Newbie needs help something probably easy to fix

Thread Starter

alpha beatz

Joined Aug 2, 2017
5
Hi dont know if this is the correct section so sorry if it is not .i purchased a vhf diy amp kit from a market place twice 1st time i thought i blew the final output so obtained another one put it all together and was working and again same thing no out put .

i also this time round brought two spare outputs incase it was to do with them so i replaced outputs and still no out put could this be a cap problem in the lpf or something?

https://picclick.ca/100W-FM-VHF-80Mhz-170Mhz-RF-Power-Amplifier-Board-282715575081.html

The 100w virsion is the same as the 170w one just difrent chips i have tryd two 170w versions with same problem after wireing up to a dummy load and running once no out put the replaceing output with new ones still no out put
 

Dodgydave

Joined Jun 22, 2012
8,367
This is a Vhf RF power amp, have you got the circuit diagram with the kit, what test equipment have you got?
 

Thread Starter

alpha beatz

Joined Aug 2, 2017
5
@Dodgydave i have no test equipment other then a multie meter and a power swr meter.oh and a cheap frq counter a sdr dongle but dont use it .im not a pro just an old chap who is board at home and trying out a hobby for fun .i understand a few bits but not a lot but at same time like to learn trail and error .


@BR549 the input is a 1w tx and the psu is a 28v switch mode jobie probly from china the dummy load is 1K can with oil in with umr67 50ohm coax for connecting all meters and dummy loads

i brought a load of broke armature stuff from a boot fair to tinker with im aware its on the broadcast band but am able to go up more in frq the tx go from 50mhz-500mhz its on 87 atm as thats band 2 not band 3 to my knowledge
 

BR-549

Joined Sep 22, 2013
4,936
Put your voltmeter across pwr supply output while keying. What does it say before and during key down?

What current is the pwr supply rated at?

Put swr meter between source and amp.....how does it look?

I do not follow your frequency comments.
 

Thread Starter

alpha beatz

Joined Aug 2, 2017
5
it shows 1watt from tx to amp input the chip on amp gets warm as if its working powersupply shows 28volts dc .so all looks like its working just not on the output stage of the amp .

when i said about tx frq i mean it is Variable you can tune it to a number of frq .thank you for your reply
 
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