Faint hum from 6505 +

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Sjkuessel
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Faint hum from 6505 +

Post by Sjkuessel » Wed Mar 01, 2017 10:44 am

I've been trying to get rid of a little hum I have on an amp I bought. It was shipped to me and plugged it in and had considerable hum. I opened it up and found if I pushed down on a connector coming off the fx loop tube the hum decreased in volume. I could almost live with it. Used the amp for gig and loooovveed it. Sounds amazing. Next day, probably from moving it around a lot, the hum was back. So I opened it up, took it apart, and reflowed the solder on all the main circuit board connections. Put it back together and the amp is dead quiet. No hum at all. Then I remembered I forgot to reconnect the bias pot board via its 2 wire connector. So I hooked that back up and the faint hum is back. I pulled the pi tube and hum is gone. Next I pulled the fx loop tube after putting pi back in and hum is gone. Then I pulled the next tube and hum is still there. So seems like fx loop tube is the culprit right? Or why did not hooking up the bias pot stop the hum? Any thoughts or help would be appreciated

Sjkuessel
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Re: Faint hum from 6505 +

Post by Sjkuessel » Wed Mar 01, 2017 10:55 am

Also just to clarify, the hum is there with or without the fx loop on. Also retubed the whole amp. Hum was there before and after

dequelo
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Re: Faint hum from 6505 +

Post by dequelo » Mon Mar 06, 2017 3:01 pm

I have the same hum in my 6505+. Before and after retube. I guess it's normal for high gain amps, or at least that's what I have been told.

I had a strange issue happening after several hours of play. The amp would sound like I had a dirty preamp tube and I could solve the problem, for a short period of time, by reseating any preamp tube. Also noticed some scratching sounds when I adjusted the post knob on the clean channel. I used contact cleaner on all tubes and no fix. I tried several different new tubes and still no luck. I adjusted the bias potentiometer to 12 o'clock (was at 10 o'clock from factory, but was only reading 53.2 volts DC) and so far I have not had the issue again. I have not checked bias voltage after the adjustment, but plan to do so tonight.

But perhaps you could try some low-gain preamp tubes and see if that reduces the hum. I put a Tong Sol 12ax7 in V1 and a Sovtek 12ax7LPS in V4, it didn't rid the hum, but the tone is great!

Metallium
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Re: Faint hum from 6505 +

Post by Metallium » Mon Mar 06, 2017 7:37 pm

dequelo wrote:I have the same hum in my 6505+. Before and after retube. I guess it's normal for high gain amps, or at least that's what I have been told.

I had a strange issue happening after several hours of play. The amp would sound like I had a dirty preamp tube and I could solve the problem, for a short period of time, by reseating any preamp tube. Also noticed some scratching sounds when I adjusted the post knob on the clean channel. I used contact cleaner on all tubes and no fix. I tried several different new tubes and still no luck. I adjusted the bias potentiometer to 12 o'clock (was at 10 o'clock from factory, but was only reading 53.2 volts DC) and so far I have not had the issue again. I have not checked bias voltage after the adjustment, but plan to do so tonight.

But perhaps you could try some low-gain preamp tubes and see if that reduces the hum. I put a Tong Sol 12ax7 in V1 and a Sovtek 12ax7LPS in V4, it didn't rid the hum, but the tone is great!
Yeah, all the amps has some hum in badroom or silent environment, it is normal. You can't hear this hum at "normal" volume use. I mean, with a band playing together. Just when everyone stops or you're alone with the amp. You can try a noise gate pedal in the loop. It will eliminate the hum.
That scracth you hear when tweaking the pots are caused by moisture, dirt, oxidation inside the pot. You need to take the circuit off to clean the pots. After applying the cleaner move them a bit...from 0 to 10, back and forth...do it for each pot at time.
Don't forget to clean the loop jacks as well and exercise them wirh a 1/4 plug.

dequelo
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Re: Faint hum from 6505 +

Post by dequelo » Mon Mar 20, 2017 8:04 am

Thanks for the advice. Will def clean it a good bit!

I have noticed that the issue I am having with my amp (sounds like a dirty pre-amp tube socket after an hour or so of playing at loud volumes) may be releated to heat. I am now keeping the plate off where the pre-amp tubes are. If this proves to be the source of the issue, I may just drill more holes in the plate to allow air flow. Or maybe even install a small computer fan at the back to pull some of that heat out.

Sjkuessel
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Re: Faint hum from 6505 +

Post by Sjkuessel » Tue Mar 21, 2017 11:58 am

I ended up taking my amp to a tech. It had 2 different levels of hum. My amp would intermittently start humming louder than usual. Turned out it was the contacts of a 8 pin connector that came from around the fx loop tube pre amp board to the main pcb. The tech said one or more of the contacts inside the molex connector had black spots on them. Like the connections moved and current arced or something. Anyway he cleaned and polished the metal. Didn't cost much. Haven't had the intermittent louder humming problem since. However the amp still has the faint low level hum. I guess that's just how the amp is.

ScottMarlowe
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Re: Faint hum from 6505 +

Post by ScottMarlowe » Tue Mar 21, 2017 2:05 pm

Yeah arcing high voltage inside connectors is a common problem, not just for Peaveys either. Glad you got it sussed. When you noticed the hum changing when you pushed on a connector in your first post I immediately thought of a bad connection in there.

Glad your tech got it sussed.

Wickens
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Re: Faint hum from 6505 +

Post by Wickens » Wed Mar 22, 2017 8:08 pm

The hum on my 6505+ is tied to the Resonance knobs on both channels.

It's faint, but audible for sure. The hums volume maxes out around 7 on the resonance knobs and is barely noticeable from 4 or lower.

Waiting on a reply from peavey for this. Hopefully I dont need to send my WEEK old amp in for service.

Sjkuessel
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Re: Faint hum from 6505 +

Post by Sjkuessel » Thu Mar 23, 2017 1:24 pm

Yeah the faint hum does change in pitch a tiny bit when I turn the resonance and presence knobs. It's doesn't make it louder and the change is hardly noticeable. They are the only knobs that have any affect on the hum. The volumes, tone and pre knobs have no affect on the hum.

KTB
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Re: Faint hum from 6505 +

Post by KTB » Thu Mar 23, 2017 3:55 pm

Try the preamp out and send to another clean amps return and see if the hum is present. Then take a hum free signal and inject it into the return and see if it's there. This will tell you if the hum is preamp or post. The presence is post I believe

Wickens
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Re: Faint hum from 6505 +

Post by Wickens » Tue Mar 28, 2017 4:37 pm

Well, 4 days ago I contacted Peavey who directed me to contact the store I bought it from.
Now I'm waiting for them to hear back from peavey. Peavey's initial response was that this could be a few things that have happened.

After retubing the amp, I've come to the conclusion it's defective.

If this answer takes as long as it did to GET my amp; I should know what to do in a couple months and maybe a year from now someone will actually fix it.
Starting to hate that I bought this amp.

DaveWonamila
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Re: Faint hum from 6505 +

Post by DaveWonamila » Tue Mar 28, 2017 6:50 pm

Hmm...seems like a common issue. The hum in mine is only noticeable when it's very loud, but not when it's quiet...strangely enough.

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