hey yall, just picked up a 488mkii in awesome condition but unfortunately after a few weeks an issue has started to pop up. the recorded signal from track 8 has started to cut out regularly. when the signal's gone, even the track 8 meter shows nothing. however, when i apply a little bit of pressure to the center of the bottom plate of the unit, signal pops back in meter and all for a while until it cuts out again. my first thought was that something with the sync switch was up but no amount of wiggling or deoxit seemed to stabilize the track. i also took it apart, unplugged and cleaned all the pin connections and generally cleaned up the insides, but no luck. anyone have any idea what might be up and what else i could try? thanks!
488 mkII issue
- Thread starter max.t
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Jack Saturn
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You mention applying pressure to the "bottom plate" of the machine. Do you mean the underside of the plastic case, or the PCB? If signal is cutting out when part of the machine is flexed, it could mean there's a crack in the R/P PCB. I work on a lot of 488 / 488mkII machines, and this is not uncommon.
Also, very gently wiggle the Input Select switch on channel 8 while you're feeding it signal. Does the sound break up or drop out?
Also, very gently wiggle the Input Select switch on channel 8 while you're feeding it signal. Does the sound break up or drop out?
hey jack! you're actually working on my mt8x right now. thanks for your help. should have been clearer, i did mean the underside of the plastic case. when i had the machine open, i didn't notice any cracking on any of the PCBs but i definitely could've missed it.
wiggling the input select didn't seem to change anything. i don't think anything is wrong with the channel itself as it seems to pass line signal no matter what. it seems to just be an issue with the tape return for track 8. the tape return LED meter also cuts out along with the audio in reaction to pressure.
also, when i had the machine turned on to test that, i noticed that now the right side of the headphone out is dropping out, and once again the issue corrects itself when i put some pressure on the underside.
wiggling the input select didn't seem to change anything. i don't think anything is wrong with the channel itself as it seems to pass line signal no matter what. it seems to just be an issue with the tape return for track 8. the tape return LED meter also cuts out along with the audio in reaction to pressure.
also, when i had the machine turned on to test that, i noticed that now the right side of the headphone out is dropping out, and once again the issue corrects itself when i put some pressure on the underside.
Jack Saturn
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- A bunch of 4-tracks!
Hey Max — small world!
It's always just hypothesis unless I actually have a machine in front of me, but based on what you're describing, I still suspect a crack in the R/P PCB (the one on the bottom of the case). Often these kind of cracks are difficult to spot, or are only visible on one side of the board. Sometimes I have to remove the PCB completely and hold it up to the light before I can find the crack.
The headphone could have broken solder joints. (Again, just a guess.)
It's always just hypothesis unless I actually have a machine in front of me, but based on what you're describing, I still suspect a crack in the R/P PCB (the one on the bottom of the case). Often these kind of cracks are difficult to spot, or are only visible on one side of the board. Sometimes I have to remove the PCB completely and hold it up to the light before I can find the crack.
The headphone could have broken solder joints. (Again, just a guess.)
yeah that sounds about right. thanks for the info! maybe i'll drop this guy off when i pick up the mt8x haha
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