5 Pill homebrew linear problems

[crazy_179]

Ok i am having a new problem. I replaced some capacitors with 500 volt capacitors because i thought they blew. but when i turn on the linear receive is cut way back, people who are farther away i can no longer hear, what would cause this?

 

[mackmobile43]

Ok i am having a new problem. I replaced some capacitors with 500 volt capacitors because i thought they blew. but when i turn on the linear receive is cut way back, people who are farther away i can no longer hear, what would cause this?

Which caps did you change?

 

[MisterFatty]

when the amp is not keyed, either because power is off, or in receive mode the relay is simply bypassing the entire amplifier circuit so if your receive is down it has to be an issue with the relay or the connections to it.

Something to consider, the design of the amp is such that it is never really off, rather the relay is just being disabled. It is also possible that relay is staying energized, and the amp is oscillating. If this were the case removing it from power would probably give you back normal receive. The power transistors won't last long at all if this is the case. This could be caused by many things, you might try changing the patch cable between the radio and amp.


You will need to figure out if it is faulty relay/connections, or the latter.

 

[linearone]

relay is bad, perhaps you got the contacts too hot when soldering and they shifted. if that box went into oscillation you would hear the high pitched whine and then pop pop fizz...

 

[MisterFatty]

if that box went into oscillation you would hear the high pitched whine and then pop pop fizz...

Not always, I've had more then one over the years that had no audible indication.

 

[Bionic Chicken]

Ok i am having a new problem. I replaced some capacitors with 500 volt capacitors because i thought they blew. but when i turn on the linear receive is cut way back, people who are farther away i can no longer hear, what would cause this?

Sounds like the relay is keying when the amp is turned on. Does the receive work ok when the amp is off? If it is that is where your problem is. Double check and make sure that you have not inadvertenly supplied a ground to the relay circuit when you changed the caps.

BC

 

[crazy_179]

I reworked the rf detection circuit again, I had the capacitor backwards. I need to pay attention to my work. I put in a new 2222a, 1n4148, 22uf electorlytic cap and the 10 pf ceramic disk cap. now relays kick in when i key. before they would kick down when i turned it on. Now i need to work on keeping it keyed on sideband

 

[Bionic Chicken]

Add a 470 mfd cap to the relay coil with the negative to ground. Fix it to where it can be switched in and out. That'll fix the relay chatter on SSB.

BC

 

[crazy_179]

Add a 470 mfd cap to the relay coil with the negative to ground. Fix it to where it can be switched in and out. That'll fix the relay chatter on SSB.

BC

i hooked it up in my mobile today with the truck running, right around 600 on am and 750 on sideband. I'm pretty happy with that, I didn't check voltage off the alternator, I imagine we're in 14-14.5 range. I will add the cap to keep ssb chatter down. thank you for all the help.

 

[pimphand442]

schematic

can you send me the schematics on that linear board i would like to see how all of it is designed there are plenty of ways to make a keyup circuit but i cant see some of the parts in your pictures can send to email sanjosebay21@yahoo.com thanks