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Old 3rd Jan 2012, 12:38 pm   #1
Farnze102
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Default Date Coding for Hunts / Erie capacitors

The following information is given for determining the manufacturing date of Hunts/Erie capacitors. This information is given in good faith.

As a young R&D Engineer working at Ferranti in 1967 I was fortunate enough to meet with the great J.D. Evans. J.D.Evans (Joe) was a key player in A.H. Hunts history and was based at their Wrexham, North Wales, plant. In 1964 he left Hunts' to become a development engineer at Ferranti R&D division. This is what I learned from Joe all those years ago.

A.H. Hunt started business in 1901 and specialised in selling batteries. In May 1961 A.H. Hunt set up a capacitor design and manufacturing capability. The name was changed to A.H. Hunt (Capacitors) Ltd.
The new business was started on 21 May 1961, which happens to be week 21 of the year, and the preceding Sunday for that week was Whitsun day. So someone decided to use the codename WHITSUNDAY for dating capacitors - why? because it contained 10 none duplicated letters of the alphabet. Also the letters needed to have a corresponding number sequence so 0987654321 was used.

The format of the date coded is simply last digit for year followed by the week number.

So here we have it:

WHITSUNDAY
0987654321

Now take this a step further. Everyone working at A.H. Hunts was very happy to be in the capacitor business and the starting week for the change was 21 week of 1961. Work this date for the code and we get YAY. It will not be lost on you that YAY is also an old expression denoting joy and happiness.

The code was designed to run for 10 years. On the 11 year it recycles itself and starts with YWY (1971 week 1) and continues. The ten year duration was considered long enough to provide separation of the dates.

Now you know the rest of the story!

Hope this will be of some use to you.
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Old 4th Jan 2012, 8:13 pm   #2
Framer Dave
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Default Re: Date Coding for Hunts / Erie capacitors

Hello and welcome to the forum.

I don't wish to cast doubt on what you say, but I've just finished restoring a radio which was built in 1955 and was packed with Hunts capacitors. Also, I was at school in Wrecsam until 1961 and a friend of mine's mother was employed by Hunts on the Wrecsam Industrial Estate from at least 1958.

Time plays trick with memories (including mine!), is it possible that a new firm was established in 1961 on the back of an existing business?

Regards,
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Old 6th Jan 2012, 7:53 pm   #3
Lucien Nunes
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Default Re: Date Coding for Hunts / Erie capacitors

I too think there must be some other explanation for the significance of May 1961, perhaps when capacitor manufacturing was moved from Wandsworth to Wrexham or some similar restructuring? There is some more history in this thread: https://www.vintage-radio.net/forum/...ead.php?t=1756

It will be interesting to test this coding scheme and if it works it will be very helpful indeed. I often need to date 1950s and 1960s amplifiers in my quest to document the history of Compton organs. In the 1950s they used primarily TCC capacitors, which have a reliable alphabetical code, enabling the chassis to be dated quite precisely. During the 1960s they started to use Hunts in an increasing number of products, which have not been so easy to date as a result.

Conveniently, there are a couple of chassis in the office with Hunts electrolytics alongside Mullard C296 mylars which can also be roughly dated. I will try comparing the two later.

Lucien
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Old 6th Jan 2012, 10:32 pm   #4
Lucien Nunes
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Default Re: Date Coding for Hunts / Erie capacitors

I think it needs tweaking. The first three amplifiers I've checked produce some odd results using that code. Some capacitors have illegible codes or are hidden, some might be replacements, so I've included the caps that are fairly certain. All capacitors are a mixture of Moldseals and various kinds of electrolytic, plastic cased, wire-ended alu cans and multi-section chassis mount. Unfortunately none of these three amps have other trustworthy components to give a clear idea of what to date expect, other than that I think amp 3 is a year or two newer than amp 1, all somewhere around the mid 60s.

Amp 1:
TIT 787
TWT 707
TAT 727
YNS 146
WYS 016
YHT 197
ITS 876
HAS 926 (might be a replacement)

Amp 2:
YUT 157
HTT 977*
WTT 077*
TII 788
*These might be the same code, in which case they could be either H or W

Amp 3:
UYA 512
UYA 512 (same code on totally different type of capacitor)
YNT 147
UWW 500

Observations:
All the letters of Whitsunday except D have appeared so far.
Many invalid week codes, with the middle digit having fairly uniform distribution instead of being confined to 0-5.
There is a week 0 (UWW)
Year digit also seems rather randomly distributed, on each amp having a minimum spread of 4 years.
There is a hint of correlation amongst the final digits of amps 1 & 2, with a minimum spread of 1 year.
The codes are often printed with wider spacing between digits 1 & 2, than between 2 & 3. This could mean that the first digit is a separate changed on different occasions to the other two, which would agree with the Year Week Week system.

I'll check more examples as they surface, as it's worth getting to grips with. Thanks Farnze102 for getting the ball rolling...

Lucien
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Old 9th Jan 2012, 11:34 am   #5
Farnze102
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Default Re: Date Coding for Hunts / Erie capacitors

First off I need to apologise for placing my first post in the wrong section. Sorry mods you have enough work to do without sorting postings.

@Framer Dave. I agree with your comments. It would be great if someone could substantiate the information I was given. To be fair. Did I listen carefully to what Joe had to say. Did Joe give me the facts. I guess there must be someone out there that knows the history but time is now short. I wonder if it is worth posing the question in the local newspaper!!

@Lucien Nunes. I read the posts you indicated. Brilliant piece of work by all contributors. Yes I agree that there are anomalies in the system and it is precisely the problem that needs sorting. We need a code cracker here. All the Hunts/Erie caps I have date correctly.
Thanks for taking the time and trouble to check out your amps. There is a good mix of date codes; including improbable combinations.

Computer programming is beyond me. Cracking this code seems to be an ideal candidate for a math whizz - good at computer programming. I wonder what did start on the 21-May all those years ago. I shall continue to make enquiries and post back anything I found out. What is certain is the the date code is derived from WHITSUNDAY - .

Regards, Ed
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Old 10th Jan 2012, 4:49 pm   #6
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Default Re: Date Coding for Hunts / Erie capacitors

Hi, I think you need more data to "crack it" and a bright spark to explain how you can have more than 52 weeks in a year. (Of course you could divide the year into groups of 4 days - this would give a count up to 92 - but this seems very awkward.)

Based on the data so far, the year digit (which cannot be evenly distributed) can only be the last digit. This is consistent with Amp 1 = 1967, Amp 2 = 1968, & Amp3 = 1972 and fits generally with Lucien's description.

If the scheme of dividing the year in days-of-4 was applied the first 2 digits must be read backwards, otherwise numbers greater than 92 appear with the data. Reading the first 2 digits backwards may explain why the first digit is away from the others - this digit must be changed every 4 days - it is the most often changed digit.

Another possibility is dividing each week into a first and second half (Mon - Wed, Thur - Sat). This would break up the year into a total of 104 parts. 100 parts can be encoded with the 3 letter scheme leaving 2 weeks that cannot be encoded - this could be Christmas when there is no production. Who knows?

I have this strange feeling that I am about to look stupid when the answer is revealed but it is all about having a go!

Peter

Last edited by dinkydi; 10th Jan 2012 at 5:03 pm.
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Old 10th Jan 2012, 5:33 pm   #7
Lucien Nunes
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Default Re: Date Coding for Hunts / Erie capacitors

I have another three amps by the same maker to check, with at least the likelihood that I can arrange them in date order by serial number. They should contain up to a dozen Hunts caps with date codes (the small caps don't have them) unless any have been recapped.

I have an idea that this will turn into a pursuit of its own, to create a comprehensive table of all known manufacturers' date coding systems.

Lucien
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Old 11th Jan 2012, 7:23 am   #8
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Default Re: Date Coding for Hunts / Erie capacitors

Hi Lucien, I, and no doubt many others, await with interest the new data from your investigations.

Peter
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Old 24th Jan 2012, 3:15 pm   #9
Farnze102
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Default Re: Date Coding for Hunts / Erie capacitors

Hi to all,
I have managed to gain some information from a mathematical whizz.

After giving him the story he came back with revisions to my original remarks. Hmm!! He seemed to think that the 1961 scenario was bogus and in actual fact what happen was 1961 was simply a 10 year point in which the code changed.

Now this bit is interesting. Apparently the WHITSUNDAY code is fine but what *has* to be determined is whether the date code, on Whitsunday 1961, was shifted left by one digit, shifted right by one digit or was the code reversed.
By introducing a one-digit shift will effectively generate another 10 years worth of date codes.
The only way to find out is that one must have an accurately dated capacitor (or two) to establish the true code combination.

So can anyone take this further ??

regards. Ed.
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Old 24th Jan 2012, 4:28 pm   #10
Lucien Nunes
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Default Re: Date Coding for Hunts / Erie capacitors

Why did they play silly games like this? I'll post some more permutations when I get the other amplifiers to hand in the next week or so.

Lucien
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Old 24th Jan 2012, 9:38 pm   #11
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Default Re: Date Coding for Hunts / Erie capacitors

I've just opened a bag of five, NOS, W49 B503K, Hunts, metallised, 1uf capacitors. I'm not sure of their vintage, but I'd guess early 1960's?

Here are their codes
HHT
HYT
ISU
SWI
WHT

No matter how I shift the numbers to the left, right or reverse the codes don't make sense. I can only guess that the numbers were assigned to the letters in a non sequential way

David
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Old 24th Jan 2012, 10:03 pm   #12
Lucien Nunes
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Default Re: Date Coding for Hunts / Erie capacitors

No matter how the cipher was constructed, if the first or second symbol is the final digit of the year then the pack contains components from four batches spanning more than two years. Even if the third digit is year, there are still three batches spanning more than one year. This seems very unlikely, if it is an original Hunts pack and not one assembled by grabbing components from a retailer's parts bin. Still no letter D, probably not statistically significant yet though.

Lucien
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Old 24th Jan 2012, 11:17 pm   #13
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Default Re: Date Coding for Hunts / Erie capacitors

Thanks for the info, David.

If you work out the minimum number span for each digit of your data, we get:
Digit 1 = 5
Digit 2 = 6
Digit 3 = 4

Assuming that the Date Digit for the caps in your bag is most likely to have the least span (due to stock turnover and being assembled at one moment of time), this data is consistent with Lucien's data, with the Date Digit being the third digit.

This indicates that the dates for your caps could be 1955 to 1958.

The HHT (= 997) code is an interesting one because that indicates that the date code does not use the idea that I first proposed of dividing the year into 4-day segments. My second scheme of dividing the week into "halves" which deals with a 99 code is now more likely.

I welcome more data!

Peter
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Old 24th Jan 2012, 11:30 pm   #14
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Default Re: Date Coding for Hunts / Erie capacitors

Hi Lucien, I think that the parts must have come from a retailer's parts bin, as you suggest.

Peter
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Old 24th Jan 2012, 11:56 pm   #15
Mr Moose
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Default Re: Date Coding for Hunts / Erie capacitors

Hello,

I have about 60 NOS Hunts electrolytic capacitors with the following codes:-

32 + 32uF......... N YS, N WW, and N WI

40 + 20 + 10uF......... D YW

8 + 16uF......... N YT

8 + 8uF......... SYA and YIY

On all but the 8 + 8uF there is a space between the first and second two letters.
The letter D appears for the first time.

Yours, Richard
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Old 25th Jan 2012, 12:12 am   #16
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Default Re: Date Coding for Hunts / Erie capacitors

I would agree with the consensus that the third letter represents the year.
Fortunately I have recently re-capped a Racal RA17 receiver and have codes for 34 which I belive to be original. I also belive my RA17 was built in 1961.
In no particular order;
WSW-12
YHW-1
HIW-6
WSY-5
WYW-1
WAY-1
YIW-1
HYW-4
WHY-1
YHW-1
TWY-1
If the third digit does represent the year, then we have W and Y. But that would give (196)0 and (196)1, which would predate 1961.
Logically, for W and Y to be consecutive, they can only represent 9 and 0, or 0 and 1.
It doesn't seem to fit either way, unless it's years after 1961, ie 0=1961,1=1962
These are all L45 caps, can we assume the date code is identical to all types?
Some more from the junk box, vintage unknown;
WSU
?WY
TYN
TAN

Yet another angle, maybe two different factories used different week codes,
Factory A - weeks 1-50, Factory B - weeks 51-(1)00
Yes I know there are 52 weeks in a year, but I'm sure a plant like that would have a shutdown for a week every few months.
Rob.
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Old 25th Jan 2012, 12:16 am   #17
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Default Re: Date Coding for Hunts / Erie capacitors

Thanks Richard.

Are you able to provide any more data? For example, were the caps purchased in lots (that is, a group)? which caps were in which lot? when was each lot purchased?

Peter
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Old 25th Jan 2012, 12:49 am   #18
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Default Re: Date Coding for Hunts / Erie capacitors

Thanks Rob, Is there a problem?

It seems to me the data fits well and confirms that the last digit is certainly the year. Most caps were made in 1960 and some in 1961 when the Racal was built. There is only one "difficult" cap code and that is TWY (= 701) which may decode to the second half of 1961 and so the cap may not have been on the shelf long before it was used - but that is fine.

You could check on the dates on other components (that are easier to read!) inside the Racal to confirm the build date of 1961.

Peter
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Old 25th Jan 2012, 8:56 am   #19
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Default Re: Date Coding for Hunts / Erie capacitors

Quote:
Originally Posted by Lucien Nunes View Post
Why did they play silly games like this?
Lucien
Well I can't speak for Hunts, but a company I was associated with had a similar regime for dating acceptance sheets used on their equipment. The reason being was to keep the "punters" from noticing if they were receiving equipment that was accepted a year or so prior to delivery, but at the same time providing an in-house date reference for warranty, stock and bean counting purposes.
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Old 25th Jan 2012, 9:54 am   #20
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Default Re: Date Coding for Hunts / Erie capacitors

As far as I can see 'A' representing 2 hasn't been seen in the first position so far, but all other letters of WHITSUNDAY have.

It might be an idea to list the week numbers, read both forward and backwards, to check the spread.
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