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It is currently 20 Oct 2018, 19:44

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 Post subject: Re: KT120 Oddblocks
PostPosted: 03 May 2018, 20:14 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, My experience with these has been that when the input and output are nearly the same ...4 volts would be in that set...then either the resistor to ground from the adjust pin is not connected or of the correct value or the LR8 has failed and will not adjust. I would check the resistors and put a load on them to see what is up.

One unusual possibility exists as well. If the LR8 senses a fault the output will not adjust and only removing the power from it completely will restore normal operation. Usually if this happens the LR8 will fall back to some low voltage output and current limit what is produced.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 04 May 2018, 02:56 
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Joined: 25 May 2016, 16:30
Posts: 56
On the board I've built there are three regs, two set for 300v and one for 250v. All resistors are correct and correctly connected and it seems very unlikely three regs have failed instantly with no short.......I'll keep looking!


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 Post subject: Re: KT120 Oddblocks
PostPosted: 04 May 2018, 17:43 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, It sounds like a ground return issue, or perhaps an incorrect or failed B+ feed resistor. Very odd.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 06 May 2018, 12:47 
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Joined: 29 Mar 2013, 20:37
Posts: 130
Location: Italy
hi, i found the time to finish the psu boards and fix the reference voltage problem, now waiting for the wood and steel for the case to arrive.
I wanted to ask if an active pre amplifier is needed for the oddblocks to work the best (i built a forewatt in the past so I can use that) or if a passive one does the job. thank you


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 Post subject: Re: KT120 Oddblocks
PostPosted: 06 May 2018, 16:46 
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Location: Arizona, USA
Hi, For most source gear an active one will be required. The sensitivity of the amp is about 1.5 to 2.5 volts for full output. The Forewatt is designed to drive them. Modest gain and plenty of headroom.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 15 May 2018, 14:41 
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Joined: 07 Mar 2017, 03:14
Posts: 75
What should be the control voltage of the relay on the power supply circuit? A 12 V relay is needed?


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 Post subject: Re: KT120 Oddblocks
PostPosted: 15 May 2018, 15:07 
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Hi, the ones I use are 12VDC. Typical ones will usually activate at 9 or more volts.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 16 May 2018, 15:42 
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Joined: 07 Mar 2017, 03:14
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What is the voltage rating of 220uF (+) capacitor on the cathode of 12SL7 tube?


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 Post subject: Re: KT120 Oddblocks
PostPosted: 16 May 2018, 21:08 
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Hi, 16-25 volts is fine.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 19 May 2018, 14:02 
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What should be resistor (220R) watt rating which is parallel to relay and serial to 0.1 uF X2 type capacitor?


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