Type 1A4 dissassembly


Sean Turner
 

Hi,

Wondering if any folks here know exactly how to get the variable control shaft to come free. I have a fix for my broken plastic problem thanks to Jim Adney, but after studying the mechanical diagram in the manual, I still have no idea what is retaining this. Essentially, I need to slip it out so I can get Jim's metal ring in to screw over the broken plastic bit.

Thanks!

Sean


Dave Wise
 

?Sorry, just a guess.

The 1A4's VAR pot is special, with (a) a rear hole for the shaft to continue to the slide switch, and (b) a push-pull detent. I think the latter is molded contiguous with the setscrew cross.


If this is the case, then I think to remove the shaft, you

1- Loosen the forward screw in the slide switch coupler

2- Loosen the pot's own setscrew.


At that point I think you can pull the knob and slide the rod out of the coupler then out of the pot.


FWIW,

Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Sean Turner via groups.io <sdturne=q.com@groups.io>
Sent: Friday, April 02, 2021 4:55 PM
To: TekScopes@groups.io
Subject: [TekScopes] Type 1A4 dissassembly

Hi,

Wondering if any folks here know exactly how to get the variable control shaft to come free. I have a fix for my broken plastic problem thanks to Jim Adney, but after studying the mechanical diagram in the manual, I still have no idea what is retaining this. Essentially, I need to slip it out so I can get Jim's metal ring in to screw over the broken plastic bit.

Thanks!

Sean


Sean Turner
 

No worries, thanks!

I'll have to get it on the bench again, but I have a question. When you say "pot's own setscrew" is this the one that is in the broken plastic bit or is there another one I'm missing?

Sean

On Fri, Apr 2, 2021 at 05:24 PM, Dave Wise wrote:


?Sorry, just a guess.

The 1A4's VAR pot is special, with (a) a rear hole for the shaft to continue
to the slide switch, and (b) a push-pull detent. I think the latter is molded
contiguous with the setscrew cross.

If this is the case, then I think to remove the shaft, you

1- Loosen the forward screw in the slide switch coupler

2- Loosen the pot's own setscrew.

At that point I think you can pull the knob and slide the rod out of the
coupler then out of the pot.

FWIW,

Dave Wise


Dave Wise
 

?Exactly, Sean. The second screw to back out below is the one in the pot's broken plastic cross. With the rod gone, you should be able to disconnect the pot, slip it out, and fit it with an Adney Ring.


I hope you only have to fix outer pots, #1 or #4. Looks like you might need a laparoscope for #2 and #3 :)


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Sean Turner via groups.io <sdturne=q.com@groups.io>
Sent: Saturday, April 03, 2021 3:33 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Type 1A4 dissassembly

No worries, thanks!

I'll have to get it on the bench again, but I have a question. When you say "pot's own setscrew" is this the one that is in the broken plastic bit or is there another one I'm missing?

Sean

On Fri, Apr 2, 2021 at 05:24 PM, Dave Wise wrote:


?Sorry, just a guess.

The 1A4's VAR pot is special, with (a) a rear hole for the shaft to continue
to the slide switch, and (b) a push-pull detent. I think the latter is molded
contiguous with the setscrew cross.

If this is the case, then I think to remove the shaft, you

1- Loosen the forward screw in the slide switch coupler

2- Loosen the pot's own setscrew.

At that point I think you can pull the knob and slide the rod out of the
coupler then out of the pot.

FWIW,

Dave Wise


Jim Adney
 

I'm not at all familiar with the 1A4, but after reading these comments and looking at the photos on TekWiki, I don't understand how these pots work. I gather that the innermost rod is a push/pull control of a slide switch. If that's the same rod that turns the Tek made pots, then there has to be some way for that rod to slide within the pot while also being able to turn it. Either that, or the pot is turned by a larger concentric sleeve.

Oh, wait, do I see that the pots are on sliding mounts, so that they can slide in and out with the shafts? In that case, it looks like this should not be so difficult, even for channels 2 & 3.

1) Loosen the setscrew in the slide switch coupler.

2) Remove the setscrew in the pot.

3) Pull the shaft out the front.

4) Slide each pot toward the rear, far enough to provide clearance to slip the Adney (love calling them that!) ring over the cruciform part of the pot.

5) Rotate the ring to align the new set screw with the old setscrew hole in the pot.

6) Insert the shaft, tighten all the setscrews, and check to see if anything needs to be repositioned.

Now that I think I understand how this all works, it doesn't sound too difficult.


Dave Wise
 

Exactly. The 1A4 VAR knob has two control axes, push-pull for invert and turn for variable.

The pot slides on indexing posts as you push and pull.

The pigtail wires off the pot are crimped into female contacts that mate with square pins on the board. If you pull off the contacts after withdrawing the rod, you can remove the pot entirely to install the ring.


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Jim Adney via groups.io <jadney=vwtype3.org@groups.io>
Sent: Sunday, April 04, 2021 9:29:28 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Type 1A4 dissassembly

I'm not at all familiar with the 1A4, but after reading these comments and looking at the photos on TekWiki, I don't understand how these pots work. I gather that the innermost rod is a push/pull control of a slide switch. If that's the same rod that turns the Tek made pots, then there has to be some way for that rod to slide within the pot while also being able to turn it. Either that, or the pot is turned by a larger concentric sleeve.

Oh, wait, do I see that the pots are on sliding mounts, so that they can slide in and out with the shafts? In that case, it looks like this should not be so difficult, even for channels 2 & 3.

1) Loosen the setscrew in the slide switch coupler.

2) Remove the setscrew in the pot.

3) Pull the shaft out the front.

4) Slide each pot toward the rear, far enough to provide clearance to slip the Adney (love calling them that!) ring over the cruciform part of the pot.

5) Rotate the ring to align the new set screw with the old setscrew hole in the pot.

6) Insert the shaft, tighten all the setscrews, and check to see if anything needs to be repositioned.

Now that I think I understand how this all works, it doesn't sound too difficult.


Sean Turner
 

Going to get this on the bench again this weekend and tinker with it. I couldn't get the shaft to come free; was afraid of breaking something. Will need to examine again.

Sean