Just gonna say this. I posted elsewhere before. HG tolerance and quality are horrible. Your basically using the equivalent of Harbor Freight.
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New 32 pill is a dog :(
- Thread starter groundwire
- Start date
That's a great way to put it.... Lot's of what we're getting anymore is harbor freight grade... Not even the Icon, more like the Pittsburgh line.. Sad state but like groundwire says, it's what we have to work with
That combiner quite obviously had an extreme imbalance placed across it, for the resistor to be that burnt up. It is exactly what I would expect if one of those four transistors closest to the combiner, has failed. This would place more than 100 Watts across that two watt resistor and burn it up within a matter of seconds.
That leads me to believe the transistor most likely failed during your last transmission. The easiest place to begin, would be to look at the 10 ohm resistors (brown, black, black), across the bases of these four transistors, closest to the burnt up combiner. If any of those are darker or discolored, you've found the transistor that has failed.
That leads me to believe the transistor most likely failed during your last transmission. The easiest place to begin, would be to look at the 10 ohm resistors (brown, black, black), across the bases of these four transistors, closest to the burnt up combiner. If any of those are darker or discolored, you've found the transistor that has failed.
i would also strongly suggest that you limit the maximum total output of the amplifier to 3.2KW. the next "weakest link" could reveal itself at any time as long as you insist on exceeding the rated output of the total devices in use. the increase from 3.2KW to 4.5KW yields an increase of only 1.48 dB. gain.
when the fault occurred the transistors were producing approximately 140W apiece. I think that is "A Touch TOO Much."
i promise that they won't "Walk All Over You."
when the fault occurred the transistors were producing approximately 140W apiece. I think that is "A Touch TOO Much."
i promise that they won't "Walk All Over You."
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I think the weak link isnt so much the output watts being too high. My toshiba 4 pill with 100 watts peak drive makes 1k peak and the 16 2k with that same 100 watts in. That 32 driven right should make 4k with out a struggle.
I think the issue is trying to match 32 "meh" quality transistors or maybe the lack of proper matching. Toshiba quality allowed builders to pile 32 or more in a box and make them work but not so much with HG. I personally wouldn't have an HG amp bigger than a 4x16. I think a 4 HG 454 X 16 HG 2879C amp would be interesting.
I bet to get 32 properly matched HG 2879 16D08 pills you would have to test a couple hundred or more pills.
Not knocking the builder but i bet he/she didn't take the time rather took the manufacturers word.
In the end i think the amp is too big for the quality of the transistors you're working with.
Im no expert but i did trash a room at a Holiday Inn express last night...
I think the issue is trying to match 32 "meh" quality transistors or maybe the lack of proper matching. Toshiba quality allowed builders to pile 32 or more in a box and make them work but not so much with HG. I personally wouldn't have an HG amp bigger than a 4x16. I think a 4 HG 454 X 16 HG 2879C amp would be interesting.
I bet to get 32 properly matched HG 2879 16D08 pills you would have to test a couple hundred or more pills.
Not knocking the builder but i bet he/she didn't take the time rather took the manufacturers word.
In the end i think the amp is too big for the quality of the transistors you're working with.
Im no expert but i did trash a room at a Holiday Inn express last night...
Anything above a 4 pill ... I'd go with a tube amp
Your gonna pay a ridiculous price for transistors and have better stability on a tube amp
Your gonna pay a ridiculous price for transistors and have better stability on a tube amp
Looking at the 3rd picture you posted. With all the finals in it. The 6th from the left, top row. You can see the 10 ohm went poof and that stage's combiner (of 4 finals total, before the final or last combiner) 100 ohm is roasted. When a final takes a dump like this, you now effectively have only one of the 2 push pull stages functioning. Combiner can work with an 1/8th watt resistor, being 100 ohms is due to the two 50 ohm output stages. Because as long as both stages feeding that combiner are producing the same amplitude the resistor does nothing but not let the filed induced in the transformer (combiner) "teeter totter"
Anyhow you only need a guy who can replace the (Pair!) Of HG finals and the other resistors that took a dump. 10 ohm base and the different combiner balance resistors.
Oh and the input and output tunes can be adjusted with the big brass tubes. They're big ass variable capacitors.
I didn't pour over everything. But basically besides your tuning issue what happened here is known as infant mortality in the electronicals business. Morbid I know.
Find you an engineering student that's a HAM and most likely they could square you away. Or do it yourself.
Honestly shipping that beast is riskier then you learning to solder....
Anyhow you only need a guy who can replace the (Pair!) Of HG finals and the other resistors that took a dump. 10 ohm base and the different combiner balance resistors.
Oh and the input and output tunes can be adjusted with the big brass tubes. They're big ass variable capacitors.
I didn't pour over everything. But basically besides your tuning issue what happened here is known as infant mortality in the electronicals business. Morbid I know.
Find you an engineering student that's a HAM and most likely they could square you away. Or do it yourself.
Honestly shipping that beast is riskier then you learning to solder....
Its already back with the builder. He is gonna redo it. Its brand spankin new so back to him it went for repair.
Damn right!SSB on a 32 pill
I think you should request, order, buy what have you a few matched pairs of finals from your builder when he is ready to ship it back.
I produce guitar amps. Tube amps. I include a variety of power tubes that can be plugged in with no need for adjustments by the artist. Tubes can fail. So can transistors.
The day might come when I manufacture RF amps and depending on the format. I will absolutely include matching, spare finals.
Any tech worth their salt can identify, and replace, repair flange mount rf output devices and associated small parts that get taken out with them.
Far safer and faster to repair locally then ship something like you have.
Also, the builder should have been straight with you and say "blown pills are a part of life with things like this" after all. Anyone willing to make a 32 pill 14vdc linear amplifier is also willing to squeeze 10 pounds of shit out of a 5 pound bag. The market expects that. You expect that. May not realize you expect that. But if you expect anymore then 3kw PEP from that box, then your holding a 5 pound bag but asking for 10.
Will the amp do more? Oh hell yeah it will. And it'll blow finals along the way. And if you don't catch it right away it'll cascade and take down more sections.
Should have LED status lights for each 2 pill section and status lights for the input and output combiners..
Maybe think about LDMOS next amp build. As long as you don't foul up their bias scheme they'll survive anything a CBer can throw at them.
Most hams use tube amps for that amount of power. But at home. Some folks don't like being that close to a 3,5,10kw RF field while driving to get some coldies. But most hams are complete tools too, so to hell with what I say.
Hope the builder does right by you.
Order extra pills dude. You'll be glad you did.
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