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 Post subject: Silvertone (Howard) 7171 Dial
PostPosted: Aug Fri 13, 2021 5:45 am 
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So, in taking a break from a Philco 42-22CL I started working on a Silvertone 7171 made by Howard.

The set must have been well loved originally, because the writing on the chassis and stickers on the cabinet indicate it was serviced as late as 1959. It was fully recapped around that time, and I went through and recapped it again. I still have 4 out of tolerance resistors to replace, but the set works fairly well. I had a bad feedback problem with the 6F5G until I put a shield around it. No evidence that the tube was shielded from the factory (unlike the 6D6 that has a tube shield and tube shield receptacle riveted to the chassis).

The big problem is that in the distant past they put 46 type pilot lamps in instead of 40s, and it melted the plastic tuner disc and the plastic dial face.

Attachment:
File comment: Burned dial face, disc that turns the tuner is in pieces and not attached to the cabinet anymore.
Screen Shot 2021-08-12 at 10.22.17 PM.png
Screen Shot 2021-08-12 at 10.22.17 PM.png [ 1.51 MiB | Viewed 1940 times ]


The tuner operates by a free turning shaft at the center-bottom, with two copper pressed-on discs that "grip" a big plastic disc with friction. That disc is held onto the front of the tuning condenser via a pressed on fitting. But the disk after melting became brittle and broke off the tuning condenser shaft, and I don't even have most of the pieces that go to the center of this plastic disc. The disc also serves as a light diffuser for the pilot lamps.

Attachment:
File comment: The remaining pieces of the dial tuning disc.
Screen Shot 2021-08-12 at 10.22.31 PM.png
Screen Shot 2021-08-12 at 10.22.31 PM.png [ 700.34 KiB | Viewed 1940 times ]


So after about 8 hours of pulling apart the pressed together tuning knob shaft, and giving up repeated attempts to take apart the tuning condenser's shaft, I came up with this idea of using a R-31 size O-ring as a tuning belt. I need to buy some snap-rings to hold the knob's shaft back on the chassis. There's adequate tension on the O-ring but it just spins on the knob's shaft so I think I will have to insert it, apply the snap rings, and then paint liquid electrical tape over it so it can "grip" better.

Attachment:
File comment: Shaft that the knob attaches to, after hours of fighting with it to take it apart & remove it from the chassis. Its pressed together and was VERY VERY tight!
Screen Shot 2021-08-12 at 10.22.41 PM.png
Screen Shot 2021-08-12 at 10.22.41 PM.png [ 1.17 MiB | Viewed 1940 times ]


Attachment:
File comment: O ring mock up.
Screen Shot 2021-08-12 at 10.23.04 PM.png
Screen Shot 2021-08-12 at 10.23.04 PM.png [ 960.88 KiB | Viewed 1940 times ]


Attachment:
File comment: O ring mockup, side view
Screen Shot 2021-08-12 at 10.23.11 PM.png
Screen Shot 2021-08-12 at 10.23.11 PM.png [ 894.34 KiB | Viewed 1940 times ]


Then I have to hope that the lower of the two pilot lamps doesn't melt the O-ring. Worst comes to worst I think I could tap into the filament string with a circuit using some diodes and LEDs to illuminate the dial (which, will have to be reproduced given the burn damage).

Anyone do any of this before? Am I on the right path? If I could get the tuning condenser shaft apart I would consider remaking the plastic disc but that thing is pressed together so tight it makes doing modern pressed in ball joints on front car suspensions look easy.


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Fri 13, 2021 6:00 am 
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Not relevant but interesting: The set works great with 6F5Gs, I tried using a 6F5 metal type thinking that way I would not need to add a shield to the set, but the set will not work with a metal 6F5 in it. Pin#1 is wired to chassis so there's no problem with that part of it.

I ended up putting a goat shield over the 6F5G and drilled a hole on the top of the shield to run a wire to an already existing hole near by on the chassis. This shields the tube but no modifications have been made to the chassis and it would be completely reversible.


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Fri 13, 2021 7:52 am 
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Have used theatrical sprit gum before. Sold in small bottle with insert brush. Works fantastic. For dial lights see Pin Ball life for LED direct replacement. No heat comes in any color you want.


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Fri 13, 2021 11:51 am 
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What needs to happen above all else is to get rid of those pilot lamps. They look like 300mA types and I have seen many which have burnt holes in that type of dial material. As far as I can see these were made for the round bulb, 150mA types. In other words the others are too hot when close to the dial. I will neither install, nor replace bulbs in that sort of dial assy with 300mA types ever.

Even non original LEDs would be safer.

Marcc


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Fri 13, 2021 3:55 pm 
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Marcc wrote:
What needs to happen above all else is to get rid of those pilot lamps. They look like 300mA types and I have seen many which have burnt holes in that type of dial material. As far as I can see these were made for the round bulb, 150mA types. In other words the others are too hot when close to the dial. I will neither install, nor replace bulbs in that sort of dial assy with 300mA types ever.
Even non original LEDs would be safer.
Marcc

I agree. For my future projects, I'm going to start getting rid of the hot lamps and replace with LED.


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Fri 13, 2021 5:03 pm 
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I can't find any suitable LED drop in replacements at Pinball Life, they don't have screw in base models just bayonets.

I already replaced the LEDs with 150ma ones over the 300mas that were there, but think going to LEDs is inevitable.


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Fri 13, 2021 5:56 pm 
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Remove the tips from the LED bayonet bulb. Will fit into screw socket. A dab of solder holds in place. Works fine every time.


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Sat 14, 2021 12:36 am 
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+1 on removing the envelope & salvaging the socket. This will be helped by de-soldering the wires. In some cases I have actually used flying lead Lilliput lamps in those sockets and a diode and some full wave rectifiers will fit in the centre. I have seen some direct replacements.

Only a matter of choice rather, than difficulty in solving the problem.

Marc


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Sun 15, 2021 4:24 am 
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I cannot for the life of me get the O-ring to "grip" to the bottom shaft. I tried coating the shaft in liquid electrical tape, but that did not improve the situation. I tried going up and down in O-ring sizes, but that just made the situation worse. I believe I have the correct size for the application if I can get the shaft to "grip" it.

So then I took a hacksaw blade and cut ribs into the inside of the O-ring thinking that would improve friction. It did, but not in a meaningful enough degree to fix the problem.

Next, I had a spray bottle of tack-grip that is used in sports for things like making baseball bat handles extra slip resistant. I forget who, but someone on the forum recommended that idea for slipping dials to me years ago and it has bailed me out on many occasions. I tried spraying the upper tuning condenser shaft, the lower knob shaft, and every surface of the O-ring. The O-ring I gave half a dozen applications. Everything is super tacky-feeling and "grippy" but, the knob shaft just sits there and spins.

To make matters worse, once I get the problem solved, I will have to JB-weld or epoxy on a small washer to the end of the knob shaft because removing it buggered it up enough to where C-clip/snap on retainer rings don't stay on it in the grove anymore. :cry:

So, my next thought is to give up on the O-ring idea and reappraise.

My next thought is, get or make two clear-plastic gears that I can then put on both shafts to turn the set into a gear drive tuner. Or hire a machinist to mill me some kind of direct drive system?!? Thing is, I know nothing at all about how to design gear systems and suspect its not as simple as having the diameters of each gear. If my measurements are right I could get by with something in the neighborhood of a 10mm max dia gear on the knob shaft and a 106mm for the tuner.

Since the gears would be clear plastic, the LEDs behind them would still be able to illuminate the dial. They would probably have to be a few mm thick to hold up and then be epoxied onto their respective shafts.

Someone must have attempted to repair this radio in the past and given up due to the tuner problems. The dial pointer is a brass pressed-on fitting that goes over the original shattered plastic tension disc, and behind that is a pot metal part that clamps onto the tuning condenser shaft via two set screws. One set screw was broken out, and the other is seized due to the pot metal swelling with age.

I hate to give up on a working radio over a mechanical problem.


Attachments:
Scan.png
Scan.png [ 362.78 KiB | Viewed 1846 times ]
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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Sun 15, 2021 6:53 am 
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Do note that "O" ring material also comes in square & rectangular and is not necessarily a Hardware store Item. The square offers more surface & do make sure that which is to be moved is free and not binding. I need to see the pulley grooves /scores to speculate on it being something like a sewing machine belt?

Marcc


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Wed 18, 2021 1:37 am 
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Marcc wrote:
Do note that "O" ring material also comes in square & rectangular and is not necessarily a Hardware store Item. The square offers more surface & do make sure that which is to be moved is free and not binding. I need to see the pulley grooves /scores to speculate on it being something like a sewing machine belt?

Marcc


I did not know that O-ring material came in other shapes. I will be ordering some length of square shaped material to make my own belt and see how that goes. It may take a while to come in (from China).

I hear from googling it that you can attach the ends to each other using superglue?

My other thought is to increase the diameter of the lower shaft, there's enough room inside its bracket to be as large as 10mm in diameter, which would give more surface area to grip the belt with.


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Aug Wed 18, 2021 4:56 am 
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One of the traps is the shape of the pulley score. Its width and curvature (if any) along with tangent and tension all add up to critical. It is not as simple as it looks. Often you will see "Flat" idler pulleys running on the backs of "Power Belts" (These are specially made with reinforced outers for the tensioner pulley to run on). It is important to match the belt to the score and it shape. Which is why I am pointing this out. Engineering & Industrial suppliers normally carry this stuff and the correct quality super glue to join it.

There is no such thing as a perfectly flat pulley. It will be domed. That's in accordance with Bernoulli's theorem, otherwise it will run off.

Marc


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Sep Sun 05, 2021 2:29 am 
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I think I am edging closure to solving this puzzle. I tried making my own O-ring and still had slippage, which I figured was now owing to how much torque is needed to spin the tuning condenser with such a tiny diameter shaft at the tuning cap for the O-ring material to grip to. If I could make that part of the system larger, then less force is needed to spin the tuner, which elevates the amount of slippage at the tuning knob. Or so my thinking goes.

It took me a significant amount of careful cutting, filing, and grinding by hand but I freed the dial mount from the tuning capacitor. I had to cut away a pot metal part by hand (which took me about 4 hours), which had already been broken in one spot from whoever gave up on this radio before I bought it (it is obvious that the tuner problems is why the radio was not restored and was resold by whoever had it in the past as one of the tabs in the dial mount circle was broken off from disassembly as well).

Attachment:
File comment: Dial mount removed
Screen Shot 2021-09-04 at 9.14.59 PM.png
Screen Shot 2021-09-04 at 9.14.59 PM.png [ 1.47 MiB | Viewed 1466 times ]


I went through my parts bins and parts sets and found this tiny pulley (originally would have been a tensioner on a AA5 slide rule dial). I was able to mount it inside the pressed-together knob shaft. My method of thinking is the larger I could make the diameter of this shaft, the less slippage there will be. Unfortunately the design of the dial mount prohibits this area from containing a modest sized pulley.

Attachment:
File comment: Small pulley
Screen Shot 2021-09-04 at 9.15.53 PM.png
Screen Shot 2021-09-04 at 9.15.53 PM.png [ 963.62 KiB | Viewed 1466 times ]


I then found the largest tuning condenser pulley I could find among my parts that also had the right diameter hole for this tuning condenser (they are apparently not standardized across the era and some use different sized rotor shafts).

Attachment:
File comment: Large pulley
Screen Shot 2021-09-04 at 9.17.58 PM.png
Screen Shot 2021-09-04 at 9.17.58 PM.png [ 847.43 KiB | Viewed 1466 times ]


With the dial mount reattached this looks something like this:

Attachment:
File comment: Dial mount reattached
Screen Shot 2021-09-04 at 9.19.58 PM.png
Screen Shot 2021-09-04 at 9.19.58 PM.png [ 1.15 MiB | Viewed 1466 times ]


The problem is that the large pulley is too thick and hangs up on the inside of the dial mount. Its tight enough that I am not going to sand or file my way out of the problem (say by making the large pulley thinner or by trying to open up the inside of the dial mount or some combination thereof).

Attachment:
File comment: Tight and binding
Screen Shot 2021-09-04 at 9.22.04 PM.png
Screen Shot 2021-09-04 at 9.22.04 PM.png [ 732.61 KiB | Viewed 1466 times ]


Now I am thinking I need to cut down the back side of the dial mount assembly, so that it clears the large pulley. I'd then need to make some new way of mounting it to the chassis, perhaps by way of some bolts near where the knob's shaft is located on the front side of the chassis. Unfortunately there is a very inconveniently placed 3/4" hole near this location, and a coil I don't want to mess with on the inside of the chassis. The small pulley for the knob will inevitably be a few mm off of the plane of the large pulley so hopefully the belt or string (whichever ends up working best) doesn't keep coming off.

The tuning condenser by the way only turns 180 degrees stop-to-stop. I don't know if this is standardized/typical or not.

Part of me is still eager to try a two-gear system but, I feel like what I'm piecing together is well on its way to working.

Still haven't given up & still working on it.


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Sep Sun 05, 2021 5:58 am 
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Albeit hard to see due to high contrast & some sort of grott that small driver shaft appears to have a flattish bottomed score rather than U shaped? If this is the case you are looking for a flat belt.

At tensioner is not a problem, it can be a simple roller bearing wider than the belt, albeit with a dodgy one on a stove I turned an annulus & slipped it over the bearing to form the grooved pulley required. The ideal is to have it close to the lower pulley to increase the tangent to place more belt on the pulley.

There is a choice of an "L" shape tensioner, or a cantilever. One mower here has a cantilever both sides as its reversible.

Marcc


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Sep Sun 05, 2021 11:49 pm 
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The lower pulley is a U-shape, just as the large pulley mounted to the tuning cap is. The round-type Oring material seems to grip it better than the square-type I bought on eBay.

Getting the two pulleys on the same plane is not exactly feasible. Part of my geometry limitations is that the shaft on the tuning cap only protrudes so far forward (most of the protruding forward-shaft length was made up of the pot-metal end I had to cut away).

With the large pulley mounted to the tuning cap shaft as far forward as it can be, its about 1/2" too far towards the back of the chassis relative the position of the small pulley.

I cut away the back side of the dial-mount, and this fixed the large pulley binding problems, and allowed me to move the small knob-pulley 1/4" closure to the back of the chassis.

So now the large pulley and small pulley are on different axis about 1/4 apart, which is as close as I can get them. Hopefully the belt or string won't like to jump the pulleys given this offset.

By removing the back of the dial mount, as a consequence, the dial is now about 1/4 further inside the cabinet than it should be. The design of the cabinet/dial has the dial and dial glass inside the cabinet (there is no dial cover & bezel assembly), so I will have to make a (preferably wooden) circle to go inside the dial opening on the cabinet to hide the fact that the dial is now further back and so that there is no visible gap/hole around the dial.

I am thinking I can mount LEDs behind the large pulley to illuminate the dial. The four spokes of the pulley will create visible shadows but there's only so much I can do here.

To mount the dial mount without messing with the delicate coil on the inside of the chassis, I used spacers of washers & hex nuts and JB Weld to attach the dial mount to the chassis. If the epoxy doesn't hold as a permanent solution, I will have to relocate that coil and drill bolt holes to bolt the dial mount to the chassis. I am hoping it does not come to that as I am not looking forward to rewiring the leads to the coil & making a spacer/mount for it inside the cluttered chassis.

Its funny that I am having to put so much work into a set that was very easy to get working. Even the cabinet didn't need regluing. :D


Attachments:
File comment: Dial mount & JB Weld setting
Screen Shot 2021-09-05 at 6.28.18 PM.png
Screen Shot 2021-09-05 at 6.28.18 PM.png [ 1.09 MiB | Viewed 1183 times ]
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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Sep Mon 06, 2021 12:48 am 
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I am starting to wonder if the drum is a foreigner. However 1/2" is a big error. and I wonder if the drum is fouling"? It looks to be a type for cordage. Now could you confirm that the shaft on the gang has been shortened? What is the hole in the middle of the shaft for? It could possibly be used (or was used) to extend the shaft if that is the problem by just adding a bit more shaft?

I have attached a photo of a shaft extender type which I often make and one to the size of that shaft, is not an issue. This one is Aluminium.

Marcc


Attachments:
extender-pot.jpg
extender-pot.jpg [ 684.43 KiB | Viewed 1175 times ]
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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Sep Mon 06, 2021 3:47 am 
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The pot metal part I had to cut away was basically a shaft adapter/extender like your picture only shaped a bit different. On the forward face of it was a brass pressed on part maybe as thick as a quarter with a very small (dia & length) shaft where the threaded hole that the dial pointer/needle & screw attached onto.

This brass pressed-on part is what originally held the center of the plastic light-diffuser / friction turned tuner controller that was melted & broken sending me down this long road of deconstructing the tuning assembly. So when the tuning knob rotated its shaft, what it was really doing is rotating these two pressed-together brass washers, which grabbed the large plastic diffuser/tuner controller disc, which was pressed onto the shaft extender/pot metal part, which turned the tuner rotor.

If its not original, someone went to some pretty crazy lengths to make up the system that failed. Model is obscure enough I can't find pictures of another.

Real radio manufacturer was Howard, who made it for Silvertone. I have no experience with Howard sets & how they normally did things.

I have my fingers crossed that after the JB Weld cures I'll be able to string it with something and not have it jump the deep groves of the two pulleys.


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Sep Mon 06, 2021 5:42 am 
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OK that is looking like an easy fix (says he with a lathe) if you only need around 1/2" of shaft, or so. You could use a cup end as sample (stronger Keeps it straight), or you could use a small slug the right diameter, centre bored. To stop it slipping you can drill (a) shallow hole/s in between the two bits, assembled & pour solder into it. A longer high tensile centre screw may be needed to hold it all together?

Marcc


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Sep Mon 06, 2021 8:19 pm 
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I am tantalizingly close to getting the tuner to operate again.

The JB Weld is still tacky but holding well so I decided to string it with used dial string off a parts chassis (totally different brand & model #) I have been cannibalizing parts off of.

I googled dial string diagrams and found this one for a Philco that looks pretty close so I tried to duplicate it.

Attachment:
File comment: Philco dial string diagram
Screen Shot 2021-09-06 at 3.13.24 PM.png
Screen Shot 2021-09-06 at 3.13.24 PM.png [ 23.23 KiB | Viewed 1100 times ]


And then the knob was able to operate the tuner.

....for a brief period.

Then the string came off the small pulley, binded itself up between the pulley and the chassis, and the entire assembly locked into position.

I tried anywhere from 1 to 4 loops around the lower pulley, different spring strengths & spring mounting positions on the large pulley. All had the same failure, with a loop coming off the small pulley (either side of it, it was not consistently off onto the chassis side) and then the whole thing would bind up.

I have a length of o-ring material sitting in epoxy to see if a dial belt will solve the problem. Assuming the epoxy holds the Oring material together.


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 Post subject: Re: Silvertone (Howard) 7171 Dial
PostPosted: Sep Tue 07, 2021 2:20 pm 
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Now that the epoxy has set, the tuner works!

The dial belt approach works the tuning cap and doesn't jump the lower pulley.

As long as the epoxy holds the Oring material, the radio will now work.

Thank you for your patience and help!


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