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	A collection of  NRD-515 oriented    diagrams and modifications
	Drawings are NOW in 2-colour BW 600 DPI TIFF format with LZW or G4 compression. They are very hi-res! Also inside the PDF's ( double compressed LZW + G4) If they won't view in your IE-browser, copy to HD first! View with an image viewer like Irfan!! DO NOT / NEVER    reduce in pixel size! Because they won't print as detailed. Latest change: Highres GIF replaced by Highres TIFF with LZW compression, in the PDF's even double with extra G4 over the LZW! Most in A3 size and rescanned in 600DPI Black&White!

Links to original Japan Radio Company NRD-515 drawings:

Item (All 2 colour 300 or 600 DPI High Res TIF files)	Highres TIF in PDF file	Original TIFF file
Principal working overview diagram Appendix 1
Rx board circuit diagram Appendix 2
Synthesizer board diagram Appendix 3
Power Supply regulator board Appendix 4
Main chassis and Front Board circuit diagram Appendix 5
Power supply - voltage distribution between IC's Appendix 6
Anti mains rattle feedthrough rectifiers on regulator board Adding extra capacitors on the AC side of the rectifiers Modified version
Safety modifications mains filter to comply with new regulations IEC power input exchange with real mains-inlet filter Click on IE icon to see a sub page with mains-inlet pictures
A PDF (only) version of the CPA-94 main tuning dial encoder board Thanks to cooperation with PA0A (Ex: PA0AWN) who did the research		X
A PDF (only) version of the CGA-68 main (triple) VCO unit		X
A redesigned PDF (only) version of the 455 kHz filter board Due to public demand I made my own layout Meant to etch your own filterboard!!		X
A very slow FTP link to the complete NRD-515 instruction manual With all the A3 diagrams inclusive!! All 600DPI, size about 5 MB		X

Links to original Japan Radio Company NDH-518 drawings:

Item	Highres TIF in PDF file	Download TIF LZW or G4
Memory Unit NDH-518 circuit diagram (made from TIFF-LZW)
Modified memory unit diagram (for the options/modifications further below) made from TIFF-G4
Complete scanned NDH-518 Memory unit instruction manual With A3 diagram inclusive		X

GOTO NWG-515 Remote VFO section on this page

<------   LOOK,  LOOK,   AAAHHHH Click over here for a scanned NCM-515 manual Made with an Acro-7 scan plugin, but compatible with Acro 5 and above I've added the very hard to obtain diagram of the connector box CQE-515 as last page.

Click over   HERE   for lots of PDF files about hardware used in the NRD-515 and in my designs.

A very simple method to Backup the Synthesizer:

Synthesizer backup circuit to retain "VFO" contents during power off

BFO control only for BFO/BC-tune button with Auto BC Tune:

English Dutch Diagram BC-Tune D/A converter and amplifier
BC-tune PCB layout - both sides
ZIP file with example eprom file + QuickBasic 4.5 eprom creation programs - comments in DUTCH

A new version of the Auto BC Tune with more recent DA-converter: English Dutch Diagram BC-Tune D/A converter and amplifier new BC-tune PCB layout - both sides

Memory NDH-518:

Up/down countercontrol add-on board PCB CAD Circuit diagram binary UP/DOWN counter control Binary to BCD decoding for displays with eprom - 64 channels p/bank Binary to BCD decoding for displays with GAL - 32 channels p/bank Zip file with GAL related JED and EQN files for new 32 channel GAL version 64 and 32 decoding chips can also be used for the following 24 channel rotary bankswitch version

Modifications executed on a NDH-515 Memory unit:

This is the least complex version, only an 8 channel bankswitch is added Binary coded decimal add-on universal (new) switch board for NDH-515 Gal array decoders - zip file with EQN and JED files Circuit diagrams are for a slightly (minor) different GAL version as NDH-518 Circuit diagram GAL expansion for NDH-515 memory unit

Accessibility Modification on a NDH-518 unit to make it
into a Remote controllable Memory:

This is the MOST complex version, NOT advised to start with!! Circuit diagram part 1of 5 for memory accessibility options Circuit diagram part 2 of 5 for memory accessibility options Circuit diagram part 3 of 5 for memory accessibility options Circuit diagram part 4 of 5 for memory accessibility options Circuit diagram part 5 of 5 for memory accessibility options PCB CAD layout for memory accessibility options inside the NDH-518 PCB CAD layout control box for memory accessibility options Front panel example control box for memory accessibility options Zip file with GAL related JED and EQN files for new 32 channel GAL version (same GAL version as NDH-518 above)

AM detector buffer:

The single diode AM detector causes a too high a-symmetric load on the last IF stage
With a small buffer with low Z-out the distortion is gone, also audible as cleaner SSB!!

Drawing of an AM detector buffer Layout of an AM detector buffer

Alternative CW crystal filter:

JRC's narrow CW crystal filters are very hard to get nowadays and too expensive
Kenwood has equivalent 250 Hz filters, same footprint type YG-455CN-1, also from the NDK factory
They won't work because wrong impedance and DC short circuit to ground
But with two minor impedance transfer and DC separation toroids it will work, even better than the original CW 300Hz filter!!!

The toroids you see are 3E25 - 14mm - AL=2200 It transfers the 600 Ohm to 2200 Ohms and back. It also gives the needed DC separation. Windings are 35 for 600 side and 66 for 2200 side. So it's about 1 to 2 in N, and 1 to 4 in Z, but slightly less.

Kokusai Filter Repair:

Kokusai Mechanical filters have a habit of deteriorating in time due to decomposing of the foam inside it.
It becomes a sticky gummy mess, which dampens the vibrations of the resonating disks.
With extreme care the shit can be dissolved with nail polish remover (in Dutch: aceton) and repaired with fresh foam.

Before the cleaning Picture © by Luuk Radiohobby

John Kolb ( KK6IL ) is a Kokusai Mechanical filter specialist and has a special site about it.... Go to John and read it over there in his own words The pictures you see over here are from a radio friend: Luuk. He also managed to repair it too. All the pictures © from Luuk in one small PDF sheet.

After the cleaning Picture © by Luuk Radiohobby

Frequency calibration:

Frequency calibration notes for the NRD-515
Example design (ref 4) of a frequency counter reference Droitwich PLL unit
Design revision no 5 of the Droitwich PLL

Blown uPB426 chip on synth board ??

This chip is the band segment decoding table out of the frequency range
Click to go to the PDF page with information how to build your own decoding chip!!

PHOTOGRAPHS section:

	Photographs from the NDH-518 memory unit with eprom BIN-BCD address decoder, push-button and rotary-opto up-down control Click here or on picture for sub-page
	Photographs from the NDH-515 memory unit with two GAL's for BIN-BCD decoding. Only one hole for extra bankswitch needed Click here or on picture for sub-page
	Photographs from the NDH-518 memory unit with two GAL's and remote control options. Most complex version Click here or on picture for sub-page
	Photographs from the NWG-515 Remote VFO A NWG-515 ?!?, a very peculiar thing. Click here or on picture for sub-page
	Mains-inlet changes Safety modifications mains filter to comply with new regulations IEC power input exchange with real mains-inlet filter. Click here or on picture for sub-page

Click over   HERE   for a direct hop over to all the other radio information on the next page.

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Copyright© 2001 - 2009 Walter Geeraert - All Rights Reserved

index515.htm
by Walter - PE1ABR - 2009-10-27