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  #16  
Old 09-21-2016, 11:59 AM
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martingitdave martingitdave is offline
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Quote:
Originally Posted by RCGuitar View Post
The RTV silicone (while not pretty) is used to hold the caps and power resistors in place and to keep them from moving during numerous hot and cold power ups. You don't want them popping a solder joint as they heat up and expand.
I agree with this. It might have been a (counterintuitive) case of too little RTV, not too much.

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  #17  
Old 09-21-2016, 02:18 PM
jonfields45 jonfields45 is offline
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My bet is they were not able to reproduce the problem and loaded it up with hot glue hoping that helps. Intermittent problems are a pain!

My friend's active bass had an intermittent condition where the output was distorted even with a fresh battery. I looked inside, did some of the usually checks and found nothing wrong (since it sounded perfect regardless of what I did). There were three tin plated connectors and I soaked them with Deoxit and gave myself credit for a "repair".

Well now a couple years later it did it again and again it worked perfectly on my bench. This time I decided to take the connectors apart to really thoroughly clean them. Low and behold that was all that was holding the circuit board in place and as soon as it came out I saw a broken solder joint with one of the many wires soldered to the back of one of the pots just laying there. I cleaned the connectors and fixed the solder joint. And again I've given myself credit for a repair...

I think the most important concession from Carvin would be an extension of the warranty for one year after their repair.

I've had my share of intermittent problems and it has motivated me to use the least expensive, high quality, least integrated solution for amplification so that I can relatively inexpensively get rid of the offending item rather than chase ghosts. Today that is a single Yamaha DBR10, a Yamaha MG06x mixer for acoustic gigs, and a Boss FDR-1 (Fender Deluxe Reverb modeling pedal) for electric gigs.
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Last edited by jonfields45; 09-21-2016 at 02:28 PM.
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  #18  
Old 09-22-2016, 07:57 AM
jonfields45 jonfields45 is offline
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A few other random thoughts...

If you send something back, put a small mark somewhere with a Sharpie; that way you can tell if you got a new or refurb instead of a repair.

To differentiate new from refurb, or repaired from no problem found, look the PCB(s) over carefully for a little shiny residue (rosin). In production that is cleaned off but in rework it is rarely removed.

For this particular problem which seems to be temperature and humidity related, and infant mortality, I would guess you have an active component (all of which will be encapsulated in non hermetic epoxy cut with silica with no RTV prior to encapsulation) with a bad wire bond. You'd be shocked how cheaply non milspec electronics are made, and still work pretty well. Why they eliminated the other PCBs from being returned must reflect some experience they have with the problem, or cost containment.

I got a replacement PCB for my T5z from Taylor earlier this year and spotted the rework rosin on all three pots. Since it was free and worked, I did not complain :~).
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  #19  
Old 12-07-2017, 09:03 PM
LowCBassStudio LowCBassStudio is offline
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Hey if anyone is still here ... I recommended the AG300 to a student Xmas 2016, and here it is Xmas 2017 and Carvin Audio is busted outa business.

This AG300 amp has a little crackle/fizz/AM-radio whine coming out of the speaker even with input volumes and master all the way down...but NOT that loud hiss that fatocaster caught on video.

However, NO noise in the headphone output nor the stereo music input jack with my iPod sound fine. So that means the preamp section is OK. So what's the problem? And has anybody found the schematic?
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