Solartron CD 1400 Oscilloscope Refurbishment

[DMcMahon]

Have completed checking all the wiring connections to Board 3. Some of the connections go to Board 2 which like Board 3 has some differences to what is shown in the manual.

My Board 2 number is 14009002, manual shows 14009102.

Mystery of why the second # 14 tag (on lower section of Board 3) did not connect to earth. The black wire on it connects to Board 2 tag 14. The tag at Board 2 end has 3 black wires plus there is another tag next to it, also with 3 black wires (this second tag is not shown in the Board 2 layout drawing). This second tag connects to the first tag via the board artwork.

Disconnecting all the black wires and buzzing them out showed that all were connected to earth and when all refitted the lower 14 tag at Board 3 then was showing an earth connection. Not sure what was going on, but some sort of bad connection, this is good because before with no earth at the second 14 tag meant that 3 components were not connected to earth which did not make any sense.

The connection to tag 15 on Board 3 is still a little bit of a mystery to me. It is a red/blue wire that connects to Board 2 tag 19, tag 19 in the manual is hatched out to reflect that only used on early models. On Board 2 tag 19 connects to resistor R108 (hashed out in manual & listed as not used). It is listed as 390 ohm 2 watt in the manual and a 390 ohm wire wound is fitted.

At the same end of the junction of tag 19 and R108, electrolytic C109 is connected, C109 is shown hatched out and listed as "Not Used" / "200uF 275 volt" in the manual. R108 and C109 are not shown in the schematics I have.

The other side of R108 connects to tag 15 (shown hatched out in manual), tag 15 connects via a blue wire to tag 19 on Board 2, from here tag 19 connects to the main transformer secondary winding tap # 11 which is one side of the 155 volt winding, there are also 2 electrolytics connected to tag 19, C201 & C202.

So one side of the 155 volt winding goes through R108 on Board 1 then through R304 on Board 3 to connect to the common ends of the Set BA, Set IPS & the Astig pots, does not make much sense at the moment this connection.

Still waiting for a new replacement for failed C304, so next (before reconnecting Board 3) I will power the chassis up (no plug in modules fitted) and check out all the various mains transformer secondary outputs & the various DC voltage at Boards 1 & 2 and see what sort of voltage is arriving at tag 15 of Board 3.

David

[Chris55000]

Hi!

I think I can explain it!

The centre–connection of the h.t. voltage–doubler at the lower end of the 155V secondary of the mains transformer/junction C201/C202 is a lower voltage h.t. point about +180V, and the two deleted components R108 & C109 were intended to provide an auxiliary h.t. supply of about +160V for other purposes, and at the same time, Solartron wanted to set the minimum B.A., I.P.S. and Astigmatism control min. potential a little more accurately, so they returned the lower end of the control network to the junction of R304 and R312, forming a potential–divider fed from this spare +160V line, giving an approx. unloaded voltage at this point of:–

160 × (27,000/45,000) = 95V approximately.

One point to note is that your unit uses a P11 blue phosphor CRT, and it's very possible that this needed higher voltages on the B.A., I.P.S. and the Astig. Anodes A3L and A3U than the standard green phosphor model CRT, so almost certainly your modification applies to very early models and those with non–standard CRT's only.

If R304 (18k) & R312 (27k) are connected across a nominal 160V supply, they would draw a current of (160/45,000 = 0.00355A or 3.55mA) and this current through a 18k ¼W resistor is close enough to it's rating to cause it to start wandering up in value gradually over many years use, until it rises in ohmic–value to the point where even a milliamp or two will burn it out!

At some point fairly early on in the production run, Solartron obviously found out (or were advised by the CRT manufacturers, 20thC. Electronics) that about 95V was too high for the minimum values of the B.A./I.P.S. and Astigmatism control potentials, so by deleting R304 from Board 3, and R108/C109 from Board 1 (as this supply wasn't needed for any other purposes) this reduced the min. potential of this electrode group to the value either recommended by the CRT makers, or simply found by trial–and–error to be correct, so they simply instructed their Draughtsman to omit these components and associated connections, board artwork lines, etc., from the circuit and PCB layout diagrams!

I will include them with an explanatory note in my diagrams now being draughted!

Chris Williams

[Chris55000]

Hi!

Further to the above, a perusal of the CX1443 standard T.B. module circuit diagram reveals that two auxiliary lower voltage h.t. lines of +220V and +160V are obtained from the two triode cathode–followers V7a and V7b, (the horizontally mounted ECC88 on the small sub–chassis) whose grids are connected to a chain of three resistors across the main +320V h.t. line, the resistor values worked out to give the correct potential voltages needed on V7a and V7b grids.

(N.B! The two cathode–followers V7a and V7b are only provided to enable low–wattage h.t. dropping resistors to be used, they do NOT provide any h.t. stabilization!)

Now I think Solartron's intention may well have been to originally obtain the +160V from the main chassis, hence the original inclusion of R108 & C109 on Board 1, with the lead off from Tag 15 of Board 1 going to either pin 1 or pin 2 of SKTA, SKTB and SKTC (the plug–in module connectors) – these two pins on each connector plug/socket are annotated in my moth–eaten Tech. Manual as "Reserved for Solartron Development".

Chris Williams

[DMcMahon]

Thank you Chris for your excellent analysis in the above 2 posts, all clear and makes a lot of sense. Later today when I check out the various voltages, I will more closely look at this.

I can now see the +220 & +160 volt supplies at the X timebase module.

My documentation does not have the "Reserved for Solartron Development" annotation,
pins 1 and 2 of SKC are the X timebase drive signals to the CRT X plates.

My new replacement for R304 (18k) was a carbon film 0.5W, of course being modern it is no larger physically than the original old failed 1/4 watt.

Plenty of spares came with the unit:-

2 x CX 1443 X timebase amplifier plug in modules (one with 3 valves missing).
1 x CX 1441 Y timebase amplifier plug in module.
1 x CX 1442 H high gain differential amplifier timebase plug in module (1 valve missing).
1 x CX 2841 Y timebase amplifier plug in module (this is solid state, so assume at this stage that not a compatible plug in for the CD 1400.

David

[DMcMahon]

Started the voltage measurements. Started with the 1,000V winding measuring the 1,000 volt side of the winding at the HV wire at Board 3 and the 0V side of the winding at Board 2 tag 30. Measured 1,300 volts which I thought was too high.

Then measured the 155 volt (tag 30 & 19) and 46 volt (tag 14 & 29) windings at Board 2 and measured voltages over twice what they should be. Then measured the +360V DC output at Board 2 tag 10 and got zero volts.

So obviously something not correct. From other measurements deduced that the physical pinout of Board 2 terminal tags were not the same as shown in the components layout drawing in the manual for Board 2.

Have just finished removing Board 2 (not easy), so can now check out what the actual connections are. Was impossible to do it properly with the board in-situ as could not see the artwork connections.

David

[DMcMahon]

Like Boards 1 & 3, Board 2 has a slightly different number (14009002) to what is shown in the manual (14009102).

Tags 31 & 33 on the short side of the board are the same as shown in the manual.

The 7 tags alongside the long side of the board left to right are:-

32 10 30 29 14 18 19

The manual shows:-

32 30 29 14 18 10 19

So only tags 32 & 19 are the same position.

So now will refit the board and restart the voltage measurements. There are 4 small insulated washers between the bottom of the board and the chassis (that the board securing screws go through), I think these will be fun to refit.

Seems somewhat strange on such a simple board that Solartron changed the artwork that resulted in the tags moving positions.

David

[DMcMahon]

Refitted Board 2 and restarted the various voltage measurements, now getting expected results, details later.

[DMcMahon]

While refitting Board 2 had to reconnect capacitor C1 +ve connection wire back to the board, while checking the associated connections found more differences from the documentation.

1. Capacitor C1 s listed as 2,000uF 16V (and shown on schematic) but fitted C1 is 5,000uF 25V. This actually is covered by note in the manual, that 2,000uF is fitted to old models.

2. Schematic shows C1 +ve connecting to mains transformer tap 14 via tag 14 of Board # 2 (which is the earth connection). C1 +ve actually connects to transformer tap 23. Which initially looked like the earth is removed from C1 +ve but see # 4 below.

3. Schematic shows transformer tap 23 linked to transformer tap 11 - Which it does not.

4. Transformer tap 23 is linked to tap 21 (schematic shows 23 linked to 14) and then tap 21 is linked to tap 14, so this transformer linking does result in C1 +ve being connected to earth.

5. Schematic shows transformer tap 18 connected to earth - Which it does not.

6. Schematic shows capacitor C5 0.01uF connected across transformer taps 12 and 11. There is no C5 fitted. Tap 12 connects out to Board 1 to a 1.0uF capacitor (maybe tag 28 ?) on input side of 100k resistor R104. This capacitor (probably C104) is not shown on the schematic but is listed in the parts list (there are two 1.0uF capacitors in this circuit) and is part of the scope calibration circuit.

7. Schematic shows the +360 volt HT supply from Board 2 connecting to pin 4 of SKA (Upper Y amp) and then daisy chained to pin 4 of SKB (Lower Y amp) and then to pin 4 of SKC (X amp). But it is only actually wired to SKC, there are no connections to pin 4 of SKA & SKB. Yet to look at the Y timebase module schematic to see if +360V is used, I assume not.

[Chris55000]

Hi!

I confirm from the better copy of the CD1400 Bookwork I received in the post this morning that the un–smoothed h.t. +360V line is not directly used by any of the plugins I have the information for!

The book that came today only had the first two pages of the CX1571 X–Y Plotter Module handbook included, has anyone got pages 3 to 6 and the circuit for the CX1571 they can upload please?

Chris Williams

[DMcMahon]

Originally Posted by DMcMahon

1. Capacitor C1 s listed as 2,000uF 16V (and shown on schematic) but fitted C1 is 5,000uF 25V. This actually is covered by note in the manual, that 2,000uF is fitted to old models.

Made mistake (as pointed out by Chris) above should have read:-

1. Capacitor C1 s listed as 2,000uF 25V (and shown on schematic) but fitted C1 is 5,000uF 25V. This actually is covered by note in the manual, that 5,000uF is fitted to early models.

[DMcMahon]

I will email Chris scanned copies of the X-Y Plotter missing pages.

[DMcMahon]

Originally Posted by DMcMahon

6. Schematic shows capacitor C5 0.01uF connected across transformer taps 12 and 11. There is no C5 fitted. Tap 12 connects out to Board 1 to a 1.0uF capacitor (maybe tag 28 ?) on input side of 100k resistor R104. This capacitor (probably C104) is not shown on the schematic but is listed in the parts list (there are two 1.0uF capacitors in this circuit) and is part of the scope calibration circuit.

Rechecked 6 above and transformer tap 12 does connect to Board 1 tag 28 as previously thought. The connection shown on the schematic from Board 1 tag 28 to Board 2 tag 29 does not exist in my scope.

This means the AC supply to the scope calibration circuit is actually taken from one end of the transformer 155 volt winding (tap 12) as against one end of the 46 volt winding (tap 13) as shown on the schematic, for reasons unknown.

[DMcMahon]

Voltage measurement results, all plug in modules removed and Board 3 not fitted, all voltages are nominal. All DC voltages measured wrt to earth/ground. AC mains ripple levels were very small when present

1. Transformer T1 1,000V winding, taps 17 to 15 = 1,020 VAC

2. T1 155 volt winding, taps 12 to 11 = 160 VAC

3. T1 46 volt winding, taps 14 to 13 = 48 VAC

4. T1 28 volt center tapped winding, taps 22 to 20 = 30 VAC

5. T1 CRT 6.3 volt heater winding, taps 26 to 25 = Not measured, CRT heaters lighting up

6. T1 6.3 volt plug in modules supply winding, taps 24 to 23 = 6.74 VAC

7. T1 6.3 volt X timebase module/Graticule lighting supply winding, taps 19 to 18 = 6.74 VAC

8. Board 2 tag 10, +360 VDC supply = +430 VDC

9. Board 2 tag 19, (ultimately ends up at Board 3 tag 15) = +215 VDC

10. Board 2 tag 18, - 56 volt supply = - 66 VDC

11. Board 2 tag 33, - 16 volt supply = - 20.5 VDC

12. Board 1 tag 26, + 7 volt supply = + 7.3 VDC

13. Board 1 tag 17, - 7 volt supply = - 7.2 VDC

14. Board 1 tag 22, +320 volt supply = + 441 VDC

15. Board 1 tag 21, +320 volt supply = + 439 VDC

16. Board 1 tag 20, +320 volt supply = + 445 VDC

17. Board MR1 calibration = 8 volt p-p 50Hz square wave

18. Board 1 tag 25, - 40 volt supply = - 68 VDC

19. Board 1 tag 24, - 40 volt supply = - 68 VDC

20. Board 1 tag 23, - 50 volt supply = - 66 VDC

21. Board 3 tags 12 to 11 = 270 VAC

22. Board 1 tag 13 = Zero (not yet connected to Board 3 tag 13)

Next will partially connect Board 3, just connecting earth, main HT supply (+360) and tag 15 supply to check out the voltage operation and range of the Set BA , IPS and Astig potentiometers. Doing it this way so that do not have to worry getting close to the EHT and -780 volt cathode voltages while adjusting the pots.

[DMcMahon]

Replaced the failed C304 8uF 450 volts by a new 10uF 450 volts, it looks a bit dwarfed by the surrounding 8uFs.

[DMcMahon]

Removed Board 1 to clean better and check component values more. Noticed that there appeared to be a broken pink wire at pin 11 of SKA (Top Y timebase module).

The schematic shows pin 11 and pin 12 to be 6.3VAC supply but there is no connection to pin 12 at SKA or to pins 11 and 12 at SKB (Lower Y timebase module), so will remove the pink wire.

Noticed the various red electrolytics (Plessey) are dated Oct 63.

[Chris55000]

Hi!

In the absence of clear pictures of the top and copper sides of Board 1, I'm going to hazard a guess that tag 12 of the mains transformer goes to tag 28 of PCB1, thence via C104 (1u) in series with R104 to the calibration voltage circuit, and C107 (also 1u) is fitted from the junction of R104 and C104 to chassis/0V on Board 1, such that C104 and C107 form a capacitive potential–divider from the 155V terminal 12 of T1 to chassis.

I suspect this may have been done because the original design called for a higher pair of calibration–voltages, e.g., 50mV and 5V as apposed to 5mV and 500mV!

Chris Williams

[DMcMahon]

Virtually correct, C107 does not connect to earth/chassis, the output side of C107 connects to R110.

So tag 28 connect to C4, the other side of C4 connects to R104, the other side of R104 connects to C107 and MR101, C107 then connects to R110.

The physical position of tag 28 is swapped over with tag 10.

R110 value varies a bit, fitted resistor is 680k (measures about 720k), value in parts list is 560k and value on schematic is 620k.

The tags along the left hand side of the board are very slightly different. Top tag 26 moves round to the top edge of the board (top left), there is an second tag 14 (earth) below the first one.

While examining the board found at least 5 very dodgy soldered connections, R107, R108, R106, C105 & C108, this board is really bad condition, will have to tidy it up.

As the MR101 is a 7.5 volt zener would not this clamp the calibration signal at its output both with the original 155 volt input and the later 46 volt input ?

[Chris55000]

Hi!

My Supplementary Documentation to cover the early and special versions of the Solartron CD1400 with different board types to that shown in the available bookwork is now in progress!

To begin with, here is a revised layout diagram for the Main Frame Board 1, Solartron P/N 14009001.

Further Documentation to follow as I complete it!

Chris Williams

[Chris55000]

Hi!

I've just realised I uploaded my diagram with the "Set Cal" preset mis-labelled as RV104 - this was a mis-print in one of my books!

The sheet attached here is correct!

Chris Williams

[DMcMahon]

That's excellent Chris, on my board the 2 sections of tag 14 artwork are joined together, I will check tomorrow to see if the artwork is actually joined or a solder bridge joining them.

I see R104 for 1400 9101 board in the components list is 27k.

David