AppleColor RGB Issue

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jsa
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I'm curious if you folks have any suggestions. Of course, I've scanned the FAQ here:

Csa2 Monitor FAQ

Here's my problem: My IIgs monitor, the AppleColor RGB, after being powered on about ten minutes or so, begins to get brighter and brighter and out of focus, until it's impossible to use.

I've read a couple hints in the FAQ... May be related to the flyback, to capacitors, different solutions to problems that aren't entirely identical.

Has anyone else had any experience with this? I managed to find an AppleColor RGB Capacitor Kit here:

Console5 AppleColor Capacitor Kit

I've also found the flyback transistor, 2SD1650.

Before I take this thing apart and attempt my first TV repair job, it would be great if others who had the same problem might narrow my hunt for the cause before I start.

Thanks!

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Dog Cow's picture
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Re: AppleColor RGB Issue

A component on the board is suffering from heat failure. You could take freeze spray and identify that component. The voltage is slowly increasing, as you'll find with a meter.

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Re: AppleColor RGB Issue

Dog Cow wrote:

A component on the board is suffering from heat failure. You could take freeze spray and identify that component. The voltage is slowly increasing, as you'll find with a meter.

Ok that makes perfect sense... When you say the "board," my understanding is that there is a main PCB and a CRT PCB. It could be on either one, right? Also, typically with the freeze spray approach...any pointers to using the spray? Do you typically freeze a larger area to localize it and narrow it down? (any really stupid things to avoid spraying?)

Thanks for the help.

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Re: AppleColor RGB Issue

before starting that task you should first locate the sircuitplan of the unit....
up to your desription the parts should be able to be located close to the path
associated with the brightness control....
maybe when the cover is removed you might also be able to locate the trouble area by smell....
sincerely speedyG

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Re: AppleColor RGB Issue

From memory its an open circuit resistor, I have a similar fault i will be working on Friday night.

here is the circuit diagram:

http://console5.com/wiki/AppleColor_RGB_Monitor_A2M6014

They are at the bottom of the page as PDF's.

I have repaired 2 of these monitors in the last few months,and they both suffer from dry joint on the Neck board. There is a power resistor in each of the three RGB drive circuits that gets very hot and on both monitors I had to desolder and resolder them.
One of the FAQ's somewhere describes similar symptoms to those you are experiencing, and from recollection is was due to a power resistor on the Power supply board.

** I MUST STRESS THAT THE VOLTAGES AROUND BOTH BOARDS CAN BE FATAL. EVEN HAVING THE MONITOR OFF FOR SEVERAL HOURS, THE VOLTAGES WILL STILL BE PRESENT **

Follow the process to discharge the EHT and ideally only use one hand whilst working the boards. Of course if you have unplugged the board and removed it from the chassis, you will be much safer.

I am working on the circuit diagrams with my service notes, IE containing voltages at various points on the circuit diagram.

The LOPT (Line Output Transformer) the one with the RED lead connecting to the tube, also had quite a few cracked/dry solder joints.
This also has high voltages on those pins.

Desolder each joint one at a time and then resolder. Joints should be solid and shiny.

The LOPT was a cause of focus and brightness issues on one of my Apple Color RGB monitors.

I seriously doubt if it is the Flyback transistor as they typically work or don't work.
The fast you have a raster tends to suggest an open circuit resistor (or dry joint).

Cheers, Martin..

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Re: AppleColor RGB Issue

mnc1959 wrote:

I have repaired 2 of these monitors in the last few months,and they both suffer from dry joint on the Neck board. There is a power resistor in each of the three RGB drive circuits that gets very hot and on both monitors I had to desolder and resolder them.
One of the FAQ's somewhere describes similar symptoms to those you are experiencing, and from recollection is was due to a power resistor on the Power supply board.

Martin, thanks for these tips, super helpful. Would a dry joint on the neck board at the faulty power resistor react to a freeze spray, or does the joint need to be resoldered before such a trick would work?

mnc1959 wrote:

** I MUST STRESS THAT THE VOLTAGES AROUND BOTH BOARDS CAN BE FATAL. EVEN HAVING THE MONITOR OFF FOR SEVERAL HOURS, THE VOLTAGES WILL STILL BE PRESENT **

I got it. Assuming I discharge the EHT using the screwdriver/ground method, should I discharge the capacitors as well directly (is that even possible)?

mnc1959 wrote:

The LOPT (Line Output Transformer) the one with the RED lead connecting to the tube, also had quite a few cracked/dry solder joints.
This also has high voltages on those pins.

Desolder each joint one at a time and then resolder. Joints should be solid and shiny.

It sounds like you are recommending that any dry joint I find should be resoldered. That's fine, but since I'm a newbie, if you happen to be staring at a dry joint and took a photo that would be amazingly helpful. Smile

mnc1959 wrote:

The LOPT was a cause of focus and brightness issues on one of my Apple Color RGB monitors.

I'm hoping that's the culprit. It was just the open resistor or dry joint in the LOPT then?

mnc1959 wrote:

Cheers, Martin..

Thanks!

-j

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Re: AppleColor RGB Issue

jsa wrote:

It sounds like you are recommending that any dry joint I find should be resoldered. That's fine, but since I'm a newbie, if you happen to be staring at a dry joint and took a photo that would be amazingly helpful. Smile

Generally called "cold" solder joints, referring to poor quality or mechanically stressed joints. Here's a good thread that I have pointed newbies to before to good effect:
http://www.polkaudio.com/forums/showthread.php?30230-What-is-a-quot-cold-solder-joint-quot

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Re: AppleColor RGB Issue

david__schmidt wrote:

Generally called "cold" solder joints, referring to poor quality or mechanically stressed joints. Here's a good thread that I have pointed newbies to before to good effect:
http://www.polkaudio.com/forums/showthread.php?30230-What-is-a-quot-cold-solder-joint-quot

Very helpful. I'll be a wizard of resoldering soon. What I also meant was a photo of the neck board in question, just so I could see what the common dry/cold joints were in his example. I suspect that if he's running into the same cold joints repeatedly, it's probably due to a combination of the assembly process and aging. This would lead me to believe those joints would be common issues, so while I had the monitor open, I'd make sure to resolder them.

My other question around freeze spray may not have been clear... Since the monitor begins to show these problems as it heats, it makes sense that freeze spray would help isolate components that fail with heat. However, if a joint or open resistor is the issue, would freeze spray still help locate the problem spot?

The last bit is about discharging... Plenty of info on the net around that. Most instructions focus on discharging the LOPT. I'm wondering if direct discharging would be smart anywhere else on the equipment. Thanks!

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Re: AppleColor RGB Issue

The first one I had it would not work correctly due to the fact that the solder joints on the flyback needed to be resoldered. This happens because the flyback has no support physically to stay in the same place. When the monitor is shipped and turned on the wrong side, the joints break.

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Re: AppleColor RGB Issue

Dry joints are typically a result of either mechanical failure from heavy components and/or crystalization of the solder from continuous heating cycles, power resistors typically get hot and conduct heat through their leads in to the solder joint.

I tried this link:

http://www.polkaudio.com/forums/showthread.php?30230-What-is-a-quot-cold-solder-joint-quot

But it tells me my IP Address has been banned.

the ONLY way to fix dry joints it to desolder and resolder. Simply reflowing the solder is not a good fix, and it will fail relatively quickly.

Here are some images from google

http://upload.wikimedia.org/wikipedia/commons/2/20/Cold_solder_joint2.jpg

This one is caused by contaminated leads and consequently the solder has not flowed and bonded to the lead

http://static.rcgroups.net/forums/attachments/2/4/5/2/2/7/a3102322-214-dry%20solder%20joint.jpg?d=1267859455

This is most likely caused by heat and a heavy component, the joint has crystallized ad cracked apart.
This should be desoldered and resoldered.

This is typical of the components on the Apple RGB monitor around the Neck board and LOPT on the main board.

Discharging the tube via the earthed screwdriver is the best way, just ensure the monitor is not switched on.
I have the monitor plugged in so i get connection to Mains earth and make sure the power out let and the monitor are switched off and discharge the tube that way.

As a rule the caps discharge fairly quickly, the main filter cap usually has a resistor across it to discharge it, leaving the unit off for a few hours or over night should be relatively safe.

I have 240V local voltage which can be lethal, where as I'm told 110V is much safer (that's a relative/subjective comparison Smile.

I have 35 years in the service industry so if you have any questions please feel to ask.

I suspect speedyG also has a wealth of knowledge and also more than happy to help.

Cheers, Martin...

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Re: AppleColor RGB Issue

I was just flicking through the CSA2 Monitor FAQ and this sound similar.

034- I picked up a IIgs RGB monitor at a garage sale. The focus is
off and it took several minutes until the display got brighter
but it's still not very good. Are there any adjustments that can
be made?

The problem you describe is consistant with low B+ going to the flyback
transformer which results in low brightness level, poor focus, and blooming
when the brightness and/or screen level is turned up. More than likely if this
monitor has been sitting around for awhile, the filter capacitors have gone to
mush. Sometimes they can be revived by leaving the monitor on for a long period
of time but, usually, they require replacement.

I'll go over mine tonight and see if i can give you a bit of a fault finding procedure to check for this fault.

You will need a digital multi meter as a minimal tool for fault finding, ideally a cathode ray oscilloscope but I will presume you just have the multi meter for now.

Been in touch soon.

Cheers, Martin...

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Re: AppleColor RGB Issue

This is all fantastic info, guys. Thanks. I'll wait for Martin's results before I start any hunting myself.

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Re: AppleColor RGB Issue

Progress report, I could use a little help.

Here is a front view of my neckboard:

While connected (carefully), I tried freeze spray on different elements on the neck board. When I freezed in this area (circled) I the monitor
returned to somewhat normal brightness and focus:

I also checked the rear of the board for cold joints, focusing on the area circled. I'm not sure I can see anything obvious though:

(I'll put a close up of this at the end)

Can any of you more experienced wizards notice anything obvious? I have replacement caps but visually, the caps seem ok. I'd like to remove
the board and work on it. Here is a side view of the board, any suggestions on how to remove it safely? I've discharged the monitor, but that big
glob of grey glue/heat/whatever seems to hold the board to the CRT:

I'm afraid of breaking the CRT or board, can I remove that clue safely and remove it, or should I try soldering this thing while still connected?

Thanks!

-j

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Re: AppleColor RGB Issue

One more thing... The BEST result I get from the freeze spray is if I spray it right on the back and above the pins on the neck board for the CRT, on those joints. Not sure if that implies a different spot. Here are those joints:

Here is a close up:

Thanks...

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Re: AppleColor RGB Issue

Hello jsa,
i´ve taken a closer view to the pictures and added some comments....
pickup the pictures from following links...:

http://www.harrowalsh.de/Upload/7mqe.jpg
http://www.harrowalsh.de/Upload/51n6.jpg
http://www.harrowalsh.de/Upload/A2M6014CRTBoardPCBSchematic.png
http://www.harrowalsh.de/Upload/A2M6014MainBoardPCBSchematic.png

and i´ve marked in violett a cable connection from main PCB to
picturetube PCB where joints should be resoldered at picturetube PCB.

sincerely speedyG

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Re: AppleColor RGB Issue

Ok, I'm on it! I'm a horrible solderer but I'm going for it.

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Re: AppleColor RGB Issue

Hi Jsa,

Unfortunately i didn't get to the monitor, family birthday etc.

Looking at your closeup there are lots of solder joint in the process of failing or have already failed (they typically become intermittent.

On all of these monitors i have found that the solder joints on R6R8, R6G8 and R6B8 were very bad and needed desoldering and resoldering.

I would suggest removing the Neck board, I take lots of photos so I know where to plug sockets back.
This way you can wok on it in a much more suitable environment, soldering on aboard not lying flat is always harder, even for seasoned repair guys.

The Blob of grey silicon is just to hold the neck board in place, ie so it doesn't work lose with vibration. You should be able to very carefully cut it it with an exacto/hobby knife or a box cutter. its very soft and easily cut into.

You should do some practice soldering before you tackle something important. Most hobby stores have basic kits to practice on.

Make sure you have a good iron, ideally temperature controlled (I use 340C) and a suitable sized tip, ie a fine tip for smaller joints and a larger tip for larger solder joints. The LOPS and neck board are reasonable sizes joints so a 3mm tip or maybe a tad larger.

A vacuum desoldering tool, ie a solder-pullit is great for removing solder, you can use solder wick, as well to remove old solder.

With soldering, cleanliness is everything. Make sure you use a good 60/40 resin cored solder, around 1mm in diameter.

Once you get the old solder off make sure the area to be resoldered is clean, as speedtG recommends, remove flux with isopropyl alcohol.

Flux is corrosive and over time will cause reliability issues with solder joints.
When I say corrosive, it isn't going to do any damage in the short term. However it obscures solder joints so you cant see if its a good joint or bad.

Make sure the tip of the iron is clean, a damp sponge is good to remove solder and flux.

Bring the iron in contact with the solder pad and the components lead (this is where a chisel shaped soldering iron bit comes in handy). Feed solder onto the junction between the solder pad, components lead and the soldering iron bit. Keep feeding until the solder pad is covered. You should end up with a solder joint that is shiny and looks like a volcano in shape. The solder should extend part the way up the lead of the component. A spherical blob of solder is not good (too much solder) and often is that shape because the component lead is contaminated with oxide or oils. This means the solder has no bonded properly with the components lead.
Once finished, use isopropyl alcohol and an old toothbrush to remove the excess flux.

A quick look on the neck board and I can see at least 1/2 a dozen potentially bad solder joints.

As a rule of thumb where there is heat or a heavy component and the equipment is old, you can expect to find dry or cracked solder joints.
Looking at the component side of the neck board, you can see the PCB has gone brown under R6R8, R6G8 and R6B8, that's why the solder joints on these components fail.

I use a jewelers loupe to inspect suspect joints. Given the cost of solder is almost nothing, i always desolder and resolder suspect looking solder joints, it might not fix the problem, but it can't do any harm and if it hasn't failed at the moment, it probably will in the near future.

I fixed a monochrome apple monitor a few weeks back. I knew the problem was in a specific area, but it took me 3 or 4 attempts at removing components and testing them before i got the right one.

Fault finding is a bit of a grey art, most of it comes from experience, however don't give in, keep plugging away.

Keep feeding back your findings and we'll keep making suggestions.

Cheers, Martin...

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Re: AppleColor RGB Issue

Hi Jsa,

Are you squirting the spray freeze on the components or the solder side of the board?

If you think you have localized an area of the board, then its time to try and locate the component that is causing the issue.

I find making a tube from paper and placing it around the component allows you to direct the freeze spray onto each components, this generally will allow you to locate the specific component.
Most spray freeze has a thin tube to direct the freeze spray onto a very localized area. If yo are not using this, now is the time to start using it.

As a rule resistors and (to a lesser degree) capacitors are not temperature sensitive, its normally diodes, fets, ICs and transistors (ie semi conductor devices) that exhibit temperature related faults. There are always exceptions to this rule, for example a dry joint on a resistor may respond to being frozen, even though the resistor is perfectly OK.

Cheers, Martin...

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Re: AppleColor RGB Issue

I resoldered a number of joints (thanks to all of your help). I also replaced some caps in a spot that seemed a little weird. Couldn't hurt.

My joints may be worse than the originals, since I'm so new at this. BUT...

Reassembled, the monitor is behaving great. It now starts off a tiny bit fuzzy and increases in focus, rather than the other way around.

I didn't resolder all the potential bad joints. I can always jump back in if it starts to go bad again.

Excellent work guys! Your mentorship really made the difference here!

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Re: AppleColor RGB Issue

If soldering is troublesome for you then I would suggest that you use some soldering flux and a wet sponge to clean the tip of your soldering iron before you do anything.

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Re: AppleColor RGB Issue

I found a bad transistor on the CRT board of the applecolor RGB monitor for the IIGS. The part was Q604 and has a part number of 60374f. Does anyone has a NTE or other cross number for this part?

thanks

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