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crackly, scratchy sound from amp

Howdy all.

I have a Fender Super 60 that a friend gave to me several months ago as "compensation" for a large favor I did for him.

Until recently I hadn't used it much. But, my playing "skill" has improved a bit, and I can actually stand to listen to my amplified noise ...er MUSIC! Now I'm having amp problems already.

Anyhow, getting to the point, here is the problem. The amp has started making a very errattic crackly-scratchy (occasionally squeally) sound. Sounds kinda like the stereotypical sound you would imagine if you were trying to imagine the sound of an electrical short.
The sound comes ONLY from the speaker.
The volume of the sound (not real loud) is the same no matter what setting I select for any of the knobs.
If I'm blasting the guitar on 6-8, I don't really notice the crackly sound. But, most of the time I try to play at a more civil volume (like 1), and the crackly-scratchy is horribly distracting.

I can feel a very slight vibration in the cabinent when I lean on the amp. It might have been doing this all along. I never really had the occasion to lean on it and peer into the back before I noticed this distracting noise.

All the tubes appear to be glowing in a consistent manner.

The crackly-scratchy sound comes and goes. Sometimes its not there at all. Other times it is extremely noticeable. The sound happens even when the guitar cord is not even plugged into the amp. I have tried turning off all the other nearby appliances (TV, computer).

Has anybody else here ever encountered this sort of problem? Any suggestions for a fix?
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Re: crackly, scratchy sound from amp

10/9/2004 5:07 PM

Randy Combs (6528) wrote:

Sounds like a preamp tube going bad.Because it does it even with the guitar not plugged in.

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Re: crackly, scratchy sound from amp

10/9/2004 5:08 PM

Randy Combs (6528) wrote:

It might need to be recapped also.

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Re: crackly, scratchy sound from amp

10/9/2004 10:27 PM

Gary Jeter (253) wrote:

What does "recapped" mean?

How can I tell which tube is the "pre-amp" tube.

Any suggestions on where is the best place to get replacement tubes?



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Re: crackly, scratchy sound from amp

10/10/2004 12:50 PM

Chuck Stensrud (13014) wrote:

Recapped means it may need new capacitors. That would be a job for a tech.

The issue of preamp tubes is a bit different. If you look at the tubes in your amp, you'll notice that there are basically two types. One type is smaller glass tubes that appear to be all glass. The other kind is larger glass tubes that have bakelite or "plastic looking" bases.

The smaller, all glass types are the preamp tubes, and the larger ones with the plastic bases are the power amp tubes. Preamp tubes are generally of the 12AX7, 12AT7, types. The best way to check is to pull one of them and take it to a music shop to buy a replacement, then replace each one of that size/type in turn to see if one of those tubes is the problem. Note that if the place you go to to buy replacements has a tube tester, the tester is not necessarily an indication of a bad tube - you still need to do a tube-by-tube replacement to check.

chuck

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Re: crackly, scratchy sound from amp

10/9/2004 11:07 PM

Anthony Sanna (869) wrote:

My friend had that problem. He dealt with in a less civil manner by whacking it really hard with something like your foot. Personally me I wouldn't whack my amp but it worked for him. He had to whack it like once a week. I don't think his kept humming thpugh when a guitar wasn't plugged in. But seriously I don't know if whacking your amp is gonna help or if its even a good idea, it sure helped my friend. He said give a good kick every couple days. I wouldn't try this at home.

AJ

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Re: crackly, scratchy sound from amp

10/10/2004 11:09 AM

Jeremy Ledford (14379) wrote:

preamp tubes, as was previously suggested. try that first, then ask again. laterz and good luck!!


germ

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Re: crackly, scratchy sound from amp

10/10/2004 3:38 PM

Gary Jeter (253) wrote:

I actually tried whacking it before I posted here. I hurt my foot the last time I tried that with an appliance. Now my wrist hurts. Amp still crackles and squeals kinda like a poltergeist is trying to squirm out around the knobs.

This unit has 5 tubes I can see.
Two big ones and three little ones.

There is a diagram with tube numbers on the inside of the cabinet.

The diagram shows that the number for each of the two big tubes is:
6L6GC.

Two of the small tubes have the same number:
12AX7A
7025
(notice that the tube number is printed on two separate lines - dunno why)

The last small tube is:
12AT7

As far as I know, the original tubes are still in the amp.

Would Guitar Center likely have these tubes?
How much would I expect to pay?
Should I buy all 5 tubes?

I know it was suggested that it is probably only the pre-amp tubes. Unless the cost is substantial, it seems like it would be worthwhile to just replace all tubes for peace of mind. Is this good logic in guitar amps?
(I really have no idea what is the normal tube life for a guitar amp.)

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Re: crackly, scratchy sound from amp

10/12/2004 4:29 PM

Gary Jeter (253) wrote:

I tried to buy new pre-amp tubes today at Guitar Center.

Luckily - I guess - they only had one of the three tubes I was trying to buy.

So, the guy at the counter - who obviously knew almost nothing about such things - asked an older guy. Who listened to my description of the problem. The older guy said if the sound builds and stops repeatedly, it is more likely the capacitor(s). That build-and-stop-build-and-stop... pattern is how my amp behaves.

They referred me to a place called Music Technology in Springfield VA. I sent an email to them. Looks like they want a $35 diagnostic fee and $80/hr for service.

A couple questions now:
1. Anybody here ever get an amp recapped - if so what price?
2. Am I throwing good money after bad to repair this old amp?
Its an OK amp. But, one of the input jacks is damaged (still works - but the plug is damaged), and it has no gizmo/switch-pedal - it has a jack for a pedal - pedal is simply missing).


Opinions and experiences welcome.
>
>



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Re: crackly, scratchy sound from amp

10/12/2004 8:04 PM

David Mackie (11057) wrote:

This isn't a highly regarded amp by Fender traditionalists, but afaik it's a Rivera design and fairly well constructed; certainly more rugged than current Fenders other than the reissues. The Music-Go-Round near me currently has one on hand, and I think it's a dandy unit, with all the power you'll most likely ever need and pretty good to excellent high-gain sounds depending on what you like. The tone controls are extremely flexible. Where it's sound is deficient imho is in that bluesy, transition from clean to dirty zone that many players covet. A good blues type overdrive pedal like a Tube Screamer would cover that pretty well. If I were in the market for an amp right now, that unit at @$300 would be on my very short list of final candidates. In fact, with it's power amp input, (to use with my Yamaha modeling preamp) I'm seriously toying with the idea of getting it anyway.

I think it's worth the likely expense of repairs. The input jack is an easy repair while they have it open, and the footswitch should not be difficult either. The amp techs could easily rig one up for you. You may want to find out what price they typically sell for in your area to see what your price limit for repairs would be, but since you didn't pay for it in the first place, it should be worth a healthy chunk o' money to get it working right. I don't think you'll find a comparable amp for anywhere near as little as you're likely to pay for getting it fixed.



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Re: crackly, scratchy sound from amp

10/12/2004 8:13 PM

Jeremy Ledford (14379) wrote:

you should still get some new preamp tubes. never hurts to have a spare set.
also, that guy at GC has no clue what hes talking about. caps cause hum problems, and splatty sounds (bad couplnig caps). they never cause squeals.
get new preamp tubes.

germ

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