Anybody repair Bessler Computer Color heads?

I have this Besler Computer Color head for my 4x5 Besler enlarger, had it for years...at times it has become balky, and I have opened it up and re-seated the circuit boards and it worked. Well.....after a two year sit, it doesn't work right as far as the display is concerned.

Yellow reads 000, the other colors register when I turn the color knobs, but the values are very, very off.

Is there anyone that repairs these, or has insight into how to fix it. I am pretty good with electronics, but I don't have a schematic for this.

Read the manual. There is a zeroing procedure if things go awry.

PE

Photo Engineer said:

Read the manual. There is a zeroing procedure if things go awry.

PE

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I have no manual. Got this head used years ago. I am familiar with the three "trim" pots accessed from underneath, they don't do much now.
Cannot get zero on any channel, and yellow channel doesn't register anything but 000.

http://www.khbphotografix.com/

They likely have the manual for sale to.

Nick Zentena said:

http://www.khbphotografix.com/

They likely have the manual for sale to.

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Just checked their site. Their used equipment is very pricey, considering the declining use of enlargers.

One of mine bit the dust and now I am rebuilding it as a 5X7 sans any electronics except a transformer and a bulb.

PHOTOTONE said:

Just checked their site. Their used equipment is very pricey, considering the declining use of enlargers.

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They are very much a pro shop. With all that implies. The rebuilt units they sell are like new. With full warranty.

Yes, at first blush their prices do seem high but that's compared to say perhaps, the auction site or labs looking to liquidate gear quickly. As Nick said, all the gear they sell has been given the once over with a very fine tooth comb.

I should disclose that I have dealt with them in the past and have been up there alot recently and Kevin is going to machine a Devere lens panel for me to take a 300 Rodagon (a less expensive option he suggested). Also keep in mind that he's not just enlargers, he tuned up and replaced several lock knobs on my Wista 8x10 when it looked like I was sol for parts. There aren't a lot of options for us up here.

Perhaps his pricing could benefit us in the end as it places a higher value on the equipment we use which could send a subtle message. Just a thought.

Back on topic, I'd get a manual from KHB. Give them a call, they might be able to help you with the colorhead problem.

Phototone,

I have two Beseler 45 dichro heads with different problems. One has a problem with power getting to the lamp. The other one has a problem similar to what you have in your unit (baseline filtration values). And just like your unit, my color heads were working fine before they were stored for years.

I am going by memory here, so I may be wrong. But if I recall correctly, the reading module circuit (the rectangular unit that plugs onto the diffusion chamber) ends in a series of on-board trim pots in the main board. It is likely that zeroing out filtration of any channel is through these pots - singly or in combination. I've never really tried it, because I told myself I would get to attend to the color heads when I had the time. (Of course I never have enough time.) Besides, having condenser head for the MX and the usual assortment of variable contrast filters assures that getting back to the color heads would be an unlikely proposition.

As you probably already surmised, the circuit that reads the light (via the module) feeds back the values onto the LED readouts above the color-coded filtration dials. The dials are purely mechanical in nature, serving only to raise or lower filter panels.

I have yet to successfully find a full schematic for a Beseler dichro head.

In the past, Calamity Jane had posted on her success in resurrecting dead or faulty Beseler color heads. It may or may not be in this forum. She may be able to help. She is also very knowledgeable about electronics. I also recall a post that pointed to www.baytronltd.com as a possible resource. Good luck on the project.

There may be two types of this head. Mine has three trim pots on the small detachable sensor that plugs into the diffusion chambers. These can be adjusted to zero the values shown on the LED display. You need a small screw driver to reach them.

Each diffusion chamber will have a different apparent color balance and will have to be adjusted individually. I have one for 4x5, 120 and 35mm. Each differs.

PE