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August 20, 2019, 11:40:47 AM

Author Topic: Reduction with Integration one channel out [resolved]  (Read 374 times)

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Offline Jefe59

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Reduction with Integration one channel out [resolved]
« on: April 24, 2018, 02:32:08 PM »
Hello,
First post here. Can anyone help? I have a reduction phono pre with integration upgrade that has bee working fine for months. The left channel has gone out. No noise or hum, just silence. The tube is not lit, the leds on the socket are not lit, and the leds on the C4s board are not lit. Can't find any bad solder joints.

Voltages: 2:   77.4
              18: 112.5
              26: 112.5
              31: 112.5
Right channel is fine. problem does not follow the tube when I switched them. Any Ideas? Thanks in advance.
« Last Edit: April 25, 2018, 03:30:08 PM by Caucasian Blackplate »

Offline Paul Birkeland

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Re: Reduction with Integration one channel out
« Reply #1 on: April 24, 2018, 04:28:25 PM »
The tube is not lit
If the tube isn't lit, then that's what you want to focus on first. Don't worry about the rest of the symptoms, they'll probably go away when you get the tube glowing again.

On pins 4 and 5 of each 9 pin socket there's a shielded twisted pair of wires that feed 6V to heat up the tube.  A loose connection at one of the sockets or up on the 5 lug strip where the other end of that STP connects will cause the tube not to light up.

Checking the DC voltage between 33 and 34, as well as 36 and 37 will let you know that at least the 6V is available to heat the tube.  If it's not, let us know and we'll pursue that further. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Jefe59

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Re: Reduction with Integration one channel out
« Reply #2 on: April 25, 2018, 01:35:26 PM »
Thanks for the reply. There was a bad solder connection on pin 4 of the tube socket. I re-did the connection and the channel came back to life.
Thanks!