Check RD30HVF1

[teckniqs]

Sounds like you've over volted the bias, you need to ensure it doesn't go above the maximum for that device.

[s2000]

When you put the new device in, did you turn the "power adjust" pot (bias control) so that it was giving out the same power as before e.g 30 watts? No more than that?

On some mosfet amplifiers there is a zener diode in the bias circuit which regulates the supply voltage to a lower level, but also dependant on it's value, it can be used so that it will limit the voltage that the mosfet gate will get (protection against too much voltage).

[Sietedj]

When you put the new device in, did you turn the "power adjust" pot (bias control) so that it was giving out the same power as before e.g 30 watts? No more than that?

On some mosfet amplifiers there is a zener diode in the bias circuit which regulates the supply voltage to a lower level, but also dependant on it's value, it can be used so that it will limit the voltage that the mosfet gate will get (protection against too much voltage).

When I put the new transistor nothing more than what I adjusted until the ammeter would 3A is as it was the last. The ammeter I have put into the power input of the transmitter.
As this transmitter uses SMD component is not clearly differentiate them.
Could I explain simply how to correctly adjust the bias? If you have to remove the RF input viewing the photo, which should be done? and how and where to measure the 0.5A?
Thanks for the help!!!
https://www.dropbox.com/s/3kx87w7wdxzh3kt/30W.jpg?dl=0

[s2000]

Yes well the way you have the ammeter connected now is how you would adjust the bias (ammeter in series with supply).

Hard to say from the photo. It may be worth contacting the manufacturer and asking if there is an easy way to disconnnect the first stage (exciter). Maybe there is a jumper you can take out or one part that can be desoldered to isolate it. Also ask them what bias current level they use for the mosfet. 0.5A may be too much bias as from looking at the datasheet, that is for 175mhz.. Also it is not clear how much rf drive the exciter is giving...

Once it is worked out how to disconnect the first stage, before you solder in the new mosfet, turn on transmitter and connect a multimeter to the input part on the pcb where the mosfet sits (gate) and measure the voltage. Turn this voltage down to zero using the bias pot (It will either be fully clockwise or anticlockwise). Turn off power supply.

Next solder in the new mosfet (with your antistatic wrist strap on), and connect the ammeter in series with the power supply and switch on. You may notice that it draws some current even though the pot is turned down to zero. This is usually the bias circuit and will usually be a few milliamps (also any leds on the board that you can't turn off will add to this current). Take note of this current (lets say it was 10mA). Turn the bias pot very slowly and observe the ammeter. It will start to draw current at a certain point. If the manufacturer has specified a quiescent current of 0.4A, set the meter so it read 0.41A (this allows for the 10mA the bias circuit needs).

I think that's how I'd try and attempt it.

[Sietedj]

S2000 Thanks for the explanation. Let's see if I get the imformation on how to remove the RF.

[Analyser]

My first move would be to wait for a reply from Hf electronics since they designed this circuit.

In case you don't get a quick reply or cannot wait then it's quite easy to disconnect the drive from the amplifier. Simply desolder the SMT capacitor which is feeding the curly microstrip line at the input to the RD30 transistor. There are two capacitors, one feeding from the previous stage (in series) and another going to ground. Just remove the series capacitor. Be careful not to damage this capacitor.

The next thing is that the exciter is also supplied from the main voltage input so it will draw some current without bias. Let's say this is 0.5A with the bias at zero volts, then you will need to add the bias current to that value, like S2000 already mentioned.
Personally I would start the bias off low, say 50mA, and see what power the circuit delivers. If it's say 10W then increase the bias a little further and see how the power is affected. The only problem is that you need to able to connect and disconnect the RF drive a few times and this may not be convenient for you.
I'd wait to see what HF electronic say!

[RF-Head]

The bias of the RD30HVF1 is limited to max bias and will be in a safe range
When you adjust the bias the transmitter will have a output power from 5 to 30W
I have many of this modules running in africa without any problems
It must be something like statics

[Sietedj]

The bias of the RD30HVF1 is limited to max bias and will be in a safe range
When you adjust the bias the transmitter will have a output power from 5 to 30W
I have many of this modules running in africa without any problems
It must be something like statics

So no need to make any adjustments? Just change the transistor?

[Sietedj]

I have already requested a new transistor to see if I have better luck.
RF- Head, Wanted to ask, What is power without putting the transistor?

[RF-Head]

Normaly you can change it for a new transistor
Do you have a power meter to check the output power?
If the transmitter is working correct you will have about 5 watt with zero bias and with max bias about 30-40W and about 4-5A
The driver transistor is giving about 1W RF

[shorty]

Site is the transmitter boxed up or is it been run as it came in module form, is the case earthed from the mains power supply, adding some extra bonding to earth the transmitter box to a water pipe may help if it is static that keeps blowing the output device, also make sure the heat sink it self is connected to the case so theres no equipotential difference.

[Sietedj]

Normaly you can change it for a new transistor
Do you have a power meter to check the output power?
If the transmitter is working correct you will have about 5 watt with zero bias and with max bias about 30-40W and about 4-5A
The driver transistor is giving about 1W RF

The meter that I have only good for me to measure SWR Watt does not measure well, it is for another frequency.
These measures are 12V?
I have the transmitter on the 103.4 and had a bias to the maximum consumption of 3A with 13V on the power supply. If under the power supply to 12V up to 4A consumption.
I do not know if these measures are normal.
That would be the right voltage?
Thank you!!

[Sietedj]

Site is the transmitter boxed up or is it been run as it came in module form, is the case earthed from the mains power supply, adding some extra bonding to earth the transmitter box to a water pipe may help if it is static that keeps blowing the output device, also make sure the heat sink it self is connected to the case so theres no equipotential difference.

The module is in a box secured with two screws on the heat sink. The box is grounded by the power supply. I have the transmitter on the roof, in a booth where amplifiers community television is. There's a bare copper wire that could connect to the box.
Some photos of the module in the box.
Thank you!!
https://www.dropbox.com/s/ie38vys6bwtwe ... 3.jpg?dl=0
https://www.dropbox.com/s/lk873aqfj1d0j ... 2.jpg?dl=0

[s2000]

What type of swr meter is it? Is it for cb frequencies? (30mhz etc)

[Sietedj]

What type of swr meter is it? Is it for cb frequencies? (30mhz etc)

It is a ZETAGI HP201, SWR ranges from 3 to 200 mhz. For power only from 26 to 30MHz.
Now I'm going to buy another: http://www.ebay.es/itm/SX20-RX20-Amateu ... 43d13afcf7 : g: o4sAAOxyTkJSTsBw
Do you think of him?

[s2000]

Yes Sietedj, I think a few people on here have that swr meter and say it is good.

I would also recommend you get yourself a good 50 ohm dummy load, you can test your transmitter on it instead of into the aerial. If the new transistor you fit blows, you will know that it is not due to external influences. Which narrows down the problem.

[Sietedj]

Yes Sietedj, I think a few people on here have that swr meter and say it is good.

I would also recommend you get yourself a good 50 ohm dummy load, you can test your transmitter on it instead of into the aerial. If the new transistor you fit blows, you will know that it is not due to external influences. Which narrows down the problem.

Thanks for the tips, S2000.
On the antenna I do not think there problem because I am using a transmitter 6W now works well, without SWR. And buy a dummy load are a bit expensive. But I'll look to see that meeting.
Leave another picture with the temperature probe on the transistor do not know if this may be the problem, although it is only a resistance to collect temperature.
Regards!!!
https://www.dropbox.com/s/9a9ckvzfrpesk ... a.jpg?dl=0

[Sietedj]

Normaly you can change it for a new transistor
Do you have a power meter to check the output power?
If the transmitter is working correct you will have about 5 watt with zero bias and with max bias about 30-40W and about 4-5A
The driver transistor is giving about 1W RF

The meter that I have only good for me to measure SWR Watt does not measure well, it is for another frequency.
These measures are 12V?
I have the transmitter on the 103.4 and had a bias to the maximum consumption of 3A with 13V on the power supply. If under the power supply to 12V up to 4A consumption.
I do not know if these measures are normal.
That would be the right voltage?
Thank you!!

RF-Head to see if I can answer this, thank you !!

[Sietedj]

Hi, I am returning this thread because I already have the new SX-20 SWR meter and the dummy load.
I have made measurements and these are the results:
With the minimum bias gives 0.3 W approximately and maximum:
87.5 - 2.4A - 26W
90.0 - 2.5A - 27W
95.7 - 2.7A - 28W
99.2 - 2.1A - 24W
108 - 2A - 19W
This is with the power supply at 12.4V, at 13 volts it goes up by 1W more or less.

They are not the same measures that RF-Head gives me, to see if they look normal or there is something that is not working well.

[Analyser]

Before continuing, quickly check your dummy load is ok. Use a multimeter and it should measure close to 50 ohms when set to read resistance.