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Switch won't latch - 7CT1N

 

I have a minor 7CT1N problem. The NPN/PNP switch won't latch in the in/PNP position, except by some careful jiggling about 3/16" of the way in.

The switch body is the 260-1356-00 that is used everywhere. I've inspected it for physical damage and I can't see anything wrong, or any difference in fact between this half switch and the other half that has the XSTR/FET switching in it.

What's the trick?

TIA

EJP
 

I have a minor 7CT1N problem. The NPN/PNP switch won't latch in the in/PNP position, except by some careful jiggling about 3/16" of the way in.
======================================================

With the front panel up, squirt a very small controlled amount of CRC 556 in the space between the square knob and the front panel. Work it in with a few cycles of the switch. Or, on the push-push switches that you can get to from behind the panel, a small controlled squirt on the switch shaft will produce the same results. This is easy on the 7CT1N but not so much on a 576 for example.

Wipe off the excess on the front panel.

Have used this method for 60 years and have yet to see a failure.

Rolynn
 

I don't see where that gets us. The problem is in the switch body, not at the pushbutton/front panel interface. The pushbutton goes in and out just fine, and the rod. It's the latch in the switch that isn't working. It has to do with the little sprung rod thing and its small sprung cover. Now I look at it the FET switch isn't latching either. Never used it. But I see no difference from the other two switches that do latch perfectly.

EJP
 

It's the latch in the switch that isn't working. It has to do with the little sprung rod thing and its small sprung cover. Now I look at it the FET switch isn't latching either. Never used it. But I see no difference from the other two switches that do latch perfectly.


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


The mechanism gets dirty.

The CRC 556 lubricates it and solves the problem.

It also cleans up the switch contacts and eliminates erratic switching.

I have repaired many 7CT1Ns and many 576s by this method. I have seven 576s that been made operational with this method.

A few drops of CRC 556 down the switch shaft while the front panel is facing up will allow the lube to enter the switch body.

Apply it and work the switch a dozen times.

RP
 

Rolynn:

Thanks for the tip- I have a 7633 scope with a similar problem (several
of the push-on/push-off switches are mechanically
uncooperative/unpredictable/cranky), and while I haven't checked to see
if the part numbers of the switches are the same as those on a 7CT1N, I
suspect that it's a similar failure mode.? Can you clarify what is "CRC
556"?? I have checked the CRC website and I don't see (maybe I am
missing it) a "556" product; can you provide a full identification for
it?? Is is an electrical product, or a lubrication product?? Doing a
"search" at the CRC website on the string "556" produces only a
"food-grade" gear oil that is available in 55 gallon drums, which is
more than I would need.

Mike Dinolfo N4MWP

On 3/20/19 9:49 PM, ROLYNN PRECHTL K7DFW wrote:
I have a minor 7CT1N problem. The NPN/PNP switch won't latch in the in/PNP position, except by some careful jiggling about 3/16" of the way in.
======================================================

With the front panel up, squirt a very small controlled amount of CRC 556 in the space between the square knob and the front panel. Work it in with a few cycles of the switch. Or, on the push-push switches that you can get to from behind the panel, a small controlled squirt on the switch shaft will produce the same results. This is easy on the 7CT1N but not so much on a 576 for example.

Wipe off the excess on the front panel.

Have used this method for 60 years and have yet to see a failure.

Rolynn
 

Thanks for the tip- I have a 7633 scope with a similar problem (several
of the push-on/push-off switches are mechanically
uncooperative/unpredictable/cranky), and while I haven't checked to see
if the part numbers of the switches are the same as those on a 7CT1N, I
suspect that it's a similar failure mode.? Can you clarify what is "CRC
556"?? I have checked the CRC website and I don't see (maybe I am
missing it) a "556" product; can you provide a full identification for
it?? Is is an electrical product, or a lubrication product?? Doing a
"search" at the CRC website on the string "556" produces only a
"food-grade" gear oil that is available in 55 gallon drums, which is
more than I would need.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Doesn't matter which switch it is, if it's a push-push switch then the problem is always the same. The mechanism gets cranky and the contacts get intermittent.

CRC 5-56 has been around for years. Google it. I should have called it by it's correct name and that is CRC 5-56.

<>

Rolynn
Tek Bvtn and Sunset 1966-1971
 

I'm sure it's dirtry, it feels that way, as does the FET switch, and as don't the two that work perfectly, but I am unable to introduce any controlled amount of anything at the top of the button in such a way that it drips all the way down the six-inch shaft and actually gets into the switch body. This seems a very roundabout way of doing something very simple, and that had no actual effect when tried.

It seems that that the little pin doesn't rotate correctly during depression when compared to the two that work. Does that suggest wear in its little track on the slide? I've seen that problem before on similar power switches, where replacement was the only option, even though the amount of material involved was tiny as far as I could tell.

Or maybe I should remove the slide and clean the track inside? Something further is needed than suggested so far.

EJP
 

In the case of switches that are not immediately behind the front panel on your 7CT1N, remove the side panel and introduce the CRC 5-56 to the switch shaft proper while the unit is standing with the front panel up. This is not a difficult procedure.

Four 5/7CT1N's have gone through here and were made operational with this method of cleaning/lubing the switches.

Rolynn
 

Good Day,

may I second Rolynn's good advice here.

Just open the side panels of your 7CT1N unit and either lubricate the latch with a suitable spray by applying it under the "clamp" or remove the C-shaped ring and relax the spring so that the upper "clamp" can be removed. You can then remove the small rod and clean and lubricate the latch mechanism. Wear safety goggles when doing this.
The picture below illustrates the little rod which is located under the mentioned "clamp". Note that this is with the clamps already removed from both switch assemblies (side note: It shows the white shaft pulled out of the switch assembly, which is *not* needed. Also, the little rod was removed from the upper switch).

Good luck,

Magnus



In the case of switches that are not immediately behind the front panel on your 7CT1N, remove the side panel and introduce the CRC 5-56 to the switch shaft proper while the unit is standing with the front panel up. This is not a difficult procedure.

Four 5/7CT1N's have gone through here and were made operational with this method of cleaning/lubing the switches.

Rolynn
 

Rolynn

I'm sure you mean well, but there are no switches on any 7CT1N that are immediately behind the front panel. The shaft in question is six inches long, as I already stated. It is already obvious that the cleaning material should be introduced directly into the switch, not via gravity feed from the front panel, which is entirely infeasible. I have already done everything mentioned here with no improvement whatsoever. Evidently the issue is mechanical damage to the small rod's track.

EJP
 

I'm sure you mean well, but there are no switches on any 7CT1N that are immediately behind the front panel.
====================================================


Yes, I was thinking of the 576 when saying that.

Rolynn
 

On Wed, Mar 20, 2019 at 08:30 PM, Mike Dinolfo wrote:


Can you clarify what is "CRC
556"
Hi: CRC 5.56 aerosol. It a highly refined mineral oil, dissolved in naphtha, with liquified (due to the pressure in the can) petroleum gases, that act as the propellant. There is some supposed anti-corrosion woo in there too.
So... basically it's a sprayable oil, that because it is solvated( and so very thin) will flow into, and be drawn into tight places. When the solvent evaporates, the oil (which is thicker) remains. The spray is very flammable. Also, don't inhale it.
 

OK, thanks!

Mike Dinolfo

On 3/25/19 2:34 AM, Roy Thistle wrote:
On Wed, Mar 20, 2019 at 08:30 PM, Mike Dinolfo wrote:

Can you clarify what is "CRC
556"
Hi: CRC 5.56 aerosol. It a highly refined mineral oil, dissolved in naphtha, with liquified (due to the pressure in the can) petroleum gases, that act as the propellant. There is some supposed anti-corrosion woo in there too.
So... basically it's a sprayable oil, that because it is solvated( and so very thin) will flow into, and be drawn into tight places. When the solvent evaporates, the oil (which is thicker) remains. The spray is very flammable. Also, don't inhale it.

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