2 Pill Low Dead Key Makes Amp Hang Up

[Wire Weasel]

Have a local buddy who has a Palomar Elite 300. (2) 1446's. He says you have to run minimum 3.75 - 4 watts from radio and all is okay. If you run a lower dead key like 2 watts, then the amp hangs up while transmitting. That is, you unkey the radio but the amp keeps on tx'ing. Have to turn amp off to kill the TX.

This sounds normal to anyone? I think the key up relay in the amp is going bad or something?

What do you guys think?

 

[Sonwatcher]

I found these related comments elsewhere from others on the web having the same problem-

Sometimes with Palomar amplifiers if the jumper is too short they hang up alittle and don't un-key. Jumpers of 3 feet or less are just too short, go with 6 or 9 feet and you won't have a problem.

I have a Galaxy 99 paired with a Palomar 450 Elite HD. I like others am having problems with it hanging up. It only does it on MED and HIGH, and only when it is cold. Once the amp starts to warm up, it operates just fine. If I remember correctly, I have a 6 ft jumper from the 99 to the amp

Could be a sticky relay. For the most part it's just a low end amplifier. Palomars are known for having poor impedance mis-matches among other issues.

I had the key relay replaced, as it eventually began sticking all the time.

 

[555]

good reply
i was also going to say jumper or relay
start with jumper lengths

 

[paws264]

Have a local buddy who has a Palomar Elite 300. (2) 1446's. He says you have to run minimum 3.75 - 4 watts from radio and all is okay. If you run a lower dead key like 2 watts, then the amp hangs up while transmitting. That is, you unkey the radio but the amp keeps on tx'ing. Have to turn amp off to kill the TX.

This sounds normal to anyone? I think the key up relay in the amp is going bad or something?

What do you guys think?

TRUE STORY: I went to my to my doctor's office and during the exam, I said, "Doctor when I do this (raise my right arm over and behind my head), it hurts". My doctor looks at me and says, "Well don't do that"!

We had a great laugh over it!

If, your amplifier works as it normally should with 4 watts in, then give the amplifier what it's happy with. When you attempt to do the "Yo-Yo Audio" swing into your amplifier it starts an oscillation that holds the RF keyer circuit activated.

What has been suggested to you is to change the lenght of the jumper on the input; this is to try to counteract the possible inbalance in tuning in the input side.

If you were to use a non-radiating Dummy Load, does it still do it? This would help to narrow down where the problem is being inserted in your amp.

If 4 watts input works, then go with it.

.

 

[Marconi]

Sounds like RF.

 

[Shockwave]

Have a local buddy who has a Palomar Elite 300. (2) 1446's. He says you have to run minimum 3.75 - 4 watts from radio and all is okay. If you run a lower dead key like 2 watts, then the amp hangs up while transmitting. That is, you unkey the radio but the amp keeps on tx'ing. Have to turn amp off to kill the TX.

This sounds normal to anyone? I think the key up relay in the amp is going bad or something?

What do you guys think?

What you are experiencing is an unstable amplifier that is breaking into RF oscillation. All the suggestions of changing jumper lengths at best may hide the problem. The real problem is within the amplifier design itself. Things that will help eliminate this problem would be the addition of negative feedback on each transistor in the amp and the use of a tuned input circuit.

 

[Wire Weasel]

Thanks for all the tips and info fellas. I'll pass this along to my bud

 

[bob85]

What you are experiencing is an unstable amplifier that is breaking into RF oscillation. All the suggestions of changing jumper lengths at best may hide the problem. The real problem is within the amplifier design itself. Things that will help eliminate this problem would be the addition of negative feedback on each transistor in the amp and the use of a tuned input circuit.

dead balls on regarding palomar elites^^

if your jumpers change the way the amp works by a significant degree then the amp is not designed correctly,

bipolar transistors used below their design frequency have high gain that needs taming with negative feedback and suitable input/output matching to have any hope of making the amp unconditionally stable.


.

 

[9C1Driver]

Those Palomar Elite 300's are set up for a higher input dead key. They seem to like 4-5 watts if I remember right. As with all Palomar junk as stated they are also picky about jumper lengths.

 

[JustinDePolis]

I've watched this thread for a while. The amplifier is going into self oscillation. This is usually due to no negative feedback, poor input design, too much bias, (although I doubt the amplifier has any bias supply)

Here's a fix that will actually do something unlike just changing jumper lengths.

Take a .01uf ceramic capacitor, and a 68ohm 1/2 watt resistor, and put them in series. Now install for each transistor or "pill" from base to collector. With the transistor's writing steight up and down, that would be from top to bottom terminals on the transistor.

This will be adding negative feedback to the amplifier which will help with self oscillation.


Example for transistor:

A
B SD1446 B
C


The connection would go from C to A

 

[Happy_Hamer]

Take a .01uf ceramic capacitor, and a 68ohm 1/2 watt resistor, and put them in series. Now install for each transistor or "pill" from base to collector. With the transistor's writing steight up and down, that would be from top to bottom terminals on the transistor.

This will be adding negative feedback to the amplifier which will help with self oscillation.


Example for transistor:

A
B SD1446 B
C


The connection would go from C to A

Like this????

 

[mackmobile43]

Like this????

Yeah, hook the resistor end to the front of the output transformer and the capacitor end to the input transformer.

 

[Shockwave]

Like this????

If you connect it like the picture shows you will burn up the transistor! The resistor and the capacitor are to be in series with each other. Not parallel. The way the picture shows it, you will over bias the transistor because you are feeding 12 volts trough 68 ohms into the base.

 

[paws264]

Like this????

If you connect it like the picture shows you will burn up the transistor! The resistor and the capacitor are to be in series with each other. Not parallel. The way the picture shows it, you will over bias the transistor because you are feeding 12 volts trough 68 ohms into the base.

I think he's just trying to mess with somebody; I know that he know's the proper configuration.

.

 

[HiDef]

If you connect it like the picture shows you will burn up the transistor! The resistor and the capacitor are to be in series with each other. Not parallel. The way the picture shows it, you will over bias the transistor because you are feeding 12 volts trough 68 ohms into the base.

That would cure the oscillation.