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 Post subject: Sherwood S5500II-tube lineup
PostPosted: Mar Sun 04, 2018 3:48 am 
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Joined: Feb Wed 04, 2015 12:26 am
Posts: 764
Hey All,

I have a Sherwood S5500II that has a noisy preamp tube, this is one with 7591.

Could I please have the preamp tube lineup for this amp? I think an 12AT7 might have been subbed in at some point for the last preamp tube, and that's the tube that's noisy. The plate structure is different.

The writing is off on ALL the tubes.

Thanks all.


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 Post subject: Re: Sherwood S5500II-tube lineup
PostPosted: Mar Sun 04, 2018 2:04 pm 
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Joined: Dec Tue 09, 2008 2:49 am
Posts: 309
Location: Farmington , Michigan
https://www.radiomuseum.org/r/sherwood_ ... _7591.html


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 Post subject: Re: Sherwood S5500II-tube lineup
PostPosted: Mar Sun 04, 2018 3:49 pm 
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Joined: Feb Wed 04, 2015 12:26 am
Posts: 764
Thank you.


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 Post subject: Re: Sherwood S5500II-tube lineup
PostPosted: Mar Sun 04, 2018 3:53 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1371
Are you getting microphonics, or a hiss? Anything in a preamp can cause noise; resistor, capacitor, cold solder joint, dirty tube pin contact, etc..

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I don't believe in experts. That's why I take my car to a plumber and my taxes to a chef.


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 Post subject: Re: Sherwood S5500II-tube lineup
PostPosted: Mar Sun 04, 2018 9:02 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5060
Location: Rochester NY USA
Some Russian and Chinese 12AX7s have very different plate structures from vintage ones. If noise is present with all inputs, try one from the phono stage.


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 Post subject: Re: Sherwood S5500II-tube lineup
PostPosted: Mar Mon 05, 2018 4:04 am 
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Joined: Feb Wed 04, 2015 12:26 am
Posts: 764
It was loud, crackling noises on the left speaker only, the volume control would kill it so it was in the preamp. The amp right now, is using a mix of old but good Mullard and Telefunken. (You can still see some of the brand markings plus the Tele has the diamond)

I might have it traced out (hopefully), apparently the three techs that worked on this before me (don't ask) missed two original coupling caps that were still left on the first preamp stage after the phono. Yes it took THREE techs to finish rebuilding it. :roll:

Replaced them and it came back up.
In test mode right now, seems to be happy so far.

Can't believe how much better it sounds also.

Thanks, guys, for the help.


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