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Dec 1, 2017
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Toshiba PF Arcade Monitors
  • PB9929
    • Microcontroller-TMP87CK38N
    • Video Amp-M52337SP
    • Deflection IC - NEC C1883CT (NEC uPC 1883)
  • PD1843
    • Microcontroller-TMP87CM38N-5NF5
    • Video Amp-LM1269NA
    • Deflection IC - NEC C1888FCT (NEC uPC 1888 )
  • PD2367
    • Microcontroller-TMP87CM38NG
    • Video Amp-LM1269NA
    • Deflection IC - NEC C1888FCT (NEC uPC 1888 )
  • PE0493
    • Micro-TMP88PS38BNG

I2C - There are 3 ICs on the I2C bus - One master and 2 slave devices. The microcontroller fills the role of the I2C master, the video amp IC is one slave device and the deflection IC is the other slave device. Below is the decoded I2C communication and some default values I observed on my test chassis. The LM1269NA is well documented and the below snippet is nothing that can't be obtained from the datasheet. The NEC C1888FCT on the other hand, couldn't find anything about it online. The below snippet was obtained by going through the extended menu while running I2C captures. This 'should' be the bulk of what is needed to re-create the MCU.

  //LM1269NA - I2C Address 0xDC
  vidAdd = 0xDC;

  vidCmd[0] = 0x3B; //R-Gain Control [6:0]
  vidCmd[1] = 0x2E; //B-Gain Control [6:0]
  vidCmd[2] = 0x32; //G-Gain Control [6:0]
  vidCmd[3] = 0x5C; //Contrast Control [6:0]
  vidCmd[4] = 0x5E; //DAC 1 [7:0]
  vidCmd[5] = 0x73; //DAC 2 [7:0]
  vidCmd[6] = 0x7D; //DAC 3 [7:0]
  vidCmd[7] = 0xB2; //DAC 4 [7:0]
  vidCmd[8] = 0x00; //DC Offset / OSD Control

  //NEC C1888FCT - I2c Address 0x8C
  defAdd = 0x8C;

  defCmd[0] = 0x00; //??? Unknown Function
  defCmd[1] = 0x5D; //H.Size
  defCmd[2] = 0x7F; //H.Position
  defCmd[3] = 0xC3; //PB (Pin Balance)
  defCmd[4] = 0x40; //PAR (Parabola)
  defCmd[5] = 0xBE; //PBT (Pin Balance Top)
  defCmd[6] = 0x3F; //PBB (Pin Balance Bottom)
  defCmd[7] = 0x32; //PCT (Pin Cushion Top)
  defCmd[8] = 0xB0; //PCB (Pin Cushion Bottom)
  defCmd[9] = 0xB3; //PIN (Pincushion)
  defCmd[10] = 0x00; //TRP (Trapazoid)
  defCmd[11] = 0x8C; //V.Size
  defCmd[12] = 0x80; //V.Position
  defCmd[13] = 0x5B; //SC (S-Correction)
  defCmd[14] = 0x3A; //CC (C-Correction)

Vertical Deflection - Chassis expects ~14mH vertical deflection yoke at ~8 ohm.

Vertical Deflection IC - LA7846N
Functions similar to op-amp. Output to vertical deflection yoke via pin 3. (Pin3 -> V.Dy -> R323 -> Gnd)
R323 - 1.0Ohm ~ 3W - Appears to be the current limiting resistor for the vertical deflection.

Horizontal Deflection - Chassis expects ~300uH horizontal deflection yoke at ~1 ohm

HOT - 2SC5422 (Ref 5)
Note - 2SC5422 only switches the horizontal deflection, it does NOT switch the primary coil on the flyback. There is a separate MOSFET that swtiches just the flyback primary coil.

Flyback - TFB5085AD

Flyback Focus Pack made by Murata. Dual focus, top load w/ dynamic focus caps (Ref 1)
Focus labeled (R) (W)
Only focus wire in (R) in factory configuration.
Flyback Focus Hole diameter 4mm

Focus wire

Dynamic Focus (Ref 6)
Many flyback pinouts show 10, maybe 11 pins. The TFB5085AD flyback has 14 pins and best I can tell the extra pins are for:
Pin 12 - W dynamic focus
Pin 13 - R dynamic focus

There is an apparent dynamic focus circuit on the Toshiba chassis. It consists of a transformer (T403 - TLN2168AH) that has the primary winding connected to the horizontal deflection circuit. The secondary winding is connected to the dynamic focus pin-13 on the flyback via a 3.3K ohm resistor. This should apply a parabolic voltage on the dynamic focus pin 13 and adjust the focus voltage to account for the flat screen. This will improve focus performance at the left and right edges of the screen and create a more uniform focus from center to edge. As noted in (Ref 3), a more robust dynamic focus circuit would include feedback from both the horizontal and vertical deflection circuits.

CRT socket - Single Focus (CR23) made by Hosiden

Auto Switching / S-Correction / Linearity Coil
As the monitor switches resolutions, components are added/removed from the horizontal deflection circuit to better tune for the different frequencies (15Khz, 24Khz, 31Khz). In general I believe you want an overall less inductive and less capacitive horizontal deflection circuit as the frequency increases.

The horizontal deflection circuit has a fixed 6.0mH linearity coil (L403). There are 3 relays that switch with frequency.
S401 bypasses a 6uH linearity coil - reducing down from 12uH to just 6uH.
S402 switches in an additional 220nF of parallel capacitance.
S403 switches in an additional 820nF of parallel capacitance.

Relay - S401 - DG1U - Active bypasses 6uH Linearity Coil
Relay - S402 - DG1U - Active adds in C424 - 220nF capacitor
Relay - S403 - DG1U - Active adds in C425 - 820nF capacitor

1. https://www.datasheetarchive.com/pdf/download.php?id=8d21ee92640912fa829f6bfa11cc09d4e38025
2. https://www.datasheetarchive.com/pdf/download.php?id=a6bee86237c0f20e88c2eb6a56a4552dcda8a9
3. https://www.raynetrepair.us/ceronix...circuit-function-and-circuit-description.html
4. http://monitor.espec.ws/files/vertical_dynamic_focus_circuit.pdf
5. https://datasheetspdf.com/pdf/239767/ToshibaSemiconductor/2SC5422/1
6. http://www.electronicrepairguide.com/monitor-flyback-transformers.html
7. https://www.genvolt.com/application-information/5220699f58080/Silicone-Cable
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To use a Toshiba PF in an Egret 3 or AWSD without doing a tube swap, you will need to perform the 3 modifications below. This will prep the chassis to be compatible with the tube. If you want a plug and play solution, you will also need to adapt from the 1.55mm pin headers on the Toshiba PF chassis to the 2.36mm pin sockets that the DY connectors and degauss connectors on the tube. Don't forget the JST connector for the earth ground on the neck board and the power connector.

1. Vertical Deflection
If using a vertical deflection yoke with a lower impedance (~ 8mH), you might notice that you can not get the picture to stretch to fill the screen vertically. This is likely due to the current limiting resistor (R323). You can slightly lower the resistance of R323 and get more vertical picture size when using a lower impedance yoke (or a yoke that just needs a larger A.p.p)

I have found that using a 0.750 ohm resistor in place of the 1.0 ohm at R323 - I can successfully fill the vertical screen when using a lower impedance yoke around ~7-8mH
R323 shown below (Already changed to a 0.750 Ohm)

2. Dual Focus
The Toshiba flyback (TFB5085AD) has a Murata focus pack that has 2 focus outputs, with only a single focus wire connected in the factory configuration. It is possible to terminate a 2nd focus wire into the focus pack. The new focus wire would need to meet 2 constraints:
-20KV or higher voltage insulation
-Diameter < 4mm to fit in flyback focus hole.

Most HV wire fails to meet the 4mm or smaller diameter constraint. CSA TV-20, TV-25, TV-30 all meets the requirements.
Genvolt (Ref 7) was the only source of CSA TV-xx wire I could locate, currently able to get TV-30 Red, stranded wire.

With some CSA TV-30 in hand, you can strip back about a 1/4" of the double-insulated conductor and tin the wire. Once the wire is tinned, snip it back to about 3/8" tinned conductor. The tinned conductor should be cleaned of any flux residue. The cleaned / tinned conductor can be inserted into the open hole on the focus pack. You will feel the wire bottom out and then with a little more force the tinned conductor terminate into the push-in style connector at the bottom of the tube. Give the focus wire a little tug to seat the teeth into the wire and confirm you have good termination. You should now have a 2nd focus wire terminated into the flyback.

2a. CRT Socket - Dual Focus (CR70) made by Hosiden
(** WARNING - These sockets need a small modification prior to use, do not install them WITHOUT modding - I didn't do any damage discovering this, but your dual-focus conversion will not work if you don't modify the socket)

The socket will have an outer grounding shield that is connected to one of the pins. The modification involves changing the pin that connects to the grounding shield.
Here is the socket as it arrives with the grounding shield installed.

You can use tweezers or some other small pointed tool and get under the grounding shield and gently work your way around the socket prying/lifting it off. Once the grounding ring is removed you can see the one special pin that has the tab sticking out to contact with the shield. (It is the left-most pin in the photo). We need to swap that pin with the pin on the other side of the connector.

The modified connector shown versus the unmodified. You can see the 'grounding pin' is moved from one side of the connector to the other. The pins all have a small tab you can depress and extract the pin. The grounding pin has a long tab that sticks out to contact the shield.

Not sure why this modification is necessary, I suppose this eBay connector may not be a CR70 and it needs to be modified to be compatible? Who knows, but this nets a usable connector at the end. I have used a CR70 connector from a Wei Ya chassis and that did NOT need any modification.

You will have to remove this cap to access the little flap that covers the solder terminals for the focus wires, but at this point you aren't going to let a little cap stand in your way, are you ?

3. Heater Resistor
The factory installed resistor that provides the correct voltage drop is 2.7 Ohm @ 2 Watts. This will produce a voltage across the heater of ~ 6.3 volts DC. (YES DC!). When connecting the Toshiba PF to an Egret 3 / AWSD tube (A68QCP891X001), the voltage across the heater will be somewhere around 5 volts. To get back to the proper 6.3 volts, we need to change the current limiting resistor from a 2.7 Ohm down to a ~1.35 Ohm resistor of at least 2 watts. I was able to find a 1.3 Ohm resistor @ 5 watts so I went with that, a bit overkill but it fits.

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I kinda want to get a backup chassis for my Matsu Tube. I know a few different components are different capacitor wise. This is some great info though appreciate it.
So nice, 2 questions please:

- on PB9929 do you think is it possible to add all geometry function missing from PD1843 with reprogramming the microcontroller
- I have 2 very nice chassis one my NNC with toshiba tube and other in spare in case "the germans" come back. and would like back to new with change some of things like the CR23 CRT Socket is it easy, and what's ref about coponent cracked on my neck board:


what's the goal about this dual focus mod? I have a tru flat toshiba.
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Technically. I don't really have any experience with dual focus tubes. I've only ever seen one in some Wells.
Dual focus tubes in theory could produce a sharper picture as they have a separate vertical and horizontal focus adjustments. Mostly, dual focus tubes are in abundance compared to single focus flat tubes. You can still find Makvision 29" flat tube and chassis - this dual focus mod would let you use that tube and ditch the Wei Yai chassis for a Toshiba PF. Also, you could use the Toshiba PF chassis on the stock tube in an Egret 3 or AWSD. The real focus win will be adding in the vertical feedback component to the existing dynamic focus circuit. That will help fix focus in both the X and Y direction - so that you can get corner focus that is as sharp as the center tube focus.
for you is it possible to add some function in the microcontroller pb9929 for more geoometry option.
I was looking at replacing the MCU with something modern and with a maintainable codebase. As far as adding functionality - it looks like according to the datasheet, most of the functions of the LM1269NA are being utilized. There is a blanking function but not much use. As far as the NEC C1888FCT - it is really a black box. Currently there are 15 functions/addresses that I have seen used on the C1888FCT, [0x00 - 0x0F]. No idea if more exist, I haven't found one scrap of a datasheet on that chip, and just some shitty scans of the C18884 datasheet.
I was looking at replacing the MCU with something modern and with a maintainable codebase. As far as adding functionality - it looks like according to the datasheet, most of the functions of the LM1269NA are being utilized. There is a blanking function but not much use. As far as the NEC C1888FCT - it is really a black box. Currently there are 15 functions/addresses that I have seen used on the C1888FCT, [0x00 - 0x0F]. No idea if more exist, I haven't found one scrap of a datasheet on that chip, and just some shitty scans of the C18884 datasheet.
I'm thinking of adding all the geometry functions missing from the PD1843 with the reprogramming of the microcontroller.
Great thread, there isn't a whole heap on info on these given that the service manuals are non-existent/non-available
This is very good information thank you for taking the time to document this.

I been wanting to look into information about substitute chassis's for these tubes for some time but looks like the information just appeared before me :)
Too late, gave away my weiya with a bad chassis and replaced with a toshiba lol.