Compact Cassette - JVC TD-W709 [C] Recertify
The JVC TD-W709 is a double cassette deck that was part of JVC’s lineup in the early 1990s. Here are some of its key specifications:
- Type: Auto reverse, double compact cassette deck
- Track System: 4-track, 2-channel stereo
- Tape Speed: 4.8 cm/s and 9.5 cm/s
- Heads: 2 x record/playback, 2 x erase
- Motor: 1 x reel, 1 x capstan, 1 x mechanism
- Tape Type: Type I, CrO2, Metal
- Noise Reduction: B, C
- Headroom Extension: HX Pro
- Frequency Response: 20Hz to 17kHz (Metal tape)
- Signal to Noise Ratio: 73dB (Dolby C)
- Wow and Flutter: 0.08%
- Total Harmonic Distortion: 0.8%
- Input: 80mV (line), 0.4mV (mic)
- Output: 0.3V (line)
- Dimensions: 435 x 134 x 328mm
- Weight: 5.1kg
- Accessories: Remote cable (optional)
The TD-W709 model is known for its solid build and reliable performance. It features auto-reverse on both decks and supports Dolby B and C noise reduction systems. It does not come with a remote control but has outputs labeled “COMPULINK-3 SYNCRO” for integration with compatible JVC systems12.
If you’re considering this model for purchase or need assistance with it, keep in mind that due to its age, it might be harder to find in mint condition or may require servicing to ensure optimal performance2. If you have any specific questions or need further information, feel free to ask! 😊
Mechanical and Visual Checks
This deck was in pristine condition when we got it from an auction site. It was acting flakey with the buttons on deck B. Looking at it closely, it looked as if the cover had never been removed. This is always a huge plus for me because in general, all the settings could be in original factory condition. From the look of the pinch rollers, head and capstans, it looked as though the machine had actually never been used. This, after buying it ‘”Parts Only’ on an auction site was a surprise.
The flakey operation turned out to be a ribbon cable connection that must ahve somehow come loose. Just remove and replace the cable fixed that.
Power Up and test play.
These tests are made using scrap tape, and a pre-recorded tape. The deck functions as expected, the tape path looks clean, and the rollers look okay. A short test recording indicates that the machine is functional for recording and reproducing and that the noise reduction systems operate. Looking at the owner’s manual I can see that fundamentally the machine is meeting operational requirements.
Check for Wow and Flutter
For a rough check, I use a 1 kHz -10db test tape. At this stage I am listening by ear for obvious worn belts and pinch rollers. Of course, the condition might have been indicated in the test play step above. In this case I think I did hear a little warble, so now on to the next issue, look inside.
Remove the cover and look for worn belts, hardened grease, and worn rollers in the tape drive. Often a simple application of a tiny bit of rubber cleaner/dressing can allow you to avoid replacing rollers and such. Any lubrication should be very slight.
This is JVC Unit C and has two deck units in it hence the term C/A and C/B
Note that this machine is an auto reverse double deck. Operations need to be checked in and directions and on both decks. Both decks record and additionally there is a high speed mode.
TD-W709 Owner Manual
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TD-W709 Service Manual
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Tape Path Alignments
There is an adjustment for the head height, and there is a standards tape for that. Putting that standards tape in the machine, adjust the height adjustment screw as shown in the service manual. The tape is shown below.
- Unit C/A = -8db Left, -8db Right Fwd / Rev
- Unit C/B = -8db Left, -8db Right Fwd / Rev
That compared to the test tape standard is a good value, and importantly, is equal in both channels indicating that the tracks are centered. This tape has been verified as a system standards tape, no additional track placement test are required
The reference numbers from a Nakamichi are show on the tape from the factory. The tape was tested at the 02:00 minute mark.
This tape has been imaged to confirm the tracking and measured with a visual scale.
M300 Test Jig
The M300 is a master plane jig used for cassette tape alignment1. It’s designed to establish track height, parallelism (tilt), and head penetration1. The shape of a cassette shell is specified by standards set by the Philips patents, and this jig is designed to ensure the heads and other parts of the deck match this standard
Instructions for the use of the M300 jig are in the service manual for this deck
Magnetic Imaging of Cassette Tape
Magnetic imaging can be a valuable tool in cassette tape restoration by providing a non-invasive way to visualize and analyze the magnetic patterns on the tape. This is particularly useful for:
Diagnosing Issues: Magnetic imaging can reveal problems such as uneven magnetic fields or areas where the magnetic particles have degraded, which can affect audio quality.
Forensic Analysis: It can help authenticate the age of recordings or detect tampering by comparing the magnetic patterns to known standards.
Data Recovery: For damaged tapes, magnetic imaging can assist in recovering audio data that may not be retrievable through conventional playback methods.
Preservation: By understanding the condition of the magnetic tape, conservators can make informed decisions about the best methods for preservation and storage.
Magnetic imaging, combined with other restoration techniques, can help extend the life of valuable recordings and ensure their continued accessibility for future generations. 😊
There are two decks in the unit deck A and B. They are both auto-reversing. This means that imaging tracks must be done in both directions. I recorded a 30 Hz Square wave at 0 Vu [Approx. 200 nwb/m] . This give a very easy to see line pattern on the tape. Square response is pretty good on cassette decks that are aligned carefully. THD in this case means very little because harmonics are hidden in the vertical patterns.
Below are the traces. Click on the image and zoom in to see them better.
See the article about how to make these traces in the ‘TEST’ area of this website
Wow and Flutter
Using the Leader LFM-39-A Wow and Flutter Meter, record a signal from the internal Oscillator and play the tape recording back to read the Wow and Flutter Specification
System Standards Azimuth for Cassette Tape
We have found a System Standards Azimuth Tape. In order to verify the azimuth on this machine, we used a standalone Oscilloscope, Hantek DSO 2 D 15 and lined up the traces . This azimuth setting will be used system wide. Below is the images of the tape and the scope trace. The Azimuth adjustment screw is indicated in the Service Manual.
This tape deck has four azimuth adjustments. Two decks and two directions. We found the adjustments to be stable in both directions when set even with the rotating head assembly. This head type can be problematic for azimuth.
The Electronic Performance and Alignment
Playback Level
Once the azimuth is set, set the playback level. Connect a VTVM to the output and playback a standard level tape. Using the service manual get the required output at either the output jacks or a test point on the circuit board.
Playback level setting is the basis for the setting of the recording level and that in turn sets the distortion at maximum recording level.
Playback level is set by using a standard level tape. In the case of this deck, and of all decks in the system, we have decided that 200 nwb/m magnetic flux = -2db on these machines. This is perhaps an arbitrary setting to some degree. The service manual for this deck wants to use a particular tape from JVC and they want to set that tape at -7.5 dBs. The consensus is that that tape is a 160 nwb/m tape and using our 200 nmb/m tape will be the same level.
We will use the Leader VTVM to set that level using the same setup as shown in the service manual.
The Leader LMV-181A, and the 200 nwb tape G-5 are system standards.
Playback Frequency Response / Equalization
The first alignment that must be performed is that of playback equalization. This is required because all subsequent adjustment are based upon the playback being set correctly.
Playback equalization can only be set by using a known standards test tape. Using this tape and electronic spectrum analysis software we can assure that the subsequent adjustments are made based upon a correct playback system.
The Service Manual indicates where these adjustment are.
We have obtained the TEAC Multi-Frequency tape MTT-117 SP which contains 40, 315, 3.15k and 14k signals recorded in a single tone. Using a spectrum analyzer, we can set the playback equalization for a flat response by looking at the spectrum of this tape played back. The TEAC MTT-117SP cassette test tape is a system standard for all cassette playback equalization.
Below is the left and right channel spectrum. We used a Software spectrum analyzer and the Behringer UCA 222 along with our mil spec laptop. The computer laptop we used is described in the computers section of this website.Together, the UCA-222 and the Spectrum Analyzer software and the Lenovo Carbon x1 Laptop are a system standard.
Bias Adjustment
This machine arrived to us and had never been adjusted from the factory standard setting. We did not change the bias settings for that reason. We checked playback frequency response curve and found it to be adequate for a two head deck. This step in the process, for us at this time is only a check
Bias adjustment is most easily accomplished using a white noise signal and spectrum analyzer. We used the software analyzer and the UCA 222. Simply tune the bias control for the flatest response. This is best done at -20db signal level. Below is the spectrum ..
Note that this Bias adjustment was used because it has the flatest response. It is possible to decrease Bias somewhat and elevate the high frequency end of the response curve, but this is done at the cost of linearity and increase of harmonic distortion. Also note that the curve was recorded at a low level. Higher recording level will saturate the tape and cause increasingly lower high frequency response.
For this set of machines and calibrations Standard Tape is \
Type I – Maxell UD
Type II – TDK SA
Type IV – TDK MA
That’s it so bolt the cover back on, and try to record something and musically verify the tuning. and of course there’s always ….
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Conclusions
- Concluding comments
1. There are two TD-V661’s in the system -Unit A and Unit B – The test results and illustrations are shown for both units. - 2. This Deck is JVC – C a third unit dedicated to playback and high-speed dubbing
- 2. This page was done engineering notebook style – Someday in the future it might be added to and typed up
3. See our list of req test equipment for detail on the gear used - 4. Take a look at some of our other re-certifications
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