Distortion

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Latteman
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Distortion

Unread post by Latteman »

I have quite a few used Nva amp boards I’ve collected over time for spares repair and general experience/ experimentation.
I’ve successfully restored a pair with no blue smoke when connected to the psu- when connecting music I have a distortion in one channel only- there is music but with distortion.
The amp tests well on all points via a multi meter except one of the resistors that measures 0.8 instead of 0.6ohmn.
What I’m asking is -what could be the cause of distortion- faulty resistors/ transistors tp142/147 or…….?
Cheers for any advice
Just to confirm these were faulty boards to begin with
Analogue Source -
Denon DP47f; AT-VM95SH
GL-59; ARB uni pivot; AT- Signet
Ifi Zen Phono
Doug Self balanced Pre amp
Akai 4000DS mk2 R2R
Digital Sources- Argon Pi4 v2; IfI iUSB 3.0, Ifi Neo idsd Dac;
Tidal / Radio Paradise
Amplification Nva 300va mono blocks
Speakers Lii Audio F-15 in Open Baffle; Ls6
Weiduka AC8.8- for digital sources
Mini BMU for analog sources

Geoff.R.G
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Re: Distortion

Unread post by Geoff.R.G »

Latteman wrote: Tue Mar 19, 2024 1:51 pm I have quite a few used Nva amp boards I’ve collected over time for spares repair and general experience/ experimentation.
I’ve successfully restored a pair with no blue smoke when connected to the psu- when connecting music I have a distortion in one channel only- there is music but with distortion.
The amp tests well on all points via a multi meter except one of the resistors that measures 0.8 instead of 0.6ohmn.
What I’m asking is -what could be the cause of distortion- faulty resistors/ transistors tp142/147 or…….?
Cheers for any advice
Just to confirm these were faulty boards to begin with
Difficult to say without a circuit diagram but, if the incorrect resistance is causing a transistor to run on a non-linear part of the curve then, yes it could be the cause.
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Latteman (Tue Mar 19, 2024 7:14 pm)

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Latteman
Posts: 1222
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Location: S. Yorkshire
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Re: Distortion

Unread post by Latteman »

Bit of progress made- changed the 7w cement resistors and renewed a lot of the general solder joins.
Had sweet music for a few mins then the distortion returned
I am waiting on a delivery of a pair of Tip - after that I wil have exhausted my basic repair knowledge
Analogue Source -
Denon DP47f; AT-VM95SH
GL-59; ARB uni pivot; AT- Signet
Ifi Zen Phono
Doug Self balanced Pre amp
Akai 4000DS mk2 R2R
Digital Sources- Argon Pi4 v2; IfI iUSB 3.0, Ifi Neo idsd Dac;
Tidal / Radio Paradise
Amplification Nva 300va mono blocks
Speakers Lii Audio F-15 in Open Baffle; Ls6
Weiduka AC8.8- for digital sources
Mini BMU for analog sources

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