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Tracking down a hum.

Today when I powered up my system, I noticed a hum from my tube pre amplifier, a Rogue Audio Model 99 (line stage only). It is worse when first powering up. It is absent through my headphones, (using an external headphone amp and the record button on the pre-amplifier)  Listening to speakers the noise is present but diminishes and eventually goes away as the system warms up.
I'm using the Rogue to send a signal to a Musical Fidelity X-P200.
I don't think the issue is the tubes as I'm using Tung-Sol 6sn7 tubes with less than 300 hours on them.
I bought this Rogue used and had to take it back to get it fixed as one channel kept cutting out because of a bad solder in the out put jack. Maybe something else failed?
TIA

dierksb
noromance's avatar
noromance
9,465 posts
 

I was on the money! 😉

thecarpathian
4,172 posts
 

So much for those two 'experienced' techs.

dierksb OP
47 posts
 

@noroamnce, kudos. I'll know more about which caps were replaced when I see the invoice on delivery.
@thecarpathian. The explanation given to me is they were unable to get schematics with values and were reluctant to work on it as such. Rogue would not provide them either.

 

thecarpathian
4,172 posts
 

Ah, thank you for clarifying.

dierksb OP
47 posts
 

Okay I got the amp back today. I was hoping for an itemized list of parts replaced. I didn't get one. It looks like the replaced all the capacitors in the board nearest the transformer, and one resistor was replaced. I'm listening now and so far so good.

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