Repairing ZX Spectrum +2A tape deck

On ZX Spectrum +2A I have a tape deck was not working. Well actually it was working, but games were not loading as it seemed like the signal was missing. I will not go into details of disassembling ZX Spectrum +2 as it is pretty obvious. You get access to PCB of tape dec right away, to turn it around You have to unscrew couple of screws and that is all.

Without any deeper investigation after disassembly I decided to do couple of things right away:

  • replace all electrolytic capacitors with new ones,
  • replace HA17324 operation amplifier with LM324

But unfortunately and to my surprise, after this hassle nothing changed, still the same issue.

Then I noticed that something wrong with the powering on the board and it seems like the ground was missing.

After some further investigation, I have found that ground on the board was delivered by two bold that was holding the board, as the board was removed, there was no ground in one part of the board. And maybe due to oxidation or something like that ground initially was an issue. I have inserted back HA17324, added a jumper between grounds just to be sure and it seems problems were solved.

So here You go, if You have ZX Spectrum +2 tape working but no signal, check ground first.

 

Removing stuck drill chuck the hard way – cutting it with grinder

Recently chuck of my Skil hammer drill (Skil 6785 750w hammer drill) got stuck while drilling some concrete.

Skil 6785 750w hammer drill
Skil 6785 750w hammer drill

After some googling found few instructions how to remove stuck drill bit. But after removing drill bit I noticed that chuck itself is not functioning normally anymore. So it had to be replaced also. But after few failed attempts to unscrew the chuck it was clear that I will not be able to do that – its stuck like it was welded. Having no more ideas I took my grinder and decided somehow to cut the chuck out.

After the first attempt, I could remove most of the chuck parts, but still not able to remove chuck itself.

After first cut with grinder
After first cut with grinder

The second attempt – removed almost all of drill chuck, still no luck to unscrew it.

Second cut
Second cut

So decided to disassemble drill itself and see maybe I will get any ideas or better grip.

Skil 6785 750w hammer drill disassembled
Skil 6785 750w hammer drill disassembled
Skil 6785 750w hammer drill shaft
Skil 6785 750w hammer drill shaft

Removed shaft with the whats left of the chuck and gear.

After some more not so accurate cutting with a grinder and few hits with the metal punch finally I was able to unscrew the chuck from the drill.

Final hit to remove whats left from chuck
Final hit to remove whats left from chuck

Noticed that while cutting I have damaged threads of the shaft, but us chuck was unscrewing nicely I hope it will be no problem to screw in the new drill chuck.

Now the tricky part of assembling the Skil drill back into its original shape. Before putting the shaft back you have to insert small springy metal that pushes “lock” button. I was tricky to figure this out as when tearing apart this spring fell out and I had to think where it was originally by myself.

Skil 6785 750w hammer drill putting it back together
Skil 6785 750w hammer drill putting it back together

Another photo so you could better see where this spring has to be seated.

Skil 6785 750w hammer drill putting it back together
Skil 6785 750w hammer drill putting it back together

Then you put the shaft back.

Insert hammer/drill switch and “lock” button into their places.

Skil 6785 750w hammer drill putting it back together
Skil 6785 750w hammer drill putting it back together

And basically that`s it, you can put the cover back. Here, after a full inspection of the drill and checking that all functions work, I am measuring shaft diameter and length, just in case, as I’m now shopping for the new drill chuck for my Skil drill and hope that it will serve me few more years.

Skil 6785 750w hammer drill some measurements
Skil 6785 750w hammer drill some measurements
Skil 6785 750w hammer drill some measurements
Skil 6785 750w hammer drill some measurements
Skil 6785 750w hammer drill - done
Skil 6785 750w hammer drill – done

Update. After visiting hardware store I found out that chucks differ in thread type, so had to come back next day with the drill itself to test it.

Brand new original China made chuck :)
Brand new original China made chuck 🙂 Miracon light duty 1/2 1.5-13mm
Repair finished
Repair finished

Repairing HAMEG HM-605 oscilloscope trigger problem

Bought used HAMEG HM605 oscilloscope with trigger problem. Tested it with sine wave and yes, cannot trigger it nor with automatic trigger neither manually. Decided to resolder all contacts near the trigger switch. Luckily it was easy accessible, just had to remove cover. After resolder next test revealed that sometimes trigger works, and sometimes not. Just a slight touch (no pressing) on external trigger button seems to be cause. So I resoldered all the contacts of ext trigger switch and some around and triggering started working as intended. Fixed.