Grundig TK120 repair

Gareth (a fine chap from the motherland) walks into the workshop with a bin bag under his arm....

"My Father-in-law's dug this tape recorder out of the attic. It's got a recording of him on it, but he says there's no sound. Can you have a look?"

Yeah ... why not?

It's a Grundig TK120, in distressed condition. It looks like it's been left rather too close to the fire!

... and after removing the tape and the top cover, the immediate issue is all the rubber parts have disintegrated....










Now the belts are no real problem... but the drive idler tyre is going to be...

After some head scratching, and some looking about for suitable parts, an O-ring is super-glued to the remaining idler wheel....







Now to replace the belts. So I unscrewed the four screws with blobs of paint on, to remove the top plate. DO NOT DO THIS!

FATANG! All the spring loaded control levers fired out of their mounts.... Thankfully their positions are quite simple to work out, but very fiddly.... several hours later and the thing is back together....

Here's how it should have been done!..

Underneath the deck is a small plate, with two screws... undo those to gain access to the bottom of the capstan flywheel....


... and work the belts about the bottom of the flywheel, through the small hole. It's still fiddly, but much less agro than re-aligning the top mechanism!



















You'll need to remove the take-up reel and clutch to replace the take-up drive belt. The belt itself is straight forward. The clutch reassembly is a bit tricky...

This is the bottom of the deck, showing the new tape counter belt... Remove the little pulley and it's clip from the take up reel shaft. There's another clip underneath and an antifriction washer. Remove those.




Turn the machine up the right way, and remove the take up spool...











This will reveal the take up clutch, and it's little three pads... if they've fallen out, don't panic... they'll be there somewhere!

Fit the belt and reassemble the clutch. Some adjustment of the clip above the small pulley we removed earlier may be required to get the right amount of friction on those pads, but it's not difficult.

The motor was a little sticky on this machine. I stripped the lower bearing off and re-lubricated it. It now spins like a top....

... there's still no sound.


This is rapidly traced back to an open-circuit HT fuse, it's replaced and there's some audio briefly. The HT (and heaters) is provided from two extra windings on the motor. There's no transformer. Clever stuff. Garrard and BSR used a similar trick on their record changers in the 60's. The electronics are a simple design with just two valves, an ECC83 and an ECL86.

The main smoothing capacitor is getting warm. A sure sign that it's had it day. It's a two section 50uF+50uF 350V part. I replace it with two suitable caps.









Switching back on and there's audio again... but it rapidly fades.... A check round the other caps proves their innocence... I'm not liking the look of the getter flash on the top of the ECL86 triode-pentode valve though, it looks like it's had a hard life.... The getter flash should be sliver or black looking, and should have nice sharp edges...





This is sort of brown looking....













... and checks on the avo valve tester show the triode is very low at 0.6 mA/V (It should be 1.5 when new) and the pentode section won't read at all! When testing the pentode section, there's a blue glow inside the anode structure, a sure sign there's some gas in there. A replacement restores operation, and the dulcet tones of a young man playing the guitar once again issue forth from the speaker... recorded some 50 years ago!


Audio quality isn't fantastic. These machines were a bit of a domestic novelty really. After transcribing the contents of the tape, Gareth described the quality as "Like a walkman with flat batteries", which isn't a bad description at all...

Mitsubish MC8000 audio system repairs.

Sadly, my friend Richard's dad passed away a while ago...

"There's some stuff here Andy, would you like it? I'd rather it went to a good home."

So it's now my duty to the man, to get it all going.....

This interesting audio unit was amongst the gear. It's a Mitsubishi MC-8000, originally sold by my old employer, B.V.Harrod (sadly long gone), and has it's original speakers and cabinet.

 ... and yes, that's the right way up, it has a vertical linear tracking turntable.


After some cursory checks, I give it some mains. There's a motor running somewhere, the turntable doesn't work, neither does the cassette, but the radio works fine!













Off with the back, and it's immediately obvious why the turntable doesn't work .... the belt's missing!

Actually it's not... Some of it is in the bottom of the cabinet, and some has stuck to the turntable flywheel. I quickly clean it up, with some wipes and a bit of IPA. Sizing of these things can be a pain, but it's easy really. Get a piece of string, and wrap it round the motor shaft and flywheel, where the belt would run, and cut the string. This will be the approximate circumference of the belt. Now belts are sold in dimensions of diameter, width and thickness, so divide the length of your string by Pi... in this case it's 200mm, and about 5mm wide.

The arm is driven by two other motors too. One raises and lowers the arm, and the other is used to track the arm across the record.

The belts that drive these functions are also in a bad way... just touching them leaves a nasty sticky black mess. A bit of IPA to clean up, and some replacement belts see the turntable working....

... now the motor continuously running is the motor in the cassette deck.... probably another belt!  It's buried right in the bottom of the cabinet. See that brown, spotted thing lying across the circuit board? That's a bit of turntable belt!







... the motor nicely dates the unit from 1980...












Getting the transport out requires a lot of disassembly, and quite a considerable amount of cussing....


















... but eventually yields ... I will not be beaten by mere machinery!












... sure enough the capstan belt has gone the same way as all the others! I'll change the lot...



















The tape transport is carefully disassembled to gain access to the belts..

..which involved removal of the record switch actuator lever. Capstan flywheel is removed to clean the remains of the belt off...

... and some suitable replacements found from the belt box. The capstan belt measures in at 71mm. There's a 2.8mm wide belt which will do nicely.










The deck is repaired, and time to contemplate re-uniting it with the rest ... look at all those screws!











Finally back into the lower part of the cabinet!

... and that reunited with the top...

Thankfully, all the plugs are nicely labelled...

... and once the transformer is re-fitted, speakers connected, it's tested...




A new stylus is fitted, and the turntable works a treat. Sounds far better than I had expected... unfortunately there's nothing but a nasty hum from the cassette deck. It appears either the wiring to the tape head, or the head itself is open circuit.... I dread having to remove the transport again. Closer inspection reveals the wiring to the head is broken, and it's been repaired before.. there's some evidence of a poor soldering job, and the wires have been left very short. Thankfully, access, although difficult, is possible through the front, after removal of the door, and the repair is completed.








Here's a quick video of the turntable in action....

And, finally, a few photo's of the original dealership who supplied the unit. These were taken on the last day of trading, back in November 2005.. a sad day.

Shop front...














Interior... looking sadly empty :(

and the workshop...

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.