Seiko 7A38 - by the numbers

Yozzer at July 15, 2015 at 3:02 PM

I had not used my Seiko 7A38 for a while, and it had stopped, so I replaced the battery with what I quickly discovered was an out of date battery, (I had bought a strip of Renata 394 some years ago, end date 2010), the watch worked, but the Chrono part was not happy. The centre second hand just twitched every 2 seconds, and the other two dials seemed to work then stop, so I ordered a couple from Ebay. I have tried both, and got it working for about 15 minutes, all dials, but then it degenerated again to the centre second hand just twitching. Having read here about fake batteries, I ordered a couple more from another dealer who was listed as a jeweler, but they worked like my original out of date Renata. Before venturing into going inside the watch, (I do fix clocks and pocket watches as a hobby), I thought I would try to find a reliable source for good, dated batteries in case that is the problem. I noted Cousins was mentioned in a number of posts, and as they are in the UK, I followed the link, but it appears they are trade only, so can somebody give me a link please to a reputable source for genuine batteries in the UK that are date marked on the packaging. (I do suspect the ones I got are fake or old stock).

A great forum by the way, lots of really good stuff, so if I need to disassemble the watch, I should be OK, but know where to go if I am still having problems after fitting a known good battery.

Please excuse the brevity of this reply, Brian.

First off, Cousins UK may be wholesalers, but despite the inference of 'Trade Only', they will deal with individuals direct. 

All you need to do is set up an account and when you complete your order (Basket / Checkout) check the disclaimer box.

Your watch may be suffering from old sticky oils in the jewels, adding friction. The best way to determine this is once you've got it mostly running on a decent battery, leave it somewhere warm overnight (say an airing cupboard) and try it in the morning. If when it cools down, the problem returns, you might just get away with stripping, cleaning and re-oiling the centre seconds bridge. Check how much pressure the centre seconds finger tension spring is applying to the end of the shaft - it should just lightly bear on it.

That is assuming you've already eliminated the most common cause of a recalitrant chrono' sweep second hand:

The all-too-common Displaced Finger Tension Spring chrono' sweep hand problem

Seiko7A38 at July 15, 2015 at 4:12 PM

Yozzer at July 15, 2015 at 3:02 PM

I had not used my Seiko 7A38 for a while, and it had stopped, so I replaced the battery with what I quickly discovered was an out of date battery, (I had bought a strip of Renata 394 some years ago, end date 2010), the watch worked, but the Chrono part was not happy. The centre second hand just twitched every 2 seconds, and the other two dials seemed to work then stop, so I ordered a couple from Ebay. I have tried both, and got it working for about 15 minutes, all dials, but then it degenerated again to the centre second hand just twitching. Having read here about fake batteries, I ordered a couple more from another dealer who was listed as a jeweler, but they worked like my original out of date Renata. Before venturing into going inside the watch, (I do fix clocks and pocket watches as a hobby), I thought I would try to find a reliable source for good, dated batteries in case that is the problem. I noted Cousins was mentioned in a number of posts, and as they are in the UK, I followed the link, but it appears they are trade only, so can somebody give me a link please to a reputable source for genuine batteries in the UK that are date marked on the packaging. (I do suspect the ones I got are fake or old stock).

A great forum by the way, lots of really good stuff, so if I need to disassemble the watch, I should be OK, but know where to go if I am still having problems after fitting a known good battery.

Please excuse the brevity of this reply, Brian.

First off, Cousins UK may be wholesalers, but despite the inference of 'Trade Only', they will deal with individuals direct. 

All you need to do is set up an account and when you complete your order (Basket / Checkout) check the disclaimer box.

Your watch may be suffering from old sticky oils in the jewels, adding friction. The best way to determine this is once you've got it mostly running on a decent battery, leave it somewhere warm overnight (say an airing cupboard) and try it in the morning. If when it cools down, the problem returns, you might just get away with stripping, cleaning and re-oiling the centre seconds bridge. Check how much pressure the centre seconds finger tension spring is applying to the end of the shaft - it should just lightly bear on it.

That is assuming you've already eliminated the most common cause of a recalitrant chrono' sweep second hand:

The all-too-common Displaced Finger Tension Spring chrono' sweep hand problem

Many thanks for the information. I joined Cousins, and ended up buying more than batteries ;0)

Having read at least some of the enourmous amount of info on this site, I had checked the displaced finger tension spring, in fact I gently loosened it a bit and moved it awy just in case, but it made no difference, (it is back in position now). I left it somewhere warm as you suggested, and the 1/10 hand seems a lot better, so I suspect it is, as you say, the oil dried out. I have never dismantled a "hybrid" like this, but I will carefully look over the notes available here. I suspect I may need to remove the face and fingers, though I must confess I am a little nervous of that due to eyesight starting to dwindle, and though I usually have no problem getting really small screws back in OK, replaceng tiny hands can be a tad difficult. I have bought some newer eye glasses from Cousins, amogst other stuff, so will see how good they are.

I will keep you informed, but it may take a few days, as we are celebrating our Golden wedding today, and have a hectic few days with the family celebrating.

Brian

Well the order arrived promptly from Cousins, and I fitted a new battery, but it was no different, so I decided, as it did work better warm, to do as suggested and try just cleaning and oiling just the rear of the movement and see how it went. Using the guides and tips in the forum, I removed the shield and spacer, and gave all I could see a good cleaning with the Ridico I had also ordered from Cousins, and I was amazed at what it picked up. I cleaned out as best I could the old oil using isopropyl, and cleaned it again, using the Rodico to pick up the bits, (I wish I had used this stuff before, pretty amazing). I re oiled carefully, cleaned all the pcb contacts etc. as advised, re assembled, and I could not believe it, at the last step, the little friction finger for the chrono second hand completely vanished just as I was placing the screw in. I have been fixing clocks and watched a while now, since I retired, and have lost the odd screw, but usually a quick sweep with my magnet finds it, but this seems to have vapourised. I complteted  assembling the watch, and everything seems to be working fine now, except the reset is a little different to the instructions I found, but it now works fine. I will have another look for the finger tension spring as it has to be somewhere. I always use a white cloth on my little work desk, so any parts dropped can be easily seen, but where it went, with very little energy behind it, at the moment is a mystery.

Many thanks for the input Seiko7A38, and the great tips on this site, it certainly helped as I had never worked on a watch like this before, apart from changing a battery.

Brian

Hi Brian, good work, it's a right bu**er when that happens I've done it loads of times with various bits :roll:. If you can't locate it I have a spare one you can have just pm me your address and I'll whizz it in the post for you

Regards Phil

That is very kind of you Phil, but I left it for the day, and when I went back up to have another look, I spotted something shiny on the floor as I walked in, a beam of sun straight on to it, and I just new what it was. It must have attached itself to me somewhere, though I did run the magnet over myself, but it was a bit squashed so I must have walked on it, perhaps stuck to my slippers, but half an hours tweaking to straighten it and it went sraight in first time. Perhaps I should ask my wife to make me a little tent that fits over my head and droops on the the desk to catch flying objects, or perhaps a special hat.

Many thanks again for your very kind offer,

Regards to you all, Brian

Good doo Brian, it's not a bad idea that, a head tent, I had a click spring vanish whilst I was servicing an ETA 2824 m and had to order another one it cost £8 and a week to come,  went to fit it again and the same thing happened pinged off onto the carpet somewhere and I spent half the morning on my hands n knees with a magnet again with no luck so had to order another one finally got it in and working but it's very frustrating and potentially very costly. Glad you found it 

Regards Phil

Please note:

If you have any requests for Seiko part number information for 7Axx models (not covered in the 7A38-xxxx model specific threads)

Please post them here in the relevant forum section:

Parts Info, Tech Tips and Tinkering The place to ask questions; hopefully get some help - and share advice.

Patrick's (BusBoyT2) recent posts have now been moved there: http://www.seiko7a38.com/apps/forums/topics/show/13428695

Is there any way to get hold of "home made" replacements for the red plastic pushers on the 7a28-6000 "Bishop" model? Considering how often they seem to be cracked or missing on the models that turn up for sale, you'd think that someone knowledgeable would have seen a business opportunity by now...

Hi all,

I'm thinking about throwing my search a little wider than the stainless steel white dial 7a38 7280 I was targetting...

I have been looking at the model specific forums and searching what I can elsewhere online but I find it a little difficult to distinguish  between white dials and silver dials (which just won't do!).

Am I right in thinking the 710L dial no. is the fully white version and the 708L is a more silvery white? And if so, how many other models are there with the 710L?

Just looking at photos, I find it difficult to tell if, for example, the 7A38 7090 or 7060 have white dials or silver?

Would be great if anybody could suggest / post photos of their own white dial 7a38s? 7a28s acceptable too...

Many thanks for any help!

Joe

Hi, Joe.

Good question. To answer simplisticly, very few dials used in Seiko 7Axx's are pure white (or for that matter, black). The white dials often have a slight tinge of metallic (silver) or 'pearlescence' to them. You are correct in assuming that the 710L dial used in the stainless 7A38-7090, 7A38-7190 and 7A38-7280 / -7289 is less silvery than the 708L dial used in the stainless 7A38-7060, but it's a country mile from being pure white. The painted rings around the rims of the 710L's sub-dials (which themselves can sometimes be difficult to capture in photos) are actually pale silver.

Funnily enough, if you search Seiko Oceania's database on any (in fact, almost all) of the stainless or two-tone models that you might first regard as having white dials, you'll find the colour is actually shown as 'SILVER'. One of the few 7A38 dials that is pure white, but may be a little too ornate for your tastes, is the 718L dial used in the two-tone 7A38-726A and gold-tone 7A38-7260.

A few years ago, I built this two-tone 7A38-(7289 based) Franken using a 718L dial.

Great, thanks for the very informative answer! I'll keep an eye out for the 7190 and 7090 too then.

Re the 726 models you mention - I always thought I'd only ever have a watch with lugs, but for some reason with these 7a38s I majorly prefer the case shapes that have an integrated bracelet. I think your Franken is the best of both worlds - it looks much better than the original two tone 7289.