This one really has me scratching my head...

[Azvaquero]

Hello all,

I have a small Peavey Blazer 158 amp that I use for practicing. Got it used. When I turn it up (up a little bit, but not to huge clipping type levels), its output is a little fuzzy/distorted. Sounds just like a fried IC.

Right next to this amp is sitting basically the exact same amp (a Peavey Rage 158), basically same thing except it does not have reverb. It is not blown, and sounds great, nice and clean, so I have a good reference to compare the Blazer to. The Blazer cannot be turned up even half as loud with the distortion getting pretty heavy. So I am near 100% certain that the amp was just turned up too loud and the IC overheated. Have had this problem on other small wattage amps before and have replaced the ICs and fixed the problem every time.

The IC in this amp is a TDA 2040. I ordered 5 of them in a pack.

When I replaced the old IC just today with a new one, no sound. Nothing. No pops, no hiss, nothing whatsover from the speaker.

I put the old original one back in, just to see if I had accidentally bumped something else. Amp worked just as before (full sound, with the distortion of course).

Took the original back out, put in a second IC (not the first one I tried), thinking maybe the first one was bad. Nothing. Again.

Something is obviously up with the IC's that I have. They must not be the correct ones. Am I missing something?

The original IC says: TDA 2040 ; 80A905; SING . The replacements say TDA 2040 ; 82H411 ; SING

Any ideas why the replacements would not work?

Thanks in advance!

[Enzo]

Did you buy them on ebay? They may be counterfeit ICs.

Put the working old one back in. Plug a strong signal into the CD IN jack. How does that sound out the speaker?

Try headphones. Does it sound low and distorted there too, or does it sound like the other amp through the phones?

Any chance it is the speaker itself? You could exchange speakers between the two amps as a test.

Turn the reverb up midway, and rock the amp to crash the reverb springs. Does the crash sound bad like the rest or does it come out strong?

[Azvaquero]

Thanks Enzo, for the suggestions. Yes, I bought them off Ebay. I buy parts off there when I need them (I'm in a small town and not much choice around here locally) and have not had any problems yet. Could be a first time though.

I'll do as you suggest and will post back, probably tomorrow if I can get to it. Very good suggestions. Thank you.

[Azvaquero]

Just a followup. Enzo, it appears that you are right about the IC's being counterfeit.

I pulled the non-working Chinese IC (labeled "SING"), and installed the known good IC out of my working amp, the Rage, into the Blazer. Both use the same IC, a TDA2040. Now the Blazer works great (except the reverb now quit working for some reason, which is the entire reason I wanted the Blazer to work in the first place!).

The Chinese IC's were completely dead. I tried two out of the five that I ordered, but I will assume they were all the same. With the amp on, they "performed" as if they were not even in the circuit at all. No speaker sound, no headphones, nothing. Not even hiss or a pop when the power button was turned on.

So it appears that for the sake of a few bucks, the Chinese thought it worth their time and effort to make up some fake IC's (or maybe relabel some odd inventory they had sitting around that was otherwise obsolete and useless), and sell them to some dumb Americano (me!)

I have now ordered two out of Miami, so hopefully I will be able to get one to work in my Rage to get it back up and running.

Thank you Enzo for your help, and your expertise. The lesson to be learned I guess (which is why I am posting this for all to read), is that things that you could not possibly imagine the Chinese being able to profitably fake, can in fact be profitably faked. With the facts layed out as I have outlined them above, I cannot draw any other conclusion.

One final question -- the reverb. Is there anything anyone could suggest that I could focus on (outside of a loose wire or something), in general, that commonly goes wrong with them? It is a simple spring reverb. Can they for instance be unplugged from the board and tested with an ohmometer? Is there anything else that commonly goes wrong when one goes out?

Thanks!

[Leo_Gnardo]

It is a simple spring reverb. Can they for instance be unplugged from the board and tested with an ohmometer? Is there anything else that commonly goes wrong when one goes out?

Yes, you typically see about 200 ohms on a reverb output, and anywhere from 1 to 200 ohms on the input, depending on what circuit intends to drive it.

What else can go wrong? The springs fall out. That pretty well does 'em in.

[TomCarlos]

What Leo said.... I have also seen the wires connecting to the transducer fall off.

What this video for more info... Guitar Amp Spring Reverb Diagnostics.

[AmpFix]

Buying ICs on eBay is a sure way to get counterfeits, especially when the seller is in Asia.

eBay does have some good sellers in the UK, Canada and USA as well as a few in Poland and Turkey. You really have to do your research and talk to the seller in terms of the origin of the parts.

Mouser is always my #1 source but for certain hard to find items or out of production, eBay can be a decent source.

Make sure you leave negative feedback!

[rjb]

Buying ICs on eBay is a sure way to get counterfeits, especially when the seller is in Asia.

On the other hand, I would feel pretty safe buying directly from Tayda.
Headquartered in Bangkok, they ship from Singapore, Thailand, and U.S.A.
I've never gotten bogus parts from them.

EDIT: Tayda stocks TDA2040 at $1.92 each
https://www.taydaelectronics.com/cat...ult/?q=tda2040

[Sock Puppet]

Don't forget the fake transistors. I ended up scrapping an amp before the penny dropped/

2SC5200 on the left, copper base. Pretend version from China on the right (steel base) ... just enough silicon to test like a transistor!

[Azvaquero]

Thank you everybody for your input. I have filed an "item not as described" case so the seller can eat shipping both ways if he wants the bogus parts back. I'm still mind boggled by the fact that someone would bother faking some parts worth so little. When I told my teenage son about it, he shook his head and said something about "just a bunch of dogs scrapping for a bone~"!

I got the reverb working -- just had to pull the connector from the transformer/coil/whatever it is called, on one side, to get a better connection. One side measured around 200 ohms, the other around 50 ohms. Does this sound right? The reverb is not very strong, even cranked clear up. Usually I don't like too much -- I keep reverb on most of my amps down to 2 or 3 on the dial. This one I max out and it still doesn't have enough. Seems to have less than it did before, but I'm not sure -- maybe I'm not remembering correctly.

[Enzo]

ANy chance the two connectors are on each other's posts?

[Azvaquero]

ANy chance the two connectors are on each other's posts?

Yes, the tank sits on foam pads, stuck down with double sided tape. Pretty hi-tech, in other words. It came off while I was monkeying with the authentic bogus Chinese parts, so I stuck it back down and must have initially put the connector to the board on backwards. When I took a resistance reading, one side did not read either, but started reading after I pulled and reconnected the connector at the transducer. So it could have been one or both. It's working now, but not very strongly it seems.

I simply cannot understand the logic of the Chinese. They go to the effort to make bogus parts, knowing some people will try them right away and find out they don't work, file a case against them, they then eat the parts and the shipping, and for all their trouble and effort, disappoint a customer who will then be afraid to buy parts from China, and many of whom will talk about it on a forum like this, making even more wary customers, etc, etc. makes no economic sense to me! I,m still scratching my head on this one, but now for a different reason!

[Enzo]

You are making a HUGE mistake. You are asking about "the Chinese" as if you could ask such a question about "Americans". Some AMericans rob banks, other invest in them. Some Americans support Donald Trump, others Hillary. Some Americans like huge SUVs, while others like to drive a Prius. Some Americans like meat, others are vegans. Some Americans like rock and roll, other like droning dreary chamber music. Some Chinese run scams, others are honest businessmen. The scan isn;t because they are Chinese, the scam is because they are dishonest individuals, just like dishonest Americans who scam people.

I live in an old folks home. Every day we get calls from AMericans trying to run scams to get money from us. Fake IRS agents demanding we settle tax bills on the phone. FAke American computer people telling us we have a virus, and they need our passwords to remove it. Americans coming to our homes to "contract" us for paving the driveway, they take the check and you never see them again. Oh, and the American who drives up to your house with a freezer full of meat, telling you he had a cancelled order from a restaurant he cannot take back, and would sell to you cheap. None of tht is because they are Americans, it is because they are dishonest individuals.

Your Chinese guys know most people won;t take the trouble to file a report. They also know that the crap they sell is virtually worthless, as in costs little, so if a few orders get their payments yanked, it is just the cost of doing business. It makes economic sense because they can make huge sums of money cheating people. it isn't fair or moral, but like many scams, it pays off.

[DrGonz78]

The scam artist knows has no borders. To the hard working and honest folks all around it is sacrilege how they earn their living. However, with every burnt chip the scam artist's karma will be sealed and in the next life they will return as a fake LM391N chip, surely burnt up in some Polytone meltdown.

[Enzo]

Maybe he can come back as a pack of bovine insemination gloves.