307 Amps 2X6 Base Amp Issue

[Shadetree Mechanic]

With a 5w dead key making 150w carrier out of the amp, it makes me wonder. That's about what you would get with a 4 pill amp. Usually the problem with multiple stages is that you can't get the dead key low enough out of the radio to run the final stages safely. It would be worth having the ability to switch off the two pill driver.

If the radio has crappy audio in SSB by itself, then that's the problem. Right?

 

[AK #5]

I believe so. I'm sure I could send it out and have Jim configure it that way.

 

[Dr_DX]

It's six 2879C's. The 150 watt transistors.

Pretty sure they are regular HG2879's. The "16D08" version has been the "defacto" Toshiba 2SC2879 drop in replacement for several years now.

The HG2879C, a different animal, is marked as such on the transistor.

 

[Dr_DX]

I can't tell for sure, but the upper right 100 ohm 2 watt carbon resistor on your 3 port combiner looks like it might have gotten hot. It appears to be discolored unless that is just the shadow.

 

[Dr_DX]

This switch you mention sounds like it can turn the bias on/off. With no bias on SSB the relays chatter.

Huh?

Bias has nothing to do with relay chatter. Try running a Texas Star (passive A/B bias) on SSB without the SSB button pushed in (adds the cap) - the relay will chatter like crazy.

Relay chatter on SSB is due to the keying circuit not staying energized between syllables/words. By adding the additional charge that the electrolytic cap provides, it keeps the keying circuit energized between modulation peaks on SSB. The same thing can be accomplished with a foot switch by grounding out the low side of the amp's relay coil or using a "relay" circuit controlled by the radio - this works best as the amp relay will never chatter and there is no delay when you unkey.

 

[Xracerx13]

Bias has nothing to do with relay chatter.

Its supposed to say delay but I could not catch it in time to edit it.

 

[AK #5]

I can't tell for sure, but the upper right 100 ohm 2 watt carbon resistor on your 3 port combiner looks like it might have gotten hot. It appears to be discolored unless that is just the shadow.

I'll take a better picture later today. Can you copy the picture, then circle the resistor in question, indicating which one you're referencing, and post it?

 

[Dr_DX]

Its supposed to say delay but I could not catch it in time to edit it.

LOL Ok cool. I do the same thing.

 

[Dr_DX]

I'll take a better picture later today. Can you copy the picture, then circle the resistor in question, indicating which one you're referencing, and post it?

Here is a snip of the 3 port combiner from your picture in post # 20. You can see the 3 100 ohm 2 watt carbon resistors in a triangle shape on the top of it.. The bottom resistor appears to be fine. The upper left resistor, even in the shadow, appears to be fine. The upper right one however, appears to be discolored or "dirty". But, it may just be the shadow.

 

[Xracerx13]

Here is a snip of the 3 port combiner from your picture in post # 20.

See a better pic from post #21 below. All 3 look OK to me.

 

[AK #5]

See a better pic from post #21 below. All 3 look OK to me.

Look at the one to the right of the PL 259. It looks strange, almost cooked.

 

[AK #5]

I wasn't able to get to it today, but I will shoot a detailed close up video tomorrow, and post it.

 

[AK #5]

Here are the pictures. I couldn't don't anything burnt, or out of place.

 

[AK #5]

After consulting a few techs, I have determined that stray RF is the cause of all of my problems. Have to do a few things before I'm able to use the amplifier. Like properly grounding my equipment and antenna, and get some ferrite beads to use on the feedpoints on the connections.

Again, much thanks to all of you for taking the time to comment.

 

[Xracerx13]

Have to do a few things before I'm able to use the amplifier.

And maybe change the 4 foot jumper to a 3 foot jumper from the radio to the amp. That should help too.