The story of my aquisition of the Siera TR-5842 (Aiwa CS-600 in disguise)

Hello,

Although I was born in 1970 I never really owned a Ghettoblaster. By that I mean the upright grey ones with the big speakers. Until yesterday when I found it in a shopping window of a store that sells various stuff (the owner empties houses on request). The store never seemed open but I had seen the boombox a previous time. I could read that it was Siera. Well, yesterday the door was open and two people were inside so I asked how much the boombox was. "20 €, plays fine". The owner hooked it up and the radio played fine. But I was interested in the tape part too. Of course the tape player was broken. The reels didn't turn and there was a big hum in the speakers. That got the price down to 10 € and home I went. When I hooked it up to the mains I could hear a hum coming from inside the machine. I thought the power supply was broken. After some googling I found out that it's in fact a rebranded Aiwa C-600. Not a bad machine at all.
I proceeded to whipe most of the dust away and open up the machine. There I found belts that had turned to goo and a capstan motor that was constantly spinning loudly. That was causing the buzz, not the power supply.
Because the belt had broken, the tape mechanism was in constant play mode. I managed to turn the capstan by hand to quiet down the motor.

I immediately fell in love with the sound of this machine ! It has a warmth to it that's hard to define. Especially listening at low volume with the loudness on !

I already ordered new belts and they are on the way to me right now.
I also have a new capstan motor (I repair and restore cassette decks as a hobby so I ordered a few capstan motors in one batch a few months ago).

I sure hope that when I replace the capstan motor, the hum the current worn out motor induces will be gone.

Anyone got any tips on restoring the boombox ?
I'm also looking for a service manual (Aiwa C-600). I've been able to download a few pages from Radiomuseum.org (http://www.radiomuseum.org/r/aiwa_stereo_600_4_band_stereo_2.html)

I will probably need a service manual for the MD-3 tape mechanism. This isn't included in the service manual of the boombox but requieres a seperate service manual.

Thanks in advance for any thoughts, insites and help !

 

Sorry, it alsready late when I'm writing this. The title of the thread should read :
The story of my aquisition of the Siera TR-5842 (Aiwa CS-600 in disguise)

 

Hi, thanks for your reaction. That service manual, is that the one that became available a few days ago on hifiengine ?
If it is : I'm the one who made it available.

Anyway : This afternoon I had a terrible thing happening to my CS-600 : While I was changing the belts on the mechanism and I wanted to try something out I must have made a short circuit ! I saw a bit of smoke and the unit is now completely DEAD.

At first I put it away, I couldn't take the dissapointment. In these few days I have become very attached to it. It just sounds so splendid !
I'm not so great on electronics, but then this evening I took a closer look and I managed to identify the capacitors that have gone dead.
But I wonder if replacing the capacitors will solve the problem.

The ones that have blown out is is one on the power supply and then also some on the rec/play amp board.
But maybe something else has gone dead too ?

As for the capstan motor : My replacement motor turned out much smaller but fits perfectly (I got it on aliexpress). I didn't have the chance to test it out as the unit died before I was able to test the mechanism with the new motor. But I wondered if the old one would maybe still be good after adding some oil to the shaft. I tested it's operation while it was detached from the mechanism and that's when I must have created a short circuit.

I will try again replacing the capacitors but if that doesn't work I might have to give up on the unit. Keep it for spares and buy another one. But it won't be for 10 euro I fear. That was really a bargain.

So if anyone has any tips I would be very glad to hear them.
Here's the id of some capacitors that have melted : C5 (on the power supply) , c163, c 164, c167, c157.
There are a few other ones down the line too but I haven't been able to identify them.

 

something strange must have happened for so many capacitors to blow. Maybe you shorted out a voltage regulator, put the unit into 110v mode (did that once with a brand new £3000 disc drive at work ) or something similar.

In the past I have always suggested that people run boomboxes from batteries when attempting repairs. Safer for both you and the box.

 

That's very kind ! I definately had the power switch correct on 220V. What happened was that I started the motor by pressing play on the mechanism without the motor being attached to the mech. Then I put the exterior of the motor on the mech to hear if there was hum induced into the audio signal. Maybe (I'm not sure) I touched the mech with the + pole of the motor. There was a little bit of smoke.
I just took some photo's of the caps i think melted. But i'm not sure if they are really melted or glued to the board (there's some kind of black glue used elsewhere in the unit : to attach wires to the plastic, hence my doubt). Take a look (I already took one capacitor and a heat sink out) :

Edit to add : I checked one of the fuses and it has apparantly blown too which gives me some hope.

 

And this is the Siera a few days ago, all cleaned up and awaiting the new belts :

 

I have a Aiwa 600 too but I just have not gotten around to repairing mine just yet.

 

Looks like glue to me. Usef by the manufacturer to stop the leads breaking under vibration like transport by car.

Another repair tip. Always take lots of photos before you start. Then you can refer to them later when you are thinking where did this bit go?

 

Something does look wrong near the bottom left on the photo ending 283.
I can't make out what the white thing is. Second opinions please.

 

I just discovered it is in fact glue. I didn't know until now that on some capacitors adhesive was added to absorb vibrations. That means the fuse did it's job. When I say smoke, it was just a very little bit of smoke for just a second or maybe 2.

The white thing on that photo is some wraparound paper around a component. You can see the same paper cones (actually cylinders) on the first picture in the left.

 

Oh another thing : The Service Manual. I looked and looked on the net but it seemed that I could only download it if I payed for it.
Then I found out that on radiomuseumdotorg the service manual was available but in seperate pdf pages. I could only download 3 pages per day.
Well, I worked around that and then I combined all the pages into one pdf.
I noticed it had some details missing on the cassette mechanism. It referred to a dedicated service manual for the MD-3 cassette mechanism.
I then found out that the CS-880 has the same mechanism and I took 4 pages of that service manual and inserted them at the appropriate place in the CS-600 service manual to make it more complete than it originally was.

I had to remove a lot of logo's that radiomuseum automatically adds to the pdf's I downloaded.

On the CAPSTAN motor : I have repaired many cassette decks in the past and I think it's a generic capstan motor that I encountered many times. The biggest size you can find in a general cassette deck. So a replacement motor shouldn't be hard to find in a donor deck.
Pretty remarkable that a boombox has such a decent cassette mechanism. The flywheel is metal and heavy (hence the low wow and flutter numbers for a portable unit)

 

Good news : it seems my Siera survived the short-circuit.
Today I replaced the fuse and got it working again.
Even the cassette was playing.
I put it to the side to have lunch, then I put everything together again.
Then the cassettedeck didn't respond any more. I reopen the unit and it seems the motor has died.
So I'm on the lookout for a replacement motor.
It's a rather big motor. Any advice on where to look for a replacement ?
I think any motor from a seventies-early eighties deck will do.
But do shoebox cassetteplayers from that era have an equal size of capstan motor ?
(capstan motors got smaller towards the end of the eighties for most decks)

 

A quick update : today I replaced the motor with a motor from a donor deck. Unfortunately, that replacement motor is not as big and when I tested it it indeed lacked torque.
What you need to replace this motor : a motor from an old mechanism (pre 1982 I would guess). From a deck. Motors from portable units probably aren't 12 V.

There's also another option : the universal capstan motor from Universal Audio.
http://www.tapeheads.net/showthread.php?t=32263
It seems to have the same dimensions.
New capstan motors of this size seem to be unobtainable new.

As the shipping costs to Europe will be high I'm going to try to find an old silver donor deck before taking the Universal Audio option...

 

As all size is relative... How big is this motor big?
back in May of this year I repaired a Aiwa TPR-926 AU and it has I guess a large motor. I didn't measure the size of the motor.
I was & I will post all my pictures elsewhere but here is the best picture I took of my motor (again not taking pictures of the motor and my hand is there to show the size )
in the box I repaired this past May 2017
IMG_6304 Aiwa TPR-926 AU tar My hands are large as my span is just over Ten inches and I can Palm a basketball and I am certain you can also relate to the tarrish stuff on my hands

 

The motor is about 35mm wide and the height is about 38 mm.
Come to think of it it is quite incredible how much smaller capstan motors became in the eighties and nineties.
Those tiny walkmans pull the same amount of tape with a much much smaller motor. The crown cork of a local excellent beer is there for size reference.

I seem to have found a supplier of those motors in India but they only ship nationally and it's not clear whether this motor is CW or CCW.
http://rees52.com/106-35000-rpm-motor-non-geared-12v-dc.html

 

Today I found a donor deck at a flea market. When I got home with it I had the motor out in less than ten minutes.
Then I put the motor in the ghettoblaster : not enough torque.
When I turn the flywheel by hand to help the motor a little to get the heads risen then the motor can run on it's own. But not very good. Tape speed is too slow.

As this motor has the exactly the same dimensions as the old one this has me puzzled.
This can only mean two things : Either there is something wrong with the mechanism (can't think why and what that should be) or the motor is not getting enough power. I measured the voltage going to the motor and it was around 13V. But I didn't measure the amps.

I'm now suspect that a component feeding the motor has gone bad. After all there was a little bit of smoke when I created the short circuit a few days ago.

I'm lucky that there aren't many components between the power supply and the motor.
But for the moment I have had it with the tape part of the boombox. I've spent far too much time on it already.

These are the components between the power line and the motor :
R212 = 1 ohm 1/2W (Fuse Resistor)
L106 = choke coil 36 μH
C183= 220μF / 25V

If anyone has any tips please let me know. I guess the Fuse Resistor is the prime suspect. But if it did react then shouldn't the power line to the motor be completely dead ? I have no means to measure it for the moment as my multimeter took a blow when trying to measure the voltage of a 48V litium battery.