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Friday, 12 July 2019

Sharp RG-3915 In-car radio cassette repairs and restoration.

I bought this on eBay..



"Why?"  I hear you ask...













Because I've been spurred on by the warm summer evenings to finish off the green thing lurking in the garage... and it needs some suitable retro sounds. (Sorry if you're still waiting for the final Sony 9-306 YouTube video)

The RG-9305 is an auto-reverse radio cassette, released in 1983 (OK, it's a bit newer than my car, but hey..) It produced a trouser flapping 8 watts per channel (although some have appeared to have escaped.. read on!)

The seller assured me it was "working when removed" ... which I can only assume was sometime in 1985 ;) Thankfully I use the usual eBay translator for such. "Working when removed" means been sat in a damp shed for 30 years+ and the seller can't be ars bothered to test it. (For more eBay description translations check this out)

... and sure enough I'm not disappointed... the cassette deck doesn't work, and the radio is weak and distorted. The radio comes on for a few moments, then the volume fades away rapidly.

Let's tackle the tape first.

Take off the knobs and the securing nuts and remove the faceplate(s) ...













Remove the two screws holding the front panel. It should just pull away.. The remove the four screws to remove the top panel (two on the top in the label, and two on the front). Remove the top panel by gently prising it up with a small screwdriver.








The cassette mechanism is held in place with two screws on the front panel. Disconnect the motor/control plug adjacent to the motor, and the head wiring plug next to the volume pot.

Pop the eject button off (bottom left), and, although it's tight, you should now be able to extract the mechanism complete...

Excellent. Turn it over....















.. and remove the two screws holding down the capstan flywheel retaining plate.

Remove the two offending belts, find suitable replacements in the belt box, and replace them...









Yeah, they're shot ... ;)



















Here's an interesting manufacturing technique... real printed components...

It looks like R120, R62 et al are just printed blobs of some carbon type of material, not dissimilar to the "thick film" type of construction used in some TV's back in the day, but those were usually printed on ceramic, not ordinary PCB material. Even the tracks on this side of the board don't appear to be copper, but some form of conductive paint or ink. What if there's been some flexing and vibration going on and there's a microscopic track break? This fills me with dread ... let's see what happens.

On test and the output is low and distorted. There's about 3VDC appearing on the speaker outputs. Not good.

Reverse engineering the circuit shows the output amplifier is coupled to the speakers by two capacitors. They're leaking.











As there's a few others right close to the amplifier, I change the lot...












Ok... things are better, but there's still precious little output, and what there is, is still distorted and thin sounding. Tracing the circuit back from the amplifier, I get to a uPC1228 op amp. It's a dual amp, but in a single in line (SIL) package, and made from unobtainium.. The DC conditions around the amp are odd... There's a DC off-set on the input, which is building over the first second or so the unit is switched on. The audio is coupled in via two capacitors, and loaded by two of those printed resistors I mentioned earlier... and they prove to be open circuit.

An educated guess is made, and two 100K resistors are duly lashed up. One between pin 1 and gnd, and the other between 6 and gnd.

Audio is restored :)









The replacement resistors are properly mounted.



















Now the case has a chunk missing out of it, across the top where the cassette goes..













I used the remaining corner to bend a piece of tinned copper wire to get the outline shape. This is then flipped over, and warmed up with a soldering iron and melted into the plastic case...

It's rubbed down a bit, and covered with capton tape.










Some car body filler is mixed up, and used to fill against the tape. Once the filler has hardened, the tape's removed and the filler trimmed with a craft knife to the rough shape required.











A little more filler is added...













... and finally sanded down to get the final shape.


















A trip to a local paint supplier to get a matching colour ... a quick browse through the racks shows this Pastikote radiator paint looks a damn good match ...
















The front panel is carefully masked off...













... and painted. I'm rather pleased with the colour match and end result...
































The faceplate gets a coat too to get rid of a few scuff marks, and the unit mounted in an under-dash box ready for fitting


and I've got one of these bluetooth FM transmitter devices so I can play music from my phone! (£7.22 on eBay!)


Another saved from landfill :)

Sunday, 16 June 2019

Beko DW686 dishwasher repair

It's been busy lately. If you follow my YouTube channel, you'll be waiting for an update on the Sony 9-306. It may be a little while, as other things have got in the way.

Anyway, came downstairs in the morning, ready for a cup of coffee and a bit of breakfast before going to work, and I step in a pool of water... Ugh.

The dishwasher (aka "the magic chipboard") has leaked everywhere, and not washed the plates either!

I got home and needed to tackle the repair. I have an irrational hatred of dishwashers.

I reset it and it pumped the remaining water out. I tried to run a cycle, but it wasn't having it...




I dragged the thing out and removed the front lower panel. It's full of water, and there's bound to be a float switch in there ..











.. (probably behind that central polystyrene float) that stops it from running when the sump is flooded.
















I tipped the machine forward slightly to empty the sump, but it still wasn't running correctly.

I thought perhaps the level switch wasn't working, so it didn't know how much water it had let in (hence the flooding) I removed the side panel and started looking for a pressure type level switch...














... there isn't one...
















...however there's this. It's a small flowmeter in the inlet pipe.

I did a spot of googling, and found some information about a test mode.














Hold these two buttons down and switch on.











After lighting up all the display segments, this is displayed... hit the play/pause (!) button to start the test running....











After going through the motions, Er2 is displayed. Er2 is the error code for "no water", despite the fact that there's definitely water going in, as I can see it gurgling through the pipes ...









OK, suspicion turns to the flowmeter. I decided to remove it and inspect.

Undo the two pipe clips...












Slide the pipes off (easiest to do the bottom one first). Expect a bit of water to leak out...


















And remove the electrical connector....














With the flowmeter removed, I blew through it. I can hear the impeller turning. I can test to see if there's an output by measuring continuity across the device. Those two oval holes provide access, rather than trying to probe the connector.

It seems to be open circuit.

A new one is about £11 eBay. I decided to see if this one could be fixed...



I removed the small green PCB, and it contains a magnetic reed switch. This is simply a small switch in a glass bead which closes when there's a magnet near it. I stick a magnet near it, and it's still open circuit ...







A quick trip to NP Harding provides a slack handful of suitable looking reeds...











One is duly fitted, and tested... it still reads open circuit with or without magnet.... hang on? What I hadn't done, was check the meter was working correctly! It wasn't. It appears one of the probes has gone open circuit! Aggggggghhhh!

Replacement probes fitted, and the flowmeter tests perfectly. I test the reed I've removed ... it tests perfectly .... damn , I've wasted a lot of time ... I'm so cross with myself!

Right, back to the kitchen and re-install the flowmeter.

Run the test again. Same results Er2. No Water. I measure the voltage on one pin of the flowmeter, and there's a solid 12 volts there.... on the other side there's a varying voltage (because of the pulse train) ... OK , that's working....

There's a fault finding flowchart in the service manual (download it here). It says the next step is to check/replace the controller board... It's mounted in the door....

Undo the screws either side of the latch, and the two holding the decor panel on (if fitted, mine's a built in thing) I chose to remove the decor panel completely, as it's front-heavy with it attached)

Another two screws down each side, and you can pop out the plastic top, and gain access to the electronics.

Note the new meter probes! The plug you see removed here has the two purple wires from the flowmeter. Sure enough one is open circuit! I bet myself a nice cup of tea that it's where the wiring goes round the hinge of the door.....

A wire is temporarily fitted to each end...




























and the test mode run again...

and it passes :)










Now to route a new wire in. I thought I may use the old wire to pull through the new one... no chance as it's completely broken... Just long enough to indicate the break is indeed in the hinge... :(













... So the door has to completely come apart. Disconnect both the springs from the door and use something to support it whilst doing this. I found it easiest to lower the spring tension as much as possible with the two plastic adjusters that are just down from the top of the door aperture behind the seal. You'll need to remove the other side panel as well if you haven't already done so.

A word of warning here ... this panel is sharp. Damn sharp. Wear some thick gardening gloves or similar.


And there's the wiring....












The new wire is threaded through (better to start at the top and work down) , soldered at both ends and given a coat of liquid insulation tape (because I've not got any heatshrink at the moment!)









The machine is reassembled, and test mode gets to P3, which has passed the water inlet issue :)











Eventually it's all back together and washing the plates again... for now. What about those other dozen-or-so wires going via the hinge? I'll worry about those another day!

Another saved from land fill (for now!)

... and I won my bet, and have a nice cup of tea ;)

Monday, 13 May 2019

Ekco U353 - a quick restoration.

Ages ago Steve was good enough to bring up Sam's Queen Anne for some repairs. Also in the boot of Steve's car was a broken Ekco U353. Now, I have one of these, (see here!) which I repaired ages ago. It's a basket case, and remains unused as it's knobs are missing.  The knobs are an essential electrical safety item, as the chassis is connected directly to the neutral of our mains supply (common practice back then).

Anyway here's Steve's...


Much better nick than mine, although there's a crack to the right hand side of the cabinet... 











... and the back's a little distressed where the heat from the rectifier and output valve has made the back brittle, and damage has occurred. Some of the brackets are in poor shape too.










Removal of the chassis is straight forward, off with the knobs (there are two small grub screws to undo), and removal of four screws on the underside of the case.










It all looks very clean and unmolested.












Amongst the dust in the bottom of the cabinet, a tell-tale blob of wax shows something's been getting hot...











... and sure enough ...












... C61 has had a right sweat on! As usual, these waxy caps will all be shot, if not now, in the very near future, and will all be evicted. C61 is the mains input filter cap, so it's replaced with a brand new X2 class safety capacitor. It's 0.01uF.







Now in my example, the output valve had been cooked as the cathode bypass capacitor had failed short, so this is also replaced. In fact there's very few capacitors in the whole receiver, so every electrolytic, paper/wax and hunts capacitor is replaced, except the main multi-section smoothing capacitor.








The cathode bypass capacitor is C55. C50, C49, C46, C1 and C20 are all replaced. C1 is a horrible black hunts thing.






After the caps are replaced, it's time for action. The receiver is connected to the variac, and the voltage slowly increased for about an hour, monitoring the HT voltage, and periodically checking the temperature of the main multi-section smoothing capacitor to see if it's getting warm. It wasn't.

After a quick tune about, stations are coming in, and the FM seems to working too. The receiver is aligned in accordance with the service sheet, and it's performing well, except the exclamation mark magic-eye isn't illuminated :(

R14 (68K) has risen in value to many megohms, and crumbles as I remove it! After it's replaced the exclamation mark works as it should.









The guilty parties!












... and the elusive knobs ...












A piece of car body re-enforcing mesh is cut out to cover the damaged areas of the back...











... and it's filled, drilled and painted. Not the tidiest job in the world, but it'll render the set electrically safe, and allow the required ventilation.









The set's plug is fitted with a more suitable 3A fuse (there's another 13A fuse I've gained!!) and it's reassembled and given a nice long soak test.










Another saved from landfill :)