Reg Mods Update

[gflores71]

There seems to be much interest still on the TDI-SL mods that our friend Reginald Sniff made. I often find old emails in my junk box from people trying to get the mods. I apologize for not replying as I find them late and often busy with day chores.
I will share what I still have left from my conversations with Reg many years ago. Most were over the phone as he had difficulty typing on the keyboard. I took notes and why I have the last picture with a summary of the three mods.

Correspondence

Reg,

Thanks for the picture. I do have a few questions regarding my early model SL.

1- you had mentioned in another thread about doing something also with D20 and D21. We spoke only on changing C20, C21 and removing C56. What is the purpose of the D20,21 Mod?

2- Are C20,21 Polarized? what is the direction of flow ? ( thinking about building a board with a toggle switch to change from OEM to modified.} just in case the mod has an effect on my using my BIG coil.

3. If I did a board would the cables running from the capacitor board to the detector board need to be shielded?

I just ordered the Reidman battery.

Thanks

Gilbert

EMAIL sent by Reg in response:

I mentioned mods  added in 2015 to the SL to correct a problem in Australia.  The mods to correct that problem included D20 and D21..  The D20 and D21 were part of that mod as was C56.  You can remove D20 and short out D21 with a simple jumper to complete the Aussie mods.  This will smooth out the ground balancing a little.

If you use the proper caps, C20 and C21 are not polarized.  Do not use polarized caps.

I don't recommend a board to be added.  Just tweak the Delay a little if the cap mod increases the sensitivity too much.

On the latest pic I sent you, you will see an arrow pointing to C42.  Adding a jumper across this cap will increase the gain and make very weak signals more reliable.  Adding a jumper is easy.  Simply look for two test points  TP2 and TP31.  They are near C42.  Simply add a jumper from one test point to the other jumpers C42 and takes care of the problem.  C42 and R75 are a high pass filter that isn't needed and causes problems.  Eric added them when he had a drift problem and thought they would help.  The drift was coming from some place else he later found out.

 

Reg

 

( caps being removed are C20 &21, .47uf and will be replaced with .22uf. Use 50v Panasonic, or Rubicon Stacked Metal Film Polyester type ) from another post by Reg

 

Picture sent by Reg

My Summary of all three TDI-SL  REG mods

 

 

Gilbert

 

 

[Jim in Idaho]

Bear in mind that on SL's made since 2015 have D20, and D21 removed, and the jumper across the correct 2 legs of D21. This was a factory mod. if you want to perfor4m this mod on your pre-2015 model here's a pic showing which legs the jumper goes across on D21. It also shows D20, and C56, which can be removed.

Jim

[gflores71]

Jim,

 

Thanks for clarifying , that pic makes it much easier to understand.

[Jim in Idaho]

Both D20 and 21 are three-lead diodes. The jumper only goes across 2 of the 3 connections on diode D21. It goes across the bottom 2 connections in the pic, as shown. Also, everybody interested in this mod should understand these are very tiny components. They require a magnifying light, and good soldering skills, with a decent quality soldering station. At least IMHO...LOL I was a radar tech in the Air Force, and doing this mod taxed my skills. I've done 2 of Reg's mods to my 2013 unit, and I recommend them. At some point in then future I'm going to do the jumper across Test Points 2 and 31, too. I wasn't aware of that until Gilbert's post, so a shoutout to him, and a thumbs-up

Jim

[gflores71]

I am afraid to do the high gain mod, I run a 25 inch and 19 inch NF coil on my SL. 
Looking to get a second as back up.

[gflores71]

[Jim in Idaho]

I'm thinking, Gil, that a switch for the hi-gain might be a nice feature.

Jim

[gflores71]

Yes Jim, a toggle switch would do it.
 

[CaliGold]

On 1/8/2022 at 10:01 PM, gflores71 said:

There seems to be much interest still on the TDI-SL mods that our friend Reginald Sniff made. I often find old emails in my junk box from people trying to get the mods. I apologize for not replying as I find them late and often busy with day chores.
I will share what I still have left from my conversations with Reg many years ago. Most were over the phone as he had difficulty typing on the keyboard. I took notes and why I have the last picture with a summary of the three mods.

Correspondence

Reg,

Thanks for the picture. I do have a few questions regarding my early model SL.

1- you had mentioned in another thread about doing something also with D20 and D21. We spoke only on changing C20, C21 and removing C56. What is the purpose of the D20,21 Mod?

2- Are C20,21 Polarized? what is the direction of flow ? ( thinking about building a board with a toggle switch to change from OEM to modified.} just in case the mod has an effect on my using my BIG coil.

3. If I did a board would the cables running from the capacitor board to the detector board need to be shielded?

I just ordered the Reidman battery.

Thanks

Gilbert

EMAIL sent by Reg in response:

I mentioned mods  added in 2015 to the SL to correct a problem in Australia.  The mods to correct that problem included D20 and D21..  The D20 and D21 were part of that mod as was C56.  You can remove D20 and short out D21 with a simple jumper to complete the Aussie mods.  This will smooth out the ground balancing a little.

If you use the proper caps, C20 and C21 are not polarized.  Do not use polarized caps.

I don't recommend a board to be added.  Just tweak the Delay a little if the cap mod increases the sensitivity too much.

On the latest pic I sent you, you will see an arrow pointing to C42.  Adding a jumper across this cap will increase the gain and make very weak signals more reliable.  Adding a jumper is easy.  Simply look for two test points  TP2 and TP31.  They are near C42.  Simply add a jumper from one test point to the other jumpers C42 and takes care of the problem.  C42 and R75 are a high pass filter that isn't needed and causes problems.  Eric added them when he had a drift problem and thought they would help.  The drift was coming from some place else he later found out.

 

Reg

 

( caps being removed are C20 &21, .47uf and will be replaced with .22uf. Use 50v Panasonic, or Rubicon Stacked Metal Film Polyester type ) from another post by Reg

 

Picture sent by Reg

My Summary of all three TDI-SL  REG mods

 

 

Gilbert

 

 

Hi Gilbert

I have been modding my TDI SL lately. (just the battery and coil resistors as the diodes and jumper were done at factory.  I want to complete the sweep speed cap replacement (c20, c21) as the .47uf are still installed but cant find the panasonic caps of that spec ANYWHERE and digikey parts says theyre obselete now and suggests below replacement. The difference is? There is also a 2% tolerance instead of 1% difference that someone mentioned earlier thread I think it was @Jim in Idaho. Does that matter? Any lead on the .22uf 50v 1% throughole caps would be much appreciated. 

 

Patrick

[CaliGold]

@gflores71 on making the "jumper" on c42... How and  what am I soldering together here? The two test points mentioned or? The nomenclature from the email got me a little confused...  I see how the three pad diode smd was removed at d21 a  "jumper" was completed but the c42 is a two pad resistor smd. Are we wiring the two c43 pads together after removal of resistor or one of the test points to one of the pads or both? I'm lost...  Also,Does R75 resistor get removed/jumpered too? Thanks and sorry to pry but I'd like to complete this mod asap and get some testing / results posted for any other folks out there that were left looking for more sensitivity from the TDI SL.

@Jim in Idaho please freel free to share your knowledge on how this mod would be completed too (C42 and R75)

Thanks so much again to everyone. 

Pat