CurtPalme.com Home Theater Forum

macgyver655 · Joined: 22 Aug 2007 Posts: 6950

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Sweet. Thanks for the offer as well Curt. I have tested most of the boards to be working with the exception of the nasty ones removed from a Runco machine that I bought basically because you had just redone the focus and convergence boards. Those I put in my 9PG. I have more parts for this damn thing then I care to admit honestly. 3-4 sets of good tubes. 3-4 of each board. Plastics and chassis. Power supplies and so on.

I will be in touch anyhow. I still need that stuff from you for the Marquee.

draganm · Joined: 08 Mar 2006 Posts: 5080 Location: Colorado

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

I could be a possibility Dragan. Although I do not have carpet in my work area. Could happen though.

I have yet to check the voltages but it does seem logical that a low voltage could cause an issue.

Getting into the base of the chassis will not be easy and from what I see from the diagrams of that board the check points are on the connector at the bottom. Is that what you meant by needing those NEC boards Curt? If so I am probably just going to send them both to you. the one with no video output and the one with low output.

**Curt Palme** · Posted: Thu Apr 21, 2011 2:13 pm Post subject:

Yeah, you'd have to individually solder wires to a test point to bring them out of the set where you can measure them. I've done it with an XG system board once, spent 6 hours on it, and still didn't get it going. I've never seen those extender boards, and haven't had the time to build any.

macgyver655 · Joined: 22 Aug 2007 Posts: 6950

macgyver655 · Joined: 22 Aug 2007 Posts: 6950

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

ha, ha. Don't know why I didn't think of that.....

Am I correct in assuming that the top row of that bottom connector is "A" and the pin on the far left is "1" component side up? I did not see a pin diagram in the board level repair manual.

As always thanks guys. Is it not human nature to overlook the simplest things and think the worst sometimes. Plus I build, tune and sell car parts. Electronics is just an interest of mine. I learning slowly and I do mean slow..........

James

macgyver655 · Joined: 22 Aug 2007 Posts: 6950

macgyver655 · Joined: 22 Aug 2007 Posts: 6950

macgyver655 · Joined: 22 Aug 2007 Posts: 6950

I tried to vaguely answer your question on capacitor values and changing them because as I said ,the answer is much larger then yes or no.

As rule of thumb in the electronics world you can increase both voltage and/or value without any consequences, however, there are some circuit that don't like either being altered. Mostly because changing the value can change impedance and if the circuit relies on a specific resonant frequency is may not be achieved and may not function. Or function poorly.

This can also be affected by the voltage value increase because the larger leeds, plates and fluid volume can on a much lesser degree affect impedance.

I wanted to find a document that gets more involved in this explanation and I found this one that is of interest.

http://www.tnt-audio.com/clinica/regulators2_impedance1_e.html

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Awesome Mac thank you for that post. I will read it and then read it and probably read it a third and fourth time just to make sense of what is going on and retain what I can.

If you do not mind my asking what affects in this peticular circuit would even changing the ESR of a capacitor have? i.e using a cap not listed as low ESR or a higher rated ESR than what was there.

Would it affect the white balance trim pots by introducing a higher resistance in those lines or would that be so minor it is a non issue?

As far as the manual I have several of them. The only one with schematics for the boards is the + models. The board level manual I have for the plains only has block diagrams and no schematics.

Thanks again my friend.

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Ok, so I was looking at the diagrams that I have and I can see that the 12v+ line feeds the 3 C3*09 caps that do indeed go to those chips.

I can also see that that 12v+ line is regulated by a 7812 positive regulator. driven by the +15V line on the main connector.

My plan is to attach a lead to the output and input line on that regulator and see if there is the correct voltage on those lines then go from there. Should be fun! I will let you guys know how I make out.

If it turns out that regulator is bad I will order a bunch and replace that. Then go on from there.

Thank-you all for the help

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Well, Tested that regulator and it has 11.9v out and 15.2 in so that is within spec in my eyes. I am going to now look to see if I can find what the output of those gain chips should be. I have video but no control over how bright that video signal is. I suspect that they might be blown.

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

Well it is either the Gain Jfet or the LM chip that is bad I suppose. I do not have a scope to test the output on the LM chip.

Would a blown cap really take out 3 Jfets or the three Lm chips? I do not remember if it was backwards I just tore it out when I saw it was bad and put in a new one.

macgyver655 · Joined: 22 Aug 2007 Posts: 6950

I really don't want to discuss this much further in open forum because I believe we have already passed the recapping part of the original discussion.

So I will offer 1 last question. Did you check "ALL" of the incoming voltages to that board like I told you to?

CxTurbo · Joined: 13 Oct 2008 Posts: 387 Location: Ontario, Canada

I respect that.

I will go over them again and double check.

Thanks for the advice.