switch
leaf and the PCB and depress the leaf with your finger.

Withdraw the paper and the gentle abrasiveness of the paper will
clean the

contacts.

Thanks for the kick in the right direction. It did ended up being the switch
contacts. I tried the tek cleaning procedure and that got me to where I was.
I was much more aggressive at cleaning the switches and it seems to have
worked very well. Qtip and iso with some elbow grease. All the ranges are
working even the slowest at 50 Seconds/div on the scope I cant even get a
full cycle on the screen. Any one know why something would need to run this
SLOW? 0.002 Hz?

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Tom Lee
Sent: Sunday, January 24, 2021 12:18 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] A problem filled FG507

Yes that is absolutely the "right" procedure, but for a 2MHz instrument it
is overkill. Deoxit works very well and does not appear to leave a residue
of any significance here. I've used it for dozens of FG50x function gens
with no problems at all.

Tom

Sent from an iThing; please excuse the terseness and typos

On Jan 23, 2021, at 21:02, "Jared Cabot via groups.io"
<jaredcabot=protonmail.com@groups.io> wrote:

If it's those gold PCB mount flat spring contacts used in the cam

switches, the Tek approved way of cleaning them is with plain white paper.

You don't want any residue left on them at all or you'll attract dust etc,

so I wouldn't use deoxit here.

Flush them with isopropyl alcohol to wash yhem then after removing the cam

assembly, carefully(!) slip some plain white paper between the switch leaf
and the PCB and depress the leaf with your finger.

Withdraw the paper and the gentle abrasiveness of the paper will clean the

contacts.

On Mon, Jan 25, 2021 at 12:02 PM, Jim Ford wrote:

an aircraft cockpit vibrating at about 8 Hz, below the range of human
hearing.  Very hard to fly a plane or do anything useful when you're bouncing
around like that!

Very true! One only needs to look at the problem of "pogo oscillation" of liquid fueled rockets to see how important "low frequency" is and how dangerous it can be to both machines and the people who crew them.

The Saturn V had some unexpected and very near catastrophic episodes of this "pogo" vibration. It was (wrongly) thought that the problem was limited to "smaller" boosters and would not be a problem for the Saturn V. Unfortunately Apollo 6 (unmanned), 10 and 13 were subjected to approximately 11-16 Hz pogo, of different intensities. This pogo was reported to have been sufficient to have killed the crew on Apollo 6 (had the flight been manned). Changes were made to the F-1 engines, but pogo still made it nearly impossible for the crew of Apollo 10 to read the instruments and the astronauts were slammed violently out of and back into their seats, in spite of their restraints. Work on F1 pogo was ongoing, less violent (but still dangerous) on Apollo 10 and very slight on Apollo 13. These changes never completely eliminated the F-1 engine problem, however, the team succeeded in reducing the violence of the original oscillation to a manageable level.

Unfortunately, the pogo problems also persisted in the J-2 2nd stage. Apollo 13 J-2 2nd stage had a center engine shutdown because of a violent 34G and 16Hz pogo. Had the computers not shut down the malfunctioning center engine, the loss of the vehicle was inevitable This problem was finally mitigated with changes to the J2 engines on Apollo 14 and subsequent launches.

The Soviet N-1 "moon rocket" launches were all failures because of the same pogo phenomenon. It has been reported that Soviet scientists "fixed" the problem on paper, but their program was cancelled before the "fix" could be proven by a successful launch of the vehicle.

Tom,

The AS-508 J-2 Center Engine was reported to have flexed the engine thrust frame of the second stage 5.25 INCHES (p/p) during this event. The flex was localized to the Engine thrust frame, but was still serious enough to cause a shutdown. If anyone has ever looked at these component parts, they are very substantial components (even in the relatively small J-2 engine). The forces are huge and can be deadly.

Holy Metal Fatigue, Batman! As an aero-astro friend once said to me
after the Challenger disaster, "It's not so much a question of 'why did
it fail', but rather 'why did it ever work?'".

-- Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/25/2021 11:53, Michael W. Lynch via groups.io wrote:

Tom,

The AS-508 J-2 Center Engine was reported to have flexed the engine thrust
frame of the second stage 5.25 INCHES (p/p) during this event. The flex
was localized to the Engine thrust frame, but was still serious enough to
cause a shutdown. If anyone has ever looked at these component parts,
they are very substantial components (even in the relatively small J-2
engine). The forces are huge and can be deadly.

On Mon, Jan 25, 2021 at 02:14 PM, Jim Ford wrote:

Some of my colleagues at Lockheed worked on the SR-71 Blackbird, not that much
different from a rocket, and the vibration specs were outrageous.  I worked
on the U-2, much more benign

Jim, i would not call the U2 "benign". Anything that Kelly Johnson and the Skunk Works developed was far removed from benign. There is very little in aviation history that has interested me more than the SR71/A12 project. Just goes to show what you can do with a slide rule, a great leader/manager, a lot of brilliant minds and a Black Budget.