USSR transistor identification (Zenit NV-100 nightvision)

[Macbeth]

I'm attempting to repair the HV board on an old Zenit NV-100 nightvision scope and have found a strange transistor arrangement. It is wrapped in a coil of wire that is soldered to a transformer pin that the collector of this transistor is also connected to. The other end of the coil is just floating. What on earth is this for? It's not even insulated so not being used as a coil. Perhaps a heatsink? But this runs from 2xAA batteries and consumes almost no power. 

The transistor checks out as a PNP and is obviously used as an oscillator to drive the step up transformer. I've lifted up the coil to show the part number. What is a "K<>C4" exactly?
 

[Fraser]

Looks like some form of capacitive coupling to ensure oscillation whilst avoiding transients that may cause damage. If you sketch out the circuit around the transistor it may make more sense to readers and we may be able to help further.

Aurora

[Macbeth]

Looks like some form of capacitive coupling to ensure oscillation whilst avoiding transients that may cause damage. If you sketch out the circuit around the transistor it may make more sense to readers and we may be able to help further.

Aurora

Yes, I am doing that now. I have to desolder the transformer taps to make any sense of it as it has 8 pins and lots of them are showing up as shorts between each other while in circuit, being very low ohm coils. Unfortunately it is using microscopic gauge enameled copper wire and difficult to work with!

Just a strange thing with the transistor I haven't seen before. Like I said, the transistor collector is wired directly to the same pin of the transformer, by its copper track under the board.

[Fraser]

I sometimes treat the transformer as a 'block' and just show the connections going to it from the other components. I am often able to work out where the windings should be and their purpose. In the case of a faulty transformer winding, reverse engineering using resistance readings can be problematic 

A photo of the top and bottom of the PCB would be welcomed  I have lots of the Russian Night Vision viewers in my attic but I do not think I have the NV100 as that was sadly known to use tubes with a lot of imperfections in the phosphor. I bought all mine at Izmaylovsky outdoor market in Moscow and paid less than $100 each for them. The cheapest were around $30 and the $100 units have the best optics and tubes available at the time (1996-1998). I was buying them as soon as the new models were released by the factories. They were too cheap to pass over. They are all GEN 1 technology so you cannot expect too much from them. I was amazed to see $30 models like the NV100 being sold in the UK for almost £200. I have a Russian made bright yellow marine night sight in the garage that may be very similar to the NV100 as it looks to be from the same era. I bought it a few weeks ago as a project as it has battery leakage damage to the battery contacts. I have already X-Rayed it but nothing very exciting inside. Hence why I would love to see pictures of your units internals to compare them.

Aurora

[Fraser]

Looking at other Russian NV equipment....at least you have a unit that contains a PCB !

[Fraser]

These are what I was picking up for $30 in Moscow:

http://blog.gruppa-l.com/review-cyclop-1-nvg/

The Cyclop-1

Works well actually but the battery compartment will not take a modern alkaline PP3, it was designed for slightly smaller PP3 dimensions as found with the old Zinc Carbon versions.

There is an interesting web page on NV technology here:

http://www.nivitech.com/nightvision-gns.htm

Your unit is GEN-1.

Aurora

[T3sl4co1l]

Should be "KS4" since the 'C' glyph transliterates to 'S' in Latin script.  Whether that helps any...??!

Guessing the circuit is a good old fashioned high voltage charger thing, and probably anything would work, e.g. 2N4403.

Tim

[wraper]

KT209K http://www.qrz.ru/reference/marking/mark20.htm

[Macbeth]

Perhaps far more effort than this thing deserves, but here is the circuit diagram I managed to reverse from the PCB. First time I've used Tina-TI as I fancy using this schematic to learn how to SPICE. Glutton for punishment I'm sure! (Some touch up done in MS Paint).

I found the L1 winding had gone O/C. I've opened the transformer up and thankfully its just where the fine wire leaves the wound coil before going to its pin and so I should be able to carefully solder a new wire to the tiny bit of stub left and hot glue it down. I've put in the resistances of the coils. [Edit: updated schematic posted below]


...and the PCB top... I just guessed D1 is a 1N4148 because every signal diode like that just is
I have no clue what D2 is with its 2 black stripes, but its forward voltage is 760mV.
I took T1 out of circuit to check on my transistor tester and got PNP 123=CBE B=122 Uf=641mV. hFE is 67.



...bottom of PCB... Some lifted pads under the transformer that were not going anywhere.



Aurora, $30 is amazingly cheap! I paid £100 for this at Costco about 15 years ago. I'll get more photos of its internals when I gather the rest of it. I put this on a shelf in bits years ago. I just hope the EHT voltage multiplier hasn't gone too as that is all encapsulated and impossible to service.

[wraper]

D1 likely is a zener. D2 - KD522. It has 2x less forward current  than 1n4148. BTW according to your schematic, D1 being a diode would make no sense.

[Macbeth]

KT209K http://www.qrz.ru/reference/marking/mark20.htm

Thank you. A page worth bookmarking. Now for the datasheet and spice model...

[hli]

KT209K http://www.qrz.ru/reference/marking/mark20.htm

Thank you. A page worth bookmarking. Now for the datasheet and spice model...

I should have a data sheet at home, or at least some basic data from my east german data books. I will look it up when I come home. A spice model will be difficult though...

[Macbeth]

D1 likely is a zener. D2 - KD522. It has 2x less forward current  than 1n4148. BTW according to your schematic, D1 being a diode would make no sense.

Aah, yes. Also the thick band at the end of the diode that I have been conditioned into thinking is the cathode is actually the anode on the KD522! I checked D1 and it is also backwards.  (or maybe its a 0.8V zener?)

[abyrvalg]

KT209K data: http://www.radiolibrary.ru/reference/transistor/kt209k.html
Uc-b max 45V
Uc-e max 45V
Ic max 300mA
Ic max (pulse) 500mA
Pc max 0.2W
hFE 80-160
Ic reverse <=1uA
Fmax >= 5MHz
Noise coefficient <=5dB

[abyrvalg]

D1 - is the ring blue or green? Looks like this to me: http://www.chipdip.ru/product/ks220zh/
20V zener

[Fraser]

Excellent progress 

I am pleased that the fault is relatively simple. Thanks for the schematic. I was hunting for such last night in the hope that I could assist further but surprisingly no one appears to have dismantled a Russian NV scope and documented it in the public domain.

I am still uncertain of the exact function of the coil around the transistor. A cheap heat-sink design did cross my mind but why connect it to the transistor at all ?  The transformer provides all the feedback required for the oscillator so I do not see a need for some sort of capacitive coupling to the transistor.

By the way, there has been some talk in the past regarding X-Ray generation within the tube and proximity of such to the users eye. I am unsure about such concerns as the intensifier tube does not have a heated cathode and the EHT is around 16kV which would not normally be enough for a cold cathode X-Ray tube to do much at all. Be aware however that IF the tube is capable of producing X-Rays in its current configuration, they would be "Soft" and may be heavily attenuated by even thin aluminium. The issue is whether the Ocular path provides adequate attenuation as Soft X-Ray is absorbed by soft tissues and so particularly unhealthy.  I have an X-Ray capability and all the necessary low KeV meters so shall do a quick check this week on the X-Ray emissions of my Night Vision Scopes. they are much the same as your NV100 in terms of construction.

Please do not think that my comments regarding the NV100 tube means that it is useless, it is not. I was in a position to be able to buy perfect and near perfect phosphor NV equipment so did so. The Russian sellers just advised that the NV100 COULD have some pretty iffy intensifier tubes due to its low cost and the batch sorting of tubes that took place. If yours is bright and without the appearance that someone has shaken pepper all over the phosphor, its a good one 

Well worth repairing and you have helped the wider community by documenting your unit so well 

I shall reverse engineer my faulty maritime NV scope shortly and add it to this forum mass of useful information.

Aurora

[Macbeth]

D1 - is the ring blue or green? Looks like this to me: http://www.chipdip.ru/product/ks220zh/
20V zener

Bingo! It is green. That darned "cathode" band confusing me again. I put my PSU on it and its breakdown is at 21.3V with a 10mA current limit and 30V over it. The other way the forward voltage is 0.8V which is kind of what I would expect from a signal diode with a normal cathode marking 

Updated schematic



Now for equivalents with spice models?

T1 - KT209K - MPS404A
D1 - KS220ZH - 1N968
D2 - KD522B - 1N4148

I've no idea how to model the transformer just yet. 

[dannyf]

It is wrapped in a coil of wire that is soldered to a transformer pin that the collector of this transistor is also connected to.

Heatsinking or shielding?

[wraper]

Bingo! It is green. That darned "cathode" band confusing me again. I put my PSU on it and its breakdown is at 21.3V with a 10mA current limit and 30V over it. The other way the forward voltage is 0.8V which is kind of what I would expect from a signal diode with a normal cathode marking

Most Russian diodes do have polarity marking opposite to what westerners would expect  . In my childhood when I used a lot of Soviet/Russian parts, I always checked polarity with multimeter before soldering as you are never sure about them .

[abyrvalg]

I'm not sure is MPS404A a correct replacement for KT209K. According to MPS404A datasheet many parameters are different (i.e. halved Ic max).

[hli]

I'm not sure is MPS404A a correct replacement for KT209K. According to MPS404A datasheet many parameters are different (i.e. halved Ic max).

According to my comparision lists there is no directly equivalent to the KT209. If you need, I have 12 pages worth of data sheet (its in German, but all the short names for parameters are international), with all the parameters and curves.
According to it, the KT209 is a PNP low frequency (audio frequency) transistor with low saturation voltage and increased base-emitter-voltage capabilities, inteded to be used as amplifier and switch. In addition to what abyrvalg already wrote:
- hfe is listed as 80-300 with 160 typical
- base current=300mA max
- 300mW power dissipation
- Vbe 20V max
- Vcesat 400mV max, 115mV typ. at 300mA, 50mV at 100mA, 22mV at 10mA, 115mV at 500mA (all typ. values)
- transit frequency 5MHz min, 18MHz typ

So look for something like that.

If you need a scan of the complete data sheet, send me a PM (or is this of general interest?).

[Macbeth]

Thanks for the transistor data hli. I won't need the complete datasheet, I just want something to go on to use in a spice simulation.

I identified the transformer as faulty and fixed the open circuit coil, but upon soldering it back I noticed the HV output coil had gone open circuit too! Indeed, looking at it's initial resistance measurement it seemed far to high for a tiny little coil (23.8K ohm) so I expect this was faulty all along. Unfortunately that coil was inaccessible as it was glued down in the ferrite bobbin. I attempted surgery but ended up making a dogs dinner out of it and had to junk the transformer.

Anyway, Aurora and others may be interested in some pictures of the Zenit NV-100 night vision image intensifier tube.

SIDE ON


EYEPIECE END


OBJECTIVE END

[Macbeth]

Ok, the transformer is dead, but I want to make sure the image intensifier tube and multiplier is working.

Here is the tube mounted in its housing. The EHT multiplier is embedded in the side.



My foolhardy method of testing involved getting an old mains transformer from a wall-wart and wiring it in reverse with the input coming from my signal generator...



After some experimenting I settled on 230VAC as the input to the multiplier, generated from a 7v p-p square wave @ 13.65kHz



Phosphors lit up



The phosphors are way too bright, I may be overdriving it, but the light is on in the room. In the dark they dim down a lot.

[Fraser]

Sorry to hear the news that the transformer is beyond help.

Good news that the intensifier tube and multiplier is still OK. Thanks for the close -up pictures of the tube. These Gen 1 tubes are weird looking things and very different in shape to the Gen 2 and later types.

Be careful when powering the tube in a lit room. The original power supply design self limits the tube current. Without such protection it is easy to destroy the tube due to over-illumination. This also needs to be considered when building a replacement power supply.

Aurora

[Alexei.Polkhanov]

One thing I don't understand is ...
That factory in Rostov that made these -  "Rostov optical-mechanical plant" - on their website they mostly have recruiting info, open positions, salary, mostly engineering, Verilog, C programmers, electronics engineers, etc. But then I found this - "chocolatière", permanent position.

They take their chocolate seriously!