Repair Questions - Any Quick Fixes?

[bucko170]

1. Hughes module, digits scroll from left to right across the display when the command is pressed first time and stop on the second press.

2. Green Sears Roebuck, digits race at a zillion mph during setting.

3. Pulsar, seen this one display 1 : but nothing else, is the potting gel a later addition?

[bruce wegmann]

Don't know about the Hughes or Sears, but the P2 module is totally original. This is the circuit board most P1s were re-fitted with [a few have the even later, smaller board with the vertical light sensor]. I think most of the idea behind the pottng gel was to hide the circuit board, but it had the unfortunate side-effect of trapping moisture underneath, and thus promoting, rather than inhibiting, corrosion. I have one or two working modules of this type that were neither potted or sprayed black; hard to believe that was an oversight at the factory...I'm guessing people ordered them that way so you could see the innards...I always thought the insides looked pretty cool...

[bucko170]

The Sears Green LED watch is setting OK again, I cleaned up the traces on the PCB with a fibreglass tipped pen and gave it a wipe with some Isopropyl alcohol put it back together and it set as it should although I'm not sure if this was down to my actions or if taking the batteries in and out had simply just reset everything.

I did the same with the Hughes and it set and worked OK to start with but then went back to showing the digits one at a time from left to right although I did notice that the digits showed the correct time

Thanks for the info on the Pulsar Bruce, I doubt if I will look at this one as I would probably only make matters worse.

[bruce wegmann]

If the P2 module is doing the single-frozen-digit thing, certainly it would be worth a trial quartz replacement...takes only a few minutes and might pay off big...a little work for a major gain.

[azimuth_pl]

the early P2 is also mentioned here:
http://www.dwf.nu/viewtopic.php?t=3929

if kept in proper condition the potted modules prove to be more reliable than the later painted versions as the silicone had a strong grip and secured the circuitry from battery acids.

btw.
as mentioned in the other thread I'd like to correct some data on the naming of the P2 modules.
Dennis once said that the 2800 symbol for these potted P2 modules is not correct. I have used this term by describing these modules on my website back in 2005. some people have used it ever since. I'm not sure but I might even have invented the 2800 symbol by downgrading from the known 2900 module.
the other thread by Ed clearly shows a third (or rather first) P2 version without a large quartz cavity.

there are no alternatives so do you guys have any suggestions on proper symbols for the P2 modules?
perhaps:
2800 v.1
2800 v.2 (marked 2925 on substrate)
2900 / 3100 (marked 3005 on substrate)

[bucko170]

Thanks for the info azimuth; also thanks for the vinegar bath tip you gave in an earlier post, 2 out of the 6 I have dipped are now working which is great considering all 6 where ones I had put into the junk pile.

BRUCE WROTE

If the P2 module is doing the single-frozen-digit thing, certainly it would be worth a trial quartz replacement

Tried a QC change but without success, it is now in the hands of someone with far greater skills than my own, hopefully he can work his magic and get the old girl going.

[azimuth_pl]

good to hear that vinegar proves to be useful.
besides a quartz swap or a bath it's also worth to check the trimmers which tend to oxidize or rust due to battery leakage.
unscrewing the trimmer (capacitor) on the back, cleaning and assembling it back sometimes solves problems with poor conductivity.
cleaning the front trimmer with vinegar and with a few additional turns of the trimmer screw removes old residues.

another quick fix with the early P2 is to check if the wire in the upper left corner is rusted or broken. the same goes for the capacitor next to that wire which can be exchanged with a 10pF capacitor.

[Led-Time]

I must try the vinegar dip, will malt vinegar be ok or does it have to be white.

[azimuth_pl]

it's the acid that counts so it can also be lemon juice.
I would use clear vinegar but you might use the one you have.
a warm solution works best.