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Loud phono hum on High Fidelity Stereo Amplifier 608

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Arjen
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Arjen Posted: Tue, Feb 26 2019 11:06 AM

I recently bought a High Fidelity Stereo Amplifier 608. It was in a very bad state but I loved the way it looked.

So, without being burdened with any technical knowledge I bought the amplifier and replaced the tubes with new ones I found online in the Ukraine.

The radio I connected worked fine, but when I connected a record player (I tried my Thorens and a Dual) I only get a very loud hum and a faint sound that should be the music.

Does anybody know where to look to solve the loud hum?

P.S.: if somebody could point me to where I could find the original knobs (or somewhat original looking) I'd very much appreciate that.

 

 

Dillen
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Dillen replied on Tue, Feb 26 2019 1:01 PM

Have you set the input sensitivity correctly?
Grounds connected correctly?
Correct DIN pins used in the socket (if DIN version)?

Martin

Arjen
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Arjen replied on Tue, Feb 26 2019 1:30 PM

How does one set the input sensitivity?

Ground is connected but I could only connect the ground wire directly to a pin on the amplifier's metal case. There is no grounding screw or something similar on the amplifier. The Thorens does not need grounding and had the same problem.

The amplifier only has RCA connections. Even I cannot do anything wrong here.

Arjen

Dillen
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Dillen replied on Tue, Feb 26 2019 4:52 PM

Has the two preamplifier boards (915H23B) been removed or bypassed?
Can you tell, if 915H50 (adapter for crystal pickup) or 915H24 (adapter for B&O SP2 etc. and some Ortofon) is fitted?

Martin

Arjen
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Arjen replied on Wed, Feb 27 2019 10:23 AM

Thank you for trying to help me.

Unfortunately, I didn't recognize the codes you gave me and because I'm not really tech-savvy I decided to upload some pictures. An overview and plates with numbers (597F52). I hope that helps.

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