Hi All, I'm new to S2G but not to tape decks, fair experience with Sony TC-D5M. I just purchased my first Walkman in 40 years... a WM-D6C and of course it needs a lot of work. Similarities to the D5M certainly. I have spent a few days cleaning and ordering some spares like belts and tires etc. I encountered the frozen FF/REW idler lever and resolved that plus a few more. Installed generic belt and a new pinch roller. So far so good. I removed/lubed the capstan which required me to remove the motor of course. I found fabulous tutorials here to help me and everything seemed fine. Reassembly went well. Wow/Flutter is poor (0.08%) but I am waiting for a new capstan ring, idler tires and correct belts to see if that improves. Set playback levels with a Dolby ref tape, record levels per the Valentin Tutorial, great... Azimuth followed and sadly I found that I cannot maximize signal AND stay in phase. Perfect phase has one channel WAY stronger than the other (by 40mV), and the only setting where signal levels are close AND in phase is pretty low (~27mV). Thereafter, I found freq resp was AWFUL (40 - 9kHz -3dB) so I checked bias and found the bias capacitance was set to 43pF which seemed extreme. Lowering to 22pF and redoing FR got me to 40-12kHz (-3dB) but this is still a long way from 40-15kHz. I have ESR tested the caps in the eq section and all is well there. So, any ideas what to try next? Please tell me I am overlooking the obvious Am I right to fear that the azimuth imbalance between channels sounds like a head issue? The Amorphous heads look in great shape but could be flat-spotted I guess, no pitting anyway.
W&F is acceptable at 0.08% although not great for this unit. Apart from replacing the capstan ring, sanding the motor spindle and adjusting the motor position can help in reducing W&F. Don't forget to adjust the servo (PLL disconnected, adjust for 3090Hz, reconnect) as that adjustment also impacts W&F. As far as the azimuth goes, SONY manuals mention (page 17 of D6C manual) there are 3 good Lissajous patterns: in phase, 45° and 90°. I know some will disagree with this, but I think if you can manage to maximize both channels while at the same time obtaining one of the 3 phases mentioned, you're good. Wouldn't rely on 0° phase alone as an absolute indicator of perfect azimuth, because phase between channels depends on other variables not just the angle of the head. Do keep in mind phase is only relevant if you're using a full-track tape (assume you do), otherwise it means very little. In my opinion, a more accurate/repeatable adjustment is done by using a white noise tape and adjusting for flat frequency response. This takes the phase completely out of the equation. As far as bias goes, if azimuth is wrong (or head worn or less likely head height is incorrect) you will be unable to adjust bias correctly. So you need to figure the head first, before adjusting bias. If the head has no pittings (you really need to remove door on D6C to properly see the head, otherwise it looks good even when it's not) wear can be excluded.
