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Author: Subject: Repairing Infrared Spectrophotometers
benzylchloride1
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Repairing Infrared Spectrophotometers

I am starting a thread on older infrared spectrophotometers, pre-FTIR and how to repair them. I purchased a Perkin- Elmer 467 Dispersive Infrared Spectrophotometer off of Ebay. This Instrument powers on, but seems to have a problem with the built in chart recorder. The pen slides down to 0% transmittance and stays there. A relay is missing from the circut that controls the chart recorder. I have the manual, but it does not specify which relays go were. Does anyone on the forum have any experience with this instrument? See attachments for manual and pictures of this instrument.

benzylchloride1
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Here are some more pictures:

benzylchloride1
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Here is another picture:

Dr.3vil
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hmmm, I'm in the same boat. I have Spectronic 2000 UV/VIS that is no longer operational. Right now its on the back burner of things to get to since school will be starting in a few weeks.

your going to have to take it apart and try to develop an electrical schematic before any real attempt can be made to repair it. good'ol reverse engineering. I assume, or at least hope you know basic electronics (V=IR, how to use a voltmeter, how to read a schematic and all that jazz).

rather then trying to repair it, I would venture a DIY approach (at least thats what I plan to do with mine)

A Spectrophotometer has a few key parts, assemble them and it should work

1) light source, Tungsten / Deuterium (hotwire for IR)
2) Monochromator (Duel or single beam)
3) sample compartment
4) Photomultiplier tube (aka the detector)

The electronics to drive all of this is rather simple. especially in the age of PIC's or PC's. The output of the PMT is simply a electric current measured against a reference. now that hardest part of all of this has to be calibration. Monochromators are pretty complex, and must change their configuration during the scan to obtain different wavelengths.

The DIY approach aside, I would try an figure out what parts of the device function. Does the IR source work? if you stick you hand in the light path does it feel warm? can you start a scan? what sounds does it make when it powers on? all of those things can help you determine just how broken it really is.

keep us posted...

DR.3vil

- Paper chemistry works the first time every time -
benzylchloride1
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The IR source works, and the instrument runs except for the fact that a relay is missing from the circut that runs the chart drive. I contacted Perkin-Elmer about this instrument, but they never got back to me, probably because it is a dinosaur from circa 1970 and they currently do not service these instruments. At least they carry chart paper and pens, but at a price: $30 for 3 pens, and$33 for 1 roll of IR spectrum paper.
unionised
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Does the manual have a circuit diagram and can you post that?
len1
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There could be more things wrong with it, but my suggestion is to take the shortest route possible first.

Relays are to a great degree interchangeable.

Key parameters are:

working voltage of coil - 6, 12, 24 (higher very unusual but if it uses valves as you say, maybe possible)

number of poles 1 or 2 most common ie SPDT or DPDT

max voltage of contacts (240v)

max current of contacts (10A)

Choose the last two parameter as given, for what you have its almost certain they are OK.

next determine the workingvoltage by measuring the energising voltage with a meter. The number of poles is determined by the additional leads running if its <=3 its SPDT, or 1 pole. then buy appropriate relay, solder in, see if works. If you have trouble a picture of relay socket contacts will help

[Edited on 14-8-2008 by len1]
benzylchloride1
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I did some more work on the instrument and I succeded in setting the recorder pen to 100% transmittance! I think the detector or something related to the detector will need to be replaced. The instrument does not respond to the light path being blocked which indicates a detector problem.
vecktor
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first off check that the ac line frequency you are using is the same as the machine is designed for, 60hz machines will not work on 50hz power and vice versa. this has to do with the stepper motor that drives the beam chopper. there is no way round this problem other than replacing the stepper motor, and with machines this old finding the desired stepper motor is going to be tricky.

I am no expert on PE machines, having worked on Unicam and beckman. this pe machine is a beam chopping dual beam machine works pretty much like a beckmann IR5

check that the pickups from the shaft on the chopper are working, these are either optical or magnetic and if they don't work you will waste a huge amount of time fault finding.

there will also most likely be a neon bulb in the machine next to a photodetector, this enables the machine to reference the line frequency, when this neon dies it stops the machine but it is easy to replace.

secondly check that the mechanical bits are all free moving and free of corrosion things like the v shaped attenuator which slides across the reference beam is free to move check also that the slit mechanism is sitting on the 'program' cam, the cam is designed so that the slit opens and closes as the spectrum is scanned.
check the alignment of the mirrors, do not adjust them unless you are sure they are grossly misaligned!!!! they are probably fine, but put a mirror in front of the detector and angle it make sure you can see the source with the chopper in both positions.
the detector is usually indestructible provided it hasn't got damp. the amplifier circuit and servo drive circuits are also pretty indestructible. there will be test points on the detector amplifier circuit.

the relay you talk about sounds like it is probably the relay that controls the chart feed motor, and is linked to the start scan stop scan circuit, other than not feeding paper it shouldn't make any difference. the machine should still start and run through a scan but not move the paper. as this is a chart feed not a platen machine the scan start scan stop must be switched from the scanning optics not from the chart position

take the cover off take close up pictures and post them here, and it is probably possible to figure out what is what.

these older instruments are much easier to deal with than the first and second generation FTIR's with their dodgy computer code, ropey tilt servos and scan servos and stick moving mirrors. God bless the inventor of the self aligning corner cube mirror, but unless it was under service contract I would choose not have an FTIR.
it would be an interesting project to take an old FTIR and use modern DSP's and software to synthesise all the drive and control signals, and just use the optics and detector. most of the hugely irritating problems with the earlier FTIR's are due to dodgy software and computer hardware.

[Edited on 24-8-2008 by vecktor]
Vogelzang
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The spectrophotometer here appears to have an AC chopper motor which uses magnets and reed relays for detecting the position of the chopper (rotating sector mirror).
http://www.geocities.com/antiquesci/PE337/PE337-1.htm

You can see on the 5th page a discussion about the chart recorder and the balance control.
http://www.geocities.com/antiquesci/PE337/PE337-5.htm

Here's the schematic.
http://home.ripway.com/2005-6/337500/PE337/Schematic1-1200dp...

There's a lot of people here http://www.diyaudio.com/ that will help you with tube electronics.

There's a lot of articles here about IR spectroscopy.
http://www.4shared.com/dir/2077108/ab6c3d06/sharing.html
benzylchloride1
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I wish that I could post pictures of the internal parts of my infrared spectrophotometer, but internet connection fails each time when I try to upload pictures to this forum. I contacted a service technician that had worked on model 467 instruments. He said that the dectector was probably faulty, and that detectors are not available. Does any one on Sciencemadness know where to obtain a detector for this instrument? The insturment runs through a spectrum just fine, but the pen currently stays at 100%. The chart drive works, the chopper motor and the rest of the mechanical parts work fine. I think that its an electronic issue. If I could obtain a service manual, a neighbor who has much experience with electronics could probably fix it. If someone has a service manual for this instrument, could they please post it?

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ender
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The detector is a thermopile, essentially a thermocouple at the focal point of a parabolic mirror. If you follow the series of links posted by Vogelzand, you'll see a picture of such a detector in a PE337 instrument:

Perhaps your best bet would be to cannibalize another instrument of this type, specifically, the "Infracords" made by Perkin Elmer from the PE137 through the PE783:

see:

http://www.ijvs.com/volume6/edition1/index.html

Relays on the PE337 are controlled by limit switches at the end of the mechanical range of motion on the mechanism that pivots the grating. Is this the relay you're referring to, or is it associated with the drive of the strip chart?

Personally, I'd dump the notion of getting the paper drive to work at all unless I was motivated to restore the instrument to original condition. I'd tap into the detector output and record the DC voltage signal with a data acquisition rig. I used this one on a PE337:

Here's a comparison of what a dispersive intrument of this type can do head-to-head with a more modern FT-IR:

The resolution is clearly good enough in comparison with reference spectra:

Your PE467 is probably from the 1966-1973 era.

One nice aspect of these early instruments are their discrete electronics layout in the pre-"solid state" era of integrated circuits. Makes trouble shooting the electronics easier.

Here's a close-up of the detector board on the PE337:

[Edited on 6-6-2009 by ender]
12AX7
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TOOBZ!

Eww, all those molded black capacitors -- they're probably going leaky. Fixed a tube TV last month, old piece of crap -- after replacing all the caps it worked perfectly.

Bizarre... I've never seen a double sided circuit board with tubes sticking out of it.

Tim

Seven Transistor Labs LLC http://seventransistorlabs.com/
Electronic Design, from Concept to Layout.
Need engineering assistance? Drop me a message!
Vogelzang
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Some more Perkin Elmer IR spec patents.

US 3363259 Chart recorders
467 etc. chart recorder?

triangular mirror, 700 series

US 3529889 OPTICAL FILTER CHANGING MECHANISM
727 filter changer

US 3529898 MOUNT FOR OPTICAL ATTENUATOR
700 series comb attentuator

US 3565515 MOUNTS FOR OPTICAL ELEMENTS
700 series mirror and detector

http://pat2pdf.org

[Edited on 6-6-2009 by Vogelzang]

[Edited on 6-6-2009 by Vogelzang]
benzylchloride1
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The instrument I have has tubes and transistors. The 467 seems to be a limited production model with several add ons to the model 457. I spoke to a service technician about the missing relay. The relay that is missing keeps the pen from moving when the filters change, the instrument can run with out it. The detector window is made of cesium iodide which is very hydroscopic and the service technician said that this detector usually would fail after about 12 years. I will have to either cannabilize a detector or buy a solid state detector, build a power supply for it and connect it to the preamplifier board. I was able to obtain a service manual for the model 137 instrument from the guy who constructed the Geocities site. This site has been very useful for me. The main amplifier board in the model 137 is similar to the board in my instrument. The 5Y3-GT tube in my instrument has been substituted with a solid state device. I bought 4 new 12AX7 tubes for the instrument along with the power supply regulator tube, no difference in operation. I will have to check the electrolytic capacitors. What is the best way of checking these? My electronic knowledge is fairly limited. I checked the limiting switchs with an Ohm meter and they work perfectly.

[Edited on 6-6-2009 by benzylchloride1]

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Biginelli
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I have a question then to anyone who has at least some experience with Hitachi infrared line. My spectrophotometer is called model 270-30; manufactured around 1989, it has a built-in computer, a floppy-drive option, so it won't be a problem to record digitized version of a spectrum (all that paper makes me crazy).

But one problem remains - a deteriorated detector, a high-sensitive vacuum thermocouple, which has a designation:

> Infrared detector.
> Part No. 260-0010
> Serial No. 60-67-28
> KRS-5 0.4x1.5

A KRS-5 (mixture of thallium salts) windows covers the entrance of the detector.

All my requests to Hitachi High Technologies have failed so far - no response at all. Their IR device line was closed appr. 15 years ago, and no service is available.

Does anyone can advice on where to find a data sheet for this sensor, or a data sheet for the device itself? I have a user manual, but it doesn't even have a circuit diagram. No results were obtained after searching at datasheetarchive.com, allofdatasheets.com and so on.

If there is no data sheet, what can I do to measure the detector's characteristics in order to find something to replace it with?

Forward thanks.

[Edited on 24-6-2009 by Biginelli]
benzylchloride1
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I am considering purchasing a modern solid state infrared dectector and putting it in the place of the thermocouple. This may be the best way to go to fix your Hitachi IR. I tested the voltage test points on the amplifier board and they are not the right voltages; the 0 volt reference reads at about -100 volts. The high voltage 210, 350 voltage test points only read at about 20 volts. There must be a problem with the amplifier or the power supply to it. All of the vacuum tubes have been replaced with new tubes. I cannot determine if the dectector is faulty due to the problems with the amplifier. The scanning system works and the controls that have nothing to do with the amplifier work. The problem with the amplifier must be a component that effects the entire circuit due to the voltage problems. All of the tubes glow. I am considering purchasing a Perkin Elmer 1300 series IR if I can find one for a reasonable cost because the pyroelectric detector seldom fails, and the electronics is easy to access.

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Biginelli
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Interesting.

According to my data, almost all solid-state modern detectors already have a built-in amplifier, thus requiring additional power supply. I think, this means I have to rip away the device's transformer preamp.

>I tested the voltage test points on the amplifier board and they are not the right voltages; the 0 volt reference reads at about -100 volts.

Did you utilize a standard tester or was it an oscilloscope?

>All of the tubes glow

Well, that's no indication of their functionality, isn't it? Perhaps, the emission rate is just not enough, or something else. I think, a tube tester is required; I do not understand much in tube electronics - so I have no idea.

And yes, all modern detectors have totally different form-factors, I'll have to adjust them. Well, a laser pointer should do it...

Anyway, thanks.

[Edited on 24-6-2009 by Biginelli]
Vogelzang
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This website http://antiquesci.50webs.com/index.htm
seems to be faster and more reliable than http://antiquesci.freewebpage.org/index.htm
so its now at two websites with more added.

There's an article here questioning the IPCC's global warming hysteria.
http://www.ijvs.com/volume1/edition2/section1.html#feature3

[Edited on 29-11-2009 by Vogelzang]
doublefocusing
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I am(belatedly) pleased.Now I want to see one of you fellows hit the high res.circuit and set the remnants of an old 21-110 MS or even an AEI MS-9.

 Sciencemadness Discussion Board » Fundamentals » Organic Chemistry » Repairing Infrared Spectrophotometers Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues