This venerable (but mono) tape recorder, still very clean, was used to record music many years ago (on 1/4" reel-to-reel tapes). The recordings were on both the "Normal" and the "Exchange" tracks in each direction of the tape. For years, the playback sound level of the two tracks was comparable in loudness -- with the volume knob left at the same position for playback on either track. Recently, and after not using the tape recorder for several years, playback of those tapes occurs at much lower (and much more noisy) level on the Exchange track than on the normal track. This is true no matter what tape I use among the old tapes recorded on this machine. And remains so regardless of whether I use the built-in speaker of the tape recorder or send the signal through a receiver by using the tape recorder's P.B. Monitor or the Line-Out outputs. I used Deoxit on the contacts of the Record/Playback switch on a little board inside the unit, and on some other contacts, but that did not help the above problem, although it got rid of the small amount of static noise that was present when I was changing the volume level. Also, I tried recording something new on a tape and play it back. The Normal track records and plays back very nicely (both through the built-in speaker and through a receiver), but the Exchange track is both very faint and very noisy. Both the old recordings and the new one were done on each track with the unit's "Magic Eye Recording Indicator" at the recommended level, i.e., with the two lights of the indicator "fan" almost touching, but not overlapping, except for momentary peaks in the signal. PLEASE, help! Any idea/suggestion will be greatly appreciated. It's the only machine I have to play back those old friends/tapes, and I do not want to lose half of the recorded tracks. Is my following (beginner's) thinking correct? 1. It is unlikely that the Exchange REC/Playback head went out of alignment while the Normal head remained OK, since both are rigid with respect to each other. And if this is true, playing with the azimuth adjustment will not help, because it moves both the Normal and the Exchange heads together, right? 2. It leaves me with the (only?) possibility that the Exchange head is worn out, but the Normal head is OK. 3. If new REC/Playback heads are needed (part # PP 15-2902), will desoldering and soldering be needed to replace the heads and, if so, should it be done at the four wires right at the back of the heads or at the circuit board inside the unit -- I have not yet looked where those four wires go under the top cover. And would my 30W soldering iron be sufficient for this job? 4. If new REC/Playback heads are installed, is it necessary to also replace the erase heads -- other than the, I assume, obvious reason that new heads will function better than old ones? I do not plan to do any new (mono) recording on this machine. I just want to be able to listen to the old tapes. Thanks in advance for any help.