X-Force 600HD Smoked

[Shadetree Mechanic]

I want to take it easy on the amp instead of running it like it has Toshibas in it. With the drive I was giving it, along with some heat from operating, I was kicking its butt for sure. The PowerMax fan would kick into high speed sometimes and that should have been my clue to stop talking for a few but sometimes I just kept talking. I turned the voltage down on the PowerMax 100 as low as it would go. It was 14.5v and now 13v. I also turned the radio power supply down until I was able to get about 40w peak out at 10.5v down from about 60w peak at 14.5v. It seems to be ok at 10.5v so I will keep an eye on it to make sure it doesn't get hot or something funny.

 

[Shadetree Mechanic]

I hooked up the amp and measured the temperature of the transistors and resistors before I keyed up to get a baseline temperature. Then I keyed it a few times and measured again. The temperature of the transistors seemed to be consistent with each other and the output balance resistor did not get warm so it seems to be good to go.

I used a cheapie Harbor Freight infrared thermometer and it seemed to be repeatable. For comparative purposes it does fine and the emissivity is adjustable which can be handy for measuring different materials.

 

[Shadetree Mechanic]

The amp is finally back in its home, but it still needs a little work. The input tune needs help because it is showing 2:1 swr on the Stryker. I think I have an Arco trimmer that will work. I would also like to optimize the output tune, is there an easy way to do this? I have read about using an antenna analyzer into the output but I don't have one yet.

 

[loosecannon]

shadetree,

there is probably a mica or metal cap on the output combiner right where it connects to the relay going to ground.
this would be the cap to make variable in order to tune the output.

you can get a trombone cap from ICA manufacturing if there is room for it inside the amp. (if you do get one, grab another and i'll buy it from you LOL. i need one and don't want to pay their crazy shipping costs)

also, your best friend when it comes to replacing pill type transistors is a set of dental picks.
you can get underneath the tabs while heating them and lift them off the board.
makes it much easier and much less likely to damage the transistors.
LC

 

[543_Dallas]

I finally got around to checking the output capacitor. It read 130pf and is marked 150pf with 20% tolerance. So I guess its ok. I put it back in for now until I can figure out how to figure out what it needs to be.

This is the Chinese checker that I got.


View attachment 34170

This doesn't necessarily apply to the Chinese pills that I know nothing about. 130pf is what you wanted with Toshiba pills. Old Xforce and the Dave amps used a 150pf in series with a 1000pf on the output to get 130. People started cutting corners and a 150 was close enough. I have a stash of 68pf caps that I parallel to get there.

For the input swr issue try a 6 or 12 foot jumper between the radio and amp...just for grins. You can try putting a trimmer cap on the input to see if you can adjust it down. If that don't work you could build a little pi network with a couple of trimmers a small coil. It will be trial and error but you might end up with a proper tuned input circuit.

 

[Shadetree Mechanic]

shadetree,

there is probably a mica or metal cap on the output combiner right where it connects to the relay going to ground.
this would be the cap to make variable in order to tune the output.

you can get a trombone cap from ICA manufacturing if there is room for it inside the amp. (if you do get one, grab another and i'll buy it from you LOL. i need one and don't want to pay their crazy shipping costs)

also, your best friend when it comes to replacing pill type transistors is a set of dental picks.
you can get underneath the tabs while heating them and lift them off the board.
makes it much easier and much less likely to damage the transistors.
LC

They didn't leave any room for a big trombone, but I might be able to scab one on to the side of the chassis with the cover off just to see what value I need. I will let you know when I place the order. I am planning on getting some stuff to make a 2 pill from the left over transistors so I am still putting a list together. Dental picks are on the list too, thanks.

 

[2NC995]

If that don't work you could build a little pi network with a couple of trimmers a small coil. It will be trial and error but you might end up with a proper tuned input circuit.

When I was dabbling with mine someone here (pretty sure without looking it was shockwave) recommended starting with a 5 turn coil of ~1/2” and a pair of 464 trimmers.

Still hadn’t gotten around to it.

 

[Shadetree Mechanic]

This doesn't necessarily apply to the Chinese pills that I know nothing about. 130pf is what you wanted with Toshiba pills. Old Xforce and the Dave amps used a 150pf in series with a 1000pf on the output to get 130. People started cutting corners and a 150 was close enough. I have a stash of 68pf caps that I parallel to get there.

For the input swr issue try a 6 or 12 foot jumper between the radio and amp...just for grins. You can try putting a trimmer cap on the input to see if you can adjust it down. If that don't work you could build a little pi network with a couple of trimmers a small coil. It will be trial and error but you might end up with a proper tuned input circuit.

Still trying to figure out a way to check for output tune without an antenna analyzer. Maybe its like a tube amp and tune for maximum output? The input already has a 10 foot jumper of 400 flex. I was thinking about mounting the Arco trimmer near the side so I can drill a hole in the cover and play with it that way.

 

[2NC995]

Dental picks are on the list too, thanks.

Hydraulics shops eat picks on a daily basis. Just the nature of the beast when you’re pulling seals all day.

This a decent set...IMO.

EDIT: Amazon link doesn’t want to play.

Check out “Park Tool Utility Pick Set”.

 

[543_Dallas]

Still trying to figure out a way to check for output tune without an antenna analyzer. Maybe its like a tube amp and tune for maximum output? The input already has a 10 foot jumper of 400 flex. I was thinking about mounting the Arco trimmer near the side so I can drill a hole in the cover and play with it that way.

The analyzer thing is for the LC network in larger amps. It doesn't get talked about much because it's funny watching the dumb builders try to tune an 8 pill.

For the output tune on that one I would tune for max pep output and lower the cap value until the power starts to drop off. There are probably better ways but I don't have that kind of equipment. Some guys use a FM stereo on the bench and tune for minimum interference.

 

[loosecannon]

Still trying to figure out a way to check for output tune without an antenna analyzer. Maybe its like a tube amp and tune for maximum output? The input already has a 10 foot jumper of 400 flex. I was thinking about mounting the Arco trimmer near the side so I can drill a hole in the cover and play with it that way.

so what im going to give you is a quick and dirty way to get your amp's output in the ballpark, and it often does better than that.

you need a meter that can monitor power and SWR at the same time.
use a real antenna with a known good SWR of 1.5 or less.

what you want to do is find that sweet spot where the power goes up and the SWR goes down. kind of like finding the dip in a tube amp.

along the way you will find areas where the SWR and the power both go high, a place where the SWR seems to go way down but so does the power output, and everything in between.

no this is not the ideal way to tune an amp, but if you do your tuning quick and avoid long key ups, you should be able to get it pretty good.
LC

 

[2NC995]

Shade, Just out of curiosity, what’s the amp producing now with the lower drive and less voltage?

Also, is there a reason you dropped the voltage on the radio as opposed to just dropping the RF power? Granted I only use mine on SSB, so I don’t have to worry about changing the carrier...but it works for me.

 

[9C1Driver]

The amp is finally back in its home, but it still needs a little work. The input tune needs help because it is showing 2:1 swr on the Stryker. I think I have an Arco trimmer that will work. I would also like to optimize the output tune, is there an easy way to do this? I have read about using an antenna analyzer into the output but I don't have one yet.

View attachment 34174

Nice, from the picture I see the amplifier in question is actually a class B TnT 600 (made by X-Force). I really like those and they also made a line prior to that called Magna Force. They came in a redish case and were also class B for SSB use.

 

[Shadetree Mechanic]

Nice, from the picture I see the amplifier in question is actually a class B TnT 600 (made by X-Force). I really like those and they also made a line prior to that called Magna Force. They came in a redish case and were also class B for SSB use.

I had wanted to get one of these 600HD a while ago, but did not get the chance before they stopped making amps. Then I lucked out. And someone gave me a great deal on a slightly used one. It doesn't say TNT so I wasn't sure if it was really just class C. I was happy to find out that it is class B after I started digging into it.

 

[Shadetree Mechanic]

The analyzer thing is for the LC network in larger amps. It doesn't get talked about much because it's funny watching the dumb builders try to tune an 8 pill.

For the output tune on that one I would tune for max pep output and lower the cap value until the power starts to drop off. There are probably better ways but I don't have that kind of equipment. Some guys use a FM stereo on the bench and tune for minimum interference.

so what im going to give you is a quick and dirty way to get your amp's output in the ballpark, and it often does better than that.

you need a meter that can monitor power and SWR at the same time.
use a real antenna with a known good SWR of 1.5 or less.

what you want to do is find that sweet spot where the power goes up and the SWR goes down. kind of like finding the dip in a tube amp.

along the way you will find areas where the SWR and the power both go high, a place where the SWR seems to go way down but so does the power output, and everything in between.

no this is not the ideal way to tune an amp, but if you do your tuning quick and avoid long key ups, you should be able to get it pretty good.
LC

I figured that I should fix the input tune first, because I have seen input tune issues cause output SWR problems. I installed an Arco trimmer and connected it to the input combiner with a piece of solid 18awg. I was thinking this would be a good place to wind a coil but started with a straight wire first.

I drilled a hole in the side of the case so I could get to it with my screwdriver and checked the value of the original cap to set the variable to the same value. I hooked it back up in the shack to check it out. Now when I key up it is 1.2 on the input, where it was 2 before, and this is without adjusting it any. Seems strange to have such a big difference with the same value? Maybe the solid wire has a little inductance in it and that is the difference that I see?

Edit: Maybe that little bend in the wire at the combiner has some inductance?