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help replacing speaker / general repairs
Old 27th February 2014
  #1
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blackmajik2021's Avatar
 
🎧 10 years
help replacing speaker / general repairs

I'm trying to repair this peavy TNT 100 (I think its from the 70's or 80's). Basically the thing sounds horrible. Its very buzzy, the pots crackle when turned, and many notes (especially the low end crackle).

The amp also sounds like its being overdriven the whole time its played. I cant any kind of clean sound out of it.

I was going to replace the speaker first to see if that helps, and go from there (ordered a multimeter to test the capacitors)

Its a 150w amp with a 15" 8ohm speaker. Can anyone recommend a speaker? I was looking on parts express but I'm not sure what to get / what will work.

thanks.

Sorry the images are sideways, they weren't that way on my phone / computer.
Attached Thumbnails
help replacing speaker / general repairs-photo-1.jpg   help replacing speaker / general repairs-photo-3.jpg  
Old 27th February 2014
  #2
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🎧 5 years
Clean all of the pots and jacks first. I don't think Peavey put aluminum dust caps on any speakers other than their Black Widows, and if that is indeed a BW it's probably not your problem (they're rated for something like 350watts RMS).
Old 27th February 2014
  #3
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can you tell just from looking at these pics if any parts are bad? It looks to me like those crusty ones have seen better days.
Attached Thumbnails
help replacing speaker / general repairs-photo-1.jpg   help replacing speaker / general repairs-photo-2.jpg  
Old 28th February 2014
  #4
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I ran the speaker through another amp (blues junior III) and it actually sounds pretty solid.

that means the problem has to do with the board. Bummer.
Old 28th February 2014
  #5
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John Eppstein's Avatar
 
58 Reviews written
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That's a REALLY old TNT - looks all discrete, no chips! Unfortunately those old aluminum knob Peaveys were not the greatest amps to begin with.

Cant tell much from the pics. If by "crusty" you mean the clear goop on the transformer that's just the lacquer dip they use to seal the coils. Can't tell much else. If any of the capacitors have greyish stuff leaking out the ends or show signs of swelling they're bad but not showing that doesn't necessarily mean they're good. A couple of the caps have silicon bathtub goo on them to keep them from vibrating loose.

It looks like there are a couple of large ceramic power resistors that are discolored. Those have probably overheated and and may be off value. Check and replace. My guess is that those are the emitter resistors for the power transistors (If they're emitter resistors you'll need a meter with an accurate low ohms scale to test them. The values will be a fraction of an ohm - somewhere between .27 and .47 most likely.) If those have overheated in MAY be a sign that the transistors are leaky and need replacing. I don't remember if Peavey used house numbered parts back then or not - if you can't find direct replacements commercially you might have to contact Peavey for them.

To really troubleshoot a distortion problem I'd need to put the amp on my bench and signal trace it with a scope. If you can get a factory schematic that shows voltage test points you may be able to get somewhere with just a meter but otherwise I'd say take it to a tech.

Troubleshooting solid state amps is nowhere near as straightforward as tube amps, although the TNT isn't that bad as SS amps go.
Old 28th February 2014
  #6
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🎧 10 years
first of all thanks for the detailed reply.

second, it is SUPER old. It was made 10/4/77 by "mary m."

I know a guy who fixes hi-fi equipment who might be able to help me out. I may just get a nice tube head and use the cab if it becomes too much of a pain.
Old 28th February 2014
  #7
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🎧 5 years
Like I said, clean the pots and jacks before you try anything else. A dirty pot can cause sound to drop out or become crackly.
Old 28th February 2014
  #8
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Quote:
Originally Posted by blackmajik2021 ➑️
I was going to replace the speaker first to see if that helps, and go from there (ordered a multimeter to test the capacitors)
Look for a used EV 15L or Altec 421. I see them all the time on CL for $50-75.

Quote:
I was looking on parts express but I'm not sure what to get / what will work.
Their Eminence 15" instrument speaker. http://www.parts-express.com/eminenc...eaker--290-497
Old 28th February 2014 | Show parent
  #9
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🎧 5 years
Quote:
Originally Posted by Frank_Case ➑️
Look for a used EV 15L or Altec 421. I see them all the time on CL for $50-75.
The speaker is fine, as per post #4.
Old 28th February 2014
  #10
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So I just ripped the speaker out to see what it was. Has anyone ever heard of these?
Attached Thumbnails
help replacing speaker / general repairs-photo.jpg  
Old 28th February 2014 | Show parent
  #11
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Quote:
Originally Posted by Frodebro ➑️
The speaker is fine, as per post #4.
So??? He asked for a speaker suggestion. Maybe he'd like to put in something better.
Old 28th February 2014 | Show parent
  #12
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Quote:
Originally Posted by blackmajik2021 ➑️
that means the problem has to do with the board. Bummer.

If by buzz you actually mean hum, then...

Change out the electrolytics in the PS. To get rid of the crackle, spray the pots down with Deoxit.

If by buzz, you mean the amp is distorting, then...

Old SS amps can distort when electrolytic coupling and bypass caps start to go bad, because the caps start to leak, which in turn can cause biasing to mess up in various places. No guarantees, but that may be your problem. If you feel lucky, recap it. Good reliable caps such as Panasonic FRs are very cheap these days.

Your situation is actually a lot better than if the amp was dead on arrival because that would potentially indicate blown transistors somewhere inside, which are hard to find and could easily blow out again after replacing them if you didn't troubleshoot the source of the problem correctly.
Old 28th February 2014 | Show parent
  #13
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🎧 5 years
Quote:
Originally Posted by Frank_Case ➑️
So??? He asked for a speaker suggestion. Maybe he'd like to put in something better.
He's trying to troubleshoot a buzzy sound, and was thinking it might be the speaker. Since he has discovered that it isn't the speaker, now he's trying to troubleshoot the problem with the speaker eliminated as the culprit.
Old 28th February 2014
  #14
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🎧 10 years
That RCF driver is a good quality speaker very much like a EV or Altec, probably rated for way more power than the amp produces my guess is it's not the problem. The Crackle in these things is usually in th pre amp section and not necessarily dirty pots don't let that keep you from trying a can of deoxit to them, It can't hurt. This is a common problem with the older Peavy stuff. I had one ( It was given to me) and the Bass player in the band I was in used just the power amp section with a external rack preamp using the insert/ efects loop return jack and it worked fine for him that way but the crackling in the pre amp section could not be used. it's been years since I looked inside one But I vaguely remember a grounding scheme where the jacks grounded by surface to surfaced contact. and over time the corroded very badly.
Old 1st March 2014
  #15
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🎧 10 years
I just got my multimeter & the schematic. Can anyone give me some tips on where to start? I've been watching youtube videos and reading about this all day. Not nearly as much info in the world of SS repair as tube repair.
Old 2nd March 2014 | Show parent
  #16
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John Eppstein's Avatar
 
58 Reviews written
🎧 10 years
Quote:
Originally Posted by blackmajik2021 ➑️
So I just ripped the speaker out to see what it was. Has anyone ever heard of these?
Oh f*ck! It's an RCF? Italian made, damn good speaker. Meyer was using RCFs for awhile, but they did test them and rejected the ones they didn't like. Still, good company.
Old 2nd March 2014
  #17
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John Eppstein's Avatar
 
58 Reviews written
🎧 10 years
Please refer to my first post. I used to be an authorized Peavey service center when I worked at Don Wehr's Music City in the early '80s. It's been a while but I still remember a fair amount about those amps.
Old 30th April 2014
  #18
Here for the gear
 
🎧 5 years
Hi all,

I am new to this forum and I recently bought a TNT 100 as well (a 1977 model). I am also considering replacing the stock speaker that came with the combo (in my case the original Peavey speaker). I have the following questions:

Does anybody know at how much watt the stock speakers are rated? (the manual doesn't reveal much on this issue)

ideally how much watt should a replacement speaker have (as not to damage amp and/or speaker)?

Many thanks in advance!
Old 30th April 2014 | Show parent
  #19
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John Eppstein's Avatar
 
58 Reviews written
🎧 10 years
Quote:
Originally Posted by ace14 ➑️
Hi all,

I am new to this forum and I recently bought a TNT 100 as well (a 1977 model). I am also considering replacing the stock speaker that came with the combo (in my case the original Peavey speaker). I have the following questions:

Does anybody know at how much watt the stock speakers are rated? (the manual doesn't reveal much on this issue)

ideally how much watt should a replacement speaker have (as not to damage amp and/or speaker)?

Many thanks in advance!
The amp is rated at 100 watts. You will need at least a 100 watt speaker.

Why are you thinking of replacing it? Is it damaged? What type of speaker is it? Some Peavey speakers are quite good speakers.

If the speaker is an RCF like the other one in this thread it is a good speaker, probably worth more than the amp.
Old 30th April 2014 | Show parent
  #20
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John Eppstein's Avatar
 
58 Reviews written
🎧 10 years
Quote:
Originally Posted by blackmajik2021 ➑️
I just got my multimeter & the schematic. Can anyone give me some tips on where to start? I've been watching youtube videos and reading about this all day. Not nearly as much info in the world of SS repair as tube repair.
If you're not experienced in amp repair take it to a tech. There is virtually nothing you can do without a scope and signal generator.
Old 1st May 2014
  #21
Here for the gear
 
🎧 5 years
Hi John,

First of all thank you for your response. The speaker (though old) itself is in good condition, but the frame is rather rusty. I am not an expert on dating stuff, but i understand you can retrace the origin of a speaker by certain codes that are stamped on it. I took the speaker out yesterday and found the following codes on the square magnet.

on one side :130034 7-7616
on the other side 15838H 67 7762

It looks pretty similar to the CTS and Eminence speakers that were used for Amgeg B-15s in the day
Old 2nd May 2014 | Show parent
  #22
Gear Guru
 
John Eppstein's Avatar
 
58 Reviews written
🎧 10 years
Quote:
Originally Posted by ace14 ➑️
Hi John,

First of all thank you for your response. The speaker (though old) itself is in good condition, but the frame is rather rusty. I am not an expert on dating stuff, but i understand you can retrace the origin of a speaker by certain codes that are stamped on it. I took the speaker out yesterday and found the following codes on the square magnet.

on one side :130034 7-7616
on the other side 15838H 67 7762

It looks pretty similar to the CTS and Eminence speakers that were used for Amgeg B-15s in the day
The 67 indicates that it's an Eminence.

Here's a good site for manufacturer codes.
Old 2nd May 2014
  #23
Here for the gear
 
🎧 5 years
Once again thanks, also for the very insightful website. Okay, so the original speaker that came with the combo is an Eminence: how big of a deal is this exactly (especially after almost 40 years of service)? Won't a new speaker sound better than an Eminence that has been used for 4 decades?
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