CurtPalme.com Home Theater Forum

[Ohmess]

So, I've been modifying my Marquee, sort of following relying on the Marquee Modifications and Performance Enhancement thread here and I have a question.

How do those of you who do mods check your work after you are done?

I've done the fan mods and resistor mods on my LVPS; got the projector to fire back up. I did the resitors on my HVPS; fired back up. I did the .47ohm 1/2 watt fusible resistors on the VDM, along with the CVA resistors, including the 48 1.2 ohm resistors, and after some tinkering the I got my baby to fire up again.

Over the weekend, I worked on my neck boards (but have not yet put the modified ones in), and did the 12 .47 1/2 watt resistors on the VDM. After changing only these 12 resistors, I am having trouble getting my projector to fire up again. I get a handful of clicks, but no whoosh, and then an LVPS error light.

So, are they tests I can do to narrow down my problem? (My second projector is still in storage several hundred miles away).

[Nashou66]

I always do a few part swaps and test, but with the VDM and the CVA its hard to do as you have to put it all back together to test, so i did the whole upgrade at once and tested. make sure you have the connectors on right, if the connectors are of by one pin you wont get it to fire up. But i never got a LVPS error if they are not on right. pull teh LVPS and look at it closely. make sure nothing has gone bad and check the fuses. First check the front of the LVPS for any of the diagnostics lights. if any are on let us know. The VDm has +/- 5 and 15 volt I don't think it has a +/- 24, thats on the CVA for sure. make sure none of the fusible resistor you put in burned. Aslo check your solder joins and make sure you didnt cross anything . I also do one part at a time, i dont remove all the poarts and then put in all new, its too easy to possibly mix up locations or forget a part all together.
So what tinkering did you have to do on the VDM? that is most likely the place to look first.

Athanasios

[Ohmess]

[Tim in Phoenix]

Hello

Pop the lower front cover, try another power-up, and see if any lvps leds stay on, indicating a shorted rail.


.

[Ohmess]

Ok -- so I checked all the resistors I installed, and one of them was way off. I replaced that puppy, and put everything back together.

I appear to still have an LVPS problem.

When I hit the power button, I hear the relays click as they normally should, but right when I should get the whoosh, she shuts down. I get no error lights.

If I then hit the power button again, the LVPS light comes on in the back, and the third light from the right on the front of the LVPS blinks. (My projector is on the ceiling, so this would be the third light from the left if it were on a table.)

Thoughts?

[Nashou66]

Thats the -24 volt line, for future reference from left to right floor mounted: +15=-85=-24=+5=+24=+85=+15. what resistor was off and what do you mean by off? as In Ohms?Or as in Mounted/soldered location? From the looking at a spare rear set of boards i have it have to be on the CVA board, the VDM doesnt have a 24 VDC line.

Athanasios

[Ohmess]

The changes were to the CVA board. The resistor was in the right place, but the resistance of the resistor was nowhere near where it was supposed to be. I believe it was R318, and the measurement was in kohms, not fractional ohms as I had expected. The VDM changes were made earlier, and I have had the projector running since I made the VDM changes. This problem arose after changing the same .47 ohm resistors in the CVA that I had changed in the VDM earlier.

What can I tell or check based on the LVPS light that is on?

[Nashou66]

That is on the green convergence circiut, I would recheck it, also I think the PJ will fire up if you disconnect the convergence amp, DO NOT DISCONNECT THE VDM !!!!!. But i am not to sure of that as the LVPS might not let the PJ fire up if does not sense a load on the 24 volt rail, but i think Tim would know better. Well you can try two things then Disconnect the main connector to the CVA the one that has the two small PCB'a and ribbon cable. Or first try disconnecting each of the connetors on the CVA that go to the convergence coils. But if something is shorted on the CVA the convergence connector removal wont help as the circuit will still be in play.

I had a simmilar problem on my FCM where i added resistance to the 24 V line and it blew 6 mosfets. I would go through the entire Green circuit and measure the resistors again and if your MM has a diode checker you can check the mosfets too or just measure the resistance trough the different pins , compare to ones on one of the channels you did not put the wrong resistor in. if any are different it could be bad. when I get time i have a spare CVA i can check the Mosfets and diodes.

but recheck 318, also check these resistors R321(300ohm), R323(68ohm), R310(100ohm) for the mosfets and diodes it could be any of them in the green channel.

I have added the CVA schematics so you can look along the lines where R318 are tied into, but ciurcuits are complicated and any think can go.


Athanasios

[Ohmess]

Ok. Went through disconnecting each of the connectors to the convergence coils; no joy. Tried disconnecting the ribbon cable, no joy.

So, I started checking resistors: R318 reads 9.6 ohms; R317 reads .874M ohms (and this one read fine prior to this latest round of tests). So, these need to be replaced again.

R310 reads 1.7 ohms (and R 301 reads .3 ohms). More problem children.

R321 and R323 are ok.

In addition, R415 reads 282.2 ohms, as does R515 on the blue circuit. What should I replace these with?

So, I found some things that need replacing.

Can you describe please how to check the mosfets and diodes? What am I measuring, and where do I take the measurements?

[Nashou66]

when you pulled the ribbon cable was there an error still on the LVPS?

Athanasios

[Ohmess]

Well, I hadn't kept track of whether I had an LVPS error when just pulling the ribbon connector, and I had taken the projector apart to check the resistors. I put the projector back together, and without the ribbon connector attached it fired up! Not only did the relays click, but I got a whoosh and a picture.

I turned the projector off, attached the ribbon, and tried it again. I got an LVPS error this time. I pulled the ribbon off and it fired up again.

[Nashou66]

Yepp a short is on your CVA somewhere I bet one of the mosfets went bad or a diode and maybe soem more resistors. I need to check the value of what you listed before on my board as resistance values can vary while on a board. In a few hours. At least you know its the CVA now.

Athanasios

[Ohmess]

Thanks for your replies. That is very helpful.

I have another CVA, so I am pretty sure about the bad resistors I have identified. R317 and R318, of course, are the .47 ohm resistors I just replaced.

Both R301 and R310 should be 100 ohm. I was going to buy 100 ohm, 2w 400 volt resistors part number 588-OY-100-E to replace these.

I asked about the replacement for R415 and R515 because I don't know a lot about the different types of resistors. I can tell they should be 560 ohm 3w resistors, but in looking for replacements I am not sure what type of resistor to buy and the proper voltage. Can you help with that?

Also, I could use some guidance on the basics of measuring mosfets and diodes.

Cheers...

[Nashou66]

here is how to test diodes and transistors

http://www.electronics-radio.com/articles/test-methods/meters/multimeter-diode-transistor-test.php

here is how to test a mosfet, some meters do not put a high enough voltage to the mosfet for testing .

http://www.4qdtec.com/mostest.html

Athanasios

[Nashou66]

I dont think for those 100ohm you need that high a wattage, 1/2 watt is fine i think, let me look at the service manual parts lis as they some times list the wattage also and material.

Athanasios

[Ohmess]

You are correct. 1/2 w metal film according to the parts list I have. thx.

[Nashou66]

Since you have a spare you can use that to compare parts reading to your bad board. But remember some parts measure best if out of the PCB. Some capacitors still have voltage in them and current can still be running through the circuit. So you may have to remove the mosfets for measureing, measuer all diodes and transistors too. Its up to you though if you want to go through all this as you have another board. But i love to find out what went wrong and would keep pressing on. Over the past year I have learned much on electronics and especially the theory of the Marquees working. i must have read the entire service manual 100 times and each time a little more sinks in.

Athanasios

[Ohmess]

Yes, I have another board, but I have done the 24 1.2 kohm resistors, the 12 10uf 350 VDC and 18 22uf 100VDC caps, and replaced all the milar caps with Wima Poly caps. So, I am getting rather attached to this particular board.

I found that diode D300 is kaput. Can someone help me translate what I need. My lack of basic circuitry knowledge is holding me up again.

The parts list I have lists "DIODE - REC IN4003 1A 200V" Athanasios has three pictures of the red circuit version of this same diode in his CVA modification pictures in the Marquee Maintenance and Mods thread, on P13 where he illustrates the installation of the 1.2 k ohm resistors. The red circuit diode is in location D100.

Also, transistor Q 301 is no good. The parts list I have reads: "D45VH10 PNP 80V 15A" One of these is pictured in that same tread. In the second and fourth picture dealing with the 1.2 k ohm resistor install, you can see Q101, which is the fourth transistor from the right in these pics. That is the red circuit version of the same transistor I need to replace.

Any help would be appreciated.

Cheers,

[Nashou66]

http://www.newark.com/35C0674/semiconductors-discretes/product.us0?sku=fairchild-semiconductor-1n4003

http://www.newark.com/26K3588/semiconductors-discretes/product.us0?sku=on-semiconductor-d45vh10g&_requestid=88431

think you need these

nashou

[Nashou66]

oh and order extras in case mre are blown or something eles i wrong and you blow those too

Athansios