XForce 1KW supply voltage.

[Jim5570091]

Replaced all the caps on the input side. Only thing I didn’t replace is the combiner. But it seems to test ok.

 

[Monk]

I have tested and replaced everything I can think of except transistors. Is it possible some transistors are shorted and preventing drive to reach other transistors? And how can I test them?

Hi Jim,

A very handy piece of test equipment its a "RF Probe". It takes RF and converts it to DC voltage so you can use your volt meter to trace where there signal stops. I also use it to check multi transistor amps; Key up and use the probe on the input (base) and then the output (collector). This will show the balance of the transistors and also show which transistor is not amplifying.
Not all bad transistors blow by shorting and frying the 10 ohm resistor, some open and don't let out the 10 ohm smoke.
The RF Probe is very simple to build and is worth it's weight in gold if you don't own an oscilloscope. Do a search and you will see there are only three electronic pieces used. A diode, resistor and a capacitor.

https://qrpkits.com/files/RF_Probe_How_To.pdf

Hope this helps
Monk

 

[Jim5570091]

Roger that. I found a video building a probe on YouTube. I built the one in the screen shot. It seemed to show RF on almost every thing. So I ordered a transistor tester also screen shot. I’m going to take all 10 out and test them to be 100% for sure. I don’t mind buying test equipment. I really appreciate everyone’s responses.

 

[Jim5570091]

Tested and found 3 with a diode fault,one with leg broken off. I likely broke it removing it.3 had HFE of 2. 1 was a 3 HFE. The other 2 tested 16&17 HFE. Think the diode shorts caused the 0 output? Now got to figure out what I want to replace them with.

 

[linearone]

Tested and found 3 with a diode fault,one with leg broken off. I likely broke it removing it.3 had HFE of 2. 1 was a 3 HFE. The other 2 tested 16&17 HFE. Think the diode shorts caused the 0 output? Now got to figure out what I want to replace them with.
View attachment 71398

Aint transistors fun?

 

[Jim5570091]

Right. The Chinese knock off actually held up for 3 years before they gave up the ghost. Do you know if HGs will fit in the same hole as these? Carl said they need a regulated power supply if I use them. I also thought about using a variable voltage and reducing the 115 vac to a lower voltage. What’s your thoughts? Reduce the ac into the transformers should reduce the DC output. I would think it would be ok as long as it don’t drop below 12.5vdc when keyed.

 

[Jim5570091]

What’s your thoughts on the variable ac voltage transformer to tame down the unregulated power supply? I have a matched set of HG 2sc2879 16D08 on the way. What effects will an unregulated power supply have on the HGs? Thanks again.

 

[Jim5570091]

The new set of matched HGs from ICA seems to have fixed the issue. I have only put 10 watts in and get 150 out. I still nervous about driving it with the 150 in. The built in unregulated power supply supplies about 21 vdc tapped on the 115v source. I really would like your opinion on using the variable ac unit between the wall outlet and the amp plug. Reducing that voltage should drop that 21 vdc down. What VDC range would you recommend running the HGs at? Again I really thank everyone who helped me with this repair.

 

[linearone]

View attachment 71510The new set of matched HGs from ICA seems to have fixed the issue. I have only put 10 watts in and get 150 out. I still nervous about driving it with the 150 in. The built in unregulated power supply supplies about 21 vdc tapped on the 115v source. I really would like your opinion on using the variable ac unit between the wall outlet and the amp plug. Reducing that voltage should drop that 21 vdc down. What VDC range would you recommend running the HGs at? Again I really thank everyone who helped me with this repair.

You can buy dc supplies on amazon for $19 each that will give you a solid 25a regulated. Buy a bunch, put them in parallel. Problem solved.