The Pommie Solar Pool Heater.

I've just returned from a trip to Western Australia, to see my sister and brother-in-law.

I had a great time.

Now winter is coming in WA.... temperatures could plummet to 20°C!!

My brother-in-law, Karl, is worried about the temperature of his pool. It's unheated.

"What you need there, Karl, is a solar panel."

"Yeah, but I've been quoted $5000...."

.... ouch.... surely we can do better than that!

So, the evening came, a few ideas mooted over a number of cold beers....












The idea is to get some "reticulation" (or irrigation pipe to the rest of us), which is an inexpensive black PVC pipe. I was concerned about it's longevity when exposed to sunlight, but there's lengths of it exposed in the garden already, and it's showing no signs of distress after a number of years.  We'll get lengths of it, and stick it on the garage roof. The water will be pumped by the existing pool filter pump, which runs for 6 hours a day to keep the water conditioned.


The following day, a trip is made to the reticulation shop, and 25m of 25mm pipe is purchased as a test to see if the pump has enough head to get the water to the roof of the garage. After a bit of faffing about, the pipe is connected to the unused water feature outlet, and water is sprayed everywhere, thankfully some of it showing we have plenty of head to get to the garage roof. A celebration is held by means of rapid consumption of a cold beer .....













... and an emergency fishing trip or two....












So, some more pipe and a few fittings are purchased. A small trench is dug in record time by Karl, and some pipes buried to take the water to the roof, and up to the garage roof and back....
















... followed by a couple of emergency fishing trips ...



















... finally the array is assembled on the ground...













... and hauled up on the roof....







 secured by steel straps and zip ties ...

... by two strapping guys ;) .....


















... and a worried Karl tests the water coming out to see if the barmy Pommie has wasted a few $100 of his money ;)

The pump timer is reset to run the pump from 9AM when the sun hits the roof, to 3PM when it moves off the roof.

After testing the water temperature, it appears to be gaining about 2°C at around 10 litres per minute. Which isn't bad!












So we have a couple of cool beers, and a celebratory fishing trip....

















So here's my 2016 Holiday video.....

Pioneer CT-F1250 Cassette deck repairs.

"Frequent flyer" John called..

"Can you look at my late father's cassette deck? It's not working, there's no reel drive and it's chewing up cassettes..."

Yeah... why not.

So this turns up...

It's a large deck, dating from the late 70's, it's a three head machine (one record/play, one erase and one play only), two motor machine, and built like a brick outhouse. A check of the heads show little signs of wear.

Disassembly of the machine is fairly straight forward. My immediate attention is drawn to the rewind and take-up mechanism, as this will have undoubtedly suffered the ravages of time. In usual fashion, there is a set of idlers and clutches arranged to provide drive, and these usually suffer with age-related issues, as they're made from rubber. They all appear in good condition, however.

Stripping the front panel off allows better access to the deck mechanism, and careful cleaning of the rubber tyres on the idlers proves no improvement at all. There's just no drive to the reels.









Further investigation proves one of the motors is no longer running. Giving the motor a sharp tap with a screwdriver handle and it temporarily struggles into life. It's short-lived. It's spinning freely enough, just not when it's powered up. I wonder if it has a stuck brush or similar?

I see if there's any chance of getting a new motor. Nope. None. It's very obsolete.

Removal of the deck from the machine is required to get the motor out. Not a particularly easy task, so I took plenty of pictures, which I promptly managed to delete from my new camera by accident! Agh!

So, with the motor in my hand, I can see that it's been spot welded together. No chance really of repair. With nothing to lose, I drop the motor into the ultra-sonic cleaning tank, and leave it fizzing away for an hour. Plenty of nasty looking black gunge floats to the surface of the tank.

After removing the motor from the tank, I blow some compressed air through it to dry it and leave it somewhere warm overnight to thoroughly dry out.

I'm a bit worried about having washed all the lubrication out of the motor, so I squirt a bit of silicone grease through the mounting holes, in an attempt to re-lubricate it.

Refitting the motor, and.....



.... it runs! I give the unit a long soak test, checking all modes, play, rewind, fast forward etc. It seems to be a reliable repair!










Here's a quick video of the unit running, and a demo of the bias calibration function.

Junque Box Boutique amplifier - making the cabinet

Having completed the electronics for the amplifier (see post here), a cabinet was needed.

I liked the idea of a simple box, similar to the type I built for the workshop video rack, so I sketched out a simple design, and asked my friend Julian to cut me some 18mm MDF to the sizes required. Now I'm no carpenter, and Julian has got just the right kit for cutting things square!








I marked out the exterior of the joins, 9mm in, also marking the positions of the screws.











I clamped up each side, using a piece of right-angled aluminium bracket to hold everything square whilst I drilled pilot holes, and screwed each piece together.









After the outer 4 sides were assembled, I test fitted the chassis. Everything is upside down at this stage. Looking good!











A quick test fitting of the speaker baffle board shows everything is nice and square.











I remove the baffle board, and mark it's centre. A screw is temporarily inserted in the centre, and I mark out the cut out for the speaker...











... and cut it out with a jigsaw. An important note here. There are some health hazards associated with MDF dust, so it's prudent to wear a dust-mask when doing any cutting.










... and, after a bit (quite a lot actually) of fettling, the speaker fits snugly in the hole...










Having marked out the position of the amplifier chassis, I mount up 4 small brackets to the sides to hold it in place...










Works nicely ...













Another trial fit of the parts, and it's coming together...











I make up a small back panel, so I've got something to mount a cover on to, to stop prying fingers finding the HT on top of the power supply, and to give somewhere to store the mains lead and footswitch. Once this is screwed into position, it's time to decorate!















MDF is a bit tricky to paint, as it's so absorbent. If you don't use the right primer first, it will suck the paint straight in, and you'll come back and wonder if you ever painted it at all!

I carefully remove any dust with a rag moistened in white spirit, and paint it with MDF sealer....













.... and put it in the garden to dry in the sun....

... and the sun promptly disappears for the weekend! Great British weather, eh?

A couple of coats will be required, especially on the edges.







Now, the edges aren't quite flush, despite by best efforts, so I smooth them over with some car body filler.....

... and rub it down ....

A quick coat of primer, followed by some nice gloss black....




and assemble the electronics...



.... and the final article! (Actually I'm thinking about making a proper front panel...)

1971 GEC Colour 2103 TV repairs. 2040 Chassis

My colleague Nathan came into work. He's just moved house.

"There's an old telly in the loft. Do you want it?"

Yeah, why not....

I take the set home, much to the delight of Mrs. Doz











The cabinet has seen much better days, and it looks like it's been damp at some stage in it's life...











No model number, as the sticker's fallen off, but some research shows it to be a 2103, dating from 1971. It's a single standard (625 line PAL) colour set.

... it looks to be complete...












... and un-molested...












Removal of the line output stage screening can, shows the anode lead to the line output valve's insulation has failed, leading to a bit of a burn-up











... and there's a resistor on the side of the line output transformer which falls into pieces as soon as I touch it. This is replaced, and the wiring made good.









The CRT is tested...

... and doesn't look good initially, but after a couple of hours wait, the meters rise into the green as the tube wakes from it's long sleep!











Some mains is gently applied to the set via the variac... nothing. The mains fuse is open circuit, so a new one is fitted... and as the valves warm up....

... a blurry green raster appears ...

.... and after some tweaking, some rugby players appear. The convergence is awful, and the picture isn't in colour, but it proves that the set is viable...









The tuner is seized solid as always, so it's removed...

... and cleaned up...












Being careful not to stress those rusted in plastic nuts!












The tuner is refitted once it's all moving freely, and I start fault finding on the lack of colour.

I prevent the colour from being removed from the picture (for when black and white programmes were broadcast) by disabling a circuit called the colour killer. There's still no colour, so it's likely the reference oscillator isn't running...  Just as I'm about to start looking at that fault, the sound and picture disappear! The set is still operating, but there's nothing coming out of the IF (Intermediate frequency) stages after the tuner. Damn.

There are 3 stages of combined IF amplifier. These amplify and filter both the sound and vision the signals together, coming from the tuner. The signals are then split off, and amplified further, the audio being separated and decoded from the video. As both sound and picture went off together, I suspect the fault lies in the combined amplifiers.... I check all three stages, all appears well. Perhaps the tuner has failed? A super chap called Gary has a spare, but it makes no difference....

After some further checks, largely out of desperation, I check through the vision amplfier, and find there's an emitter follower amplifier, and the transistor has failed. It's a BF194 HF bi-polar transistor. A replacement is fitted, and pictures are restored! Still no sound. I look at the first sound IF, and , sure enough there's another failed transistor. A BF194... still no sound!... I check the ratio detector, which is used to demodulate the FM sound, and.... it's another failed BF194! Sound a pictures restored, I look back to the colour decoder.

I check the reference oscillator, and it's running fine, producing a locked 4.43MHz signal. Good. I check through the stages, and find 3 faults. Two of the faults are transistors in the R-Y (Red minus lumenance) and B-Y (blue minus lumenance) ... guess what .... BF194's. Also the colour bust transistor is open circuit... you've guessed this next bit ... it's a BF194...

There have been questions raised on various forums in the past about the reliability of BFxxx and BCxxx lockfit type transistors. It's quite possible that that un-reliability (they are 40+ years old!) is what's been at work here. It's possible that flash over when the insulation failed on the anode lead in the line stage caused a spike which saw off the transistors, but the BF197's and BF196's in the IF stage survived, as did other transistors in the decoder...

After replacing this little lot, and a couple of suspect and corroded looking capacitors, things are shaping up. There's some hum evident on the power supply, and I find a very sad looking cap in the power supply. It's got a nasty bulge in it... It's changed out.







I replace the line output valve and boost rectifier (PL519 and PY500) and the width is better, set up the convergence on the tube, so the three colour guns are lining up correctly, and I'm rewarded with reasonable results.

Note quite sure what I'm going to do about the tatty cabinet though...

The guilty parties....