fixed my baby. The cb shop at the pilot in Indianapolis is very good. talked to him and he said he has worded with the fet finals. He said he usually gets 50 watts or more out of cobras.
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mosfets
- Thread starter bushwacker
- Start date
lords
Active Member
well good for you...now learn of this mod ,snap a picture if it is different from the standard mod and post it
share share share
share share share
I did the cbtricks mod. I looked at this thread and added a 4.7k resistor from the gate of the 2030 to the positive side of c116.
that brought the dk up to 6w.
I also jumpered r123 and r58 as stated would maybe be ok. my radio lasted one dk and modulated one time in it then it died. the power is still on but I have no tx or rx. I replaced the driver (1957 to a 2314) and removed the jumpers but still no joy. I guess my final is bad. I checked the radio and the transformer in the back close to the power plug was hot as a firecracker. Maybe thats bad too.
that brought the dk up to 6w.
I also jumpered r123 and r58 as stated would maybe be ok. my radio lasted one dk and modulated one time in it then it died. the power is still on but I have no tx or rx. I replaced the driver (1957 to a 2314) and removed the jumpers but still no joy. I guess my final is bad. I checked the radio and the transformer in the back close to the power plug was hot as a firecracker. Maybe thats bad too.
That small transformer in the back is not a transformer.... its just a choke.... its basically a filter choke to filter the power coming into the radio.
When you start peaking up radios to high levels of power you have to beef up certain sections. That choke is definatly one of them. The chassis your working on was designed for about 2 amps draw max. When you increase the output power you are also increasing the CURRENT draw of the radio... the more output power the more amps it draws.
So when you peaked up the radio, it started to draw alot of more amps..... and it draws all those amps right through that small little filter choke. Thats why its getting hot. Its common to see those melted.
When trying to get max power out of these radios you have to look at thier limitations... what limitations does a cobra 29 style radio have that would prevent it from putting out more power... can it supply enough current for a high powered mod....
Already you have noticed the choke heating up from current draw..... does that current go directly to the rf amp..... NO..... it goes to the audio amp... then to the final.
Whats one component that high powered radios have that a cobra 29 doesnt have......... a regulator.
This is what limits the power on a cobra 29.... the CURRENT, VOLTAGE, AND AUDIO all come in from the audio amp through the audio transformer to the rf amp.
Basically what Ièm saying here is when you increase the output power of the radio, the rf amp draws more amps.. which comes through the audio transformer... and through the audio amp IC.
The voltage and current supply to the rf amp come in with the audio from the audio ic.... How much current can you draw through that small audio IC.. not a heck of alot.
So when the rf amp start drawing more power you are putting an increased strain on the audio IC... which is drawing more current and putting a strain on the input filtering.
Thats why the filter choke is hot... your audio ic is more than likly running hot as well.
If you want to get more power out of this radio, set up the rf amp to run linear and draw the power directly from the power plug.
With the problem mentioned above... it sounds as if a component did not hold and shorted out. If there is a short in a component and no fuse in line, the radio will keep drawing more and more and more amps until something else overheats and pops. Its one way you can tell there is a direct short in the radio... the radio will draw a large amount of current.
This could also be what heated up the filter choke.
Sound like everything was fine until you modulated. I will say those erf2030s are not the most forgiving transistor. But they can take a decent amount of voltage.
No doubt you will figure out the problem Bionic... you are very capable. Check the power to the final and for a shorted component.
Take care
I still dont like these fets LOL
When you start peaking up radios to high levels of power you have to beef up certain sections. That choke is definatly one of them. The chassis your working on was designed for about 2 amps draw max. When you increase the output power you are also increasing the CURRENT draw of the radio... the more output power the more amps it draws.
So when you peaked up the radio, it started to draw alot of more amps..... and it draws all those amps right through that small little filter choke. Thats why its getting hot. Its common to see those melted.
When trying to get max power out of these radios you have to look at thier limitations... what limitations does a cobra 29 style radio have that would prevent it from putting out more power... can it supply enough current for a high powered mod....
Already you have noticed the choke heating up from current draw..... does that current go directly to the rf amp..... NO..... it goes to the audio amp... then to the final.
Whats one component that high powered radios have that a cobra 29 doesnt have......... a regulator.
This is what limits the power on a cobra 29.... the CURRENT, VOLTAGE, AND AUDIO all come in from the audio amp through the audio transformer to the rf amp.
Basically what Ièm saying here is when you increase the output power of the radio, the rf amp draws more amps.. which comes through the audio transformer... and through the audio amp IC.
The voltage and current supply to the rf amp come in with the audio from the audio ic.... How much current can you draw through that small audio IC.. not a heck of alot.
So when the rf amp start drawing more power you are putting an increased strain on the audio IC... which is drawing more current and putting a strain on the input filtering.
Thats why the filter choke is hot... your audio ic is more than likly running hot as well.
If you want to get more power out of this radio, set up the rf amp to run linear and draw the power directly from the power plug.
With the problem mentioned above... it sounds as if a component did not hold and shorted out. If there is a short in a component and no fuse in line, the radio will keep drawing more and more and more amps until something else overheats and pops. Its one way you can tell there is a direct short in the radio... the radio will draw a large amount of current.
This could also be what heated up the filter choke.
Sound like everything was fine until you modulated. I will say those erf2030s are not the most forgiving transistor. But they can take a decent amount of voltage.
No doubt you will figure out the problem Bionic... you are very capable. Check the power to the final and for a shorted component.
Take care
I still dont like these fets LOL
I am nowhere near tech level!!!
I just copied this from CBTRICKS Mosfet Experimentals Info Notes for EKL Mosfets. NOTE THE BOLD THAT I ADDED TO HIGHLIGHT ONLY!!! Maybe it depends on the rig?
Schematic of the EKL ENXXX's
The following was posted on the forum from a member of the site.
Just for the record I thought I'd try the single mosfet in a DX33HML using the directions provided.
In all honesty I have to admit it worked rather well.
I posted some wattage readings below with notes.
2SC1969:
25.615 - deadkey = 8.5 watts - 28 watts peak
26.965 - deadkey = 9.0 watts - 31 watts peak
27.865 - deadkey = 9.0 watts - 30 watts peak
ERF2030:
25.615 - deadkey = 8.3 watts - 38 watts peak
26.965 - deadkey = 9.5 watts - 43 watts peak
27.865 - deadkey = 9.4 watts - 40 watts peak
Notes:
Peak power readings on IFR1200 Communications test set.
No modulation limiters removed.
Full modulation with no flat topping.
Current draw same on both devices.
68pf cap not recommend (causes less output)
Do not remove L33 slug (required to balance power on upper and lower bands.)
ERF2030 has slight impedance mismatch on the output. (not bad)
Like I said, I am not a tech. I am a starter ONLY! I am researching.. BASICALLY STANDING ON THE SHOULDERS OF GENIUSES, TO GET A BETTER VIEW!
BEFORE BLOWING MY STUFF UP!!!- No one is chatting at the moment.
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