AX-190 receiver

[tgbrail]

Hi , if anyone has advice here .
I picked up a AX-190 ham receiver .
The receive is just a slight hiss with the headphones on . Ive found one forum that talks about possible faults .
Im not really savy on radios but can replace small components no problem .
Receiver lights up but no audio or s meter movement .
Nothing has been tampered with internally .
Age got to it and something has given up .
Any advice would be appreciated
Thankyou

[Bluerunner]

Lotsa info on the internet but I have no personal experience with it.

Comments suggest you can expect it to not be very sensitive over 20 meters (14.000 mhz) but pretty good below that. Most short wave radios need a long wire antenna, 50' or more for good general coverage.

[tgbrail]

Thanks for the reply .
Its not totally dead after all . I replaced a resistor in the power supply but needs more than that .
I transmitted from my cb walkie talkie right next to the ax190 .
It was able to receive an audible signal and s meter reading but should be far stronger than what its picking up.
So its not dead

[MDYoungblood]

Cool radio, Realistic '70 to '72 era. I wasn't working at RS when they came out, had moved on to bigger things. They are solid state so the first thing to look at are the capacitors, watch out for the big ones on the power transformer, they can kick you to the floor or worse.
Like Bluerunner said, check out the internet for more info and manuals.

3's

Greg

[tgbrail]

Anyone have any idea what power supply is used in the radio shack / Allied AX-190 or SX-190 receiver ?
Thanks, Craig

[tgbrail]

My AX-190 receiver has a hum only when its plugged into the 120 AC outlet .
12 volt supply is nice and quiet

[MDYoungblood]

The hum is because the AC filtering caps are bad. If it is working with the 12v source and you are okay that way, run it until you can find a schematic with part numbers to get the caps. As old as it is my guess is all the old electrolytic caps will need replacing soon.

3's

Greg

[tgbrail]

Hi , i replaced the caps a day ago . maybe it needs a larger cap . the original cap was big as opposed to the new ones are very small

[tgbrail]

MY AX-190 IS ALIVE AND RECEIVING GREAT ! ONE RESISTOR WAS BAD !
FINALLY I SCREWED THE LID BACK ON AND ITS RECEIVING NICE !
THANKS FOR YOUR INPUT !

[MDYoungblood]

Glad to hear it's up and running.

3's

Greg

[tgbrail]

Have you heard of putting a .1 uf disc ceramic capacitor somewhere in the receiver on the transformer on the 120 vac side to eliminate the AC hum ? Ive changed all the caps and still have this AC hum ..
Puzzling !!

[MDYoungblood]

I believe that receiver will also work off 12v, have you tried that and see if the hum is still there. That will determine if the problem is the internal power supply or the hum is an outside source.

Oops, should have back read, this has already been done. Next is to find out if the "Hum" is in the radio or traveling on the AC receptacle. Most houses are loaded with things that make noise on the radio through the power lines, might not even be your house/apt but a neighbors.

3's

Greg

[nosaj]

If it's a 2 prong plug flip it over and see if it sounds better.
Nosaj
N1EBC

[tgbrail]

Hi , it has a ground prong also with the 2 AC prongs .
I wish it would be that easy though .
Thankyou for the reply though !

[nosaj]

Next is to find out if the "Hum" is in the radio or traveling on the AC receptacle. Most houses are loaded with things that make noise on the radio through the power lines, might not even be your house/apt but a neighbors.

3's

Greg

Try the above, try another room , another house, turn off any lights in the room, etc.

nosaj
N1EBC

[MDYoungblood]

Hi , it has a ground prong also with the 2 AC prongs .
I wish it would be that easy though .
Thankyou for the reply though !

Originally that radio only had a regular 2 wire plug so someone had installed the grounded one. If you look on the bottom side to where the AC power goes there should be a disc cap on it. of it is easy to get to, lift the ground from the cord and see if the hum goes away.

3's

Greg

[tgbrail]

Hi , thanks for the info . I didnt know these came with just a 2 prong .
I located the 200v 0.001 uf oil capacitor . changing it with a better cap made no difference .
The filter cap on the supply board is a 25v 2200uf. Replacing it with a 4700uf cap almost totally eliminated the AC hum plus I replaced the new audio caps with even higher uf caps . Hope others can put this info. to good use .

[tgbrail]

Hi , thanks for the info . I didnt know these came with just a 2 prong .
I located the 200v 0.001 uf oil capacitor . changing it with a better cap made no difference .
The filter cap on the supply board is a 25v 2200uf. Replacing it with a 4700uf cap almost totally eliminated the AC hum plus I replaced the audio caps with higher uf caps . Hope others can put this info. to good use .

[tgbrail]

Okay ! Here's what I did to shut the radio up as far as AC "hum" . In the power supply pcb , the main cap was
2200uf 25v . I used 2 4700uf 25v caps side by side . Any other caps , I doubled the uf of each cap .
Its more than safe to do that .
The oil cap for the AC is a 0.001 600v with a 3.3k / 1/2 watt resistor .
Replaced the resistor with a new one and a way higher uf mica cap of 600v .
Zero AC hum now !!!
The better 600v cap alone wont do it . Its the main 2200uf 25v cap power supply cap is the issue in these Allied AX, SX -190 shortwave and ham receiver .
If anyone can advise me on what white led and what resistor to use on these , all is welcome .
I tried a few combinations and went right back to the original bulbs .
There must be a good LED substitute .

[tgbrail]

Okay ! Here's what I did to shut the radio up as far as AC "hum" . In the power supply pcb , the main cap was
2200uf 25v . I used 2 4700uf 25v caps side by side . Any other caps , I doubled the uf of each cap .
Its more than safe to do that .
The oil cap for the AC is a 0.001 600v with a 3.3k / 1/2 watt resistor .
Replaced the resistor with a new one and a 4700 pf 600v mica cap .

Zero AC hum now !!!

The better 600v cap alone wont do it for some reason . Its the main 2200uf 25v power supply cap is the issue in these Allied AX, SX -190 shortwave and ham receiver .
If anyone can advise me on what white led and what resistor to use on these , all ideas are welcome .
I tried a few combinations and went right back to the original bulbs .
There must be a good LED substitute .

[MDYoungblood]

Cool, usually leaving the value the same but increasing the voltage isn't a problem. In a filtering circuit increasing the value and voltage never hurts. Good to hear you got it fixed.

3's

Greg

[tgbrail]

From what I understand , you can increase the UF but "not" lower !
The voltage rating must stay the same to what ever the original capacitor is . In power supplies and IF circuits you will benefit by increasing the UF . With my receiver , it eliminated any AC hum and improved the audio.
Same would work for CB's I would guess .