Well to back track a bit..... The popping only occurs once I have started playing a tape in MONT. mode i.e. it pops each time I RW, FW, STOP that tape, and it is only a single pop. As far as something hitting the deck, no.....I simply hit the transport buttons. When I'm playing back a track at a standard listening level, the pop is loud enough to where the speaker cone could blow, that's what worries me. And it happens across the board, not one track in particular.
The way my deck was designed, you have INPUT, NORM, and MONT. modes. Input is pretty straightforward, NORM. is playing a tape back from the record head. Norm mode is how you overdub, BUT (and the manual says this as well), NORM mode could be used to completely utilize the deck (Record, playback, overdub), all off that one setting.
MONT. mode is simply a non-recordable mode (only off the playback head).
The problem with running everything off the NORM mode, is that you cannot properly calibrate.......Which is where the MONT. mode comes into play......You can only calibrate the deck by using the monitor head.......
Long story short, in order to calibrate the deck you have to record a test tone (starting in INPUT mode), then as the tape rolls, switch the deck into MONT. mode (so you are hearing the signal PLAYBACK on the tape and can adjust). The problem: That has not been working for about a month or two.....Each time I attempt to do that, as soon as I switch to MONT. mode, the signal comes in really weak and has a slapback delay sound. This started around the same time the popping did. And the popping issue occurs whenever I use that mode.
After learning that blocking capacitors can affect the input and output signal, I believed that fixing this popping issue would fix the delay issue; because it really sounds like the signal is bleeding through the NORM head and the MONT. head at the same time, like their is a bad component somewhere.
When I am not in calibration mode (what I mentioned above) and am simply playing back a tape normally, the signal comes in fine, but I still always get the popping.
Harald mentioning the power supply also does make some sense-- I have had a few power outages (i.e. where my house has lost power or Ive blown a fuse) and the deck has been shut off while functioning. It was around the last time that happened where the popping issue began.
If I didn't explain something clearly, message me. I can give a more detailed explanation. FOR NOW, my main focus is the popping because I believe whatever is causing that will also be the cause for the slapback problem.
This is significant because as most of you know, if you can't calibrate a deck, it's practically useless.