To: W0KIE@mail-list.com, W0KIE@mail-list.com From: Gary Bourgois Subject: [W0KIE] Re: Janeil SP 2000 Stereo Processor Modification ------------------------------------------------------------------------ ------ THE ORIGINAL MESSAGE WAS POSTED TO THE USENET BY BOB WIER ------- ------------ (original posting date unknown) -------------------------- ------------------------------------------------------------------------ Note - Here is my PRELIMINARY version of the Janiel Bandwidth Lock mod. Unfortunately, I don't have my satellite system here, so I won't be able to actually test it until I go home for the Thanksgiving holidays - but all of the test equipment in the lab says that it's working properly (switching, etc). The inside of the Janiel is pretty nice - certainly worth the $40 - $50 they are currently running if you can find one. The layout is tight on the analog board, but not to the extent of current VLSI tranceivers. Things are not too tight on the digital board. The analog board looks well laid out, although there are a LOT of zero ohm resistors (also known as jumpers :-) on the digital board. But a double sided board probably would have been a lot more expensive. Someone asked about computer control. The unit actually is computer controlled by the built in microprocessor. I note there is a single line going out to the "remote" jack on the back panel. Obviously a serial communications line. I think it would be difficult to mod the processor directly to run via computer control, but if one could get the data format to send commands to the micro... Unfortunately, this is information which would probably come from the AP 2000 antenna positioner. If anyone has the code information on this, I'd love to have it! ---enjoy! --Bob W. ---------------------------------------------------------------------------- Selectable Bandwith Lock Modification for the Janiel SP2000/2000.B Stereo Processor by Robert R. Wier, WB5KXH The Janiel unit features automatic selection of the proper bandwidth for satellite subcarrier audio reception. Unfortunately, it can be "faked out" by unusual program content or by somewhat non standard transponder formats, such as are heard on the Canadian birds. The following modification enables the manual selection of either the narrow (150Khz ) or wide (400 Khz) IF filters. Original automatic selection of the appropriate bandwidth is also retained as an option. This modification has a number of features: - Simple and cheap: only 6 wires, 4 resistors, and a switch are needed, with an approximate cost of $5. - Unambigious indication of narrow versus wide bandwidth selection in both manual and automatic modes. - Bandwidth display indicator requires no supplemental display hardware. - Modification is applied to the component side (top) of the PC board, eliminating the removal of the board from the chassies (easy access). - no PC foil traces are cut and only 2 resistors need be opened from the top side of the board. If the display option is not required, no removal of any components is required. - low frequency signals are used, eliminating possible RF circuitry problems. - no adjustments or modifications to the tricky stereo discriminator circuits is required (or encouraged!). The modification adds resistors in parallel with the existing bias voltage resistors on the two bi polar transistors which control the switching selection of narrow or wideband circuitry. By shifting the bias voltage, either transistor can be forced on causing that particular mode to be selected. By switching out the added resistors, normal operation (automatic) is restored. In order to display which bandwidth has been selected, the decimal point in both channel frequency displays are used. By driving them from the bandwidth selection flip / flop a visiual indication is given as to which is being used. This display option operates both in stereo and monaral modes, locked and automatic. Since the frequency range is about 5.00 to 8.50 there is essentially no reason for the decimal point to be displayed execpt for cosmetic reasons. Thus its use as a bandwidth indicator does not produce any loss of tuning information. NOTES: A close reading of the service manual point out that automatic bandswitching is performed only on the basis of the signal being received on channel "A". Normally this is not a problem, since if monaural is selected channel "A" is used. However, if channel "A" is not on station, and channel "B" is used to tune a signal then the automatic bandwidth will NOT function even if deep modulation is heard. The use of channel "A" versus channel "B" is not important when the frequency selection is locked by the added selection switch. To make the mod: The modification is not difficult, but it is somewhat tight on the chassies (but not terribly so). You'll need nimble fingers and about a 15 watt soldering iron. You'll also need: Small diameter insulated wire (maybe 24 or 26 gauge wire - no significant current is carried). four 10K ohm resistors - exact value unimportant 1 DPDT CENTER OFF mini - switch (such as Radio Shack 275-620) - 1/4" drill bit required for drilling mounting hole Bandwidth modification: Disassemble the cover unit. Be careful as the front panel is plastic and the attachment tabs to the chassies might easily be broken. Determine where you will mount the switch - I put mine on the back panel above and between the "audio subcarrier in" jack and the "audio out" jacks. The back panel steel is amazingly hard. Cut two lenths of wire sufficient to run between transistors Q216 and Q217 and the switch. Wrap one wire around the BASE lead of each transistor (labelled "B" - these are in-line lead transistors - the base lead is on the end - not in the center). Carefully solder the wire to the base lead. Run the wires to the center lugs on the switch, one transistor base to one center lug. Solder one end of a 10K ohm resistor to each of the 4 corner lugs. Connect the other ends of the 10K ohm resistors together which are on DIAGONAL lugs on the back of the switch. Thus, if the switch is oriented vertically, the center lugs would be at the East / West positions (where the wires to the base of the transistors are attached) and also NW/SE (attach the far end of the two resistors together) and NE/SW (ditto). Connect +8 volts to one set of the resistors (doesn't matter which - it will just change the position the switch selects narrow vs. wide functions). A handy place to get this voltage is from the top end of L201. This inductor looks like a large green resistor mounted up on end. It is close to the front panel on the right hand circuit board as viewed from the front. Q216 is to the immediate left of L201 (about an inch). Q217 is NW from Q216 about another inch (as viewed from the front). Attach ground to the other two resistors (a handy place to get ground is from pin 7 of IC 201, immediately to the right of Q217 - you'll need to find it for the display modification anyway). Chassies ground MAY be ok, but I havn't verified that. The idea here is to pull the base of one transistor high thru a 10K ohm resistor while simultaneously pulling the base of the other transistor low thru another 10K ohm resistor. When the switch is put in the opposite position the transistor base pull up / pull down are reversed. For the display mod (highly recommended so you can see what the ##(&(*@@ is going on :-) Locate IC 304 and IC 305 on the digital board behind the LED number displays on the front panel. To the left of each, you'll find resistors R330 (right) and R 339 (left). Cut the end of the resistor towards the BACK of the unit, and bend them up (gently) so that you can solder a wire onto them. Connect a wire from cut end of the right resistor to pin 8 of IC 201 (just solder directly onto the leg of the IC above the circuit board) - don't cut the leg of the IC. Connect another wire from the left resistor to pin 11 of IC 201 (ditto). That completes the modification. USE: When the switch is in the center (off) position, automatic bandswitching will still be in effect. One or the other of the display decimal points will be lit (but not both) indicating the bandwidth in use (left d.p. normally indicates wide, but this may be reversed if you switched any of the signals - it doesn't really matter). In locked mode, moving the switch off center in one direction will select narrow, the other direction will select wide. POTENTIAL PROBLEMS: There MAY be some interaction between the locked bandwidth setting and the MUTE function. This has not been verified. DISCLAIMER: Although the above has been wired and tested, and is believed to be accurate, R. Wier accepts absolutely no liability for inaccuracies, typos, or equipment damage resulting from these suggestions. All responsibilities lie solely with the owner, and there is no guarantee either expressed or implied. This limitation is effective from the beginning of the world to the end of time, so there! currently wier@merlin.etsu.edu or wier@hipp.etsu.edu ----------------