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Old 18th February 2017, 2:11 PM   #16
aXLe Thread Starter
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Ok - probed the supply pin to this chip (pin 9) and nothing - zero volts.

Tracing back I found that I had 28V on the input side of resistor 3563 (top right of the last picture above - also highlighted in pink below.

This resistor is a 4R7 0.33W resistor - measuring it in circuit showed it as an open circuit so I removed to double check it. Yep - it was dead.

I replaced it and tested again - still no vertical deflection and both the vertical IC and the resistor were getting quite hot.

Measuring the voltage either side of the resistor I found I had 27V on one side, and 22V on the other - a 5V drop across it.



Using Ohms law, the current through it is therefore V/R = 5/4.7 = just over 1 amp. Note that the 28V rail has sagged to 27V under this load.

Power dissipation would be = I * V = 1A x 5V = 5W!

The original part was a 0.3W resistor - you can see why it measured open circuit - it cooked.

So where is this current flowing? The only place it can go (other than through the capacitor 2563 - I checked this cap and its fine) is through the chip.

Looking at the datasheet for the TDA3653, the total supply current (with no load) should typically be 50mA with a max of 85mA.



To be sure I unplugged the deflection coils and the current draw was the same.

Thus, I'm sure that this chip is dead so I've now got to hunt down another!

I feel I'm getting somewhere at least.

Last edited by aXLe; 18th February 2017 at 2:18 PM.
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Old 18th February 2017, 4:16 PM   #17
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Love your work man Wish I has them electronic abilities.
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Old 19th February 2017, 10:19 PM   #18
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Well the chip is out, and I have one on the way - it's coming from the UK though so will take a week or so.

Removing large SIL packages like this is super fast with a 32mm blade tip You can heat all the leads at once, and pull it out. Then a quick clean of the pads with some braid, and the boards all ready to accept the new part.



While I'm waiting on the new part to arrive, during the week I'll have a look at the degauss function on the monitor. When I first received the unit I noticed that the it wasn't degaussing when powered up (that thump you hear on some CRT's when they first power on) - or at least it didn't sound like it was working - I'll be checking out the posistor, which may possibly be faulty.

I must say that this monitor has been an excellent one for learning about monitors! It had a fair number of issues, but I reckon I'm pretty close now to having it going again

Last edited by aXLe; 19th February 2017 at 11:14 PM.
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Old 25th February 2017, 12:30 PM   #19
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This is a great thread.

Do you have any more information on that high voltage probe you're using? I want to make one.


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So where is this current flowing? The only place it can go (other than through the capacitor 2563 - I checked this cap and its fine) is through the chip.
What method did you use to check the cap? It's possible for a capacitor to measure open circuit with a multimeter but still have high leakage at rated voltage.

You can test this by removing the cap and placing it in series with a resistor with 28V across both (then just measure current draw of power supply or voltage over resistor).
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Old 25th February 2017, 7:30 PM   #20
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This is a great thread.

Do you have any more information on that high voltage probe you're using? I want to make one.




What method did you use to check the cap? It's possible for a capacitor to measure open circuit with a multimeter but still have high leakage at rated voltage.

You can test this by removing the cap and placing it in series with a resistor with 28V across both (then just measure current draw of power supply or voltage over resistor).
Check my signature for links to my retro projects including the probe I can supply my KiCAD project if interested.

In regard to the cap, I removed it from circuit and checked capacitance and ESR - tested ok.

I'm still waiting on the replacement vertical IC - should arrive this week I hope.
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Old 28th February 2017, 9:22 PM   #21
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The vertical IC(s) arrived today!



Bargain at 50p a pop so I couldn't resist getting 10 of them - never know when you might need one

I fitted one into the board and soldered it in place, then the moment of truth - do I have vertical deflection??

YES!



Hard to tell from the photo I know, but with the brightness cranked up the screen is now being painted by the electron beam. Quite a bit of burn in is noticeable on this screen (must have been used for one specific application for some time I suspect). Still, it's not too bad when you have something running on it - fades into the background.

So the ultimate test was to drag out my Apple 2gs and plug it in using the RGB cable that I made when fixing the 1084S monitor previously.

Woohoo!



Looks good

I've also pretty much finished the PCB layout for my version of Bob Parkers LOPT/FBT Tester which I've designed to fit in a UM5 jiffy box. Front PCB artwork which gives full credit to the original designer (my makers marks is on the the back):



I've actually added the sensitivity selection function but otherwise the design is much the same (other than being surface mount).

Still deciding whether to use a blue soldermask or black. Components are mounted on the rear of the board, including OSRAM reverse mount LED's which shine back up through the holes on the PCB.

Anyways, there is not much left to do on this monitor - I still need to take a quick look at the degauss and fit a replacement diode for the one that I bypassed (I'll fit a higher voltage part to prevent the monitor going into HV shutdown).

I'll probably let it run a few hours at the weekend to be sure its all good and then it goes back to Mikro (who has been very patient!) for his Atari STe

Last edited by aXLe; 28th February 2017 at 10:04 PM.
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Old 28th February 2017, 9:29 PM   #22
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Amazing work on this yet again - it must be a thrill to see them come back to life. Love a good CRT.
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Old 28th February 2017, 10:26 PM   #23
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Fantastic job, Mikro's been stalking this thread every day. :-)

So the culprit was the flyback and the vertical IC?

Btw great to hear about your progress on the ring tester, after seeing all this I'm sure I want one, I hope it will be available for purchase soon.

Once again, hats off mate, one hell of a job.
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Old 28th February 2017, 11:27 PM   #24
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Quote:
Originally Posted by badmofo View Post
Amazing work on this yet again - it must be a thrill to see them come back to life. Love a good CRT.
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Fantastic job, Mikro's been stalking this thread every day. :-)

So the culprit was the flyback and the vertical IC?

Btw great to hear about your progress on the ring tester, after seeing all this I'm sure I want one, I hope it will be available for purchase soon.

Once again, hats off mate, one hell of a job.
Thanks guys - I did enjoy working on this one and learnt a lot from it It does give a warm fuzzy feeling when you finally get it running.

Yes - the culprits were the flyback and vertical IC - I replaced the horizontal output transistor and snubber cap plus a couple of filter caps on the B+ line just for good measure as they do get a hard time, but the original parts were still ok.

I will have a few ring tester boards available - I haven't used the OSRAM PointLED's before so I just want to check the currents at required brightness before I commit the design and have the boards made



Last edited by aXLe; 28th February 2017 at 11:34 PM.
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Old 27th March 2017, 7:32 PM   #25
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Great to see this thing running!

I used to have one. Mine also had a rotating stand that clicked into the bottom. I recognise that board.

Opened the monitor up to do some very fine adjustments. It produced quite a good picture once it was all set up properly. Sharpness and geometry were pretty good compared to many of the cheapies I saw being used on a lot of PCs at the time.

Mine copped a lot of abuse and kept going. Ran it at fairly low brightness so never had a problem with burn in. Also a lot of gaming meant that the picture changed quite often anyway.

Thanks for the detail in this thread. Electronics repair certainly is a dying art, especially when it comes to CRT monitors.
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Old 27th March 2017, 8:24 PM   #26
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Great thread, really interesting and informative.

Bit O/T - but looks like you're using a JBC soldering iron kit, am I right?

How do you find it?

We use C245 handles (well when I worked ther) with cartridges C245030, C245731, C245906 though tip 030 was used to melt plastic around a CCD, found the unit pretty good tbh, heated up the tips pretty quickly to 300 and 350 degrees

Kind of miss my old job with all the gadgets, torque drivers, spare parts, tools etc etc etc...
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Old 27th March 2017, 8:43 PM   #27
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Yeah I use JBC - I have compact station with the T245 handpiece, plus I also have a micro-tweezer station.

Ideally I'd like to trade up to a four tool station, but by the time you buy all the tool stands etc its rather pricey!

I like the fast heat-up, thermal capacity, short hand to tip distance, the fast cartridge changes.

I think the menu system could be a bit better, but it's handy to have a few temps that you can quickly switch between.

Before the JBC I had a Hakko 936 which I still have, but it's tucked away for emergency use only. Very hard to go back to a 936 when you've just a JBC

I wouldn't mind getting a T210 handpiece and a couple of small cartridges for the really tiny stuff - my compact station would accept that handpiece as well.
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Old 27th March 2017, 9:16 PM   #28
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Quote:
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Yeah I use JBC - I have compact station with the T245 handpiece, plus I also have a micro-tweezer station.

Ideally I'd like to trade up to a four tool station, but by the time you buy all the tool stands etc its rather pricey!

I like the fast heat-up, thermal capacity, short hand to tip distance, the fast cartridge changes.

I think the menu system could be a bit better, but it's handy to have a few temps that you can quickly switch between.

Before the JBC I had a Hakko 936 which I still have, but it's tucked away for emergency use only. Very hard to go back to a 936 when you've just a JBC

I wouldn't mind getting a T210 handpiece and a couple of small cartridges for the really tiny stuff - my compact station would accept that handpiece as well.
Good feedback. Your right, they were rather pricey but I liked the units.

I believe the idea for us also changing over was so that we could 'log' the temps used when soldering, as we needed to write down two different temperatures for two different tasks (as we used different types of solder), but in the end we still ended up writing that down manually on a form.

Your right in regards to going back to the older units. Before that, we used Weller from memory (WSD81? I can't remember), but its in my garage now too since they wanted to get rid of them. Nothing wrong with them either I guess, but not sure I'd go back to one handle piece when the JBC allows you to have two hooked up

Did you ever look at the new type of Weller units to compare? At the time of choosing, we did get one of the new Weller units (think it was a WX2). Personally I never got to use it, but I think it was the preferred unit by our Tech Liason but because it was so new, Weller couldn't deliver the units in time and were having supply issues if I recall correctly.

Oh the memories and playing with tech...
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Old 15th April 2017, 1:50 AM   #29
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Just wanted to add, epic thread! Love your work Axle.
Very interesting and informative.
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Old 15th April 2017, 8:18 AM   #30
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Awesome thread nice work
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