hifi engine

1992 model G16S with Firmware ver. 1.10



1992 model G16S with Firmware ver. 1.10

The current service manual available on the web is for the 1991 model, Copyright, March, 1991, with Firmware ver 1.00. The Dolby processor in the ver 1.00 R/P boards is listed as a "SBX1654", & is not capable of digital control interface. The upgrade in the ver 1.10 model is a "Sony, CXA1417Q" & is digital control compatible with the Fostex computer controller. Aside from that, the improvement in the Dolby processing over the previous design chip, is light years advanced. It is in one word, awesome!

All of these models are 4 speed capable. IE: 3.75 ips, 7.5 ips, 15 ips, & 30 ips.

This feature is interfaced to the digital control, but it has only two states, Hi, & Low speed. Only two speeds can be accessed using the computer interface, where those selected speeds are preset on the capstan motor, using two switch jumpers.

There is 3 possible combinations used by these switch jumpers. 3.75 ips/Low & 7.5 ips/Hi is the lowest setting. The middle setting is 7.5 ips/Low & 15 ips/Hi. this combination is the factory default setting, while the computer is default programed in the Hi speed mode. The last combination is the 15 ips/Low & 30 ips/Hi setting on the capstan motor.

By manually moving the two switch jumpers from the middle to the low or high setting, while the computer is default set to "Hi", you can obtain 3 possible usable speeds, 7.5 ips, 15 ips, & 30 ips. Since the EQ is the same +8dB @ 15khz, for all 3 of the above listed speeds, no EQ changes are necessary to use these speed settings in either record or play.

Since I don't know the method of inputting the speed change from Hi to Low into the computer, I have no idea how you could use the 3.75 ips speed, so the +18dB EQ for that speed is irrelivent.

It might be possible to hard wire a manual Hi Low switch to the capstan motor, bypassing the computer controller. The interface point for this speed function switch is "J3" on the capstan motor pc board. It would be easy to draw the truth table to the path of the data lines, in order to determine just how to switch the data lines at "J3", to obtain the Hi Low function using a manual switching device. Alternately, you can just remove the rear panel, & reset the two jumper switches on the capstan motor, to use any of the 3 speeds available in the Hi program mode, IE: 7.5 ~ 30 ips.

Just remember to keep the two jumper switches together on adjacent switch post. Note there are white divider lines on the pc board marked with the following. each group of pins are a Hi Low, with the computer default programed to Hi. See: 3.75/7.5 //divider line// 7.5/15 //divider line// 15/30 ips. The two jumpers for the 30 ips speed would be located in the 15/30 segment of pins.

The default 15 ips speed is in the middle segment marked 7.5/15 ips, while the lowest speed obtainable without switching the computer controller to the Low state, is found in the 3.75/7.5 jumper switch segment, & defaults to 7.5 ips.

This speed saves head ware, doubles the usable length of time from 32 minutes, to 64 minutes of R/P, giving up to 8 stereo pairs of one hour each, or 8 hours on a 2500 foot 10 inch reel tape. The quality is better than digital CD @ 7.5 ips with the Dolby digital enabled. Using ARTA spectrum analyzer, & pink noise, the 7.5 ips is flat to 27khz when calibrated properly, using AGFA PEM458.

The only flaw in using the manual speed switching instead of programing the speed from Hi (default) to Low speed, is the timing of the timer readout is not switched by the computer, & continues to readout the time based on tape movement. That means the display still reads 32 minutes @ any manually switched speed. IE: 30 ips is only 16 minutes per 2500 foot of tape. I programed the "F" segment from the default 30 frame to 2 frames, while 20 frame setting would give you 1/10th of a second resolution, & the 2 frame gives you the passage of 1 second of time per frame.

The last point to make with the speed control in the Fostex reel machines, that use the digital DD capstan motor. It may be, the firmware does not have the code in it to switch Hi/Low speed. This point likely is why no one knows how to program it. Likely the ROM mask did not have enough room to store the code to change the speed, so the programmers of the day just neglected to increase the size of the ROM to have room for the code.

If reel machines were not killed by the manufactures, by adopting the CD rom disc, to make more money using a cheaper lower quality system design, likely successive models of Fostex reel machines would have had the speed functions added to the Firmware program. It is a computer, like any computer today, but was limited in what it could do by cost restraints. It is a basic 8 bit binary BCD code. It does not use keyscan or IRQ's, so it is truly a basic binary computer. I don't really think the firmware is flashable, so there is little chance of upgrading the program functionality.

The Reel Tron will never die.......I hope!