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Amplifier help

Capt Crunch

Capt Crunch

Captain Crunch NJ Mobile
Nov 3, 2015
169
215
73
New Jersey
www.iamawesome.com
I have a Carl Built 400HD(4 2879 hg's) with bias. I run a Galaxy 979 stock radio with it with low swr throughout. One day I checked swr at the amp and noticed I was only getting about 10 watts swinging to 40 out the amp. I looked in through the vents because it has a warranty strip and can't open it and saw a resistor? blown out. The ohter 3 like it have a gold stripe on one side and looks like brown, black, and brown on the other side but the one I am showing in the picture is blown. The transistors look ok, at a glance so really can't tell.
Any idea why that would blow?
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Here is a video of the meter readings- Here is a vido of the amp-
 

100 Ohm resistor bit the dust, might have been overheated without the schematic not much to say, but it needs being made, and amp checked.
if you didn't overdrive it it can just bee a faulty component or fault in the amp.
 
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Justme said:
100 Ohm resistor bit the dust, might have been overheated without the schematic not much to say, but it needs being made, and amp checked.
if you didn't overdrive it it can just bee a faulty component or fault in the amp.
Click to expand...
Thank you. Thats what I think as well, faulty amp, but I am no tech by far. I mentioned when i switched the SSB switch it would make a noise sometimes through my radios speaker. He wasn'tpositive that was a warning sign but did not exclude it. SWR was/ is low at radio and after amp. Ran it with a 979 at 5 watts swinging to about 25 on LMR400UF to a puck mount with a Skipshooter, Predator K27, or a 102 in SS whip with a 10 inch riser. Sending it today, we will see how much Carl stands by his stuff as he claims all over the place. Already Carl told me on a FB message its a 90 day warranty which would still be in effect but the guy Frank I talked to said 30. We will see. P.S. He shows the inside in the video, not sure if you can see it better.
 
Output SWR/tuning can cause that, excessive voltage on the amp, and excessive input drive. Those three things are usually the cause of a transistor going bad, but I have seen cases where a transistor just simply fails. Had that happen recently to my T/S 667V. There is an outside chance that there was a fault in the bias circuit, but highly doubtful in the case of Carl-built stuff, as Carl knows what he's doing.


Definitely looks like the output combiner resistor has failed, so I suspect at least 1 bad transistor. The real story is if the transistor failed short or open. If it failed open, it won't take out the 10 ohm resistor that goes between the base and emitter, while a shorted transistor will cook that 10 ohm resistor.

Keep us posted on what happens, but definitely send it in if it's under warranty.


~Cheers~
 
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ExitThirteen said:
Output SWR/tuning can cause that, excessive voltage on the amp, and excessive input drive. Those three things are usually the cause of a transistor going bad, but I have seen cases where a transistor just simply fails. Had that happen recently to my T/S 667V. There is an outside chance that there was a fault in the bias circuit, but highly doubtful in the case of Carl-built stuff, as Carl knows what he's doing.


Definitely looks like the output combiner resistor has failed, so I suspect at least 1 bad transistor. The real story is if the transistor failed short or open. If it failed open, it won't take out the 10 ohm resistor that goes between the base and emitter, while a shorted transistor will cook that 10 ohm resistor.

Keep us posted on what happens, but definitely send it in if it's under warranty.


~Cheers~
Click to expand...
Thanks, and will do. Yeah not sure but I do know SWR is/was low at radio and amp, as I have read and asked about where the meter should be for tuning. I have one in the radio and one after the amp. The SWR went up slightly when I turned on the amp after the issue and wattage dropped down as per the meter video.
 
As stated in post, when switched to SSB you could here a buzzing noise. If the amp has HG transistors, they do not like to be biased. They run away into oscillation very easily. I have tried it on a few amps. You actually have to bias just a little under where they are being turned on. Which at that point, what’s the point? They only need about 0.5V to turn on. I have not tried it on the HG -C version.
 
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HG are very sensitive to mismatch. If your driving the snot out of them, best to run at lower voltage and keep the SWR near flat. Also worth mentioning, the tuning is more critical. On the Japanese that everyone is use to running. You could be off on the Tune by 20-30pf and they still make good power. Not so on the HG. They are a lot finickier. Especially on output. Usually within 3-5pf max. I always over-couple input. Seems to clean up signal some. Gets rid of some of those ghost watts. The wattmeter don’t discriminate. But that’s what we have readily available, this is what we are stuck with.
 
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Crusher said:
HG are very sensitive to mismatch. If your driving the snot out of them, best to run at lower voltage and keep the SWR near flat. Also worth mentioning, the tuning is more critical. On the Japanese that everyone is use to running. You could be off on the Tune by 20-30pf and they still make good power. Not so on the HG. They are a lot finickier. Especially on output. Usually within 3-5pf max. I always over-couple input. Seems to clean up signal some. Gets rid of some of those ghost watts. The wattmeter don’t discriminate. But that’s what we have readily available, this is what we are stuck with.
Click to expand...
Just running a Galaxy 979 stock radio doing about 5 watts swings to 20ish. If you see the video, the swr is low. Below 1.5 after amp and it's exactly the same at the radio. I painstakingly tuned them perfectly, with all three of my antennas. After it happened the swr was higher at the radio and didn't match as before. The meter by the amp which is in the video stayed about the same. Suks because I know HGs suk and DEIs suk which is what is in Texas Stars now. Now I am seeing there is a 2879 C, so who knows anymore. I did alot of research and reading on builders and I thought Carl would be the right choice. Remains to be seen because I already have to drop money into shipping it back now. I should have kept my TS500DX and got it fixed. Suks. LOL
 
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Crusher said:
As stated in post, when switched to SSB you could here a buzzing noise. If the amp has HG transistors, they do not like to be biased. They run away into oscillation very easily. I have tried it on a few amps. You actually have to bias just a little under where they are being turned on. Which at that point, what’s the point? They only need about 0.5V to turn on. I have not tried it on the HG -C version.
Click to expand...

So is it best to stay away from builders such as Carl, Hopper and their B bias amps? I hate C amps but from your experience and expertise, with the curent crop of transistors that may be the only option in having an amp built. Sounds like a C amp and an external low pass filter may be as good as it gets at this point in times
 
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