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Whites TDI Motherboard


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10 hours ago, Geotech said:

Yes, 3 positions, on-off-on.

Hi Carl, thanks again.

I still had a few questions:

- Do the Pulse Scan TDI/TDI Pro and TDI SL turntables have big differences (performance), if so which ones?

- Are the Reg changes applicable on the Pulse Scan and should they be made to improve? If so, what are the matches of the C20-C21 capacitors to be set to 0.22uF, the C56 capacitor to be removed, D20-D21 diodes, jump over the C42?

Regards.

David

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7 hours ago, Melano87 said:

Hi Carl, thanks again.

I still had a few questions:

- Do the Pulse Scan TDI/TDI Pro and TDI SL turntables have big differences (performance), if so which ones?

- Are the Reg changes applicable on the Pulse Scan and should they be made to improve? If so, what are the matches of the C20-C21 capacitors to be set to 0.22uF, the C56 capacitor to be removed, D20-D21 diodes, jump over the C42?

Regards.

David

Those mods apply to the TDI SL, not the TDI Pulse Scan. The mod for the original TDI's was to smooth the threshold.

Jim

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25 minutes ago, Jim in Idaho said:

Those mods apply to the TDI SL, not the TDI Pulse Scan. The mod for the original TDI's was to smooth the threshold.

Jim

Hi Jim, thanks,

What are the mod, because despite my research I can't find an explanation?

David

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3 hours ago, Melano87 said:

Hi Jim, thanks,

What are the mod, because despite my research I can't find an explanation?

David

There hasn't been near as much posted on the threshold-smoothing mods for the Pulse Scan.  I own an SL model, so didn't get involved on the mods for the TDI. I'll look around, but I'm not sure I have a copy of the TDI mods....only the SL.

Jim

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1 hour ago, Jim in Idaho said:

There hasn't been near as much posted on the threshold-smoothing mods for the Pulse Scan.  I own an SL model, so didn't get involved on the mods for the TDI. I'll look around, but I'm not sure I have a copy of the TDI mods....only the SL.

Jim

Here's all I have on the smoothing mods. This was a post, a few years back, from Reg Sniff.

"

I don't do the mods myself.  My hands don't work that well any more so I have a friend do them.  He does the work and keeps all the money since the mod is somewhat labor intensive and does require a pcb trace mod. 

A full TDI mod costs about $125 (return shipping included with $500 insurance) and that includes replacing the preamp with a much better IC, the addition of a small pc board to reduce the noise, a filter change so the regular TDI is upgraded to the filtering of the Pro for a faster response.  The mod also includes calibration of certain stages to 1 millivolt to assure the mod works as designed.  This TDI pro filter mod makes the regular TDI like the Pro but without the extra GB pot and volume control.  The volume control was added to help reduce the noise problem, but with the noise reduction mod, is not needed for that purpose any more.

One additional mod is to short out a capacitor which eliminates a third filter that is not needed and can cause weak signal problems.  This mod does increase the gain which in turn increases the noise level.  Fortunately, reducing the gain using the gain control about 20% or so makes it back to normal.  You do gain a little depth but more noise with this mod.  One advantage of this mod is weak signals become more reliable. 

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On 9/8/2022 at 11:43 PM, Melano87 said:

- Do the Pulse Scan TDI/TDI Pro and TDI SL turntables have big differences (performance), if so which ones?

I'm not sure what you mean by "turntables."

Quote

- Are the Reg changes applicable on the Pulse Scan and should they be made to improve? If so, what are the matches of the C20-C21 capacitors to be set to 0.22uF, the C56 capacitor to be removed, D20-D21 diodes, jump over the C42?

In the TDI, C59-C60 (same as C20-C21) are already 0.22uF but you could decrease them to 0.1uF to equal the SL speed improvement. The 2 caps need to be matched to 1% or better. The TDI has no C56 or D20-21, and C42 is C50 in the TDI and can be shorted.

I'm not familiar with the other mods in Jim's post. I think the preamp replacement was the LME49990 but without some other changes just replacing the opamp won't do much.

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52 minutes ago, Geotech said:

I'm not sure what you mean by "turntables."

In the TDI, C59-C60 (same as C20-C21) are already 0.22uF but you could decrease them to 0.1uF to equal the SL speed improvement. The 2 caps need to be matched to 1% or better. The TDI has no C56 or D20-21, and C42 is C50 in the TDI and can be shorted.

I'm not familiar with the other mods in Jim's post. I think the preamp replacement was the LME49990 but without some other changes just replacing the opamp won't do much.

« Turntables », my english is poor… Board

Very interesting, thanks Carl.

Will lowering the two capacitors to 0.1 lead to something else (loss of depth)?

Do you think this is useful as it was done by Reg on the TDI SL?

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1 hour ago, Melano87 said:

« Turntables », my english is poor… Board

The SL board is a newer design and has some changes to make it quieter. It was intended that the TDI would switch to the SL board but it never did. The SL board has more options for mods.

Quote

Will lowering the two capacitors to 0.1 lead to something else (loss of depth)?

Do you think this is useful as it was done by Reg on the TDI SL?

Yes, lowering the cap values makes the demods faster with a slight loss of depth. I would leave them alone, I'm not even sure why Reg lowered them on the SL as it also tends to be noisier.

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I came across photos on another forum showing the wiring of connectors and switches on the Pulse Scan. (The photos are like this on the site, not of very good quality)

I don't understand why zener diodes everywhere.

Is the wiring of the conductivity switch just unlikely?

I have the impression that on the white connector the two wires in the middle are connected via a zener diode (?) One on the wire on the right and one on the wire on the left... I don't understand anything.

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