Telequipment D1011 scope

[retiredeng]

Hello people
I have one of these scopes and i am trying to get it working.
my problems.
1 I have a trace for both channels BUT the traces are showing only on the right hand 1/3 of the display.
2. if I connect to a test signal 1KHZ square wave it does show but i cant get a stable lock, i can slow it to nearly stationary with the variable trigger knob.
so i guess the trigger circuit is not working??
The traces are not sharp but blurred a bit.


I have the original manual for the scope which is great but understanding it mmmh? I have read many of the old posts on this site to use as guidance and have tested many components . i have also replaced the D type flip flops and the HEX invertor, I bought a spare ca3086 and replaced one at a time in the various boards. All of the supplies are within tolerance ie 175,+22 -22 +14 +5.
the X plate voltages I have adjusted to give 90 volts on each.
I have repaired two of the selector switches on the channel amps. What a pain.

One last thing, in the course of testing The CA3086 they all seem to have a diode connection between pins 13 and 14. the datasheet says that pin 13 is connected to the substrate anyone know what this means and are all the chips the same.

I hope someone on the forum can help me please.

[Keith956]

Originally Posted by retiredeng

One last thing, in the course of testing The CA3086 they all seem to have a diode connection between pins 13 and 14. the datasheet says that pin 13 is connected to the substrate anyone know what this means and are all the chips the same.

Yes the transistors in the CA3086 are fabricated in a common P type substrate. Each transistor's N type collector then forms a parasitic PN diode with that substrate.

In practice it means pin 13 must be connected to the most negative voltage in the circuit else those diodes could become forward biassed.

Sorry can't help with the scope problem though!

[Radio Wrangler]

Every IC has a substrate connection. Often it isn't mentioned in data sheets, the chip designer just connects it to the most (usually) negative power pin. All the rest of the nodes of the circuit then isolate themselves from the substrate by being surrounded by a skin of reverse-biased diode junction. The substrate is what the circuit was manufactured from, provides physical support and is the heat removal path.

On the symbol for MOSFETs, the pointy arrow element from the source to the channel represents the substrate diode surface surrounding the channel and acting as a 'Back Gate' Substrate-to-channel voltage affects the channel conductivity and the gate-source threshold voltage.

On power MOSFETs you'll sometimes get a source to drain diode drawn in to remind you that the drain connection is isolated from the substrate (and source pin) by a large diode junction.

A nasty little quirk is that substrate diodes are just engineered to sit there, reverse-biased. They lack some of the processing details used to make fast diodes. They are slow. On high power MOSFETs they are much much slower than the transistor itself. SMPS designers have to take precautions to make sure the substrate diode never turns on, because if it does it stays on long enough for Kabloom! So, in some SMPS designs, you'll see schottky diodes across source and drain. If any current flows that would have turned on the substrate diode, the lower voltage drop Schottky carries all the current and the substrate diode is protected from turning on. This isn't just a matter for power supply MOSFETs, it also applies to RF power devices.

So, substrates are everywhere, and they can hit you with a few subtleties. Analogue switches are one area where they get a lot of people into trouble.

Fortunately RCA mentions them and even provides a dedicated pin. If you're using a transistor array you might be using cascode structures or diff amps with a long-tail current source. Knowing where the substrate is connected tells you which transistor to have in bottom place in the tree, otherwise all sorts of confusion ensues.

David

[WME_bill]

Telequipment D1010-1011.
1. Sound like half the X Amplifier has failed. So replace IC4 the CA3086 (or similar CA3045-46, which ever you can get). While doing this, I suggest you fit a 14 pin socket so that you can just plug the replacement in. It is not unknown for these to fail when under load. And if one of the transistors has gone, then it can affect all the others.
Then check the voltages around the two X plate driver transistors, use video transistors BF467 or similar, by keeping switched to External X and use the X shift to move the spot across the full width of the screen.
2. Sounds as though no trigger signal is getting through. Even with an unstable trace, you should be able to trace a signal (say from the calibrator) through the Trigger circuits into the timebase at D70 / TR71. Suspect switches or IC1, another CA3086.
3. Blurred traces. In which directions: vertical, horizontal, both?
This could suggest trouble in Y Amplifier, X Amp or Power supplies in general.
4. Those front panel switches are very fragile as the plastic perishes, and probably the cause of your Trigger troubles. Check contacts are made as expected with your ohm-meter. Several people have rebuilt them in earlier postings here on the Forum.
5. Be particularly careful just testing or replacing one part after another, as these actions can so easily provoke other faults. Check the voltages everywhere first. The manual is very helpful in indicating what to expect. Power rails within 10% quite good enough to get it working, and remember on transistors, the emitter will be about 0.6v positive of base (for NPN) and the collector much higher or at 0.2v if fully on with emitter very positive of base.
wme.bill

[retiredeng]

Hello Gents
Thank you for you prompt reply.

I must apologise for my poor explanation in my original post, I am not to good at explaining what I Mean.
Tthank you for the detail about substrate diodes, you learn something every day.

Back to the scope.

On reading the manual again I had forgotten that only channel 2 provides a trigger signal. I was trying to use channel 1 so no lock, tried channel 2 and I have a stable test signal on 1/3 of the screen, right hand side only.

I have bought 2 CA3086 chips so i will swap IC 4 out today. I also bought at least one spare transistor of each type of those available. The FET chip seems to be a problem, any suggestions welcome. One of my FET chips has been replaced with a BFW1118 with bent legs. Can't seem to find these for sale.

I should point out that all of the IC's and transistors are in sockets on my scope so are easy to change.
The two X plate driver transistors I have replaced but the made no difference.
I will report back with any news.
Thank you again

[frsimen]

I worked on Telequipment D1016 with a fault in the Y amplifier, the trace only appearing in the top half of the display. That proved to be a transistor that was loose in its socket. If you haven't already done so, check that the all the transistors in the timebase circuit are firmly plugged in.

Paula

[retiredeng]

Hello once again.

i changed the ic4 with a new chip but made no difference.

I also now notice that the trace if very dim even with the intensity set to max.

I wonder if the tube is on it way to failure or is the HT voltage falling . i checked around the HT resistors and diodes plus the zenner and seem ok.
Unfortunatly i cant measure the HT voltage unless someone can suggest a method

thank you for the suggestion about loose transistors in sockets. I will look at that.

[WME_bill]

Telequipment D1011.
The Y input FET are Teledyne SU2603M. The board layout permits the later SU2603K as an alternative, which you may be able to find. The BFW1118 appears to be a contract dual FET produced by Philips. Never offered commercially.
Alternatives are from the Siliconix U401 to U406 series. I have used two 2N5484 clipped together, similar to the Philips BFS21. Process 50, for low Idss and matched if possible. Not too critical.
The CRT used is Mullard 58610 / 56803 /58619. It appears to be a contract version of the Philips D14-250 / 251 /252.
Trigger source can be selected from the switch on the X Amplifier side of the panel. Sounds as though you need to check that switch .
wme_bill

[retiredeng]

I bought two Ca3086 chips from a uk supplier but they dont work at all , there is a lot rubbish being sold on the net.
I dismantled the trigger switch S3 and the centre blade is missing?? someone has been here before ( there are no blade fragments or any bits to see inside the gray case. only evidence are the two broken plastic support pillar remnants.) So on checking over the schematic S3b
puts a short to ground onto TR4 collector, so to get around the problem for now i have shorted out R36 which has the same effect.( so long as i leave the switch in auto.)
so after trying not so good 3086 chips and putting originals back I now dont have a trace even with the beam finder pressed.

I have unsoldered the high voltage capacitors on the EHT circuit and cleanded them up they were really dirty with black hard to remove crud.I thought the dirt may be causing a reduced ht voltage. I also checked the HV diodes while i was in there and they test ok . but the four diodes are made up of eight in total with two diodes in series at each positon ( where they short of the correct type) still nothing on screen.

Does any one know where to get some working 3086 chips Please.
Its getting to the stage where a need another scope to fault find.

[Keith956]

The CA3046 is I believe an equivalent to the CA3086, in fact looking at the datasheets they seem to be the same thing.

Cricklewood have the CA3046 as do CPC/Farnell.

[WME_bill]

Telequipment D1011.
Try looking for CA3046 as well as CA3086. It has a tighter specification. I see Cricklewood are offering it by SGS at a lower price than the CA3086.
The last lot I bought, well before Covid, came from RS Components. But I see that they no longer keep it. Neither do Farnell. Both catalogues extraordinarily difficult to use with very poor indexing or else I am being stupid.
Used to be a commodity circuit, made by lots of firms: LM3086, SL3086, SG3086, MC3086. But always difficult to find as they were hidden away in a small category at the back, under Transistor Arrays.
At one time, I considered using a 14 pin header, and soldering 5 individual transistors onto the pins. It is only the two on pins 1-5 which have to be clipped together and selected for similar hfe. A batch of 8 should be enough to find two similar and provide for the others. Any commodity NPN small signal would be fine -eg 2N3904.
Particularly as 2N3906 is the usually suggested replacement for the PNP MPS6518 as it seems more reliable.

Good luck with rebuilding the moulded panel switch. You will end up doing a bit of engineering to fit something in. S1-3pole 3 way. I have made up the little metal contact blade using copper screening foil off a uhf TV tuner. Rotary will be just luck to find, but perhaps one of those 3 position slide switches would do.
wme_bill

[Chris55000]

. . .Regarding the disintegrating T.Q. plastic lever switches, it IS possible to repair these providing you can find the wiper fingers – look very carefully in the bottom of your Oscilloscope, particularly amongst the PCB components, you might find them floating about in the bits somewhere!

. . .Once you've found the wipers, you can secure them where they originally fitted using M1.5 nuts and screws in the places where the original broken pegs were – use the tip of a fine soldering iron bit to start a small depression in the plastic, then drill out two holes with a 1.5 mm drill

Once you've fixed the wipers with screws and nuts, apply a dab of superglue, varnish or nail–varnish to lock the nuts, then reassemble the switch to the board – if the Switch Assemblies were riveted to the board, drill out the rivet carefully by rotating a large drill bit of suitable size by hand, or with a hand–drill, turning it only SLOWLY so you can stop as soon as you've removed enough of the rivet to dismantle the switch from the PCB!

. . .A nylon nut and screw can be used to refix the switch assembly to the PCB afterwards, securing the nut with varnish, etc., as before!

. . .Check your scope carefully, you might still find your contact finger/wiper in there!

. . .If you can't find the original contact finger, you might be able to get one from a cheap Omeg P20 potentiometer that you can adapt to replace the original with a bit of judicious bending and cutting!

. . .(If I remember correctly, the PCB tracking itself provides the fixed part of the switch contact!)

Chris Williams

[retiredeng]

Hello Chris
thank you for the advice with the switch. I will look for the missing bit.

todays update

Regarding the trace that disappeared, By removing IC401 the trace comes back in its limited 1/3 RHS of the screen. I'm trying to check all the diodes and resistors in the trigger, sweep and blanking circuit but cant find any faults. Also one of the X amp driver transistors is getting really hot even with a small heat sink attached?? the collector volts on each driver transistor are about 90 volts. suggestions please.

[WME_bill]

Telequipment D1011.
There were detailed threads upon repairing those switches, with suggestions upon making the contact rotor & glueing or melting it in place. Have you done a search under D1011. In March 2022, October 2012. Also on operation of the X Amplifier in March 2012.

Limited X Sweep. Have you checked the X Amplifier operation. As you can only go 1/3 across the screen, suggests something is sticking somewhere on one side. Switch to X-Y and with no inputs, move the spot across the full width of the screen with the X shift. All voltages on the IC CA3086 sectons IC4c and IC4d and also in common tail IC4e and around the two BF467 - Tr78 & 81 should move in opposition on either side IC4d+Tr78 versus IC4c +Tr81.
If removing IC4 restores limited trace with no X shift, then fault lies with Tr78 & 81 or associated diodes/zeners or voltage feeds. Checking the voltages will have revealed that already.
wme_bill

[Chris55000]

. . .I know I've got an incomplete T.Q. with a spare PC245 board to assist the O.P. but try as I might today I couldn't see where I'd put the thing! – I'll have another look for it tomorrow!

. . .(I know the D1010, D1011, D1015, D1016 and the "A" suffixed '1015/'1016 all have a PC245 – it's just thinking where my incomplete ones are!)

Chris Williams

[retiredeng]

Hello all

I thought i posted a reply but i must have done something wrong so here goes again

After a lot of head scratching and testing and finding very strange results I eventually came to the conclusion that the X plates are shorted together and sure enough with the plates disconnected dead short.
Is that unusual ?? I would have thought the plates would be on opposite sides of the beam with leads kept apart along the Neck of the CRT

Anyone got a spare CRT mullard /phillips type as indicated above.
this scope has been fighting me all the way, I did have a full display with a test signal on the screen but one time only. it been down hill since then
Frustrating to say the least.

[Radio Wrangler]

Sounds like damage from a hefty bump. It doesn't take that much, not enough to break the glass. With vibration. plates can fall off entirely and go rattling around.

X plates are larger, heavier, and likely to get damaged first.

David

[WME_bill]

Telequipment D1010 series.
The cathode ray tube had several numbers. 1978 to 1985 .... . So look for Mullard/Philips:
D14 -250, D14-251. Also Valvo 81D14.
The screen phosphor is denoted by 2 letters after the type number
Usual is GH green, medium short persistence = P31 or GL yellowish green, medium, short = P2 or GM yellowish green, long = P7
Also the later contract types: 58610, 56803 (this is what the manual says, but I suspect should be 58603), 568196 (or 586196 in manual), 56825, 56840.
These all have various screen phosphors suitable for oscilloscope use.
I haven't given you the Telequipment/Tektronix part numbers as the tube will be marked with the manufacturers numbers as above.
Versions of these tubes were also used in Advance OS300 series.

There are later Mullard tubes, very similar both electrically and in physical length etc but with different base connections. I suspect later developments for the same market:
D14-360, D14-361, D14-362, D14-363 or 56858, D14-363. These each with different heater warm up time or current consumption. Otherwise interchangeable. Also the Toshiba 150BT-B31 (very common in Far East scopes).
Also possible with slight changes in focus anode voltages is Mullard D14-364 used in Hameg 203 and similar Brimar D14-270.

So all is not lost, if you can find one of these alternate tubes or another scrap scope. It would be a pity to scrap your D1010 series. I can help with the tube data.
wme_bill

[retiredeng]

Thank you Bill for your wide range of options.

That gives me a lot more scope (pardon the pun) to find a replacement.

Can i assume that the HV controls on the various types wild be compatible or would it need some mods.

best regards

[retiredeng]

Oh forgot to mention upgrade

Am I allowed to mention conversion to an LCD screen , has anyone done this with a kit that can easily be adapted to an old scope. perhaps an LCD is to modern for this forum??