Tek 567 trace wandering


Keith
 

The 576 I recently acquired is on the face of it in good condition, but it's got a couple of issues. The first is the trace wanders over the screen randomly at times. Pressing the Zero button does bring the trace to a central dot OK, but it seems there is an issue with the Cal button. Any movement and the trace starts/stops wiggling. So I'm assuming the switch is dirty - is that a fair assessment? And what needs to be removed to get at it easily? Any tips on how to remove and clean it appreciated.

The second issue is the looping compensation seems very stiff, and turning it has no visible effect at all. Is it likely to have seized, and how does one get at it - again it doesn't look easy to access.

TIA, Keith.


Eric
 

On a 576 only the side panel needs to be removed to get at the invert zero
and cal switches. If I remember correctly easier access can be attained by
removing the control that covers up the switches. This can be done by
removing the knob. And pulling the entire module out gently. There is
enough slack in the wiring harness to do this with out unplugging anything
but just barely. It is not an awful job as far as I remember.

Eric

On Fri, Jan 29, 2021, 5:33 AM <keith@peardrop.co.uk> wrote:

The 576 I recently acquired is on the face of it in good condition, but
it's got a couple of issues. The first is the trace wanders over the screen
randomly at times. Pressing the Zero button does bring the trace to a
central dot OK, but it seems there is an issue with the Cal button. Any
movement and the trace starts/stops wiggling. So I'm assuming the switch is
dirty - is that a fair assessment? And what needs to be removed to get at
it easily? Any tips on how to remove and clean it appreciated.

The second issue is the looping compensation seems very stiff, and turning
it has no visible effect at all. Is it likely to have seized, and how does
one get at it - again it doesn't look easy to access.

TIA, Keith.






Michael W. Lynch
 

On Fri, Jan 29, 2021 at 04:33 AM, <keith@peardrop.co.uk> wrote:


The second issue is the looping compensation seems very stiff, and turning it
has no visible effect at all. Is it likely to have seized, and how does one
get at it - again it doesn't look easy to access.
That looping compensation control is usually stuck where the shaft passes through the chassis on the capacitor itself. You can access this a little better by removing the bottom panel, still a pain, but does give more room to work and better access. I used a bit of penetrating oil on mine and finally got it freed up.

--
Michael Lynch
Dardanelle, AR


Keith
 

Thanks Michael. When you say bottom panel, do you mean the underside of the 576? I tried taking that off and could only see access to what looked like part of the eht generator. I took the left panel off, then the brown insulating (paxolin?) board that covers the collector voltage switch etc. and could just about get access to the shaft of the looping control and the coupler to the variable capacitor. I'll try a little WD40 on the capacitor shaft to see if that helps. The control does turn, but very stiffly, I'm a bit worried that the coupler is going to break - I can see it flexing as I try and turn it.

Having said that the wandering trace is the bigger problem, I need to access the display switching board as it seems the CAL or ZERO switch may be the problem.

Keith


Eric
 

Keith, I am back in the lab and I checked you can gain access to the Zero/cal/invert switches by removing the horizontal control in its entirety without unhooking any wiring. Ill send you some more information off list.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of keith@peardrop.co.uk
Sent: Friday, January 29, 2021 3:16 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek 567 trace wandering

Thanks Michael. When you say bottom panel, do you mean the underside of the 576? I tried taking that off and could only see access to what looked like part of the eht generator. I took the left panel off, then the brown insulating (paxolin?) board that covers the collector voltage switch etc. and could just about get access to the shaft of the looping control and the coupler to the variable capacitor. I'll try a little WD40 on the capacitor shaft to see if that helps. The control does turn, but very stiffly, I'm a bit worried that the coupler is going to break - I can see it flexing as I try and turn it.

Having said that the wandering trace is the bigger problem, I need to access the display switching board as it seems the CAL or ZERO switch may be the problem.

Keith


Michael W. Lynch
 

Keith,

I would clean those switches first and get that wandering trace fixed first. You can lubricate and free that looping compensation control any time.

As far as the bottom panel. perhaps I am confused??? It has been quite some time since I have worked on the 576. As I recall, there were some screws that were just sort of floating around inside my instrument, that may have been why I had to take it off? I have stood another 576 on its back (CAREFULLY) and used a small, long handled paintbrush to reach in the left side of the instrument to dab a small quantity of KROIL onto the shaft, near where it enters the control. Gravity then causes the KROIL to wick down the shaft and to penetrate between the shaft and the bushing. This usually will free the mechanism. It may take a few careful applications, but this worked for me. If the shaft is even slightly free, WD40 probably will do the trick just fine.

Good Luck

--
Michael Lynch
Dardanelle, AR