Hi All .
Got a weird problem with a mk II Superstar 360FM with the PB-010 pcb . Now before i start I'll have to apologize as I won't be able to gain access to the radio again for a few months , so I won't be able to do any additional testing until then . I really just wanted to throw the problem out there to see what you guys thought .
I picked the radio up together with a couple of Grants a couple of months ago . It looked untouched apart from the beep , which had been disconnected . The 2SA1012 was blown and the channel display led needed replacing. Fixed those issues and did the diode 5 band (lolo and hihi) mod on it . I did a few basic checks and I was just about to close the cases when I switched it over to FM . I instantly noticed that there was no "crunch" . There was a hissing , but not the usual FM crunch . Weird . OK . Maybe it's the detection coil (L6) . Gave that a tweak . There was a difference , but I was still getting the hissing . I changed the coil anyway , and the upc1028 , but the problem was still there . I changed the 2 filters (FL1 and FL2) as well . No change .
So . Here's the weird bit . I started to connect the PL259 on the back which goes to my power meter and dummy load . As soon as I connected the center pin all hell broke loose . Loads of electrical noise . The thing is actually picking up my electric magnifying lamp . I can hear the "pops" through the speaker as I switch the 220V mains to the lamp on and off . The radio is still picking up actual 27Mhz FM transmissions , although they're badly distorted . Now . I'm pretty sure the hissing is due to the fact that it's actually receiving a small signal from somewhere . The thing is , that AM and SSB work fine . It only happens on FM . Touching the chassis seems to have an effect as well . I tightened the screws that connect the pcb to the chassis just in case . I don't have any shorts between case and ground , and the capacitors between the power socket and chassis are good too . The voltages on the 1028 were as per the manual . I've 5 or 6 other 010 radios here and they all work fine .
Anyway . I didn't have any more time to look at it . I'm working overseas at the moment , and it'll be 3 or 4 months before I see it again . I've just been sitting looking at the schematic for the last couple of weeks with a vacant look on my face trying to come up with something .
Anyway . As I said . I just wanted to throw the problem out there to see if you guys had any ideas . Thanks in advance for any help or suggestions .
Sammy
Got a weird problem with a mk II Superstar 360FM with the PB-010 pcb . Now before i start I'll have to apologize as I won't be able to gain access to the radio again for a few months , so I won't be able to do any additional testing until then . I really just wanted to throw the problem out there to see what you guys thought .
I picked the radio up together with a couple of Grants a couple of months ago . It looked untouched apart from the beep , which had been disconnected . The 2SA1012 was blown and the channel display led needed replacing. Fixed those issues and did the diode 5 band (lolo and hihi) mod on it . I did a few basic checks and I was just about to close the cases when I switched it over to FM . I instantly noticed that there was no "crunch" . There was a hissing , but not the usual FM crunch . Weird . OK . Maybe it's the detection coil (L6) . Gave that a tweak . There was a difference , but I was still getting the hissing . I changed the coil anyway , and the upc1028 , but the problem was still there . I changed the 2 filters (FL1 and FL2) as well . No change .
So . Here's the weird bit . I started to connect the PL259 on the back which goes to my power meter and dummy load . As soon as I connected the center pin all hell broke loose . Loads of electrical noise . The thing is actually picking up my electric magnifying lamp . I can hear the "pops" through the speaker as I switch the 220V mains to the lamp on and off . The radio is still picking up actual 27Mhz FM transmissions , although they're badly distorted . Now . I'm pretty sure the hissing is due to the fact that it's actually receiving a small signal from somewhere . The thing is , that AM and SSB work fine . It only happens on FM . Touching the chassis seems to have an effect as well . I tightened the screws that connect the pcb to the chassis just in case . I don't have any shorts between case and ground , and the capacitors between the power socket and chassis are good too . The voltages on the 1028 were as per the manual . I've 5 or 6 other 010 radios here and they all work fine .
Anyway . I didn't have any more time to look at it . I'm working overseas at the moment , and it'll be 3 or 4 months before I see it again . I've just been sitting looking at the schematic for the last couple of weeks with a vacant look on my face trying to come up with something .
Anyway . As I said . I just wanted to throw the problem out there to see if you guys had any ideas . Thanks in advance for any help or suggestions .
Sammy