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Question Can't adjust output voltage - using alternative transistor
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bill  
#1 Posted : Wednesday, December 6, 2017 1:14:22 AM(UTC)
bill

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I couldn't find original QN1 /2 parts and used MJE15032G instead. Is this part ok?

Input voltage is approx. 18 VAC
I set VR1 to about 440 and VR2 to 997.
Output voltage is 13.2 vdc

I cant change the output voltage by adjusting VR2 (10K).

I'm only using the positive side of a V1 Placid bipolar board.

Any help is appreciated.
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bill  
#2 Posted : Wednesday, December 6, 2017 7:50:23 PM(UTC)
bill

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I had previously found a wrong transistor QN4 and swapped it for a new correct one. Maybe others were affected?
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SCompRacer  
#3 Posted : Thursday, December 7, 2017 8:12:16 PM(UTC)
SCompRacer

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I connected transformer incorrectly and ended up with fixed voltage (21v) on positive side of HD BP 2.1.

I ended up replacing QN 3, 4, 5 and Ref1B, 2B.

Check under Twisted Pear parts page. IIRC they sell the MJF122G and LT1034IZ. Check the parts list for supplier part numbers, like Mouser, digikey.

Good luck.
Rich

http://www.twistedpearau...-Denon-DVD-3910-Mod.aspx
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bill  
#4 Posted : Friday, December 8, 2017 2:56:09 AM(UTC)
bill

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Thanks. But are MJF122G and LT1034IZ suitable for the v1 boards?
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bill  
#5 Posted : Friday, December 22, 2017 3:43:23 AM(UTC)
bill

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Anyone?
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Brian Donegan  
#6 Posted : Saturday, December 23, 2017 2:13:20 PM(UTC)
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The LT1034IZ is fine. The MJF122 will not work well with the older Placid boards, as it is a darlington. I have abunch of the older transistors (FJPF5200/1943) available. I will add them to the parts bin.
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bill  
#7 Posted : Saturday, December 23, 2017 10:31:28 PM(UTC)
bill

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Thanks Brian. I placed the order :-)
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