Hi, One of my DC2 has started to develop a issue with sound dropping out/totally muted for approx 0.5sec. This happens very occasionally, once every a couple of hours but I think it is getting more common. The sound fully disappear on both channels and then comes back. It is not related to the tape/recording. The tape continues to play during dropout, no change in speed. This happens when the player is still on a table and it’s not possible to provoke to happen by shaking or moving it. Otherwise the player works perfectly and sounds great. Power issue? The LED is less bright then in other walkmans and sometimes pulsing. Wouldn’t this cause player to stop/drop in speed? Cleaned battery contacts and also tested with bench power supply, same symptoms. Muting circuitry incorrectly kicks in for some reason? Ageing capacitors? Will start troubleshooting but appreciate any tips on what to look for or if you have seen this issue. Thanks!
Symptoms of aging capacitors are different. Decreasing capacitance on the output caps would render less sub-bass, but for this to happen the decrease has to be significant like the actual value is less than half or less than the specification. Electrolytics can also fail short-circuit (and can be intermittent), but you would hear a loud pop when DC gets to the headphones. Fact LED is pulsing is interesting, that is worth investigating further. This pulsing LED have seen on DD33 units with auto-off circuit not working correctly, but happened only in FF/REW not PLAY. More investigation needs to be done, but this is where I would start. Check the current draw also.
I think you're right regarding caps. Also I have replaced the output caps previously for better bass response. Current draw is 89mA@2.8V supply. For good measure I cleaned the S901 Power switch, I'll wait and see if that makes a difference. On a related note, is the PCB exchangeable between DC2 with the older pointed head and the newer rounded head? I'm investigating another issue with DC2 with pointed head and wanted to rule out where the problem could be.
Yes the PCBs are the exchangable. Even if you see some minor differences, theese are revisions of the same board with no functionality change. What issue are you investigating regarding the pointy head ?
Dolby C decoding not quite as it should be. Sound is great but there is a slight cutoff/compression of the reverberation in the music that I don’t hear on my other Dolby C players. I have adjusted the Dolby levels and checked the azimuth, same procedure as I’ve done on my other players. I’d like to find out if the issue is with the tape path or electronics to narrow down the search.
Let us know what you find. Electronics indeed can't be excluded, although don't think it's the most likely scenario. One possibility is head wear, case in which the head may need lapping. Seen quite a few DC2 that has bad frequency response due to wear. If you can measure the FR (with white noise tape), that's something I would check.
I have made some progress with the Dolby C issue on the DC2 with pointy head. Done from before without fixing Dolby decoding All electrolytic caps replaced Output caps replaced for better bass response Azimuth alignment - by ear + scope Dolby levels Done now: Tape path alignment - mirror tape - then: Azimuth alignment - by ear + scope These two together seem to have more or less completely solved it. It is now on a level I can't say for sure if the problem still exist or not. Often go back to original source to find out it sounds the same. Tape path alignment and mirror cassette is new to me, basically trying without knowing how to do things. I must say I couldn't see anything obvious wrong with alignment before but tried adjusting anyway to see if it made a difference which it did. ToDo: Frequency response - white noice + spectrum analyser Takeup torque - waiting for torque tape (Tested by hand in it feels similar to other DDs) Regarding wear on the head, I don't think this is the problem. The head looks brand new and so do the rest of the unit. I don't think it has seen much use. The sound from this Walkman has such a clarity and volume, happy about it.
