Introduction, Repair Progress, and Questions

[drlava]

Hi guys, since this is my first post I think an introduction is in order: my name is Andrew, I live in Ohio, USA and for about 16 years I have had the Synchronar bug after picking some up second hand. For most of the time they have sat in a protected drawer but partially because of the good info available here I recently decided to pull them out and have a go at repair.

First, they are model (mark) 1 or 2's I think. One has a brushed stainless and the other has polished finish shell.


Inside they are quite different, but I see both circuits referred to as M1 here on the forum, which is a bit confusing. Can you clarify this? Here are top photos after a soak and clean in ronsonol lighter fluid to swell and remove the silicone encapsulant:
UNIT 1


UNIT 2


On the second pic I have already replaced the transistors as the old ones had corrosion and the epoxy bubble just barely lifting up under microscope inspection.

Bottom Views:
UNIT 1


UNIT 2



As you can see I had to replace the crystal on the second unit due to corrosion. Also this second unit has bad corrosion on the display segment leads, some of which have been eaten through.

Problems:
Unit 1:
The first 'line LED display' unit is basically fully working and in great condition, except the IC has a problem of excessive bias on the seconds display selector pin. The 100k pull-down resistor here is insufficient and a 6.8k resistor is required to turn the seconds display off. This results in a 165 microAmp current draw while the unit is idling, instead of the typical 16 microAmp draw of a good unit. Also, the 'date' display comes on at full brightness and pulls 180mA, much brighter than the other modes.

So. I'm looking for a new IC for this unit.

Unit 2:
This 'dot matrix display' unit sustained widespread corrosion from battery juice, and has the crystal, transistors, and LED segment pins eaten. After replacing the transistors, most of the segments work I'm in the process of re-connecting the corroded segment leads where possible. It's a challenge because the segment plastic softens a lot when heated and can flex, leading to bond wire breakage internally. The one irreparable problem with this one is that the upper right segment output from the chip is very weak and can't turn on the transistor.

So, I'm looking for a good (or fixable) display for this unit and a replacement chip as well.

A few things I noticed, being a new member here. I see everyone referring to the sealant material as 'gel' or 'gooey stuff' but it IS just silicone elastomer, right?

This diagram:

is very helpful, but the segment order is inaccurate for some watch types. it claims to originate from dwf.cc, but that forum only has 4 threads under the synchronar section and I don't see this image anywhere.

I have ordered some 'gooey guts' from Barry Riehl and hope that they will contain the parts I need, but if not, hopefully one of you will have these things?

One more thing I'm looking for is a rear setting spring/magnet; if you have one available for sale, please let me know!

Thank you for your many informative posts here, it has become a good source of info. I hope the admin backs up the forum once in a while to preserve this knowledge.

[J Thomas]

[drlava]

Thank you Jeff, I'll give that a try.

One thing I learned about removing the silicone on these is that you probably want to remove the solar panel first and (if necessary) do it separately. The rubber backing that is attached to the cells peels off and rolls up in the solvent, which if you have your panel attached can cause extra stress. A solar panel without the rubber backing is very fragile indeed!

[clockace]

welcome to the nuthouse, i believe they are both mkI's. the 2nd module with the rectangle transistors is earlier and has the dot seg display. the other is a line seg display. you stated the secs would not turn off. did you check to see if the reed is bad? i have one that wouldn't turn on with all other displays working and it was the reed that was bad. they cleaned up nice in the ronsonol, but you do want to have the sc off first. what amount of voltage are you using? the original nicads only put out 2.4-2.8v. it seems somehow more voltage is getting to the date than the others. the only thing that changes the brightness level on a working module is the output of the sc. is the 6.8k resistor you installed part of that circuit as well? i would go back to the 100k and check the reed. that circuit looks clean enough that 2 new nimH cells might be the only other thing you need. just my 2 cents. peter

[drlava]

thanks peter! I did check the seconds reed and it's OK. I was powering them between 2.5 and 2.9V for testing. The testing was done without the solar panel, but after you mentioned it I looked closer and saw a blob of solder connecting that switch output to the solar panel contact right next to it. When the switch closed it made the control circuit think the solar panel was in bright sunlight, so thank you for that. Now the only difference between this module #1 and a brand new one back then is that it draws 165 microAmps at idle instead of 15.

Also, I sent Jeff a few PMs and he wanted me to post them here for public knowledge, so here they are:

Hello, I just made a first post in the forum and wanted to personally thank you for your posts and time here. Also (of course :) ) I have a question - do you know if the M1 and M2 models chips have the same operation, just the m2 has a pin clipped?
thanks and regards,
Andrew

Hi Andrew, both of those modules shown in your post are a variation on the Synchronar MK1. I do not know the dates they were built, but both are MK1 watches.

The MK2 Synchronar will have a cut lead on the short side of the packaged chip, at the crystal end of the board. The difference relates to the fact the MK2 only has four reed switches rather than six, and the additional chip input connection isn't needed. That is the *only* way to identify a MK1 module from a MK2.


Regards, Jeff

Ok, very good thank you. It's likely then that the chips are intercangeable if one were to bond a wire to the clipped lead of a Mk2 chip for use in a mk1. However as you say Barry has many Mk1 parts, this should be unnecessary.

Can you confirm the 15-16 microAmp draw for an idling good module? How long can you go without an outdoor (or bright lamp) recharge? I calculate from a 65mAH capacity about 140 days of idle without viewing.

Regards,
Andrew

You measured fairly close to what could be expected from a MK1 driving a bar crystal + some leakage.
It might be slightly less with a clean and low humidity environment, but the difference would be a couple micro amps at most.

There were some difference in the MK1 chips. Please post questions to the forum, and not PM, and please move these PM's to your open thread. This is important stuff that all readers should know anyway.

Regards, Jeff

[clockace]

andrew, upon closer examination your photo of unit 1 bottom view shows green corrosion between the traces on the top edge near where it says riehl. this could be causing a short or at least a bad path for the circuit. the schematic you show has been a lifesaver for a dummy like me, i just wish we could have the same info on the other side of the pcb. i never experienced any variation of the segment drivers or the digit drivers. what i did figure out is that a transistor could be either bad or at the least not making a good connection. by the way, you stated you already replaced transistors on the 2nd photo and it looks like a very neat job to me, but where did you get those rectangular transistors? peter

[drlava]

You're right there is corrosion of a few traces there, but I checked and it's not causing short or opens. But good eye!

I can draw up a diagram of the bottom if it would help people. There are only a few parts on the bottom so far it hasn't been necessary.

The transistors are standard 2n3904 and 2n3906 sot-23 type from digikey. Luckily they were already in the parts bin!

[J Thomas]

[drlava]

Nice job in removing the potting gel! The lighter fluid worked great, and the underside looks like new.

thanks, I think it was your suggestion I read in another thread to use lighter fluid with NAPHTHA as an alternative to petrol. Much easier than siphoning from my auto.

I'm impressed with your ability to change out those SOT-23 transistors, and have them perfectly aligned. That really shows your soldering skills

I've been soldering surface mount parts for many years, this was relatively easy compared to some BGA parts I've done!

Thanks for the hint about the brush, will pick one of those up. Yes, there are differences in the osc circuit, in fact I was thinking about going for a tuning fork crystal and increasing the driving resistance to decrease the battery drain a bit for longer life. On the older model, the fork crystal is being over-driven so much that I can put my scope probe (load) on its output without damping the circuit.

Also, what-the-heck are two two things soldered to the surface of the underside on the hybrid display board in the image below?

I saw the added black wire, which isn't a stock item BTW, and then I saw what looks like two tiny axial LED's. Can you clue us in on what those are? You may have exposed yet another variation on the MK1 watch

Those are in fact red LEDs although I don't know what they do. They ARE wired into the circuit, though, so they might do something. I'm suprised to hear they may be unique.

There was initially a white jump wire in place of the black wire you see now, and that was stock. It jumps the upper right segment set to the correct pin on the main PCB. I replaced the rather stiff original solid wire with a microstranded silver plated wire because the solid wire was putting too much torque on a connection that goes through the PCB to the display.

Thanks for all your help I hope the parts arrive sooner rather than later!
Andrew

[rewolf]

Also, what-the-heck are two two things soldered to the surface of the underside on the hybrid display board in the image below?

Those are in fact red LEDs although I don't know what they do. They ARE wired into the circuit, though, so they might do something. I'm suprised to hear they may be unique.

Are these LEDs maybe used as 1.6V Z-diodes? I've seen this in solar-driven pocket calculators.
Thay appear to be in the oscillator circuit. Prevent over-driving the crystal maybe?
I think we need a circuit diagram

BTW great to see another member with obviously solid knowledge in eletronics here
Is that round PCB in your 1st post a design of yours? I'm curious because of the shape - what is it? Or don't tell, just post a closeup and let us guess - maybe in a new thread ?

[drlava]

here's another view, back when the original white wire was connected:


Oh, I'll reply to your edit with an edit here: It's nice to be here where the watches get the attention they deserve :)
That is a drink coaster PCB that the fellas at advanced circuits (PCB fabrication shop) sent as a gift.

.

[J Thomas]

[clockace]

the 2 leds at the lower display edge. one of them will lite up when you are on a leap year. i think it is the lower right when facing the display. i believe andrew[charger105] has a post on this a year or so back. i am not sure what the left one does. i have a couple of modules that have these. peter

jeff, do you think the qc could be the problem with my modules blowing out in bright light? these originally had the long rectangular qc's and i replaced them with the can tuning fork type. i think you and i discussed that problem before and you said the voltage was so high in bright lite the qc would quit oscillating. i have long suspected that may be the problem because after some time the module will start up again by itself. i have one now that is off that doesn't seem to want to start up. maybe the qc is now kaput peter

[Sully008]

I had a module with those little LEDs on the display. I sent it off to be repaired, and I hope I get it back soon. I took a fuzzy iPhone pic of it once with one of those LEDs lit, but I seemed to have deleted the picture.

drlava, welcome to the site! I'm with rewolf, it's nice to see someone else with the technical ability to work with these watches. I'm just a hack with a soldering pen (although I have managed to get 3 of these back to life).

here's another view, back when the original white wire was connected:


Oh, I'll reply to your edit with an edit here: It's nice to be here where the watches get the attention they deserve :)
That is a drink coaster PCB that the fellas at advanced circuits (PCB fabrication shop) sent as a gift.

.

[drlava]

I drew up a full schematic, but don't know if it's ok to post here. One of the Rhiel brothers would have to OK it since it's their IP. However the LED anodes just go to the 'to display' pins between the seconds and first segment pin. The cathodes go to the Digit1 and Digit4 transistors.

After looking at the dot-matrix display model, the exact same functionality and control is provided via the extra decimals on the outer digits. This is why D1 and D4 transistors are used to control those LEDs. So it would appear that the LEDs are just there to provide the two indicators that were lost when he switched over from the dot matrix to the epoxy bubble display.

[rewolf]

Argh - I was totally mislead. I thought the 2 glass tubes near the oscillator circuitry at the rear end were the mentioned LEDs. Now I see one of these is a resistor and we're talking about LEDs on top of the display... I missed that. Shouldn't post near midnight...
Yes, there exist LEDs that look like little glass tubes (diodes), they are used not for lighting but as a Zener-Diode.

drlava: I'm sure it's ok to post schematics here. We do this all day with other watches like Pulsars . And it's very easy to "reverse-engineer" the rather primitive external circuitry.

[charger105]

Here's the discusion on that indicator from some time ago:
http://www.dwf.nu/viewtopic.php?t=3763&highlight=leap

I'm not sure I've ever seen the indicator at the other end of the display light up (perhaps I have, but I can't remember). Either way, I don't know what it's for. Could be for a future feature that was never implemented.

Rgds,
Andrew.

[J Thomas]

[egomon]

Hi.

I have been workin on my own barrys MK1 and MK2 and have got 4 of them working and other 4 sort of working.
I have lots of qustions to more experienced members, but that perhaps for other time.

For now just one question:

Is the MK1 and MK2 chip the same, only difference is one cut leg ?

Thank you

[J Thomas]

[J Thomas]

[drlava]

Barry got back to me and said posting the schematic was OK.
So here it is (of the bubble line display unit). The resistor values for the osc circuit were as measured, but may not be the value they should be due to corrosion. Also I didn't measure any of the capacitor values.



A thought occurred to me: I wonder if we can improve the charging characteristics slightly by replacing the diode that is in the cell charging circuit with a modern low Vf schottky? This has the potential to allow the panel to charge the battery when it is generating a few hundred mV less than stock limit.