Hi All, Thought I would describe how I have repaired two of my clock modules on my Ferguson 3V22's
Faulty Clock Display
The display unclips from the front of the machine and one plug to be removed then dismantle the case. You will be left two PCB's one with the clock electronics the other the display. You will first need to de-solder the multiple 150 ohm resistor array to separate the boards the carefully leaver the external LED cover, purple, and the led cover, white, usually forces the plastic through the board some may brake off but doesn't matter as you will put these back with a small amount of glue.
LED Cover Removed
Resistor Array Removed
You will now be left with just the faulty LED board
You will now need some Acetone to dissolve the glue over the LED's. I used Oily Nail Polish Remover but be aware that some of these products are Acetone free. I used a shallow plastic tray with just enough Acetone to cover the LED side of the board.
Leave this soaking for a few hours then lightly scrub with an old tooth brush. It will take two or three goes to get all the glue off. You will be left with microscopic LED's on the board that look to be "spot" welded to the copper track but these will come off by applying a small amount of pressure with a small screwdriver. You will be then left with a bare copper board. You will need to tin the copper ready for mounting the new LED's.
Next you will now need to mount the new LED's. I found the best to use where 0603 surface mount devices (red). 0402 are two small 0603's where correct with the correct height to mate with the display and sit across the connection tracks correctly . For those that don't know 0603 is the SMD (surface mount device) size. Very small to solder but doable. MAKE SURE you solder the LED's in the correct way around with the CORRECT POLARITY!! I used my Fluke meter to check on diode test as it just about illuminates them.
The new LEDs do not require anything like the same drive for the same brightness so you will have to replace the resistor array with individual resistors. I found 560R (preferred). For those in the know do not add resistors to the two common return lines as this will cause the LED's to pulse with the seconds LED. You will need 20 of these resistors.
Edit: 05/06/2022; I originally stated, use 4.7 or 5.6k resistors. This was incorrect, you use 560R resistors.
Glue the display covers back on after testing on your machine. I have done three of these now and its nice to see the machine fully functional again with working clock display.
All to do one mine was finish the r.f. alignment and check the picture, recorded off another aligned machine.
And the picture
Just a note to say I have never come across a duff driver pin on the clock chip when I used to service these in the early 80's
Any questions please ask
Adrian
Fantastic post Adrian ?
A very useful how-to guide, thank you for taking the time to document the process and share it with us. This is worthy of being made a sticky so its not lost, which it now is.
@crustytv Hi Crusty, thanks for leaving as a "sticky" I thought it would be useful as nearly all the ones you see have at least one duff segment! In the days of these VTR's the clock units where prohibitively expensive. Never tried to repair them then but with the advent of SMD components I thought lets give it a go. fiddly mounting the leds I rest them on the prepared board then hold with a small screwdriver blade whilst I tack one end then solder the other, wait a minuet then solder the tacked end. If you lose or melt an LED, bin it start with a fresh one as they are pennies.
It's quite an eye-opener as to just how much more efficient up-to-date LEDs are compared to their predecessors- the received wisdom of 40 years ago was 20mA for acceptable brightness, now a tenth of that is plenty with many.
Recently found my NOS stash of 1980`s LED`s and was surprised how many were very diminished in output, the boring 5mm red and green colours.
I imagined their life was estimated under working conditions, but perhaps not.
Thank you Hurty!! I have searched for years for a replacement clock/timer for my 3V16 (ex rental) and have found them to be unobtainable....
Having stumbled upon this forum via search for 3v22 clock, I was amazed at your article. I had previously stripped the clock module and determined that the LEDs were faulty but saw no way in hell to replace them as they were so small and surface mounted.
I bit the bullet and ordered the LEDs..Yes they are small!!
Amazingly cheap though. I lost three... Not through melting etc, just dropped them and couldn't find! I followed the process re. the acetone and tinned the bare board and removed excess solder with braid for a flat surface. I haven't got a temperature controlled iron (Weller needs a thermostat) but I used a very fine tipped Antex iron. I had to use a head mounted magnifier with LED, mostly due to my age but I still I found it difficult to tack the LEDs using a screwdriver as they tended to pop out under the slightest pressure. I found it easier to place the LED with a small plastic tool, maybe an old trimmer? then gently hold with a finger to tack the first joint. After that just followed the process!
As Hurty said, the meter will illuminate the LED's when in diode/junction test mode, so easy to ensure all connections are good. I think Hurty's pic shows the correct orientation for the LEDs, the cathode indicated by the large block of print on the pcb and the anode by the smaller "spidly" print. The resistor installation was fiddly but nothing in comparison to the LEDs!! Remember the links at locations 21 & 22.
Finally I powered up the unit and couldn't see that things were right and spent an hour looking for issues... I should have fitted the lens straight away as all was good, maybe the eyes were trying to translate which LEDs were on into numbers... Whatever..
it fooled me! With the lens on all is great!!!
What a fantastic Post by Hurty that has further enhanced my collection here in far away Perth Australia.
After achieving the impossible Hurty, can you devise a process to materialize obsolete control doors etc? 🙂 🙂
Regards - Mark
@markc Hi Mark, glad you found it useful. I have done 3 of mine now and it just finishes the machines off nicely. The clock modules where expensive in 1982 when I last required one. As you say it is fiddley but doable.. On your question on materializing obsolete control doors, this is now doable if you have access to a 3D printer.
Adrian
Hi Mark, What resistors did you use as they are supposed to be 560R not 5.6k!
Hi Adrian, this is a very belated reply to your last post on this topic. I'm here because I just completed my second clock rebuild using 560R limiting resistors. All is good but the display is very bright, to the point of illuminating adjacent segments. I had a look at my previous rebuild and next to an original unmodified version, it's exactly the same, so I checked my resistors and I previously used 5.6K as per the original article. I will replace the 560R resistors with 5.6K and report back. Maybe there are slight differences in clock modules used? FYI, both my rebuilds were on HR-3660/3V16 machines.
Hi Mark, I used 560 ohm resistors on the last one I did. I will be glad to hear your report back. It won't be the driver IC that is different. It will be the LEDs used as they have different luminosity across different manufactures.
Hi Adrian, with 560R resistors replaced with 5k6, the display now matches my other rebuild and also my bog standard untouched clock. I can only imagine that there must be differences in the LEDs as you suggested. I just ordered red 0603 LEDs from Ebay, so no spec sheet. My latest machine is an interesting variation on the theme, badged as His Masters Voice and with wood effect side panels!
Thanks for your help/interest.
Hi Adrian,
Have you applied this repair to the earlier HR-3300 based machines with the single event timer? I have recently acquired an Akai VC-9300 which looks to be a HR-3300 or Fergy 3292. I don't have a circuit for this clock module and the manual is difficult if not impossible to find!
Regards - Mark
Hi Adrian,
I think I have answered my own query. A close look at the earlier clock module shows it as fundamentally the same as the later ones, just with fewer LEDs and buttons. The module itself is a bit more fiddly to dismantle due to glue but still doable. The resistor pack has fewer pins but still has the 2 pass through pins at one end. I'll build this one as I did previously using 5k6 resistors and will post with the results.
Thanks - Mark
Job done. Certainly more fiddly than later models. LED copper pads are closer together making soldering difficult. I did think about reassembling the various lens components with glue but once all clipped back into the bezel, all held together nicely. I used 4k7 resistors for this one.
Hi Mark, I used 4.7k resistors on my last rebuild. I haven't rebuilt the single event unit but would not expect it to be much different as I would use the same method and replacement LEDs. Your rebuild looks good. I expect the original LEDs would have dimmed a bit over time so 4.7k should brighten them up to what they were like when new. I was starting to see a lot of these clock displays losing segments in 1982 when the machines were about 3-4 years old and replacement clock units where expensive or becoming un-obtainable so here we are 40 years later I thought I need to tackle this. It completes the machine.
