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Broken Resistor On a Palomar 255 Amp

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Old 07-24-2010, 05:36 PM
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Default Broken Resistor On a Palomar 255 Amp


I have a Galaxy 225 Amp that is an EXACT copy of a Palomar 225, blue face. I picked it up used at a cb shop for 50 bucks, the owner said it didn't have full output power. It seems to be a pretty sturdy little amp, but the problem is that it only puts out about 50 watts.

When I inspected it, I found a resistor that has broken one leg off of its solder joint, the rest of the amp seems fine. The pre amp works amazingly and the first radio check I requested got me a "you sound somewhat scratchy" but that was with a cheapo mag mount antenna on my truck and the reply was from another CBer 41 miles away in the woods!

Its my first amp and though it works great already I just want to get all the power out of it.

There is another resistor on the board that broke in the same spot that has been fixed by the previous owner. It seems he didnt even remove the board from the chassis and just put new solder on one leg of the resistor and connected it right to the board.

I have tried to remove the board but it seems to be impossible without desoldering the front switches and drilling out the rivits that hold the SO 259 connectors to the chassis. I tried to remove the four screws that hold on the faceplate, but it still was connected to the frame somehow.

My question is how can I remove the board from the chassis to solder the leg back on? Also, could I just patch it the way the previous owner did and not have to remove it?

I know that boards have a solder side and a component side but it seems that the pathways on the board are on the component side as well and the components are just soldered to parts of exposed pathways on the component side. If this is the case, I should be able to get away with just soldering the resistor back on the component side right?

Its my first amp and I'm really looking forward to a response so I can get this guy up and running and make contacts from 82 miles away!!!

I have added a few pictures to help everyone get a better idea of what's going on. The second and third pictures are of the broken resistor and the fourth is of the broken resistor that was fixed by the previous owner.











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Old 07-24-2010, 05:49 PM
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Quote:
Originally Posted by Buckshot555 View Post



Its my first amp and I'm really looking forward to a response so I can get this guy up and running and make contacts from 82 miles away!!!
82 miles?

awesome

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Old 07-24-2010, 06:00 PM
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Ha ha. Well I was saying that because getting the other pill to fire up would double my output power and maybe double my distance....

In all fairness, the other guy was 41 miles away with a tower.....

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Old 07-24-2010, 06:18 PM
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buckshot, the 820pf compensation cap is missing from the output transformer
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Old 07-24-2010, 06:22 PM
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Is that the brown square looking capacitor I saw in some other pictures of this style amp? What does it do? Can I buy another one and solder it in place?

Also would you happen to know what it is that the broken resistor controls?

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Old 07-24-2010, 08:58 PM
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Quote:
Originally Posted by Buckshot555 View Post
Is that the brown square looking capacitor I saw in some other pictures of this style amp? What does it do? Can I buy another one and solder it in place?

Also would you happen to know what it is that the broken resistor controls?
It's one of 2 feedback resistors..

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Old 07-24-2010, 09:21 PM
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the cap compensates inductive reactance in the transformer primary, you can buy one and solder it in,
the unsoldered resistor is as mack says one of the feedback resistors, along with other feedback components they do several things, lower gain, lower input/output impedance and often stabilise unstable amplifiers,
the other resistors that have had some hammer look like part of the input attenuator.
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Old 07-25-2010, 08:42 AM
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Quote:
Originally Posted by bob85 View Post
the cap compensates inductive reactance in the transformer primary, you can buy one and solder it in,
the unsoldered resistor is as mack says one of the feedback resistors, along with other feedback components they do several things, lower gain, lower input/output impedance and often stabilise unstable amplifiers,
the other resistors that have had some hammer look like part of the input attenuator.
Input padding which Bob85 eloquently stated which without the use of the smokeless resistor would failed long ago, Galaxy don't like 10ohm smoke smell.

A guy could up the wattage of that resistor and rid one's self of the ugliness but it's an easier solution to just keep the input power from the radio below 5 watts which that resistor is rated for.

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