Circuit diagram needed for Durst power supplies EST 301 and EST 450

Hi everybody,
I'm trying to repair two Durst power supplies from a friend, respectively an EST 301 and an EST 450.
I checked already the regulator board of the ES301 and it's clear that the PCB contacts of the current sensing resistors R42 and R43 and severely burned. There is a group of resistors nearby which I would like to substitute also, but it's no longer possible to read the respective value, as they have darkened considerably, like the surrounding PCB.

I didn't open the EST 450 yet, but I may likely find a similar situation, therefore I will be grateful if someone can provide me the respective schematics.

Thank you in advance,
Jose

The #1 suspect in any vintage electronic equipment is the electrolytic capacitors.

It should be easy to read their values. Replace all of them, particularly the larger ones, before you apply power.

I don't know where you're located. Here in the states you can get replacement parts from
Mouser http://www.mouser.com or
Digi-Key http://www.digikey.com
(Mouser has the best prices and no minimum. Digi-Key charges $5 for orders under $25.)

- Leigh

I just got two inverters back from CCI. Guess what? Bad capacitors! If I didn't have to deal with the manufacturer for liability reasons, I could have fixed these in a couple of hours instead of waiting weeks.

In addition to Mouser and Digikey, Newark is a pretty good vendor to deal with too. I only order a few specific parts from them, but I can get my capacitors and resistors cheaper here, and usually faster, than from the other two.

You should check with Durst.it and see if a schematic for the EST301 is available.
Durst Pro USA has a replacement regulated power supplies for both of those (EST 1500N-24). Another thought is to forgo these regulated supplies and look for the TRA450/TRA500 which is just a transformer in a box:
http://img.photobucket.com/albums/v6...TA47300_3D.jpg

If you expect any semblance of consistency (assuming you live in the US), definitely use the regulated power supplies.

AC line voltage in the US varies all over the place, particularly during the summer.

- Leigh

Regulated power supply is not needed for B&W work. The outputs of a TRA450 (unregulated) and EST450 (regulated) are shown below. Both 24.4 VAC.

http://img.photobucket.com/albums/v6...633f4bf7_z.jpg
http://img.photobucket.com/albums/v6...52d577a9_c.jpg

Your measurement on the unregulated output is meaningless.

The "120-volt" AC power in the US can drop to 100 volts or less during the summer time.
The unregulated output will follow.

- Leigh

Quote:

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Originally Posted by Leigh

Your measurement on the unregulated output is meaningless.

The "120-volt" AC power in the US can drop to 100 volts or less during the summer time.
The unregulated output will follow.

- Leigh

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So is a measurement if the supply is unloaded.

I've seen voltage at the wall socket as low as 107, and as high as 130. Unacceptable for just about anything, let alone an enlarger lamp.

Quote:

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The "120-volt" AC power in the US can drop to 100 volts or less during the summer time.
The unregulated output will follow.

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Actually it can drop to zero, in which case a 'regulated' power supply like shown will give zero output. As I posted previously it is of questionable value with B&W printing. Simple to just repeat the print when the lights come back on. Perhaps you are mistaking these PMW regulated power supplies with some sort of emergency power system.

In fact I'm hard pressed to think of any condenser enlarger that came with a regulated supply. Did you have something in mind?

I'm also wondering what kinds of problems you are experiencing with that unregulated supply. I can only tell a 1/3 stop difference in printing time between two B&W prints when side-by-side. This means with a 25 second exposure the power can go completely out for five seconds during my exposure and I'll still get a good print.

Quote:

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Originally Posted by E. von Hoegh

I've seen voltage at the wall socket as low as 107, and as high as 130. Unacceptable for just about anything, let alone an enlarger lamp.

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Tell that to the people that invented the 'Resistrol.'