Japanese date codes

Often they used the Japanese system of dating, starting from the date of coronation of the current emperor.

Geoff.

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Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM

To get the decade you have to look at the quality/font/style of the lettering

I will add yor info to my tips files

Some hints for determining the age of equipment not marked on serial plate,dating old kit. The best is date codes on ICs. These are usually 3 numbers say 712 distinct from the IC type number which is usuallly letters then numbers. For 712 12 is the number of weeks (ie march) into the year ending 7 . But is it 1977 or

1987 etc. The 70s printed numbers are usually more angular as though printed in the fonts available to an XY plotter. Also the IC series number is usually indicative of the era. For Sanyo ICs a number like 4C1 probably means 1984 from the '4'. Larger (power handling) package/hybrid ICs of the 70s were a lot less standardised than later. Other indicators dark brown paxolin board would suggest 60s rather than 70s as would carbon resistors rather than metal oxide (no bulges at the ends of the barrel). Also the sizes of 60s and 70s resistors tend to be larger than what is actually required for heat dissipating. E-line transistors come in the 80s . Places to find dates are sometimes large electrolytic capacitors, polycarbonate capacitors,large transformers,loudspeakers ,relays, microswitches,motors , some small rectangular radial lead caps ,body of air vane tuning caps and some small transistors have a datecode. Clear wrapped ribbon cable tends to be 70s, grey covered ribbon cables tend to be 80s and thin tape type with foil conductors tends to be 90s. PCB traces from 60s onwards tend to get less angular and more curved by the 90s ,double sided traces on boards tends to be 80s onwards. The year of introduction of certain types of connectors gives a lower bound. eg Scart/Peritel would not be found earlier than 1977 and those would be in French kit, the earliest date for mini-din would seem to be 1985. The pitch of IC pins of course gets less than .1 inch only 80s onwards and surface mount tends to be 90s onwards. LEDs started coming in early 70s. For Technics / Panasonic ICs of the 1970a date codes probably take the form a single number then in smaller script an underlined HEX digit. ie 9 plus small underlined D would mean 1979 14/16 ths into the year. After year 2000, eg 5007 presumably week 07 of 52 in year 2005 JRC IC maker seems to use this convention of reversing post-millenium dates - do others ? Unless you find 2 or more IC date codes from different manufactirers agreeing it is often more a feel or balance of probabilities for a date. After about 2000 pcb overlays often have the date as distinctive slanted "7 segment display " font numerals of 2 number year then 2 number week as a 4 digit code as on iCs. Date marks on mouldings and PCBs Moulding example Plastic moulding with raised print 82 83 84 85 with a small moulded pip over both 82 and 83. Then a 1 to 12 'clock face' both with an arrow next the figure 8. A centre pop dimple in the mould above 82 in 1982 and then another over 83 in 1983. Leading to raised small conical pips on the plastic. Probably means 8/12 year or August 1983 PCB example White silkscreen printed panel on the overlay of a PCB, presumably with date coding. A left panel and right panel consisting of 1 to 6 along top and 5 dots in each column so 6 x 5 dots Right panel marked 7 to 12 and similar array of dots but the third one down under the 7 was missing. Probably third week of 5 weeks of July. Central panel had marked like this 02 ?? ?? 05 The queries were probably the remnant tops of numbers from scrubbed out 03 and 04 so probably like in the plastic case 03 is scrubbed in 2003 and 04 scrubbed in 2004 but still leaving the 03 mark. So probable screen printing date of mid July 2004

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

On Thu, 11 Dec 2008 10:21:59 -0000, "N_Cook" put finger to keyboard and composed:

Thanks for the tips.

Just as an exercise, I'm listing the codes on various ICs and transistors that came out of an old Pye 3-in-1 tuner/cassette/turntable.

Sharp IR2E02 75YC 5 = 1985, Y = November, C = week 3 Toshiba TD6301AP 8720D 1987, week 20 Toshiba TC9147BP 8721H 1987, week 21 Toshiba TD6104P 8711K 1987, week 11 NEC uPC1225H 9241F - repair? NEC uPC1225H 706D 1987, week 06 ? NEC uPC1161C3 8713E 1987, week 13 NEC UPC1228HA 8728M 1987, week 28 Hitachi HA12045 6M4 6 = 1986, M = December, 4 = week 4 Rohm BA6124 706 170 1987, week/month 06 ? Rohm BA3302 507 852 1985, week/month 07 ? Rohm BA4558 701 535 1987, week/month 01 ? Rohm BA4558 705 051 1987, week/month 05 ? Sanyo 2SD313 E7E3 1987, E = May, week 3 ? Sanyo 2SD313 E7F2 1987, F = June, week 2 ?

Here are more IC codes from a National VCR:

NEC uPD75108 8802EX705 1988, week 02 of year NEC uPD4066 8734BN 1987, week 34 NEC uPC324C 8804C 1988, week 04 NEC uPC393C 8745C 1987, week 45 NEC 78M05 8802J 1988, week 02 Rohm BA15218 712 618A 1987, December (12th month) ? Rohm BA15218 712 286A 1987, December ? Rohm BA6246N 712 513 1987, December ? Sanyo LA7308 8A5 1988, A = January, week 5 of month Sanyo LA7098 7M3 1987, M = December, week 3 of month Hitachi HA17805 7H4 1987, H = August, week 4 of month Matsushita AN3215K 7D.5 (D is underscored) Matsushita AN3321K 7D.5 (D is underscored) Matsushita MN1451 41 7 (no underscore) Matsushita MN1451 39 6 (9 is underscored) Mitsubishi 5218 7Y02 1987, November 02 ? Mitsubishi M5222L 7907 1987, September 07 ? JRC 78M09A 7012 December 1987 ???

This page has some useful info (esp. for Hitachi):

I can see the patterns for Sharp, NEC, Toshiba, Sanyo, and Hitachi, and I can guess at the patterns for Rohm and Mitsubishi, but the rest are a puzzle. I see that in your notes you have suggested that the JRC year digits may be reversed, but this doesn't tally with the 78M09A part. I see what you are suggesting for the Matsushita codes, but then how do you account for the MN1451BVK parts? I tried Geoffrey's suggestion regarding Hirohito's coronation year (1926?), but I couldn't make it fit the data.

- Franc Zabkar

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Please remove one \'i\' from my address when replying by email.

Hirohito was crowned Dec 25, 1926, but the new one was crowned 7 January 1989.

Some parts made in early 1988 were date coded with a year of 62 (they start at year 1 I think), and after 25 December 1988 were dated year 63. Since it is considered unforgivably rude to prepare for the death of the Emperor, things made in early 1989 were still date coded 63 for a short time. It's also rude to continue to use the old dating system, so some companies stopped production until they could change the dates.

Very likley then things produced went from a year of (6)3 to 1.

Geoff

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM