Anilam 1100 CRT help!

[davejeske]

Hi folks,
I'm new to this forum so a quick introduction may be in order. I am a mechanical engineer who has a "real job" but I also run a side business manufacturing woodworking hand tools. I also very much enjoy manufacturing and machinery and have managed to stuff my single stall garage with way too much iron. Most of my equipment I picked up at auctions or garage sales and it all needed or needs work. I have a 40's vintage Logan 9" lathe, 15" Walker Turner drillpress, 20" Clausing drill press, 16" Walker Turner 2-speed bandsaw, Full size Table saw, old DeWalt 9" Radial Arm Saw, Two old wood lathes, a couple 10" Baldor grinders and a microwave oven! My most recent find was a Titan II Bridgeport knock-off equipped with Anilam series 1100 2-axis CNC controls. I have it up and running and am learning to program it - great fun. However, the other night the CRT went south and the display collapsed into a vrtical line. All of the control functions still worked fine but I could not read the display. I took the cover off and patched in an old computer CRT so I am running again, however, I would like to fix the old tube if possible. Anyone have any experience with this kind of thing? My father-inlaw said it was the horizontal oscilator.?? Any help would be appreciated. Anilam wants $675 for a new CRT! Ouch.

Thanks,
Dave

[Evan]

It definitely is something in the deflection circuit but if you can see a vertical line then you still have high voltage. That means the horizontal osc is still running. More likely the problem is in the horiz deflection amplifier. Not an uncommon problem and often fairly easy to repair. Usually a pair of power transistors and they aren't very critical as to specs.

[bdarin]

Could also be the yoke.

[bernie]

Evan is correct (again). It will be a transistor or 2, probably a few dried out caps and maybe a diode as well. Really not too difficult to repair.

[davejeske]

Thanks for the help. Should any electrical engineer or technician be able to track the faulty components down? Or is there a way for me to check this out? I have a good meter and am not shy about working on things. What do I look for? I understand the high potential voltage that can be stored.
Thanks,
dave

[Evan]

Dave,

Welcome aboard BTW. I don't suggest that you try to repair it yourself unless you are well aquainted with high voltage circuitry and the serious hazards involved. In particular, TVs and monitors can kill you in a heartbeat. I have many years experience working on high voltage equipment and still I refuse to do monitor repairs at my computer store. It just isn't worth the risk. At the price for an OEM replacement it is certainly worthwhile having the old one repaired.

[davejeske]

Thanks for the advice Evan,

I will search out a qualified repair person. It wouldn't do me much good to be dead now would it? Who would fix all my old machines?

Dave

[Evan]

"Who would fix all my old machines?"


Oregon isn't that far from here...

[sandman2234]

Guess the next post will be telling him to work on the monitor, so you can make the trip to Oregon? Just kidding!!! It is too far for me to make that trip.
David from jax

[mayfieldtm]

I used to fix TV's and Computer Monitors before the prices dropped down to throw-away levels.
I found that about 25% of the time with all repairs, that the problem is either a cold solder joint or a connections problem of some sort.

Tap around on various parts and the circuit board with something insulated and watch the response. You might get lucky. Just don't zap yourself.

If the display is mounted where it can get vibration (even a small amount) from the machine, this can cause such failures over time.

Tom M.

[Evan]

I see that Tom is a lot closer to Dave than I am

[darryl]

I agree with Tom's thoughts on it. Probably a bad connection, an open choke, or maybe an open yoke coil. The horizontal drive usually comes from the flyback transformer, with the in-circuit components being passive, like chokes and capacitors, rather than electronic, like transistors or ic's. As Evan said, if you can see the vertical line, you still have an operating flyback, and high voltage. Something's open in the circuit between a transformer winding and the yoke coil. It could be the flyback winding itself.

[Evan]

The number one most common failure recently in monitors and computers is the power supply. That is most often caused by dried out filter caps with a large proportion of those due to a defective electrolyte formula use to manufacture filter and bypass caps between 2000 and 2003. In a case of either industrial espionage or sabotage a Japanese employee of Japan's largest capacitor manufacturer stole the formula for a new electrolyte for aluminum caps and it ended up being used by many of the largest cap manufacturers in Taiwan. It turned out that the formula would pass every test EXCEPT extended life testing. Instead of lasting 10 to 15 years it is good for maybe three, at most.

Story here: http://www.siliconchip.com.au/cms/A_30328/article.html

Aside from the capacitor issue the most common failure I have seen over the last few decades is a product of how boards are made. The process is automated and components are soldered to the board in part by a method called "wave soldering". In this process the components are inserted in the board by machines and when the board is fully "stuffed" it is suspended a millimetre above a tank of molten solder. After a brief warmup a wave of solder is sent along the surface of the solder pool which then contacts the bottom of the board and the component leads, soldering them to the traces. The common problem is that the heavier leads such as connector pins and power devices like regulators and amplifier transistors do not become quite warm enough to solder properly. This leads to cold solder joints which eventually cause intermittents and often device failure.

A related problem applies especially to power handling devices such as regulators and amplifiers. They become hot in operation. The temperature rise causes thermal expansion of the pins and results in cracking of the solder connection at the pins with repeated thermal cycling. These cracks can be microscopic and very difficult to detect. It is an extremely common problem. A side effect of this problem is that the microcrack will usually produce an increase in resistance at the crack and then result in heating of the lead to the device eventually overwhelming the heatsinks ability to cool the device. The device then fails but the root cause was the solder joint.

A first course of action in repairing a device such as a monitor or power supply is to hand resolder all large pins with a 30 watt iron ensuring the solder is well flowed. Also, there are some major differences in the fluxes used in so called "radio solder". Some of the stuff you can buy at the local Radio Hut isn't worth squat. You should use a quality solder such as Kester 44آ® Rosin solder with a high activity flux. This makes a very big difference to the quality of a solder joint.

If this does not solve the problem then the next step is to check supply voltages and, preferably with an oscilloscope, supply filtering. I won't attempt to describe these procedures as this is getting too long already.

[This message has been edited by Evan (edited 05-12-2004).]

[davejeske]

For you electrical types: Last night I pulled the monitor cabinet apart to see what I could see. The whole assembly seems less complicated than other monitors I have seen but I still know very little about them. One thing I noticed upon close examination was a connector on the printed circuit board looks like it got very hot at some time (brown/black burn marks). It is a connector with two wires that lead up to the yoke. The other two wires that go to the yoke are on a different connector that looks fine. I have not powered it up yet to "wiggle" the connector to see the effect on the display if any. All other components looked okay. Does this give any clues for further investigation?
thanks,
dave

[Evan]

Dave,

That sounds exactly like what I described above. The heavy connector pins to the deflection yoke have a bad connection from either cold solder joint or more likely microcracks and have heated up due to the resistance at that point. It may be as simple as resoldering those pins. I suggest you don't power it up and stick your hand anywhere in there, The high voltage is around 20,000 volts for monochrome and higher for color. If there is a crack or other defect in the high voltage lead a spark can jump a long way to your hand. I know, I got zapped once with 25,000 volts. I couldn't even remember my name for about two minutes.

If possible flip it over and resolder the pins on that connector, then try it. One note, it's not a good idea to place a monitor face down on the tube. Bits of crud that may have flaked off the emitter can fall and stick to the inside of the CRT front or the shadow mask and create an annoying dark spot.

One rule for working on monitors etc. that are on is that when making adjustments or tapping parts keep your left hand in your back pocket. It makes it harder for a jolt to travel through your heart.

[This message has been edited by Evan (edited 05-13-2004).]