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Post by barclay66 on Jul 30, 2015 6:22:47 GMT -5
Also another question. Does anyone have an idea why C67 and C66 are replaced with smd versions of the same value? The resistors that where replaced where original carbon so I guess the metalfilm resistors are a bit less noisy. SMD parts show less stray inductance than their leaded counterparts. Maybe this has a positive effect. Making the capacitance of C17 bigger is also somewhat a mysterie to me. Low frequencies are less attenuated? Well, this isn't clear to me either. Maybe it creates more "punch" on the picture as the transfer level of the signal (DC block and AC pass) is increased in general. Regards, barclay66
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Post by barclay66 on Jul 30, 2015 5:56:29 GMT -5
I see it is a ESD suppressor. What does it protect? The electronics that make the heater voltage on another board? Hi, It is quite probable that these suppressors are there for protecting the LVPS. Especially if the corresponding tube experiences a heater <-> cathode short which can happen in rare occasions. I think that there are lots of fault sensing and/or protection circuits in a Marquee and that a great deal of simplification could be done to the boards (ever heard about "Muntzing"?). But I wouldn't do that. After all, the reason for modding boards should be to increase performance without sacrifying reliability... Regards,
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Post by barclay66 on Jul 30, 2015 2:09:46 GMT -5
I checked the surge protector there with the ohm meter it had some resistance far in the mega Ohms. How do you check these surge protectors? Hi, These aren't surge protectors but spark gaps (therefore their designation SG1 ... SG3). They are designed for prevention of arcing as they will allow for a controlled path for the energy to discharge. The spark will stay inside and will (hopefully) prevent other parts from being damaged. Therefore their trip voltage is shown in the schematic. There's no practical way of testing these as they normally will be the same as an open connection. The megaohms that you measured were the resistors R81 (10K) and R33 (22M) which form one resistor (22.01M) in parallel... Regards, barclay66
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Post by barclay66 on Jul 30, 2015 1:59:53 GMT -5
On my modified board the surge protectors for the heater where not original. In the picture they are the smd brown part that is close to the black part. Does anyone know what kind of surge protector this is? Would this one make less noise? Hi, This looks more like a ceramic capacitor. You could try measuring it if you have a capacitance meter... Regards, barclay66
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Post by barclay66 on Jul 29, 2015 2:49:44 GMT -5
Hi,
In order to rule out that the problem is related to the G2 section, You could try measuring the voltage after R81 (10K). For that You will need a DMM that can withstand voltages up to 1000V. If the voltage that is measured (should be around 500-800V, depending on the G2 setting) doesn't change with the brightness pulsating, then the problem is somewhere else. Like gjaky I don't think that it's the best idea to remove D10 and D12 and I don't see why it should do any performance improvement. You might want to check C17. It's the only coupling capacitor on the VNB. Maybe Your new cap (is it 43µF? It's difficult to read on Your schematic) is defective or quadrupling the original value isn't doing good...
Regards, barclay66
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Post by barclay66 on Jul 29, 2015 2:32:52 GMT -5
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Post by barclay66 on Jul 21, 2015 9:12:57 GMT -5
Not that i know of, but will doing this do anything for lag? Well, If the LimoPro is a real Line Doubler there shouldn't be any (if it does its job on a per-line level) or a maximum of one frame lag (the time it needs for digitizing an incoming frame and outputting it at double speed by duplicating each line). This is something that You will have to find out by testing. It could be measured using a two-channel oscilloscope where You feed the input signal to channel 1 (shifted to the top of the scope's screen) and the LimoPro's output to channel 2 (shifted to the bottom of the scope's screen). If the two curves have their peaks and lows at the same horizontal position then there's no lag. If channel 2 is shifted to the right, then the lag can be calculated by the distance of the shift multiplied with the timebase setting (ms/div or µs/div). I might be able to do that with the VP30 and the VP50Pro that I have... Regards, barclay66
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Post by barclay66 on Jul 20, 2015 5:27:30 GMT -5
Every second line looks 100% identical to the line above it on that mode. What I would rather, is if there is some way to retain the exact 240p image on screen, and every 2nd line be black, so the image would then appear as it should, instead of jaggy from the doubling. Im not sure if anything can do this. Hi, You might be able to acheive this if a specific signal can be found somewhere in the line doubler circuit: The signal that indicates whether an even or an odd line is being outputted. Using this signal You could blank out either all even or odd lines. Do You have any schematics of the BR909 line doubler? Regards, barclay66
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Post by barclay66 on Apr 28, 2015 6:01:33 GMT -5
Hi,
Mike Parker mentioned that the setting of the over current monitoring (R86) differs between the two board versions...
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