Please help your fellow skip shooter

[lonestarbandit]

Well gentleman,

My cheap low pass paradynamics filter smoked this evening and took my 4 pill base amp with it. I thought my President Lincoln II+ was gone too but the built in protection circuit saved it. I am grateful for small blessings. I am going to get the amp open and hope I just killed some resistors but I have a feeling I took 3 of 4 pills out. Anyone have suggestions for repair people in the event this isn't just a resistor and pill issue? Not only only has the USPS lost my new beam in transit and copper electronics seems fairly unconcerned a week later.... but happy weekend I've blown the amp so no longer can shoot skip. This Para dynamics was stinking to holy hell so it's for sure cooked off. Haven't opened it yet.

 

[lonestarbandit]

Update - kaplooey. 10 ohm smoke.
Question is do we think I took the pills out or just the resistor? I have 0 locals around here so skip is all I have and no one to consult. Can I use a 2w resistor in place of the burnt 1 watt as that's all I have on hand... I really need all of your collective expertise as there is zero help available locally.

 

[lonestarbandit]

Anyway here's the guts of that hopper If anyone is interested. Class B bias.

 

[9C1Driver]

So when you get going again you gonna skip the whole low pass filter thing? I don't know anyone locally here that even runs one.

 

[lonestarbandit]

So when you get going again you gonna skip the whole low pass filter thing? I don't know anyone locally here that even runs one.

Immediately, unfortunantly not sooner.
Sadly having it in line has potentially cost me a good bit in repairs for this amp if I cant fix it myself. Stupid pos and stupid me for having it in line. Old habits aren't always wise habits. BIG shorting scorch marks but nothing appears blown but stinks to high heaven (low pass)

 

[Shadetree Mechanic]

Update - kaplooey. 10 ohm smoke.
Question is do we think I took the pills out or just the resistor? I have 0 locals around here so skip is all I have and no one to consult. Can I use a 2w resistor in place of the burnt 1 watt as that's all I have on hand... I really need all of your collective expertise as there is zero help available locally.

I would say that the pill that has the burnt resistor is bad. If you are going to keep it, you will want to replace all 4 with a matched set.

I went down this rabbit hole a while back and the great people here helped me get it going again.

Check it out :

X-Force 600HD Smoked

Hey guys, I need some advice. I have been running my X-Force 600HD with my Stryker 955 for about a year now. The other day I was talking on it on side band and noticed the output power disappeared. I unkeyed real quick and went over to the amp shelf and smelled an electrical smell. I unplugged...

www.worldwidedx.com

 

[999]

Immediately, unfortunantly not sooner.
Sadly having it in line has potentially cost me a good bit in repairs for this amp if I cant fix it myself. Stupid pos and stupid me for having it in line. Old habits aren't always wise habits. BIG shorting scorch marks but nothing appears blown but stinks to high heaven (low pass)

That looks like it arced through the grommet.

 

[lonestarbandit]

That looks like it arced through the grommet.

It does yes. But damn that stupid device it took out my amp lol. That filter has been on there at least 3 years and for reasons unknown it suddenly decided to get all chaotic and go into meltdown.
It wasn't moved or anything. Such is life.

 

[lonestarbandit]

I would say that the pill that has the burnt resistor is bad. If you are going to keep it, you will want to replace all 4 with a matched set.

I went down this rabbit hole a while back and the great people here helped me get it going again.

Check it out :

X-Force 600HD Smoked

Hey guys, I need some advice. I have been running my X-Force 600HD with my Stryker 955 for about a year now. The other day I was talking on it on side band and noticed the output power disappeared. I unkeyed real quick and went over to the amp shelf and smelled an electrical smell. I unplugged...

www.worldwidedx.com

So no hope to replace just the one pill with another of the same gain rating then? If I have to replace all four I'd just as soon replace with a matched set of higher drive 2sc2879C pills for safety reasons on drive if drop in replacement or would that require retuning?
I'm going to go read your thread now.

 

[Shadetree Mechanic]

So no hope to replace just the one pill with another of the same gain rating then? If I have to replace all four I'd just as soon replace with a matched set of higher drive 2sc2879C pills for safety reasons on drive if drop in replacement or would that require retuning?
I'm going to go read your thread now.

You could replace just one if you had a way to measure the gain of the other ones. Then you would need to be able to buy one with the gain you need. If you go with the C version, it will need to be tuned.

 

[lonestarbandit]

You could replace just one if you had a way to measure the gain of the other ones. Then you would need to be able to buy one with the gain you need. If you go with the C version, it will need to be tuned.

Thanks so much! BBIs video and your thread was helpful as well. Mine are marked @64 gain so assuming I can locate one @ that gain I'll try that 1st. Guess ill skip the C models for now then. Much appreciated Shade.

 

[lonestarbandit]

Now that Shade has lowered my panic level (as theres genuinely no local radio users here barring some rock trucks and only radio use I have is DX AND my beam got taken out by a storm so no amp = sandbagging only) I recalled I have a back up amp for just such an occasion she ain't much but she will help! Emergency temp install completed.

 

[nomadradio]

About that question way back, is it the resistors or the transistors, too?

What smokes the 10-ohm resistors is the internal breakdown of the RF transistor. A short develops between the base and the collector terminal inside the transistor. This shoots the full supply voltage out the transistor's "input" leg, and through the 10-ohm resistor to ground. 14 Volts divide by 10 ohms is 1.4 Amps. 14 Volts times 1.4 Amps is 20 Watts, and a short life for a half-Watt resistor.

73

 

[lonestarbandit]

About that question way back, is it the resistors or the transistors, too?

What smokes the 10-ohm resistors is the internal breakdown of the RF transistor. A short develops between the base and the collector terminal inside the transistor. This shoots the full supply voltage out the transistor's "input" leg, and through the 10-ohm resistor to ground. 14 Volts divide by 10 ohms is 1.4 Amps. 14 Volts times 1.4 Amps is 20 Watts, and a short life for a half-Watt resistor.

73

Excellent explanation. Thank you!

 

[Dr_DX]

Lucky for you, they still sell a MQ HG 2SC2879 16D08 set. For $128, you can repair the amp your self. Just unsolder the old transistors and pop in the same exact new ones:

HG(HuaGao) 4 PCS 2SC2879(MQ, Match HFE) build by China HG semiconductor | eBay

New 2SC2879 is produced by HG China. Can replace Toshiba 2SC2879 well. HG 2SC2879:+2.0 USD each. We will match HFE for this 4 PCS 2SC2879. The HFE will be marked on the lids. HG 2SC2290:+1.7 USD each.

www.ebay.com

While you are at it, get some 10ohm .5 watt carbon resistors and replace the 4 that are there.

There are higher quality LP filters out there but you can probably reuse yours by simply pulling out the end of the coil that feeds through the grommet so the feedthrough wire is in the center of the hole and not pressing up against the left side of the grommet and arcing through the rubber to ground that is millimeters away. The stench is the burnt grommet.

Good Luck.