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oliverg
Joined: 15 May 2007
Posts: 800
Location: Melbourne, Australia
TV/Projector: Sony G90 X2 - Vidikron Vision 1
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| Posted: Wed Oct 10, 2007 7:26 am Post subject: Vision 1 LVPS hiccupping |
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Hi all
The Vision 1 I have here has started to hic-cup on power on. The LVPS light flashes.
Is this a problem that happens alot?
I realise it could be anything but I thought I'd check here before I started trying to rip it all apart
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oliverg
Joined: 15 May 2007
Posts: 800
Location: Melbourne, Australia
TV/Projector: Sony G90 X2 - Vidikron Vision 1
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| Posted: Wed Oct 10, 2007 7:59 am Post subject: |
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I forgot, this is a version 6 LVPS
I know there is a known issue with 240V with version 5 and below which is symptom wise is very similar - the issue is meant to be fixed in this revision
Its like there's too much of a load on it
UPDATE: when I fired it up with no load, the hic-cupping doesn't occur.
Its like there's something detecting too much current/voltage - I assume on the 24v rail because that's the one flashing
If anyone knows what the fix was (apparently it is a "send back under warranty" type repair) I'd love to know!
Kind regards
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Wed Oct 10, 2007 12:07 pm Post subject: |
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That's usually an indication that there's a load on the 24 volt rail.
remove the focus board (module between the red and green CRT's). Turn on set and see if problem with LVPS goes away.
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Tim in Phoenix
Joined: 21 Oct 2006
Posts: 4409
Location: Phoenix
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| Posted: Wed Oct 10, 2007 5:15 pm Post subject: |
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Hello
Boards that drive tube yokes can take a hit from a tube arc, so the first things to try are unplugging/removing such boards as focus, convergence, stig amp. If no luck on those, proceed to vertical amp, HDM, neck boards, contrast modulation, Acon etc. You would not get high voltage if removing HDM or vertical boards but you are looking to remove the shorted board and let 24 volts come up.
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oliverg
Joined: 15 May 2007
Posts: 800
Location: Melbourne, Australia
TV/Projector: Sony G90 X2 - Vidikron Vision 1
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| Posted: Thu Oct 11, 2007 1:08 am Post subject: |
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Thanks guys - this supply says version 6 but has the POT.
If it IS the "well known" bug that happened to the earlier supplies with 240V, does anyone know the actual fix?
This is the issue (see below) - I need to identify what the actual component was that got replaced.
TECHNICAL BULLETIN
Re: Marquee Power-up Problems
A recent engineering investigation at Electrohome has determined the cause of a problem exhibited when powering on Marquee 8000 and Marquee 9000 series projectors. The symptoms of the problem are:
The projector may take a few seconds to turn on after the power key on the keypad has been pressed. During this time, the red -24V LED on the Low Voltage Power Supply (LVPS) can be observed to flash at roughly one second intervals. This LED is visible through the grillwork on the lower front panel of the projector just below the lenses. The -24V LED is third from the left in a row of seven power supply diagnostic LEDs. If there is a decoder installed in the projector or if there is an interface installed in input 0,2 (or both), the problem may become more prevalent. The problem also appears more often when 240Vac power is used (ie. Europe). Some projectors may not turn on at all. In this case, the -24V LED can be observed to flash indefinitely (at least until the line cord is removed).
This problem has been been attributed to a component value error in issue 5 (or lower) Low Voltage Power Supplies. At fault was a component which partially determined the short circuit current limit of the power supply when providing start up current to the supply rails (specifically the -24V supply). The issue number of the LVPS is indicated on the label attached to the supply. This problem has been remedied on issue 6 LVPS.
If the above description confirms that you have a faulty Marquee LVPS, then return it under warranty to an authorized Electrohome service depot for warranty replacement. Specifically ask for an issue 6 (or higher) LVPS. For safety reasons, the LVPS can only be repaired at the Electrohome service depot. Please do not attempt to open or repair the LVPS. Doing so may void your warranty.
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oliverg
Joined: 15 May 2007
Posts: 800
Location: Melbourne, Australia
TV/Projector: Sony G90 X2 - Vidikron Vision 1
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| Posted: Fri Oct 12, 2007 4:31 am Post subject: |
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Anyone? If this was just a fault that had developed it would be much easier to fix.
If it is the "known issue" mentioned above, there isn't anything actually "faulty" that is causing it - its a design fault and a lot harder to fix.
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Fri Oct 12, 2007 12:45 pm Post subject: |
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The projector was working before? Now it is in shutdown/restart mode? That sounds alot like an overload condition on the -24V rail. The power supply is designed to shut off with an overload and then about 3/4 second later to try to come up again.
Unplug modules, one at a time, and then try to turn on should lead you to the fault.
Unplugging P14, CRT heater power connector located on mother board under blue neck card, will protect tubes from damage when deflection modules are removed.
Be careful with the ribbon cables connecting to the modules on the rear heatsink as they are easily reconnected off a row.
Scott
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Thomas Jefferson
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oliverg
Joined: 15 May 2007
Posts: 800
Location: Melbourne, Australia
TV/Projector: Sony G90 X2 - Vidikron Vision 1
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| Posted: Fri Oct 12, 2007 1:39 pm Post subject: |
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Thanks for the advice.
When we first fired it up, I wasn't sure about the supply being able to handle 240V so we used a 110V step down transformer.
Once everyone here told me that 240V was OK, I put it on the mains - that's when it stopped working (with the above fault). The step down trasnformer has gone back to its owner, otherwise I could try it out on 110V again and see what happens.
When I read in the tech bulletin "The problem also appears more often when 240Vac power is used (ie. Europe)" it dawned on me that the symptoms are identical.
The power supply in this machine is made in the USA. Were the original Electrohome projector's supplies USA made or did Vidikron commision a US based company to make the supplies (based on the schemetics they were provided). Being in the USA means they probably tested the design at 110V and didn't bother with 220/240. (quite common with UK bsaed designs) I gather that not many US Vidikrons ever made it to the UK / Europe so this isn't something we would see everyday. This is all speculation but I'd love to know the answers.
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oliverg
Joined: 15 May 2007
Posts: 800
Location: Melbourne, Australia
TV/Projector: Sony G90 X2 - Vidikron Vision 1
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| Posted: Sun Oct 14, 2007 6:40 am Post subject: |
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OK, the machine fires up with the focus board removed. It goes into hiccup mode with the focus board reinstalled but with the focus coils disconnected.
When the focus coils are re-connected it hiccups as well
We have 5 Ohms between the +15 and -15V rails, we suspect the LM675 power op/amp which are the static focus coil drivers (we think) - has anyone come across this before? Without a schematic its all guesswork
Kind regards
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oliverg
Joined: 15 May 2007
Posts: 800
Location: Melbourne, Australia
TV/Projector: Sony G90 X2 - Vidikron Vision 1
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| Posted: Sun Oct 14, 2007 11:15 am Post subject: |
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I think the 3 OpAmps are dead. I'm going to replace them with these:
MC34074DG IC, SM OP-AMP QUAD HIGH PERFORMANCE
Amplifiers, No. of:4; Voltage, supply +nom:44V; Bandwidth:4.5MHz; Voltage, input offset max:13µV; Slew rate:13 µS; Temp, op. max:70°C; Temp, op. min:0°C; Pins, No. of:14; Case style:S
I have to order in bulk so if anyone finds they need these parts, let me know and I'll send you some
PS If it wasn't for the generosity of Mike Parker, I wouldn't have been able to work this out. Thank you Mike.
Kind regards
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