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Latest Mod For My TDI Sl....


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I've always had trouble getting the GB and Threshold exactly right on my TDI SL. After seeing Karelian's thread on the vernier knob, I decided to see what I could come up with. The problem with the control the guy suggested to him was that it had limited movement. Ideally, you want the vernier to turn as many turns as need to move the potentiometer through it's full range of travel. After hours of searching I found what I needed. A solid brass and stainless vernier with a 1:6 ratio. One full turn moves the GB pot about 1 1/2 numbers. I can now easily get the GB to that "just quiet" point, and it stays put. No more tree branches, or coat sleeves inadvertently moving the controls. I can easily set the Threshold to the very edge of my hearing, and as the batteries discharge and the Threshold creeps up, I can make a tiny adjustment and it's back on the money. As far as immediate and stark difference, this is the best mod I've done. It took me several hours to machine the bases, but the way I made it requires no physical mods to the machine. Remove the pot nuts, put the base on and replace the nut. I had to make shims for the pot shafts, as the verniers are made to fit a 1/4" shaft, and the shafts on the pots Whites used are .234". Had to make some very thin-walled round shims to glue inside the vernier sockets. I'm planning on selling these kits fort $150 for both controls, or $75 for a single. If anybody is interested, you can PM me here.

Now I'm really looking forward to our Nevada trip in June! My SL is about as good as an SL will ever be. It's going to be interesting.

 

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  • 2 weeks later...

The internal mods are the ones recommended by Reg Sniff, and have been explained in  many threads. The first is changing a pair of filter capacitors to make the SL less sensitive to the sweep speed. The other is removing one capacitor, and two diodes, and putting a jumper across two legs of one of the diodes. I don't have time to get into the details this morning...I'm headed out of town. But somebody may be able to direct you to the location of the details on the mods. The second mod has been done by the factory on all SL's made since 2015, I think. Including the tan version.

Jim🙂

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You mentioned as the batteries discharge the threshold changes? Did you try rechargeable lipo aa's? Voltage on them stays constant until they are almost fully discharged. I've replaced all my batteries with rechargeable lipo's including 9v's.

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4 hours ago, Jim in Idaho said:

The internal mods are the ones recommended by Reg Sniff, and have been explained in  many threads. The first is changing a pair of filter capacitors to make the SL less sensitive to the sweep speed. The other is removing one capacitor, and two diodes, and putting a jumper across two legs of one of the diodes. I don't have time to get into the details this morning...I'm headed out of town. But somebody may be able to direct you to the location of the details on the mods. The second mod has been done by the factory on all SL's made since 2015, I think. Including the tan version.

Jim🙂

 

I am more interested in how you feel about he mods you have done.  I have read several of the threads regarding the various options.

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On 6/9/2020 at 6:31 AM, kac said:

You mentioned as the batteries discharge the threshold changes? Did you try rechargeable lipo aa's? Voltage on them stays constant until they are almost fully discharged. I've replaced all my batteries with rechargeable lipo's including 9v's.

When you charge li-ions to their max voltage of 16.8, they drop to the nominal 3.7 fairly fast...maybe an hour, or a bit more. That nominal voltage lasts for quite awhile....about 4 hours on my TDI SL. But that initial drop from 16 to 14.8 for the pack, requires a little reduction of the Threshold as the voltage drops. Unless there's something wrong with the SAT on my unit. Makes no difference which 4 cell pack I use.

Jim

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On 6/9/2020 at 8:19 AM, havingstl said:

I am more interested in how you feel about he mods you have done.  I have read several of the threads regarding the various options.

I like all the mods I've done. Wouldn't go back to an unmodded SL.

Jim

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