last updated 24 Spetember 2004

by Eddie Ciletti

Compatibility: Sony vs Panasonic
DA-60 and DA-60MKII
 Tally-Ho: DA-30 mod
Portables & Batteries
Tascam: DA-P1
All In The Family: Panasonic Issues
Error Rate Access
 Error Rate Display

For its generation, the SV-3500 had a very reliable transport primarily due to its optical mode switch and transport logic.  All other machines use  electro-mechanical switches (which are failure-prone) to report transport status back to the system controller.  Many decks also operate under capstan control in reverse play.  While there is nothing inherently wrong with this concept, it does become a problem if supply and take-up tensions are out of specification. Sony's earliest machines — the PCM 1000 / 2500 / D-10 (also from that period) — have separate reel motors, while most transports derive "reel power" from the capstan motor through belts, gears and clutches. Yuck!  (Sony created an absolutely awful  transport — the PCM-2300 was no better as the "pro" version of several consumer models.  Then, Sony created the PCM-R500, which has separate reel motors, and had a street price of about $1200.)


This is not a new cocktail drink, but it is a problem with older machines whose rotating heads get “stuck.”  This has been the case with the venerable Panasonic SV-3500 and now, with the nearly vintage SV-3700.  It is much easier to access the latter — with the cover removed — by opening the drawer halfway.  If the head is stuck, just apply a little rotational pressure in either direction.  If you can stand the occasional inconvenience, the head is otherwise functional.

COMPATIBILITY: Sony versus Panasonic

A misaligned machine will play its own tapes.  ALESIS suggests that users make their own "reference tapes" when the machine is new.  Format a new tape, date and test it for errors.  Later, when a problem arises, you'll be able to troubleshoot the problem rather than burning precious brain cells.  I suggest recording a pleasant, low-frequency tone -- 40 Hz is very soothing -- across the entire tape, just to confirm that something, in addition to absolute time code, is on the tape.   Test tapes are expensive, but a scope and a "home-made" reference tape will get you in the ballpark.  This link shows how to make the connections.

Alignment issues usually show up when tapes are sent out of house.  Contrary to hearsay, while SONY and PANASONIC make their own transport and calibration tapes, the end result — the alignment — is the same.  However, many SONY machines are less likely to hold their alignment and should therefore be suspect.  The SLANT BLOCKS are the cause of the alignment problems.  While this may be a frustrating malady, that's almost ok, because when repaired — rather than replaced — the results are better than new. This link details the Mechanical Adjustments.


Panasonic was smart when designing the SV-3500 in that the pinch roller is disengaged during reverse play operation. (Reverse-play is always used when locating Start IDs because transports always overshoot the ID by several seconds so as to not damage the tape.)  Other machines that reverse-play without the pinch roller engaged are the Casio DA-2 / DA-7, the Tascam DA-P20 and the Denon DTR-100P.  All of these portables use the same ALPS mechanism that is also found in Tascam's "tabletop"  DA-30, the exception because it does engage the pinch roller in reverse-play.  (See Figure-1.) The problem with the DA-30 is that a "soft-brake" is required to provide "back-tension" to the take-up reel table when it becomes the "supply" reel (in reverse play).  ALPS — an Original Equipment Manufacturer, or OEM — never made this "soft brake" available as a replacement part. A consciencious service center can cut a piece of felt and glue it to a non-removeable lever — a tedious task, but worth it because the tape is more delicately handled yielding faster recovery from shuttle mode.

Figure-1: The auxiliary brakes used in the ALPS mechanism.
Primary brakes and clutches are part of the reel-table assembly (not shown).

Loading problems have been common to TASCAM’S DA-30MKII and the DA-P1 portable.  Both use the same ALPS mechanism.  Deep inside the mechanism, a rubber belt the size of a dime links a motor with a worm gear.  The gear is sometimes over-lubricated.  Gravity combined with centrifugal force “spits” schmutz on to the belt causing it to slip and eventually deteriorate.

I’m no fan of the SONY “cigarette pack” portables.  While these are technical works of art, they are in no way affordably serviced.  Treat them with the utmost respect.  Don’t loan ‘em to a friend and please don’t drop them.  The two most reliable and serviceable portables are the HHB PortaDat and the SONY D-10 Pro.

Other cigar-box portables like the Tascam DA-P20 (and similar models by Casio and Denon) are worth repairing.  Less conscious humanoids have been known to accidentally reverse and force the power connector causing internal damage. Otherwise, most of the failures are mechanical.  Parts are still available because Tascam’s original DA-30 uses the same ALPS mechanism.

Batteries and power supplies are no longer available for many portables, but don’t throw out the “bad” adapter.  If the cable and connector are still intact, ECO-CHARGE @ 800-361-5666 can use them to retrofit their external rechargeable battery systems.  Their battery prices are often as good or better than the original manufacturer, about $65, with greatly improved performance.  However, because a new power supply is required, the initial investment will range from $200 to $300.  This applies to all the "discontinued" models including the ALPS portables (Casio DA-2 and DA-7, Tasam DA-P20 and Denon ???) and the Panasonic / Technics SV-25x series (these require the user to have an old battery to make the connection).  Remember what Groucho said, "the lord alps those who alps themselves!"


The following Panasonic machines all use the same transport:

PANASONIC SV-DA10 / SV-3200, SV-3700 / SV-3900 and SV-3800 / SV-4100.  The " / " and the color-coding indicates machines of the same "family."

Click here for a schematic to convert the SV-DA10 to an SV-3200.

The SV-3700 DAT machine is old enough to warrant a bit of a history lesson.  From that same time period came the SV-DA10 ( a "black" face consumer version with MASH converters).  This machine records at 48kHz only and has consumer (RCA) analog and digital I/O ports. The SV-3200 is an SV-DA10 with a "cream" face, the same consumer rear panel and selectable sample rates (44.1 khz and 48 kHz).  Inside they are essentially the same machine.  An SV-DA10 can be modified to record at 44.1 kHz.


Panasonic’s DAT transport is more serviceable than some but harder to clean than others.  Figure 2a shows about what you'll see when the cover is removed.  This heavily doctored image clearly shows that I have two left thumbs!  Step 1: Apply both thumbs to the white gears on either side of the loading cage.  Move in the direction indicated by the pretty blue arrow. Step 2:  Apply a lint free cloth dampened with 99% alcohol to the side of the head drum.  With another finger, gently rotate the head touching only the top of the drum.

Figure 2a:  Panasonic's brand of head cleaning torture

For the more mechanically inclined, Figure 2b shows how the loading tray can be swung out of the way to provide full access to the transport.  It’s even possible to play a tape using a rubber band to secure it to the mechanism.  Maybe you shouldn’t try that trick, but it sure makes it easier to see what’s going wrong.


Figure 2b:  Service access to Panasonic family of transports

In the top left corner of Figure 2b, is a "zoomed-in" view of the capstan motor shaft.  This "Shaft" can be one dirty… (shut yo mouth!)  Not many machines come in looking this bad, but sometimes I wonder which brand or batch of tape is responsible for such stubborn gook.

Removing funk from the capstan is not easy and cleaning tapes are powerless.  Alcohol must be used sparingly to avoid dissolving the bearing lubricant.  I use a special "U" shaped screwdriver to wrap a cloth part way round the shaft to get the dirt off.  Real stubborn dirt requires a mildly abrasive lapping film.

Typically, Panasonic machines have serial numbers that begin with letters, such as "AA."  Following the letters will be numbers, such as "0,"  "1,"  "2," etc., representing the year of manufacture, respectively, '90, '91, '92.  With this in mind, confirm the following:

1.) Locate the serial number.  (It may be hidden by the rack mount adapter.)

2.) Units made before 1993 ( SV-DA10, SV-3200, SV-3700 ) require a circuit trace (see Figure 3a) to be cut and a back tension lever to be replaced.

Figure 3a: Panasonic Servo board
located on underside of the transport 
of all models with the exception of the SV-3500.

An image of this lever (part number RML0090-1) will eventually appear to facilitate identification.

3.) After removing the loading tray, look for bits of broken cassette shell that might jam the mechanism. It's a good idea to turn the entire chassis upside down and shake to make sure any loose bits will fall out.  Grease on the transport will sometimes trap potentially hazardous particles.

4.) Inspect the Mode and Load switches. ( These report transport status to the system control IC. )  One is located on a yellow pcb near the capstan and the other is on the underside of the mechanism.  The contacts are gold plated, but the plating wears off.  If the silver traces that lead to the switch contacts have turned black, change both switches.

One easy test is to connect a .1uF cap in series with an unbalanced audio cable.  Momentarily connect the cap to the switch wires and listen while cycling the transport through its various functions (Play, Rewind, Shuttle, etc.)  The "normal" sound will be distinct (and very loud) pops as the DC voltage switches fro zero to five volts.  Any scratchy sounds mean the switches are fatiqued.  Test points and images for Panasonic and other Manufacturers will eventually be provided here. This test is particularly well suited to the Alesis ADAT.

5.) The primary and "soft" brakes are usually worn out after one or two years, depending on use, and should be routinely inspected and replaced.  The reverse-play soft brake is located under the take-up reel table.  Only about 1/32 of an inch makes contact with the bottom of the take-up reel table.  I have a mod for this that requires the addition of two washers.  That information will also be made available. In the mean time, click this link for more details on the subject...

6.) Repeated tape jams will chip teeth on a large transfer gear located on the underside of the mechanism.  Unusual fast-wind noise is a sign that this gear  should also be replaced.

7.) There is also a possibility that take-up tension is either too high or too low.  A smooth ten to fifteen gram/centimeters is good.  Eight gm/cm is too low.  Eighteen gm/cm is too high.  Variations are caused by a clutch (RXG0011-2). A new version of the clutch has a red dot.


One of the common causes of jamming — the machine's inability to eject a tape — concerns the length of the back tension felt.  Too long — caused by a worn or misadjusted felt and/or by heat — causes the tension arm to get in the way of the left loading/precision guide. 

FIGURE 3b (above) shows the "crash site." Pushing the tension arm in the direction of the arrow will cause it to rotate clockwise and out of the way.

"Tally" is a term that describes machine status. It is part of the language spoken within those multi-pin connectors that link machine-to-machine or machine-to- "other" devices like remote and edit controllers.  In the pre-cyanide era, the most important Tally was a light bulb labeled  RECORD READY.  If that bulb was dead, you’d be dead too after pressing record…

When an open-reel machine is in Fast Wind, no additional clues are necessary.  But ever since tape activity went indoors, we’ve relied on LEDs and LCDs for feedback.  I think most people will agree that more feedback would be better, hence this simple mod for the Tascam DA-30.

All of us are guilty of pressing buttons when, quite often, the machine is simply not ready.  Wouldn’t it be nice to know that all products could clearly communicate this "readiness?"   Tascam’s DA-30 and DA-30 MKII have a DB-15 remote connector on the rear panel.  Detailed in the schematic (shown in Figure 4) as  P1, "Control I/O," Pin 12 of the DB-15 is the STOP TALLY.  It goes "low" (to ground) when the machine is ready to do business.  Connect the anode of an LED to +5 volts (Pin 16 of either U801 or U802).  In series with the cathode is a 220W resistor that goes to pin 4 of U802  (also pin 12 of the DB-15).

Figure 4: Tascam DA-30 Remote COnnector schematic depicting STOP LED modification.

Unfortunately, 5 volts does not appear on the DB-15 connector or else you could do this without even opening the unit.  (An external supply seems silly doesn’t it?)  I put the LED just above the stop button on the machine’s front panel.  If you get that far, there’s an LED-sized hole in the plastic assembly just above the Stop button.  Just knowing that the machine will not accept any commands until the STOP LED comes on will save wear and tear on your fingers, your already short fuse and on that button assembly. 

Tascam DA-P1 Portable

From the web comes a bit of enlightenment concerning the ability of Tascam's DA-P1 to display Error Rate.  Press this link for details.

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