Densitometer replacement lamp

Todd Barlow · Aug 1, 2015

I picked up a Cosar Corp. Compuplus Combination Densitometer - Cosar-75/76 model.
When trying to to calibrate for transmission density I get an error message that states the buld is weak and needs replacement, with that I am unable to calibrate zero density.
The lamp is working and has two intensities.

1) Anyone have experiance with one of these units?
2) Other steps I can take that may resolve the issue (short of a lamp replacement)?
3) Suggestions for finding a lamp part number? I cannot find a part number for a replacement lamp, in the manual or on the lamp itself and my searches on the net have not turned up anything.

Thanks in advance

Todd

Papa Tango · Aug 3, 2015

Todd, I have replied to your PM. The bulb type is a General Electric #788 miniature 6V bi-pin halogen type--but a bit of delving about and taking a look at Cosar's design drawing for the bulb revealed an importance difference between two varieties of these.

The Newegg link I gave is for the T-2 1/4 package shape. The one the Cosar needs is the T-2 3/4 variety. A bit of difference in the top shape of the bulb. I could only find one vendor that still carries this particular version--the 1/4 is much more common:

http://www.topbulb.com/ge-788-20w-6v-halogen-lamp

Cosar drawing attached.

AgX · Aug 3, 2015

-) What would an error message "bulb is weak" mean?

-) What does "T-2 1/4 and T-2 3/4 package shape" refer too? The bulb shape? Why is it of importance? Does it indicate the filament orientation (horizontal vs. vertical)?

ic-racer · Aug 3, 2015

If the lamp lights, try cleaning the optical path to the sensor.

Todd Barlow · Aug 3, 2015

Thanks for the replies!

Attached is a photo of the lamp and the base.

I have accessed the light path from the lamp up to the head and dusted and cleaned the path - still reading "Error 02"

Patrick - did you have a name for the company that took over Cosar? I could try them for a replacement lamp and base.

Thanks

Todd

Eddiegee · Nov 15, 2024

Todd Barlow... were you ever able to find a manual and bulb? Did you get the densitometer working? I seem to be in the same boat. Thank you.

Todd Barlow · Nov 15, 2024

No, unfortunately.
I recycled it.
All the best
Todd

Eddiegee · Nov 15, 2024

Todd Barlow said:
No, unfortunately.
I recycled it.
All the best
Todd

Thank you, Todd

Papa Tango, and anyone on this thread... I am getting 2 error codes: 02, which I think means weak bulb, and 45. No clue what 45 means. Any help here? Thank you.

bettechi · Mar 21, 2025

Eddiegee said:
Thank you, Todd

Papa Tango, and anyone on this thread... I am getting 2 error codes: 02, which I think means weak bulb, and 45. No clue what 45 means. Any help here? Thank you.

Hi Eddiegee did you find the user or service manual I have same model cosar 75 & 76 and same problem error 45 , thanks in advance

Eddiegee · Mar 22, 2025

bettechi said:
Hi Eddiegee did you find the user or service manual I have same model cosar 75 & 76 and same problem error 45 , thanks in advance

Hi bettechi... No, I never found a service manual, nor the meaning of the '45' error code. The company had multiple owners, none in business now (from what I could gather). Given that fact, and no user manual ANYWHERE in the internet universe, I reluctantly recycled the densitometer. For the record, there was one company that, at one time, had a manual, but they appeared to not be in business any longer.
I was going to use the densitometer for Zone System calibrations. What I will do now, is use a 0.1N.D. (neutral density) filter on top of a film that is just film base + fog, and eyeball it for a Zone I density. Then shoot and adjust from there.
Sorry I didn't have any good news for you.

Densitometer replacement lamp

Todd Barlow

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Densitometer replacement lamp

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