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Or what to do, if your Studer Tape Recorder suffers from severe loss of memory

Wolfgang Bleier, Austria
June 2008

Audio parameter and RAM of the Studer A810

Reel to Reel tape recorders are precision equipment and require professional service by proper mechanical alignment and exact calibration of the audio parameters, otherwise a recorder will neither match the properties of the audio tape used, nor will it make or replay tapes to professional standards. The exceptional performance of precisely calibrated professional and even semi-professional tape recorders is a match for the finest audio equipment available today.

Studer's A810 is equipped with a buffer battery that keeps the audio parameter in the RAM of the recorder. My A810 has a NiMH accu made by VARTA (3/V150H 3,6V with 140mAh capacity) soldered on the MP Unit. It has three pins that prevent from connecting it in wrong polarity but make unsoldering of the accumulator a quite difficult undertaking. The numeric code printed on the plastic housing of the RAM accu-pack shown here indicates its production date. The code "063" for example means that this accumulator was produced in June 2003.

Although NiMH batteries have little to no "memory effect", it is normal that such an accu loses a substantial part of its nominal capacity after 500 to 900 charging cycles, and it should be replaced after a couple of years of operation (the lifetime usually spans over 3 to 5 years, depending on use and charging methods). In case that you have to replace the accumulator by a new one you should not forget to re-load the audio parameter into your recorder after you have completed replacement.
Especially when you play your private recorder once in a while only, I recommend that you leave your recorder switched on for some hours (or even over night) about once a week in order to charge the accumulator and to avoid total loss of the audio parameter to which your tape recorder was calibrated (if you do this with a Studer A810 it will be a good thing to set the jumper JS2 on the Capstan Motor Control print in the position "Capstan Shut Off" in order to protect the bearings of the capstan motor from unnecessary wear). You should also consider that NiMH accumulators, if not re-charged in time, may self-discharge within just a couple of months. This should be a good reason to keep a back-up copy of the audio parameters of your recorder in a safe place, if your recorder provides such feature. In case of a Studer A810, this requires a recorder equipped with the connector for serial remote control (10) and the address board (11) shown below on the image of the Studer A810 connector board.

If you are a lucky owner of a Studer A810 tape recorder and you'd like to know how to make such back-up of the audio parameters, then click here to read how to make such back-up. You can also download PDF documents in english and german language in which the Studer A810 tape recorder and making of a backup of the audio parameter is explained.

Nickel-Metal-Hydride batteries, and what I think I know about charging

The Studer A810 (obviously) applies trickle charging on its accumulator with a charging current of 1/10 (C/10) or rather 1/20 (C/20) of its capacity. Although trickle charge allows long-term overcharge up to one year, it is also known not to be the best charging method to maintain NiMh batteries perfectly conditioned. Therefore I always keep a battery in spare, which I properly condition (full discharge and charge) from time to time with a professional, electronically controlled battery charger that I set for accelerated charging (C/5 or C/3) with delta V detection for peak cut-off and additional time control.
Conditioning of such a RAM buffer battery with a relatively small capacity requires a professional battery charger that provides also a very small charge output, precise control against deep discharge and reliable delta V detection (peak cut-off) to prevent overcharge at higher charging rates, otherwise the accumulator may soon be permanently damaged.
In fact, charge currents greater than C/2 (or 0,5 C) are generally recommended for reliable delta V detection especially to cut-off charging of NiMh batteries. A higher charging current generates a more distinct voltage drop in the charge curve at full charge, which a good battery charger can easily detect also on NiMH batteries (NiCd accumulators for example have a much more distinct voltage drop at full charge than NiMH accus have). VARTA, however, does not recommend charging rates higher than C/2 for charging of small button accu-cells that are used in the A810, which in respect to a 140 mAh accu means limited fast charging at 70 mA charging current for 3 hours. VARTA also recommends normal charging at C/10 (14 mA limited to 14 to 16 hours), or accelerated charging at C/5 (28 mA limited to 7 to 8 hours).

Should you need a new accumulator, contact VRI GmbH. The people there really know about batteries and accumulators, and ship also customized battery packs for a very fair price. You may find your new accumulator also in one of the Conrad Electronic shops in Germany, Austria & Switzerland.

Without a doubt, it is quite important to keep an eye on the condition of that little battery that is installed in a Studer A810, otherwise this fine recorder will switch to factory set default audio parameters that may fall short of the performance and characteristics of the audio-tape your recorder was calibrated to.