Seiko H601 backlight issue

[steve1811uk]

Hi, I have an issue with the backlight on my Seiko H601. Backlight flashes off briefly every second when held. Battery is a new Renata SR920W. Watch is new to me so I think this could be a long standing issue. This happens even with the crown pulled out with the analogue circuit effectively shut down so I can't attribute it to the coil pulse. Does anyone know if it's normal or a way to try and fix it?

[JohnR725]

just in case you need the technical bulletin to figure this out I've attached that

H601A.pdf

[steve1811uk]

3 hours ago, JohnR725 said:

just in case you need the technical bulletin to figure this out I've attached that

H601A.pdf 169.38 kB · 0 downloads

Thanks John

I've cleaned the PCB again with distilled water and thoroughly dried but the issue remains. I notice that the battery voltage drops to approx 1.35 volts when the light is on. Not sure if that's typical or not. Only other changeable part would be the upconverter capacitor. Does anyone know if the light would be affected by the upconverter operation?

[JohnR725]

one of the modern problems with electronics repair is everything is modular. Gone are the days where it actually troubleshoot things to the component and replace that. So in the case of Seiko you would replace the circuit board. although I'm taking a quick look at the service manual they are showing more on this and they typically show actually showing world segments come from normally the circuits are just a black box it either works or it doesn't work

okay I suppose I really should've looked at the drawing it looks like the lightbulb is available separately. Doesn't mean you're going to find one but I also find the current consumption interesting because they tell you the consumption of everything and would that include the lightbulb? In a case the battery voltage shouldn't drop when the lightbulb is on unless you have a problem with your battery. To me it sounds like something is shorted out driving the lightbulb.

then I have a link to the parts list at least what was available one time but may still be available. The assumption is that everything is available online of it's not available online it doesn't exist. This is a good assumption when you're looking for old parts because if you have ties with a physical material house you can ask and often times they will have parts that don't exist because nobody bothers to ask. Although you can take the part numbers and go to their main page and do a search and see if they come up

then in the case of the life all but one time when LCD watches were relatively common they used to be generic lightbulb replacement kits so lightbulb might've been available in case for some unknown reason something wrong with yours it seems to me it either is going to work or not work which is typical with lamps.then it seems a bit expensive for the light ball but I just checked and there out of stock which of course comes as no surprise I suspect all of the parts are out of stock.

http://cgi.julesborel.com/cgi-bin/matcgi2?ref=SEK_H601A

 

 

[steve1811uk]

6 hours ago, JohnR725 said:

one of the modern problems with electronics repair is everything is modular. Gone are the days where it actually troubleshoot things to the component and replace that. So in the case of Seiko you would replace the circuit board. although I'm taking a quick look at the service manual they are showing more on this and they typically show actually showing world segments come from normally the circuits are just a black box it either works or it doesn't work

okay I suppose I really should've looked at the drawing it looks like the lightbulb is available separately. Doesn't mean you're going to find one but I also find the current consumption interesting because they tell you the consumption of everything and would that include the lightbulb? In a case the battery voltage shouldn't drop when the lightbulb is on unless you have a problem with your battery. To me it sounds like something is shorted out driving the lightbulb.

then I have a link to the parts list at least what was available one time but may still be available. The assumption is that everything is available online of it's not available online it doesn't exist. This is a good assumption when you're looking for old parts because if you have ties with a physical material house you can ask and often times they will have parts that don't exist because nobody bothers to ask. Although you can take the part numbers and go to their main page and do a search and see if they come up

then in the case of the life all but one time when LCD watches were relatively common they used to be generic lightbulb replacement kits so lightbulb might've been available in case for some unknown reason something wrong with yours it seems to me it either is going to work or not work which is typical with lamps.then it seems a bit expensive for the light ball but I just checked and there out of stock which of course comes as no surprise I suspect all of the parts are out of stock.

http://cgi.julesborel.com/cgi-bin/matcgi2?ref=SEK_H601A

 

 

Thanks John for taking the time to reply. I had another think about this and the voltage drop at the battery seems ok to me when the backlight is on. The battery has an internal resistance specified as less than 20 ohms on a Renata datasheet that I found. At worse case of 20 ohms with a 10mA load current for the lamp that will result in a 0.2 volt drop at the battery output terminal. 10mA for the lamp is a bit of a guess but I wouldn't expect it to be much less than that if any. Reason being that LEDs that were developed to replace incandescent lamps in that era did have typical load currents of around 10mA.

I need to have another look at the circuit board tracks to try and work things out but at first glance it did look like the lamp is driven directly from the battery voltage and not from any upconverter voltage.

I also need to check the circuit current but that will need to wait a while as I need to borrow the micro ammeter from my work.

Anyway, back to one of my original questions, does anyone have a H601 watch and can they check how the backlight behaves? Just to rule out a wild goose chase.

Thanks, Steve