Hello Manfred,
I am not home now so I can't be more presice about the location of the transistor.? It is on the bottom side of the motherboard close to the front panel and is connected to TP602.? If you measure the voltage at TP602 while changing the cotrast, you should see the voltage change. If it does not change, then the transistor is bad.? The transistor is nothing special, it just regulates the DC voltage. See the service manual http://www.doe.carleton.ca/~nagui/labequip/synth/manuals/e4400335.pdf, page 72 of 335.? This will show a block diagram of the contrast regulator.? It is? very simple circuit.
Let me know if this helps.?
Tom
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On Monday, March 07, 2022 05:11 EST, "Manfred Hund (DL2IAO)" <manfred.hund@...> wrote:
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Hello Tom, did you have mir informations about the transistoe which could be blown? Don't find anything in the web.
Manfred
On Sat, Mar 5, 2022 at 04:48 PM, Tom B wrote:Hello Manfred,
Good luck. The difference in the FW1 and FW is the polarity of the contrast bias.? If you put in the FW1 in the older model it will blow the transistor that supplies the contrast bias.? The later motherboard has jumpers to set the bias polarity.
There is a long thread here where someone replaced the LCD in his ESG, see:
Tom Bryan
N3AJA
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On 3/5/2022 10:17 AM, Manfred Hund (DL2IAO) wrote:
Hello Tom, i do have exactly the same problem, no jumpers on the motherboard and a?DMF-51043NFU-FW1, that will not work. The original MDF-50562NFU-FW has stopped to work, so I need a new LCD. Did you have a solution for the problem already? Best regards Manfred
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