Seiko 7A38 - by the numbers

fuser at November 16, 2013 at 9:54 AM

I finally managed to (carefully) get past the back plate, PCB and green spacer. This is about as far as I am willing to go without totally ruining the movement.

Apologies in advance for the photos. They were taken on my phone but should show in enough detail what needs to be shown.

I'm still a bit sceptical that there is enough contact between the terminal and the battery. It looks like it is making contact but can't be 100% sure.

Obviously I can see the issues caused by the battery leak but will leave it to the experts to see if they spot anything more. To my untrained eye the mechanical part of the movement looks pretty clean. The pushers and crown work as they should.

Any input in much appreciated.

I'm only quoting you because we're turning over the page, Christian ....

Hence it will save flicking back over to the page to look at your photos. 

As we suspected, there was 'hidden' battery acid damage to the PCB under that (too) shiny anti-magnetic back-plate. 

May I refer you again to the photos of other similar (some worse-looking) B.A.D. PCB's towards the bottom of this thread:

http://www.seiko7a38.com/apps/forums/topics/show/7517616-inside-the-7a38

The main problem with your PCB is here (arrowed in yellow):

That blob of Copper Sulphide / Sulphate (whatever - I'm no chemist) is right on the main feed track from the Negative contact.

You could try cleaning it up (and the Negative contact on the PCB), but you're probably wasting your time.

Likely the acid has eaten right through the track at that point, which is why your watch is completely dead. 

I think your PCB is dead 

I very recently bought a 7A38-7280 (out sniping Paul in the last few seconds). Its in very nice condition, but was dead as a dodo.

I swapped in a new movement today and hey presto, it sprang back to life.

Here's the PCB I took out

where the trouble started ...

and the underside

I did try cleaning it up, but it didn't help.

I very recently bought a 7A38-7280 (out sniping Paul in the last few seconds).

As did Christian with this 7A28-7120. So just as I said to him - Bloody well serves you right too, Simon ! 

Just a quick update on my plan of action. I'm going to take the advice of Paul and Simon and accept that the PCB is dead. While I'm searching out the PCB  I think I might as well change out both the positive and negative battery terminals as they are in far from great shape. Hopefully when rebuilt using the new parts it should spring to life.

Will keep the thread updated on my progress. If anyone comes up with some other ideas, I'm all ears.

Quick update: had a bit of a change of heart. Was going to go straight for the new replacement parts but I think I'm going to wait a little bit longer for a working donor to show up somewhere at the right price and condition. Certainly don't want to desecrate a nice example just for parts so a poor condition working watch will be perfect.

Updates to follow soon...

Any updates, Christian ?