Dolam LC-7

[Tomasz Kowalczyk]

Hi, 

I've recently purchased interesting tubes: 5 unused LC-7 tubes made by Dolam. 

While they don't look spectacular, they are extremely rare. Googling in English and Polish leads to only two places over the internet where these tubes are mentioned.

This thread on Polish forum: 

http://www.trioda.com/forum/viewtopic.php?f=9&t=19611

Note the lack of word "nixie" in the discussion, official Polish name for nixies is "wskaźnik jarzeniowy". That makes googling this tube even harder.

And this auction I've purchased them from:

http://allegro.pl/zestaw-5-lamp-nixie-dolam-lc-7-i6845565730.html

So, they aren't popular, rarer than LC-1 and LC-2, which were used comercially (LC-2, at least, source: http://www.mif.pg.gda.pl/homepages/jasiu/oldtr/OTL/index.html). The holy grail would be an LL-1, which exists so far only as "being prepared for production" in some old documents.

There is no known commercial equipment using LC-7.

There is no information about time of their production. There are some codes on the back on the tube, but they don't make much sense, as they go: xW 0812, NJ 2409, NT 8617, NW 4204 and  NY 530x (x stands for unreadable). The codes have different style from other Dolam nixies, which have codes consisting of two letters and two digits. It is very possible, that these are prototypes of LC-531, as they are very similar. The differences are:

LC-7 doesn't have a pill on the top

It has different stack of digits and pinout 

It has only right decimal point*

Digits are slightly taller and slimmer

It has polished outside of back plate (very reflective) 

It seems to contain no mercury (pure orange glow, no blue haze)

Different voltage requirement - I didn't make many tests, but the sustaining voltage is betwen 150V and 155V. I didn't measure striking voltage.

What is similar: 

They have nearly identical size and internal structure

Both have 13 wire base, same diameter, same style (circle divided in 14 parts, one wire missing)

*If the theory about LC-7 being a prototype of LC-531 is true, it might exlain why only the right decimal point is mentioned in LC-531 datasheet - LC-7 has only that one.

I've taken some photos and made a pinout for the tube. On many photos I'm comparing it to a LC-531 to make the difference more clear. LC-531 is on the left, and LC-7 on the right. Sorry for bad quality - I'm not a photographer and I have no skill in creating good lightning for photos. I've uploaded my "work" to our google drive to TEMP/Dolam LC-7.

https://drive.google.com/drive/u/1/folders/0B4bzn8WGaWL1Q0ZDNXhOZUtkblk

Here's the pinout for quicker search:

Arrow shows the front of the tube. It is almost exactly between those two pins.

And two photos for general overview (right photo shows LC-531 on the left, LC-7 on the right):

I'd like to make this thread & drive folder a comprehensive source of data about the tube. So if you'd like to see a photo from different angle, or with different lightning*, or just have any question - just ask me.

*if you have any tips how to photograph nixies without using manual white balance, I'd like to read them - I can't choose non-automatic white balance and it is 

ps. I know that these photos take alot of space. If the photos take too much space, I will try to find a way to share my own folder with neonixie google drive drive.

[Tomasz Kowalczyk]

*if you have any tips how to photograph nixies without using manual white balance, I'd like to read them - I can't choose non-automatic white balance and it is

 

 

...very problematic when taking photos of something emiting light. I knew I should've read this post once more before publishing it. 

[Paul Andrews]

One observation: The LC-7 looks like it doesn't have mercury.

Taking photos of Nixie tubes can be a trial. Experimentation and taking lots of photos is the key. If you can't manually control the exposure, you can achieve a similar effect by varying the lighting. Try lighting the back ground. Try lighting the tube. Try different brightnesses. Try different angles. Using a bright light can force the camera to stop down which can increase your depth of field - this will bring more of the elements into focus. If you want to lessen the grid, you will want less depth of field so that only the illuminated element is in focus.

Obviously a camera that allows you to use manual settings for exposure and aperture will allow you to experiment more.

And a tripod makes a world of difference!

Of course the photos you posted were just fine :)

Have fun :)

[jb-electronics]

I struggle a lot with this too, and I am not really happy with the vast
majority of the pictures on my website. Jonathan seems to have found a
good way. Perhaps it is also possible to enhance the quality by some
light post-production. Jens

[GastonP]

Just don't forget to add the disclaimer "Human and Nixie images might have been digitally enhanced" :D

[SWISSNIXIE - Jonathan F.]

Taking photos of nixies is not very easy, and can be challenging. I use a box of styropor  and place the nixie inside. I have a flash directed to the roof of the box, so the light will hit the withe roof and reflect back inside the case, this gives a filling light and does not create any flares of so. I also use a rather long exposure (1/50 to 1/25 second) so the glow has enough time to fill the picture. The only thing i do in post-processing is slightly adjusting the exposure for different digits - and cutting/rotating of course.



The absolute master of nixie photography is the guy in this topic:

https://groups.google.com/forum/#!msg/neonixie-l/TMUm534stnU/g-zVJo-MBwAJ;context-place=forum/neonixie-l

[Tomasz Kowalczyk]

Thanks alot. So the whole point is to create background lightning by using flash, but at the same time, the exposure time should be longer than with usual photo taken with flash. I'll try it when I find some space for such "nixie photographing chamber".

Now, I think that there is one thing that I missed. It is the link (this one  http://www.mif.pg.gda.pl/homepages/jasiu/oldtr/OTL/index.html) about LC-2 tubes existing in commercial products. As I was trying to google more about LC-2 nixie, I was finding photos & info about the tube made by PIE (Przemysłowy Instytut Elektroniki). However, when searching for the Dolam version of LC-2, I couldn't find anything more than posts on forums claiming it existed - until I found this one photo in the very link I posted myself:

Why was I searching for it?

I've purchased 4 LC-2s made by Dolam yesterday. I was very happy to buy 4 rare tubes and was about to walk away from that place, but then something suspicious happened: I've found two more 10 minutes later. What are the chances of buying same type of rare tube from two different people within 10 minutes? 

These ones are red paint coated - something I've never seen on Polish nixies. So far, red paint was only mentioned as a possible version of LC-531. This might be homemade or for testing purposes, though - paint is spread unevenly, it creates a thick layer and it was spread over the white text. Red paint doesn't make much sense, as these tubes look mercury-free (no blue haze). I suppose this was a test during early nixie production in Poland in case they really decided to paint their tubes.

What is the difference between LC-2s made before and post name change? PIE has anode mesh made with squares, Dolam used same hexagonal mesh as in LC-511, LC-513, LC-513A and LC-516.

At first I thought that this is some kind of reprint or something, but the placement of decimal point is exactly the same as in PIE LC-2. So Dolam LC-2 is kind of an evolutionary link between early PIE prototypes and commonly known Dolam tubes. 

If you have any other photos of LC-2 made by Dolam, please post them here or message me with a link to them.

I'd like to explain one thing: PIE invented LC-1 and LC-2 in 1963 (or 1964), and in 1965 PIE was renamed to Dolam. So it is basically the same company, if we can speak about something resembling a company under communist regime. 

Dolam using a test product from PIE times leads my mind to one thought - there might be a PIE marked LC-7 or a Dolam marked LC-1 somewhere.

I'll post photos of my tubes in few days, when I find some time (and some better place for taking photographs).

[Tomasz Kowalczyk]

W dniu wtorek, 18 lipca 2017 00:53:24 UTC+2 użytkownik Tomasz Kowalczyk napisał:

I'd like to explain one thing: PIE invented LC-1 and LC-2 in 1963 (or 1964), and in 1965 PIE was renamed to Dolam. So it is basically the same company, if we can speak about something resembling a company under communist regime. 

I've mixed up some stuff. PIE didn't change into Dolam. Dolam was a part of PIE and was started in 1961. 

Dolam was probably assigned to extend work on nixie tubes after initial success of PIE. 

[Aleksander Zawada]

As a former employee of PIE I can explain that Dolam was experimental plant of PIE from 1961 to 1965. I'm sure that new development of polish nixie tubes (maybe not all) was done in PIE to 1970's. For example, I have some negative masks for nixie digits from 1970's.

W dniu 18.07.2017 o 22:10, Tomasz Kowalczyk pisze:

[Tomasz Kowalczyk]

Thank you for clarification.

I was using your website alot yesterday. It is alot of history to digest, but definitely worth reading, thanks for sharing your research.

In a document I found on your website, "Prace Przemysłowego Instytutu Elektroniki" from 1963, I found alot of information about how LC1 was made. I found information about experimental, dome top version known from your website and from Jens collection, but there is also information about flat top, more durable version. Do you happen to know if it was actually LC-2? The document states that 400 of flat top nixies were produced, but doesn't mention any name change.

Also, I'm really cursious about early Dolam production. As seen on the image shared by OTLamp showing interiors of V552 voltmeter, LC-2 was in serial production in Dolam factory. On the other hand, I think this is the only photo of a Dolam made LC-2 I could find.

And lastly - datasheet of LC-531 states, that it could be produced with red filter (LC-531 F version). Did you see any red painted Polish nixie during your research?

[Tomasz Kowalczyk]

I've recently got my hands on a rather interesting pair of tubes: LC-531s, which have same digit stack order and pinout as LC-7. All other features (a getter structure on top, darker and non-reflective back of anode cage etc) are exactly the same as in standard LC-531. 

This is a strong evidence that LC-7 was just a prototype for LC-531 and the ones I've received are a transition state - or just the person putting them together wasn't notified he's supposed to change the layer stack.
Unfortunately, only one of these tubes has a print and only one of them is working.
Few photos with a standard LC-531 as reference (the used tube is a regular LC-531):

Standard LC-531 has digit 6 placed at front, while LC-7 pinout version has it in the back: