So i hook up my new 32 pill the other day and omg, not good. The pass thru tune is horrible and the output tune is really bad too. So i go for it anyway, i hit it lightly with the 4 pill driver. 600w carrier swing 4500w, ok not bad. Then that all so familiar smell hit me. Damn, smoked something. Wtf? Took some pics, what do you amp gurus think caused or can cause this? Resistor toasted and wagon wheel resistors got real hot. Everything else looks fine on inspection. Fyi: its not my setup, 2w reflect at 4500w, vswr is 1.02. My 24 pill, 16 pill etc all are very happy. Seems like my builders quality suffers more the bigger the box gets.
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New 32 pill is a dog :(
- Thread starter groundwire
- Start date
Imbalance between the 2 sections. One section probably has a crappy tune from a bad/weak cap so the combiner let go. Because of that, the output combiner got hot trying to balance everything back out.
That's some nice, clean looking work though.
That's some nice, clean looking work though.
Thermal camera is the only simple way I know. Pull all the caps and check to make sure they're in spec. Also, a large difference in hfe between 2 transistors in a section can cause this as the higher gain is pulled down by the weaker transistor and struggles to keep up with the "equal" section.
*edit to add*
Say one transistor has an hfe of 27 and the other is 7, the transistor is still "good" so it won't smoke the 10 ohm....yet. But the imbalance will be basically the same as it would with a blown transistor.
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Every single transistor must be pulling the same power as the others, or those fat resistors on the combiner (wagon wheel?) will get hot.
Two possible reasons. First, one failed RF power transistor. Only takes one to do this. It will look perfect on the outside even if it's no good. Can't use the appearance to judge if it's working. The thermal camera will reveal a transistor that's not pulling its load. Will be cooler than the other ones around it.
Second, a failed part connected to one of the sixteen pairs of transistors. In a new amplifier I wouldn't so much be looking for a capacitor gone bad yet, but for one that's not quite soldered correctly. More than once I have seen a brand-new amplifier with one lead on one transistor just not soldered. At all.
Won't say what brand. Any name can be counterfeited.
73
Two possible reasons. First, one failed RF power transistor. Only takes one to do this. It will look perfect on the outside even if it's no good. Can't use the appearance to judge if it's working. The thermal camera will reveal a transistor that's not pulling its load. Will be cooler than the other ones around it.
Second, a failed part connected to one of the sixteen pairs of transistors. In a new amplifier I wouldn't so much be looking for a capacitor gone bad yet, but for one that's not quite soldered correctly. More than once I have seen a brand-new amplifier with one lead on one transistor just not soldered. At all.
Won't say what brand. Any name can be counterfeited.
73
Thanks a million guys, im pretty bummed out about it. In my eyes, $4k on an amp and 4 months of waiting, it better be done right the first time and be working correctly. No bad in / out tune, loose remote jack, open hole in the cabinet, imbalance burning stuff up etc. Now i have to spend big BIG money to pack it up and send it back all the way to the E. Coast to get checked out. I hope i dont have to wait another 4 months to get it back 
It could have simply had a defective transistor from the get go. It worked and tested fine but the internals were weak and when put under load, it showed. The builder probably only gave it a few keys, checked the tune and power output then shipped it. He wouldn't have noticed anything if the lid was on and the meters were reading good. Then when you got it, things had already started breaking down and when you keyed her....she let go.Thanks a million guys, im pretty bummed out about it. In my eyes, $4k on an amp and 4 months of waiting, it better be done right the first time and be working correctly. No bad in / out tune, loose remote jack, open hole in the cabinet, imbalance burning stuff up etc. Now i have to spend big BIG money to pack it up and send it back all the way to the E. Coast to get checked out. I hope i dont have to wait another 4 months to get it back
From my experience, when I see a combiner resistor on a 4 pill section that's burnt that bad, it's more than just an imbalance from a cap. It looks more like a transistor is bad in that section.
Im not happy with the input/ output tune anyway. I get bad reflect on the pass thru tune and output as well. I know its the box because all my other ones are basically 0w reflect in and out. Oh well, back she goes
Hopefully the builder will find something covered under warranty and you'll just be stuck with shipping.
Its literally brand new. If an rf transistor fails due to manufacturing defect i better not get charged for it lol. He knows me and that i know how to properly operate radio equipment. Im pretty sure he wont charge me labor and return shipping. If i have to pay for parts, whatever no big deal. I just hate the headache of it all. Shouldn't happen, not for this kind of $$$$. Although i do understand component failure is not a persons fault. Its the cheap chinese crap we are stuck using lol.
I can see at least one burnt combiner resistor, and another one that appears to have probably got very hot.
At least you know it is one of the 4 transistors. It looks like one leg of the metal clad might be touching the flange mounting screw.