AVO VCM163 roller selector - UK Vintage Radio Repair and Restoration Discussion Forum

Fourlegsgood · 15th Apr 2017, 8:59 am

I have recently bought a second VCM163 on a whim, sight unseen but it was cheap. The meters were sort of OK, one had a broken pointer, but both had electrical continuity and so Herts Meters seem happy they can sort them (as they said, no electrical continuity means they go straight to the parts bin to help repair others).

But the roller selector has a couple of broken rollers. The previous owner rewired to use the two far right rollers but I want to go one better and actually move those good rollers over to the left where they are needed.

I have the roller assembly out of the VCM but what comes next to get the rollers apart? I don't want to just 'have ago'. That can only end in tears.

Thanks.

Dekatron · 15th Apr 2017, 9:33 am

First make sure that you use your digital camera to take a lot of photos when you disassemble the roller selector, it is sometimes very nice to go back to the photos when you assemble the roller selector.

I would start by making sure that all ends on all round rods and the square rod in the center don't have any protruding parts larger than the rods themselves, otherwise they will damage the wheels when you slide them off. You can grind down the edges with a fine file. Also remove all solder from the ends of the round rods so it doesn't damage the wheels when/if you slide them off that way.

Also don't slide off more wheels than necessary, if some are already broken the risk of breaking more when you slide them off is higher as they have probably aged poorly as a group.

I also mark the ends of the rods so I know how far they protrude on each side so that I can get them back in the same position, You can mark them with a black permanent marker and just make sure that you handle them carefully so that you don't remove that marker, never scratch them with a sharp tool as that scratch might damage the plastic and the contact inside each wheel. Also make sure that you write down and take photos as you disassemble the roller selectors as there are sometimes washers at the ends and it might also be good to know how the spacing is between the wheels and where each wheel went. When you assemble the rods you can turn them 180 degrees (or less) in their holes so that you get a side on the rod with better contact if the position they have been sitting in all the time has been ground down. I usually recommend that you don't try to clean the metal rods with anything as the silver coating is extremely thin on some of these rods and it is easily removed leaving the rod without this protection which makes the contact poorer.

You should also push the wheels off, never pull/drag them off - pushing prevents the three small plastic edges on the outer lighter grey part to break, if you pull on the outer lighter grey part those edges easily break off. You can see those three small edges on the bottom wheel in your photo if you look at the wheel from the side. You can either push on the inner darker grey part or push on the outer lighter gray part, it depends on which direction you are going to remove them, but never ever pull on the outer lighter grey part.

You should check the distance between the wheels to make sure that you get them in the same position afterwards and also number the wheels so that you put back the working ones in the same position. Also mark where the brown piece of PCB is situated sideways as that holds the metal pieces in place in the correct position. You can use pieces of perspex or other plastic and put pieces that fit snugly in between the wheels as distances to make sure that the wheels end up in the correct place, also check against the finger guard and trim them so they get into their old place.

Hope this helps!

/Martin

Fourlegsgood · 15th Apr 2017, 10:03 am

Martin,

Yes, it does help thank you. And a very quick response!

I have already started the digital photo album by recording exactly where each wire was soldered. Everything else will be photographed at each stage as if they were Royal babies!

The rods, as far as I can tell, helpfully only have a soldered connection on only one end. That leaves the opposing end unsoldered and clean. (Shown in the attached pictures.) Therefore I plan to pull through the unsoldered end for each rod and three of the rods with be therefore pulled through in the opposite direction to the others.

Nick

Fourlegsgood · 15th Apr 2017, 11:22 am

Just a long shot, in case anyone has a spare rotating selector wheel ? ? ?

Dekatron · 15th Apr 2017, 2:04 pm

It looks like there is some solder on one end without a wire, of the three without wires in one photo. The other ends looks like someone has sharpened in a pencil sharpener so they will probably slide out nicely.

Leaving the rods in place and just sliding of the wheels off sometimes works best but in other cases you will have to slide some rods out before the wheels are loose enough to slide off.

Bazz4CQJ · 15th Apr 2017, 4:43 pm

Nick; Martin and I have been trying to determine whether or not any type of lubricant was ever applied to the selectors during manufacture. Based on looking at a single example of one broken wheel of Martins, it is clear that some "product" was applied to the ball bearings, but ~50 years later, this is now totally dried out. Personally, I don't believe it was actually a lubricant, but just a paste which served to hold the balls in place during assembly.

As it now seems that the plastic is suffering some degree of embritlement, the question arises as to whether or not the addition of some *carefully* chosen lube would be beneficial. Possibly the best choice would be a fluorocarbon grease, or a lithium-based grease produced specifically for switches.

When you get to the stage of having the broken wheel out of the assembly, please let us know whether or not you can see any lube (of any form) inside it.

One thing I would recommend to you is that you should not apply any kind of liquid to the wheels; it is likley that some/all have cracks in them and that wetting those cracks may encourage them to grow.

B

Radio Wrangler · 15th Apr 2017, 6:38 pm

It might be worth creating a model for 3D printing.

David

Bazz4CQJ · 15th Apr 2017, 7:16 pm

I think that Martin may be ahead of you on that one, but I wonder what the economics of that look like?

B

Fourlegsgood · 15th Apr 2017, 8:04 pm

Quote:

Originally Posted by Bazz4CQJ

When you get to the stage of having the broken wheel out of the assembly, please let us know whether or not you can see any lube (of any form) inside it.

Bazz,

I have attached pictures of the brocken (AKA smashed) roller selector.

I can see what looks like a residual amount of white grease that would have been around the area in contact with the spring contact that connects to each rod as the wheel is rotated. I think this can be seen in the photo.

I am just going to move that wheel to the furthest right position and glue in place a remaining piece of the wheel for cosmetic purposes.

I took out all of the rods. Three from one end and the remained from the other end. They just have a small amount of silver oxide but are otherwise unworn.

I put one wheel back in pace and tested contact making to the rods. It was intermittent but after a few rotations was making good contact. Presumably after any surface film had been worn off.

Out of interest this VCM163 is number 129 which must be quite early. It has sat unused since 2005 before I got it. Hopefully it will work though.

My other VCM163 is number 1642.

Nick

Bazz4CQJ · 15th Apr 2017, 10:19 pm

Hi Nick, the dried powder on your wheel looks exactly like the stuff on Martin's.
On the latter, which is already broken and so we experimented with it, I found that the powder readily absorbs water, and it is easily removed from the plastic with a damp Q tip with just the *lightest* pressure. That is why I think it was a paste used in assembly; I believe that any trace of a lubricant would be hydrophobic and would probably be well stuck to the wheel.

B

Fourlegsgood · 17th Apr 2017, 7:01 am

The white stuff on the centre part of my broken cog feels more like a grease than a powder to the touch. It also feels like grease when it is rubbed between my fingers.

My rotating switch assembly is now going back together quite nicely. As I slide each group of cogs on the centre square brass I check for position against the slotted cover. Then with both ends in place I screwed the whole thing upside down on the top of the tester to keep it rigid. Fine tuning of the cogs position along the centre brass square rod was easy to ensure smooth and easy rotation.

Now, I just need to clean all the silver rods and slide them back in. I think this might be possible with the whole assembly still fixed to the top of the tester.

Dekatron · 17th Apr 2017, 8:44 am

Nice!

When you have soldered the wires you should check once more that the metal rods protruding from the wheels don't snag on the cogs of the wheels. Sometimes you'll have to move the brown circuit board sideways to make sure that none of these metal rods can snag on the cogs. In some cases you might need to bend the metal rods slightly at the end protruding from the brown circuit board so they flex outwards from the wheel, don't forget not to use the wheel as a lever point then as you might crack them.

/Martin

Radio Wrangler · 17th Apr 2017, 8:45 am

Probably the remains of a white grease. HP used 'Lubriplate' all over the mechanical parts of 8640 sig gens for the gearboxes and the cavity oscillator.

David

Fourlegsgood · 17th Apr 2017, 9:05 am

Thanks guys.

I have just cleaned all the oxide off the silver rods and put them back in the switch gear. In the end I found that light use of fine wire wool gave me the best control of the cleaning.

Although tedious, I have tested the continuity of all of the rotating wheels to the rods in all of the positions. It was worth doing because it showed that a couple of the wheels had intermittent contact. I suspected this was a dirty contact on the internal spring loaded lever contact and so did a bit of multiple rotations of the wheels back and forth. This cured the bad contacts.

While I have a cup of coffee before doing any more, can anyone tell me why the 4 bolts on each end of the chassis have rubber mountings? These are the bolts that are tapped in their ends for the end plate securing screws.The bolts do not appear to have any other function apart from giving a flexible mounting to the end cover plates.

karesz* · 17th Apr 2017, 11:40 am

Hello David,

HTML Code:

HP used 'Lubriplate' all over the mechanical parts of 8640 sig gens..

which type of Lubriplate was it please?

Thanks and regards, Karl

Radio Wrangler · 17th Apr 2017, 12:05 pm

The original white one, in a small tube. So I think it's L0034-086 on that page.

A friend was the main mechanical inspector and assembled a lot of the 8640 stuff (and the turrets for 606's) A tube lasted a good while.

Inside the cavities, it's all degreased and uses plastic slipper guides, but with a little grease on the drive threads.

David

karesz* · 18th Apr 2017, 1:20 am

Best tnx David!
Sincerely, Karl

Bazz4CQJ · 18th Apr 2017, 3:29 am

Did you apply any fresh lubricant Nick, or simply re-assemble? Whatever the original "substance" was, I'd guess it was not specified for a working life of 50+ years so has dried out and oxidised to some degree.

B

Fourlegsgood · 18th Apr 2017, 8:15 am

As far as I can see the brittleness of the old plastic effectively makes these a sealed unit. I certainly wasn't going to try to get them apart.The broken one is well and truly smashed so that has been relegated to TC 2 duty (ie last on right of the row of rotary selectors) and is not connected.

The assembly is now all resoldered and is back in the VCM163. All of the rotary cogs move freely. I found it just takes a little patience to line them up by sliding one way or another on the centre square bar. Also of course making sure they don't bind on the solder tags.

A visual inspection of the rest of the innards only showed one loose wire on one of the top cover sockets. That would of course have mucked up the connection to many other sockets because of the loop arrangement of wiring.

Just need to give Herts Meters a jog now. The last time I spoke to them we joked about nudging them if it got to Xmas and I hadn't heard . . . . . .

15th Apr 2017, 8:59 am	#1
Fourlegsgood Tetrode Join Date: Feb 2015 Location: Leicstershire, UK. Posts: 81	AVO VCM163 roller selector I have recently bought a second VCM163 on a whim, sight unseen but it was cheap. The meters were sort of OK, one had a broken pointer, but both had electrical continuity and so Herts Meters seem happy they can sort them (as they said, no electrical continuity means they go straight to the parts bin to help repair others). But the roller selector has a couple of broken rollers. The previous owner rewired to use the two far right rollers but I want to go one better and actually move those good rollers over to the left where they are needed. I have the roller assembly out of the VCM but what comes next to get the rollers apart? I don't want to just 'have ago'. That can only end in tears. Thanks. Attached Thumbnails

15th Apr 2017, 9:33 am	#2
Dekatron Octode Join Date: May 2009 Location: Linkoping, Sweden Posts: 1,465	Re: AVO VCM163 roller selector First make sure that you use your digital camera to take a lot of photos when you disassemble the roller selector, it is sometimes very nice to go back to the photos when you assemble the roller selector. I would start by making sure that all ends on all round rods and the square rod in the center don't have any protruding parts larger than the rods themselves, otherwise they will damage the wheels when you slide them off. You can grind down the edges with a fine file. Also remove all solder from the ends of the round rods so it doesn't damage the wheels when/if you slide them off that way. Also don't slide off more wheels than necessary, if some are already broken the risk of breaking more when you slide them off is higher as they have probably aged poorly as a group. I also mark the ends of the rods so I know how far they protrude on each side so that I can get them back in the same position, You can mark them with a black permanent marker and just make sure that you handle them carefully so that you don't remove that marker, never scratch them with a sharp tool as that scratch might damage the plastic and the contact inside each wheel. Also make sure that you write down and take photos as you disassemble the roller selectors as there are sometimes washers at the ends and it might also be good to know how the spacing is between the wheels and where each wheel went. When you assemble the rods you can turn them 180 degrees (or less) in their holes so that you get a side on the rod with better contact if the position they have been sitting in all the time has been ground down. I usually recommend that you don't try to clean the metal rods with anything as the silver coating is extremely thin on some of these rods and it is easily removed leaving the rod without this protection which makes the contact poorer. You should also push the wheels off, never pull/drag them off - pushing prevents the three small plastic edges on the outer lighter grey part to break, if you pull on the outer lighter grey part those edges easily break off. You can see those three small edges on the bottom wheel in your photo if you look at the wheel from the side. You can either push on the inner darker grey part or push on the outer lighter gray part, it depends on which direction you are going to remove them, but never ever pull on the outer lighter grey part. You should check the distance between the wheels to make sure that you get them in the same position afterwards and also number the wheels so that you put back the working ones in the same position. Also mark where the brown piece of PCB is situated sideways as that holds the metal pieces in place in the correct position. You can use pieces of perspex or other plastic and put pieces that fit snugly in between the wheels as distances to make sure that the wheels end up in the correct place, also check against the finger guard and trim them so they get into their old place. Hope this helps! /Martin __________________ Martin, Sweden

15th Apr 2017, 10:03 am	#3
Fourlegsgood Tetrode Join Date: Feb 2015 Location: Leicstershire, UK. Posts: 81	Re: AVO VCM163 roller selector Martin, Yes, it does help thank you. And a very quick response! I have already started the digital photo album by recording exactly where each wire was soldered. Everything else will be photographed at each stage as if they were Royal babies! The rods, as far as I can tell, helpfully only have a soldered connection on only one end. That leaves the opposing end unsoldered and clean. (Shown in the attached pictures.) Therefore I plan to pull through the unsoldered end for each rod and three of the rods with be therefore pulled through in the opposite direction to the others. Nick Attached Thumbnails

15th Apr 2017, 11:22 am	#4
Fourlegsgood Tetrode Join Date: Feb 2015 Location: Leicstershire, UK. Posts: 81	Re: AVO VCM163 roller selector Just a long shot, in case anyone has a spare rotating selector wheel ? ? ?

15th Apr 2017, 2:04 pm	#5
Dekatron Octode Join Date: May 2009 Location: Linkoping, Sweden Posts: 1,465	Re: AVO VCM163 roller selector It looks like there is some solder on one end without a wire, of the three without wires in one photo. The other ends looks like someone has sharpened in a pencil sharpener so they will probably slide out nicely. Leaving the rods in place and just sliding of the wheels off sometimes works best but in other cases you will have to slide some rods out before the wheels are loose enough to slide off. __________________ Martin, Sweden

15th Apr 2017, 4:43 pm	#6
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,934	Re: AVO VCM163 roller selector Nick; Martin and I have been trying to determine whether or not any type of lubricant was ever applied to the selectors during manufacture. Based on looking at a single example of one broken wheel of Martins, it is clear that some "product" was applied to the ball bearings, but ~50 years later, this is now totally dried out. Personally, I don't believe it was actually a lubricant, but just a paste which served to hold the balls in place during assembly. As it now seems that the plastic is suffering some degree of embritlement, the question arises as to whether or not the addition of some carefully chosen lube would be beneficial. Possibly the best choice would be a fluorocarbon grease, or a lithium-based grease produced specifically for switches. When you get to the stage of having the broken wheel out of the assembly, please let us know whether or not you can see any lube (of any form) inside it. One thing I would recommend to you is that you should not apply any kind of liquid to the wheels; it is likley that some/all have cracks in them and that wetting those cracks may encourage them to grow. B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

15th Apr 2017, 6:38 pm	#7
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,869	Re: AVO VCM163 roller selector It might be worth creating a model for 3D printing. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

15th Apr 2017, 7:16 pm	#8
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,934	Re: AVO VCM163 roller selector I think that Martin may be ahead of you on that one, but I wonder what the economics of that look like? B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

15th Apr 2017, 10:19 pm	#10
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,934	Re: AVO VCM163 roller selector Hi Nick, the dried powder on your wheel looks exactly like the stuff on Martin's. On the latter, which is already broken and so we experimented with it, I found that the powder readily absorbs water, and it is easily removed from the plastic with a damp Q tip with just the lightest pressure. That is why I think it was a paste used in assembly; I believe that any trace of a lubricant would be hydrophobic and would probably be well stuck to the wheel. B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

17th Apr 2017, 7:01 am	#11
Fourlegsgood Tetrode Join Date: Feb 2015 Location: Leicstershire, UK. Posts: 81	Re: AVO VCM163 roller selector The white stuff on the centre part of my broken cog feels more like a grease than a powder to the touch. It also feels like grease when it is rubbed between my fingers. My rotating switch assembly is now going back together quite nicely. As I slide each group of cogs on the centre square brass I check for position against the slotted cover. Then with both ends in place I screwed the whole thing upside down on the top of the tester to keep it rigid. Fine tuning of the cogs position along the centre brass square rod was easy to ensure smooth and easy rotation. Now, I just need to clean all the silver rods and slide them back in. I think this might be possible with the whole assembly still fixed to the top of the tester. Attached Thumbnails

17th Apr 2017, 8:44 am	#12
Dekatron Octode Join Date: May 2009 Location: Linkoping, Sweden Posts: 1,465	Re: AVO VCM163 roller selector Nice! When you have soldered the wires you should check once more that the metal rods protruding from the wheels don't snag on the cogs of the wheels. Sometimes you'll have to move the brown circuit board sideways to make sure that none of these metal rods can snag on the cogs. In some cases you might need to bend the metal rods slightly at the end protruding from the brown circuit board so they flex outwards from the wheel, don't forget not to use the wheel as a lever point then as you might crack them. /Martin __________________ Martin, Sweden

17th Apr 2017, 8:45 am	#13
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,869	Re: AVO VCM163 roller selector Probably the remains of a white grease. HP used 'Lubriplate' all over the mechanical parts of 8640 sig gens for the gearboxes and the cavity oscillator. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

17th Apr 2017, 9:05 am	#14
Fourlegsgood Tetrode Join Date: Feb 2015 Location: Leicstershire, UK. Posts: 81	Re: AVO VCM163 roller selector Thanks guys. I have just cleaned all the oxide off the silver rods and put them back in the switch gear. In the end I found that light use of fine wire wool gave me the best control of the cleaning. Although tedious, I have tested the continuity of all of the rotating wheels to the rods in all of the positions. It was worth doing because it showed that a couple of the wheels had intermittent contact. I suspected this was a dirty contact on the internal spring loaded lever contact and so did a bit of multiple rotations of the wheels back and forth. This cured the bad contacts. While I have a cup of coffee before doing any more, can anyone tell me why the 4 bolts on each end of the chassis have rubber mountings? These are the bolts that are tapped in their ends for the end plate securing screws.The bolts do not appear to have any other function apart from giving a flexible mounting to the end cover plates. Attached Thumbnails

17th Apr 2017, 11:40 am	#15
karesz* Heptode Join Date: Jun 2010 Location: Zurich, Switzerland Posts: 538	Re: AVO VCM163 roller selector Hello David, HTML Code: HP used 'Lubriplate' all over the mechanical parts of 8640 sig gens.. which type of Lubriplate was it please? Thanks and regards, Karl

17th Apr 2017, 12:05 pm	#16
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,869	Re: AVO VCM163 roller selector The original white one, in a small tube. So I think it's L0034-086 on that page. A friend was the main mechanical inspector and assembled a lot of the 8640 stuff (and the turrets for 606's) A tube lasted a good while. Inside the cavities, it's all degreased and uses plastic slipper guides, but with a little grease on the drive threads. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

18th Apr 2017, 1:20 am	#17
karesz* Heptode Join Date: Jun 2010 Location: Zurich, Switzerland Posts: 538	Re: AVO VCM163 roller selector Best tnx David! Sincerely, Karl

18th Apr 2017, 3:29 am	#18
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,934	Re: AVO VCM163 roller selector Did you apply any fresh lubricant Nick, or simply re-assemble? Whatever the original "substance" was, I'd guess it was not specified for a working life of 50+ years so has dried out and oxidised to some degree. B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

18th Apr 2017, 8:15 am	#19
Fourlegsgood Tetrode Join Date: Feb 2015 Location: Leicstershire, UK. Posts: 81	Re: AVO VCM163 roller selector As far as I can see the brittleness of the old plastic effectively makes these a sealed unit. I certainly wasn't going to try to get them apart.The broken one is well and truly smashed so that has been relegated to TC 2 duty (ie last on right of the row of rotary selectors) and is not connected. The assembly is now all resoldered and is back in the VCM163. All of the rotary cogs move freely. I found it just takes a little patience to line them up by sliding one way or another on the centre square bar. Also of course making sure they don't bind on the solder tags. A visual inspection of the rest of the innards only showed one loose wire on one of the top cover sockets. That would of course have mucked up the connection to many other sockets because of the loop arrangement of wiring. Just need to give Herts Meters a jog now. The last time I spoke to them we joked about nudging them if it got to Xmas and I hadn't heard . . . . . .