Timer/Enlarger...delay with activating light

Beseler 45.
Three different timers.

I have tried to find a pattern, but i do not see one.
Does not seem to matter if the enlarger is cold or hot...moving/pulling the power cord from timer to enlarger has no effect...pushing the timer button Hard/Easy/Slow/Fast makes no difference.

What is happening is that the light in the enlarger is coming on at all different times.
Sometimes it comes on as soon as i hit the timer button, other times it may take 1-2-3 seconds for the light to come on.
Does this problem sound familiar to any of you guys.?
Is this user error...have i got something wrong in my procedure or set-up.?
Thank You
do i need a new lamp...or do i have some dirty contacts in the enlarger.?

CMoore said:

Beseler 45.
Three different timers.

I have tried to find a pattern, but i do not see one.
Does not seem to matter if the enlarger is cold or hot...moving/pulling the power cord from timer to enlarger has no effect...pushing the timer button Hard/Easy/Slow/Fast makes no difference.

What is happening is that the light in the enlarger is coming on at all different times.
Sometimes it comes on as soon as i hit the timer button, other times it may take 1-2-3 seconds for the light to come on.
Does this problem sound familiar to any of you guys.?
Is this user error...have i got something wrong in my procedure or set-up.?
Thank You
do i need a new lamp...or do i have some dirty contacts in the enlarger.?

Click to expand...

Let me ask. Is this a dichro 45S head? The Beseler 45s heads, at least the first generation heads have this problem. It is tied to a single component on the printed circuit board.
Symptoms are you start the timer, there is a random pause before lamp comes on. Sometimes very slight delay, then much longer.
There is a "optical isolator " that goes bad I will need to check my notes. The board is marketed iso, right now I can't remember if it's iso 1 or iso 2. Beseler offered a repair kit in the past, but not for the last 15 years at least. Takes about 5 minutes to replace the opto-isolator once you get the board out. Pencil soldering gun and some rosin core solder. The part looks like a little aluminum can, says Vactrol on the side, very obsolete but you can still find on ebay etc. Newer heads don't have any problems.
Let me know if you want any more info I have all of this written down.
From what you describe if it's a 45s head, I would give 99% chance it's this little bugger.
Mike

Hey Mike -
I THINK it is the "S".....it is the color head...3 knobs on the right side...the left side has a light indicator and the power switch below that.
I guess i should pull the head...maybe shoot some digitals of the PCB for you. I imagine the circuit board is in there somewhere.?
Thank You

CMoore said:

Hey Mike -
I THINK it is the "S".....it is the color head...3 knobs on the right side...the left side has a light indicator and the power switch below that.
I guess i should pull the head...maybe shoot some digitals of the PCB for you. I imagine the circuit board is in there somewhere.?
Thank You

Click to expand...

This is a board that I pulled from a junker. The little can with OK on top is "ISO 2" it's labeled ISO-2 on the board. This is the little bugger that fails that cause the delay. I've seen this in 4 of these older heads. This board came out of a unit with May 9 1989 date on board. Replacing this component has fixed everyone I have come across . The newer heads are modern and don't have this problem. The part is labeled Vactec 8646, Vactrol, VTL 988.

My education in electronics consists of a class I took in 9th grade, (c. 1971) My understanding; this is a sort of optical relay. There is 4 leads that are soldered to the board. There is probably a modern equivalent that could be bought for 50 cents. I found a guy in Brooklyn (If you can't find it in NYC it doesn't exist) This was over 15 years ago. He was/is a dealer in obsolete stuff. He offered me 100 for 1500 bucks. We negotiated, I ended up paying 300 bucks for 10 of these little cans. I have used 4 of them If you search the forum you will find me and others discussing this. I would bet you could find these on ebay (Ebay was an infant when I found these) If you get to where you need to buy one, I will let one go at cost, since I now have 5 fully functional colorheads .

To get to the board, (my lawyer say's UNPLUG the unit) and go in from the top. It's easy to get to. You will need to pull the mixing chamber, the there is a sheet metal cover held in place by a couple of screws. The board has 4 little nuts holding it to the unit. (they come off easy, a bit harder to get back on)

This is the weak link, I have never had any other problems. This board came out of a ABUSED unit that I scrapped.

P.S. if the light won't come on at all, always check the white light "paper saver" lever. It's genius but can be confusing.

Best Mike

Great...Thank You So Much -
I will pull the relay, ask some of the Smart Guys on one of the Guitar Amp Forums, and see if i cannot find a modern day equivalent. If not, i will contact you about your offer.
Thanks Again
chip

Well Thank You VERY Much.....that seems to have fixed the Light/Delay problem...!!!

BUT...anybody have a schematic for the Color Head.?
In the process, i lost the fan.!
I pulled off all the spade connectors, to make it easier to get the PCB back in, i may have crimped a wire, or broken one, or MAYBE not slid one on tight enough.
If i had a schem it would save me a lot of time. Otherwise i am going to have to take a DMM and start a continuity test.
Judging by the PCB, I am Assuming the Fan is running on DC.?
Will have to check that also.
I am still in awe of that Board. What is all that stuff doing.?
Three or Four different types of transistors, some diodes, caps, etc etc.
I am no electronics tech.....I thought the timer could just, simply turn the enlarger light On and Off.?

Well. for some reason there was no power getting to the fan. It MIGHT be in that switch that is operated by closing the top cover.
But i did not want to fool with That...it sends power to the PCB that sends 82 Volts to the light. So i puled the fan, put 120 to it, and it worked fine. I soldered a 2 wire cord to the fan, ran it through the back cover, and now i have a fan again. I have an extra cord to deal with, but no big deal.
Maybe now i can learn to print a photo again.

not sure if this is the same one you have....

CMoore said:

Beseler 45.
Three different timers.

I have tried to find a pattern, but i do not see one.
Does not seem to matter if the enlarger is cold or hot...moving/pulling the power cord from timer to enlarger has no effect...pushing the timer button Hard/Easy/Slow/Fast makes no difference.

What is happening is that the light in the enlarger is coming on at all different times.
Sometimes it comes on as soon as i hit the timer button, other times it may take 1-2-3 seconds for the light to come on.
Does this problem sound familiar to any of you guys.?
Is this user error...have i got something wrong in my procedure or set-up.?
Thank You
do i need a new lamp...or do i have some dirty contacts in the enlarger.?

Click to expand...

my enlarger/timer combination does the same thing.I measured a 70ms delay.Sure has an effect on test strips.Nevertheless, my RHDesign timer compensates for the delay,because, I ordered a custom chip in it.

paul ron said:

not sure if this is the same one you have....

View attachment 177854

Click to expand...

Oh Man...Where did you get That...!!??!!??
It sure looks like it.
ISO #1 and #2
Two Elytic caps.
A ffew transistors.
One bias pot.
Etc etc.
Thank YOU

cmoor... whered you get the new vactrol for yours?
did you use a modern led optoisolator?
part number?

i helped a lady repair hers a few years ago. she managed to get the diagram i reverse engeneered it for her. we did put an led part in hers but i never wrote the part number down on the diagram n cant for the life of me find another replacement.

i also have this unit and could use a spare part for when mine eventually dies... id probably figure it out again but f it doesnt itch, i dont scratch. who knows, by the time mine goes, parts wont be available at all.

.

Hey Paul. A forum member sold one to me.
I took the old one apart. It sounds like you have Pretty Good Knowledge of electronics.?
Is there a way we can figure out how to make a replacement for this.?
I can shoot pictures of the one i pulled apart.
I only have a Very Basic understanding of electronics, but.......it looks like a small bulb that shines on some type of LDR... Light Resistor.?

thats a tiny neon bulb. those vactrols were used alot in guitar amps, tremelo or vibrato cuircuits.

what id like to know is the voltage at the bulb's on state? ac or dc? i dont have my unit here, my son is using it.
i think the replacement we used was a MOC3020 but im not sure... it was a long time ago.

but for reference for others, it would be nice to have the information memorialized here. i can update the diagram.

OK ...I see.
The problem for me is, i have my PCB back in the head.
Once you get the board back in there, there is no way to measure anything. All the solder connections are underneath the board, if you know what i mean.
Probably what "we" would have to do is get the board out of the Head, re-connect it (if possible) to the two Molex Connectors, and then get your numbers.?

yeah thats a problem.... i know.

but id be glad to see the original part?


⬇⬇⬇⬇ excelent!

The leads on R14 and R16 appear to be uncoated, so if you have access to the top of the board while it is mounted, and if the head door switch can be actuated easily enough, then you may be able to make the required measurements.

The problem with subbing a newer LED opto-isolator is that the neon bulb controls the current through itself, and seems to be part of the voltage regulation for the lamp. Without a specification, it is not known what value that current is. If you knew that, and had a spec sheet for the new LED opto-isolator, it may be possible to make the substitution.

Here is a place to start:
1. With the unit NOT connected to mains, measure the resistance R of R14 22k resistor. It is hard to tell from the photo, but it seems to be the one between the vactrol and the R16 pair at the edge of the board. Should have Red-Red-Orange color code.

2. With the unit operating (lamp on) measure the voltage drop V across R14 (same resistor as above).

The current through the neon bulb then should be I=V/R from above, since the current through R14 is the same as through the bulb.

3. Measure the voltage drop Vneon by putting DC voltmeter positive probe on resistor R16 (the two resistors hump backed at edge of board) lead that connects to the vactrol. Put the negative probe on R14 lead that connects to the vactrol. When the lamp is on read the voltage.

Voltage drop across the neon bulb in ISO-2 is probably about 20V. The voltage is in circuit is DC, positive, coming from BR2 bridge rectifier.

The theory is that the substitute LED, which has a Vdiode voltage drop across the P-N junction, will require a resistor that needs to drop Vneon - Vdiode volts to compensate for the neon bulb. So Rsub = (Vneon - Vdiode)/I where I is from #2 above.

A couple other notes:
1. Not sure how to figure out what is needed on the photodetector side of this. If that circuit was meant to operate where the resistance of the photodetector is important to the operation of the lamp, rather than just to trigger the lamp on by sufficiently biasing Q5, then this project is going to be painfully more difficult.
2. If the current I is at or less than 1mA, then some more effort may be needed to match in a new part. The LED needs sufficient current to drive the photodetector down to a sufficient low resistance.
3. Maybe Beseler's current model control board is compatible in the older head, and a replacement control board may not be too over the top in cost.

some possible helpful references
spec sheet of a LED opto-isolator http://datasheet.datasheetarchive.com/originals/distributors/Datasheets-316/637837.pdf
spec sheet of a neon opto-isolator http://datasheet.datasheetarchive.com/originals/scans/Scans-001/Scans-0021975.pdf


May be helpful, or may be dangerous (to the enlarger!). >michael

Hey Mike -
I will give that stuff a shot if i can get my probes down in the Head.
Regards this.......

3. Maybe Beseler's current model control board is compatible in the older head, and a replacement control board may not be too over the top in cost.

.....Are you saying that Beseler still offers a replacement board.?

Thank You
chip
BTW.....As I have said before, I just have a basic understanding of AC/DC, but.....why is so much "stuff" required to turn the enlarger light On and Off.?
Why can't the timer simply be connected to the light, and turn the power on and off, if you know what i mean.
Other than knocking the 120 down to 82-87 Volts, why are all those parts needed.?
Thanks

Its also a conditioner/regulated power supply. Yeah they complicate the heck out of it, but back then this was top of the line technology. Besides its a simple circuit compared to some of the computerized stuff out there today.

BTW If I remeber correctly, we did use a dropping resistor to accommodate the LEDs voltage.

About No. 3 it was just a thought. If the head is the same size and shape, it could be that Beseler simply redesigned the power conditioning circuit and fitted it to the same case design. It is worth an email perhaps.

As @paul ron states the circuit provides voltage regulation of AC supply to the lamp. Regulating and adjusting DC is far easier to do than for AC. Without integrated circuits, this regulator provides the required regulation, and some safety measures to prevent over-voltages, such as the full line voltage getting to the lamp before the regulator is fully energized and regulating properly. Think about this - The lamp is 250 watts at 87v. Almost 3 amps to run the lamp. And 250 watts of heat is being put off. You would have to drop 33V while still supplying almost 3 amps of current through a resistor which means the value of resistance needed is 11 ohms. The resister would have to be rated 100 watts to do that (and that R would now put off 100 watts that also has be removed from the head.)

As for #1 I have sort-of convinced myself that all the ISO-2 photocell is doing is gating the triac (Q5) and not doing any linear regulation so this is probably do-able. But some adjustment may be needed to get the photocell resistance to where it needs to be maybe by adjusting the resistors R22 and/or R21 to change the operating point to work properly with the new photocell. I don't know what the * indicates on R22 here but it may used to note a component value that is "select on test" to get to a balanced circuit or to a desired operating point. There are numerous parts marked that way and seems not very manufacturing efficient.

I am intrigued by R16 and 16A - the printed note says a board revision is taking that resistance from 3.17k to 39k, an 11 times increase. The board in the photo supplied by @mshchem shows the parallel pair with the 6.8k and 8.2k, which also conforms to the written notes by @paul ron measuring 3.17 .

michael

But take a look at the specs on Q4... Dead Link Removed

and D1 the 8.2V zenner... all appear to be low voltage.

The photocell side is not a problem since most optoisolators can handle over 250V n more.

An optoisolator does not directly switch high current. Rather, it controls a gate voltage or transistor switch with a low current drain path through it's intrinsic resistance, which depends on the amount of light it is illuminated with. What a opto-isolator actually does is isolates current loops of one circuit completely from another, so that the circuits can work in isolation. I have used them to prevent ground loops, creating electrical hazards, between two separate vehicles operating with two separate power sources that I needed to pass signals between. Think of it as a sort-of transformer device for DC circuits. Transformers only work at AC.

The circuitry connected to the DC out put of the bridge rectifiers is low current and has lots of voltage drops to keep the circuit within the breakdown voltage of the various P-N junctions in the solid state components (diodes, transistors). These devices are used in DC devices requiring steady state voltages, not alternating voltages. The triac is an exception and is the high voltage, high current device that is being controlled at their gate, for the AC. The gate resistance is very high, resulting in very low current drain so the power drain and heat generation is very low at that terminal.

All this said, I can't say that I understand how this circuitry actually works. I am not a circuit designer most days and have never studied stuff like this, but rather work with radio frequency circuits and design. Then this said, if you look closely at the circuit, the lamp current path is through both triacs, Q5 and Q6. All the other components are along high resistance paths (resulting in very low current compared to the lamp). The zener diode is what is really controlling when ISO-2 bulb is energized. Until it's avalanche voltage is reached, it will not conduct, which then results in turning on conductivity in Q4 which results in current flow through ISO-2 bulb. Then, ISO-2 bulb reduces the resistance in the ISO-2 photocell resulting in a gating voltage sent to the triac Q5 which then closes the circuit in conjunction with triac Q6 that supplies current to the lamp.

It may be that the circuit actually is "chopping" the voltage (see capacitors surrounding triac Q6). Doing this would alter the root mean square voltage (RMS) to the lamp, keeping it inside the lamp's specification. The peak voltage is greater than the 87v spec, but that number is a RMS value. The average voltage (defined by the root mean square) and current is what accumulates over time (relative to a cycle of AC current) to a power value - this power is what the lamp really needs to be able to dissipate without destruction and is the specification the lamp is rated for. Also, I have no idea what the circuit hanging off of BR-1 is doing. perhaps somehow it is affecting the voltage drop or conduction across the bridge rectifier, and somehow controls the circuit? There is a thermistor TH1 in this circuit - don't know what it is mounted to but obviously another "safe operating range" device controlling the lamp's conditioned power supply.

yes i understand optoisolators separate unlike voltages or ac from dc and yet maintain control in the other side... or effect it just like a relay would only the relay isnt fast enough.

so all we have to do s find out what we have for the vactros neon n adjust it to light an LED. the other side will not make any difference once we get an isolator in. everything else can be adjuted easily enough.

This is the ISO 2 OEM unit. I supplied Chip with one of my spares. I have repaired 4 heads that have the funky delay. I KNOW that there must be a modern LED (non-Neon) equivalent of this. If you look on the internet same thing happened to certain 23C models. Beseler quit offering repair kits sometime around 2000. I bought 10 of these little buggers from a guy in Brooklyn, 15+ years ago. This was made by Perkin Elmer, I don't know who owns the brand now. One of the units I repaired had been repaired. It didn't look like this can. I keep using the old head. I wan't to keep a virgin new head as a security blanket. Seem like one of you electronic egg heads could find a modern replacement. See below for picture of the NEW board, It looks a WHOLE lot less cluttered in the head. I think they redesigned more than the board but not sure. Mike

THIS IS THE NEW BOARD, I think this is c 2000-2004? Notice how clean it is, this is one of those people that went out and bought one of everything and then never used it. I got the whole outfit, like new 45 MCRX with a 150 Rodagon and the head for $300 bucks.


This is the old board that I sent Chip
Mike

Here's the thread from 2004
(there was a url link here which no longer exists)

paul ron said:

not sure if this is the same one you have....

View attachment 177854

Click to expand...

IS this the drawing you got from Phoebe in 2004?