Mrf9180 Keeps blowing!!

[rigmo]

I do not like you- your desktop its to clean haha

Ware You buy this heatsink for your mrf9180? i have half like yours ( old one since`90 i heve two ) and temp run under 50°C 160W run couple of hours..

[Electronically]

INSANE !

Hahaha no it's not...1400mA is recommended.
I have set Idq to 2000mA to get it in linear mode for DAB @26VDC

A low Idq is possibly the reason why it breaks so easily, you have to drive with much more power...

efficiency no good !!! I told You. recommended for what ? overheting brake it hahah... 1.3W input idq 200mA 160Watt @26V... can more but need 1.5W input and TUNE the board... 180W easy,,,

I set mine at 7100mA 21v kicking out pretty good 3 watt driver to run the amp doing allright had it on for 4 days solid works every time.

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[ronald001]

INSANE !

Hahaha no it's not...1400mA is recommended.
I have set Idq to 2000mA to get it in linear mode for DAB @26VDC

A low Idq is possibly the reason why it breaks so easily, you have to drive with much more power...

efficiency no good !!! I told You. recommended for what ? overheting brake it hahah... 1.3W input idq 200mA 160Watt @26V... can more but need 1.5W input and TUNE the board... 180W easy,,,

This is really a stupid reaction. Read my post again carefully and notice that i mentioned "lineair" and DAB. Next step is to look at the datasheet again....

[nrgkits.nz]

Why not save yourselves the hassle with these fragile devices, and buy a modern LDMOS device. The ones I have used: MRFE6VP5150N, MRFE6VP5300N, and also MRFE6VP6300H, all can take a real punch and don't fail at a rate anywhere near as what the MRF186 and MRF9180 do.

I know the fragile devices are cheap, however for the amount that you're likely to blow up - you could spend that money on one of the modern ones i've listed. The MRFE6VP5300N and MRFE6VP6300H are 300W devices and can be used almost as a straight drop in replacement on the Chinese PA board - the two key things to change are the two pieces of 25R coax to 35R (same length) and also remove a turn from the input transformer primary, so you have a total of 2 turns.

I'm working on a protection circuit, which i'll put up here soon - in the event of a bad SWR or over temperature, it will zero the bias and also cut the drive and divert the drive into a load - since some LDMOS devices still seem to have some fairly good gain with zero bias. I had the MRFE6VP5150N producing almost 40Watts with zero bias and 1W input.

[ronald001]

Why not save yourselves the hassle with these fragile devices, and buy a modern LDMOS device. The ones I have used: MRFE6VP5150N, MRFE6VP5300N, and also MRFE6VP6300H, all can take a real punch and don't fail at a rate anywhere near as what the MRF186 and MRF9180 do.

I know the fragile devices are cheap, however for the amount that you're likely to blow up - you could spend that money on one of the modern ones i've listed. The MRFE6VP5300N and MRFE6VP6300H are 300W devices and can be used almost as a straight drop in replacement on the Chinese PA board - the two key things to change are the two pieces of 25R coax to 35R (same length) and also remove a turn from the input transformer primary, so you have a total of 2 turns.

I'm working on a protection circuit, which i'll put up here soon - in the event of a bad SWR or over temperature, it will zero the bias and also cut the drive and divert the drive into a load - since some LDMOS devices still seem to have some fairly good gain with zero bias. I had the MRFE6VP5150N producing almost 40Watts with zero bias and 1W input.

Looking forward to your design!

[Bton-FM]

Another mosfet to try would be the mrf101 they are only £18 from mouser!

[teckniqs]

My pal has just started experimenting with the 101 and is easily getting 100w out with just 0.9 to 1.0w input running at reduced voltage 40v and transistor just stays stone-cold!

....And getting about 130-140w out still at around 0.9 to 1w drive at the full 48v input and still running only at a nice low heat.

[Bton-FM]

My pal has just started experimenting with the 101 and is easily getting 100w out with just 0.9 to 1.0w input running at reduced voltage 40v and transistor just stays stone-cold!

....And getting about 130-140w out still at around 0.9 to 1w drive at the full 48v input and still running only at a nice low heat.

amd they are cheap as.......

chips.jpg

[BriansBrain]

and they are cheap as.......

chips.jpg

That is NOT fair..........
I am on a no carbohydrate diet at the moment which means NO CHIPS

And I love chips

[nrgkits.nz]

and they are cheap as.......

chips.jpg

That is NOT fair..........
I am on a no carbohydrate diet at the moment which means NO CHIPS

And I love chips

Whats more with the lock down (I don't know about the UK) but here in NZ all takeaway outlets are shut including McDonalds - in fact I don't even think the RSM inspectors (ofcom equivilant in NZ) are actively enforcing any rules at the moment, and some LPFM broadcasters are running much more than the 1Watt that they're allowed to use without a license.

[Albert H]

Friend of mine in NZ called me last for a PA - he's got the 300mW / 1 Watt sorted out, and wanted 10 - 20 Watts. I did a quick PA with an RD15 FET, and it gives exactly 20 Watts with his power supply, He's happy, and his useful coverage is extended. The field strength is now enough to make it worth running stereo!

[nrgkits.nz]

Another mosfet to try would be the mrf101 they are only £18 from mouser!

They're on Digikey also, quite cheap!

I might give one of these a try. Has anyone tried running two of them in push pull?

At 50v 100W, the output impedance is going to be around 12.5 ohms, and in push pull will be twice this, 25 ohms (measured drain to drain) for roughly 200W out.

[ronald001]

This guy did, with the 300 model

https://qrpblog.com/a600-hf-6m-600w-ldmos-amplifier/

[Bton-FM]

Another mosfet to try would be the mrf101 they are only £18 from mouser!

They're on Digikey also, quite cheap!

I might give one of these a try. Has anyone tried running two of them in push pull?

At 50v 100W, the output impedance is going to be around 12.5 ohms, and in push pull will be twice this, 25 ohms (measured drain to drain) for roughly 200W out.

there is a mirrored MRF101 called the MRF101BN just for that application

[nrgkits.nz]

Another mosfet to try would be the mrf101 they are only £18 from mouser!

They're on Digikey also, quite cheap!

I might give one of these a try. Has anyone tried running two of them in push pull?

At 50v 100W, the output impedance is going to be around 12.5 ohms, and in push pull will be twice this, 25 ohms (measured drain to drain) for roughly 200W out.

there is a mirrored MRF101 called the MRF101BN just for that application

Nice, that will make board design a lot easier!

[teckniqs]

No point in wasting time with 2 of them back to back for 200w when you can just get the 300w version which costs less than the price of a pair of 101s and will give you more power.

....And as well there is also a BN version as well as the AN version for the 300w device and I've seen them back to back on 600w amps recently.

[nrgkits.nz]

No point in wasting time with 2 of them back to back for 200w when you can just get the 300w version which costs less than the price of a pair of 101s and will give you more power.

....And as well there is also a BN version as well as the AN version for the 300w device and I've seen them back to back on 600w amps recently.

Yes that’s a much better idea, I just checked the price on Digi-Key, although delivery might take a while given the current situation in the world right now.

[nrgkits.nz]

Another gotcha with these PA’s and the switch mode PSU’s, the PA needs to be shielded from the PSU even though the PSU’s are enclosed. You can still get RF leakage in through the connector terminal opening which will end up getting into the control circuit, causing arbitrary shutdowns and the output voltage to change - the latter being disastrous if it randomly goes up!

I had one meanwell supply shutdown when the PA output power was more than 120W - and it wasn’t over current, it was RF getting into the PSU control circuitry. Another larger PSU arbitrarily went down to 36v from the 50v that I had preset it at - at first I thought my PA had an issue and had me stumped for a while, eventually figured out it was the PSU. The PSU ran fine outside of the rig, so now I need to add more shielding.

[Electronically]

I would go with nrg nz idea. use MRFE6VP5150N in which case will give you just under 180 watts with a 1 watt drive. Only need around 13v.

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[rigmo]

https://www.aliexpress.com/item/32816018892.html trusted store 2 years !
I get 200W easy (short II test on 220W 15minute but heating go fast obove 48.. i stoped....) 26V my calculation get 80% efficiency... if I run only 175W 25V 8.1A run over 4h temeprature do not cross 36°C