DD-9 observations

[kingcrab]

I have purchased this DD-9 on the cheap recently. It looks great, everything checks out and all the functions work on this machine. But the playback quality just keeps bugging me. Here is my observation:

1) when playing home recorded (on other machines) and pre-recorded cassettes, the sound is distorted, kind sound like the tape is oversaturated and muffled.
2) when recording, switching between tape and source, the recorded sound seems to add a bit of oomph to the low end and lost some of the high end (sound a bit muffled). However, when the recording is then played back on my other machines, they sound very good with the right amount of low and high end. By the way, before recording I used onboard BEST system for bias, eq and level calibration.

It seems to me that recording works fine on this machine but playback is somehow out of whack? I have cleaned and demagnetized the tape path, but don't notice any difference.

Anyone has had similar experience or may have some insight into this?

http://i308.photobucket.com/albums/kk346/kingcrab_photos/JVCDD-9-1.jpg

[Scorpion8]

If the tape you recorded on the DD-9 plays back fine on other decks, then the recording system seems to work well. As far as playback on that deck, have you cleaned the heads again and again and again .....? You might need to DeOxit the balance and output sliders since signal goes thru those. (I've never been a fan of slider mechanisms). It's possible that someone improperly de-magnetized the heads and zapped them with siome residual magentism.

[Nakdoc]

Clean the play head really well.

[kingcrab]

The heads look pristine to me. But I'll give it a good cleaning again tonight and see if it makes any difference.

[Scorpion8]

The heads look pristine to me. But I'll give it a good cleaning again tonight and see if it makes any difference.

And then do it again. And again. 99.99% isolpropyl alcohol and Q-Tips....

[Kevin's Rack]

Ah yes, the DD-9. This was spec-wise JVC's finest tape deck (though I suppose some would argue that). I absolutely love the look of that deck, and I especially love being able to switch between VU and Peak, which is very rare on digital meters (there are nearly always peak reading). If the azimuth of the heads on this unit are independently adjustable (IE the record head is not welded to the play head), I think tweaking the play head's azimuth may be required. If you don't know what you're doing, don't eff with it! Be careful if you do, and most importantly, HAVE FUN! Ever see the spaghetti factory under the hood of that thing? Whew!! *eyepop*

[scan80269]

Wow! Seeing this deck brings back some fond memories, as the DD-9 was the deck that my brother and I saved up to buy in ~1981 while in college for taping LPs.

I remember this deck having a siamesed Rec/Pb head, and the head material was probably on the soft side, since I could see grooves worn on all the heads after a few years of use. I also recall the solenoid for engaging the heads in playback being a bit violent, to the point of causing an audible dropout on the tape whenever PLAY is pressed!

If playback head azimuth is off, the BEST tuning system can be fooled into compensating for the azimuth error by under-biasing and over-equalizing the tape, which can lead to higher distortion and reduced high-end headroom. If the heads are worn like on my deck, high-frequency response may not be restorable without a head replacement.

My recommendations would be to check head azimuth alignment with an azimuth test tape, and follow service manual instructions for mechanical calibration. A cassette calibration gauge such as Willy Hermann's WHS-300 will also be helpful in checking head height and stroke, in case those are off as well.

[Scorpion8]

... and the head material was probably on the soft side, since I could see grooves worn on all the heads after a few years of use.

Probably just polishing marks from the tape. *scratchchin* I doubt the tape would wear grooves in such a short time frame unless the heads were made of butter.

[scan80269]

Yesterday I finally got re-acquainted with my DD-9 that was left sitting inside a cabinet in my brother's garage for nearly 20 years. This deck was bought new back in 1981.

Not only did it power up fine, but it could even play a tape! I started cleaning the mechanism and noticed some glazing on the pinch roller, so I used a bit of 600 grit sandpaper on it and now it is in much better shape. At least it didn't completely harden like I thought it would. The idler tire had also glazed and required the same treatment. I also cleaned the brass pulley and supply and take-up reel tables.

After lubricating the capstan shaft and the pinch roller axle, W&F can get below 0.05% weighted peak (DIN), so the DD motor and drive circuitry are still doing good.

A broken wire to the erase head had to be soldered back before the deck could erase properly. The only thing still broken is the tape auto-cal (B.E.S.T.) feature. Pressing the Start button only yielded one solenoid click, but no tape motion whatsoever. This one will be interesting to troubleshoot.

[scan80269]

My 30-year old DD-9 needed some TLC as it finally developed some problems:

- B.E.S.T. auto tape calibration failure to start. This was recently diagnosed to a bad OKi MSM4051 IC on the logic board. A replacement TI CD4051 IC arrived today and this feature is now working again. *Hi5*

- Quartz lock failure for the capstan motor. This was due to a bad Oki MSL9348RS PLL motor control IC. Unfortunately this IC is unobtainium so I may never see the quartz lock indicator light up again on this unit, and it plays about 1.5% fast.

I also replaced all the electrolytic caps on the power supply board, and changed a zener diode used to set the +5V rail voltage, which was almost 0.5V too low.