Cosmic Stereo Cassette Deck Model No.CO 703D

[sureshkuranjalayil]

Hi friends,

Recently, I have got a Cosmic Stereo Cassette Deck Model No.CO 703D.

I am facing following problems which needs your help to resolve:-

1) Speed: The Deck if working perfectly for about 25 - 30 minutes, thereafter the motor becomes slow.

2) The Lamps of both the VU Meters are not working. There is a thread in the DIY section wherein forum member Greenhorn had one LED retrofitment in the VU Meter. I am planning to do the same. Advise/suggestions welcome.

3) The switches (Piano Type) has become blackish. I am planning to use Min Cream to clean the same. If there is any other method, please advise.

Regards,
Suresh Babu

 

[reubensm]

Hi friends,

Recently, I have got a Cosmic Stereo Cassette Deck Model No.CO 703D.

I am facing following problems which needs your help to resolve:-

1) Speed: The Deck if working perfectly for about 25 - 30 minutes, thereafter the motor becomes slow.

2) The Lamps of both the VU Meters are not working. There is a thread in the DIY section wherein forum member Greenhorn had one LED retrofitment in the VU Meter. I am planning to do the same. Advise/suggestions welcome.

3) The switches (Piano Type) has become blackish. I am planning to use Min Cream to clean the same. If there is any other method, please advise.

Regards,
Suresh Babu

IMO, this is what I would check first:

1) Speed: very critical aspect of your cassette deck. You have not mentioned whether the motor heats up (needs to be physically checked by touching it, when it slows down). Disengage the drive belt, let the motor do a cold start (power down and try after a few hours), feel the motor pulley (with your finger) and get a feel of the torque. The pulley would notmally exert stiff pressure on your finger, while turning, which indicates sufficient torque. After about 25-30 minutes (when you normally encounter a drop in speed), touch the motor pulley again, if the pulley easily stops or the pressure exerted on your finger is less than the earlier try (on cold start), it is almost certain that you have either bust electrolytics or a bust motor. Small DC motors running at below their optimal speed will run HOT. It is possible that your motor speed control is not feeding your cassette deck motor (assuming that we are talking about the main playback motor here) with adequate voltage rating and the motor (being on its last legs) drops speed (and torque) when it warms up. To start with, check all the electrolytic capacitors in the path between your Transformer secondary and the motor (including those on the speed control). The problem is likely to be here. If that is not the case, then you'd need to check the motor itself. All this is assuming, the drive belt of your cassette deck is in proper order and so are the mechanicals and idler wheels.

2) lamps can be easily replaced, either with similar replacement (you may not get the exact OEM spare) or with customization. LEDs are a good bet for a custom job, however please keep an eye on the electricals before you try any non-standard stuff.

3) There were broadly 3 types of keys/buttons used on the mechanism keys of old cassette decks. The first type were plastic but with a very smooth while coating (looked and felt like enamel). This type would normally become yellowish after heavy use. Not sure if the yellowing can be corrected. The second type were black solid plastic, usually painted silver to match the deck's face plate colour. If these blacken, there is no way you can restore the original paint as this would have worn off (unless its a superficial stain, which can be cleaned using stuff like mincream). The only way around would be get a paint job done. The third type were of course, authentic aluminium or stainless steel keys. Again, if they were painted, the only way to get a fix is to repaint (unless there are stains, etc on them). Stainless steel shiny keys can electroplated or buffed.

Is this a similar pic of your deck?

http://img.clasf.in/2013/04/29/Very-Good-condition-Stereo-Cassette-Cosmic-20130429032216.jpg

 

[sureshkuranjalayil]

Dear Rubin,

Thank you for your detailed reply.

I have not yet opened the Deck. I will check up the motor etc, as advised by you in this week end.

Noted your point regarding VU meter lamp.

My deck is almost similar the photograph but the switches are of different. All switches in my deck are with aluminium finish. There is also no green LED on my deck.

Thanking you once again for your immediate response.

Best wishes,

Suresh

 

[greenhorn]

1. Speed. If you have a multimeter, have an eye on the voltage across the tape deck motor - if there is some regulator upstream that is overheating due to the heat sink compound disintegrating, or possibly even the one inside the motor - that would be harder to diagnose
2. Try to get exact replacement bulbs. I had used LED's because I could not find bulbs that exact same current (50mA) - most of the ones available were 100mA or higher.
If you are putting LED's - you will need to know the voltage. With LED's current should not be an issue. But you would never know unless you have the circuit diagram.
3. If it is brushed or plated aluminum finish, tough luck. If it's a matte aluminum finish, like early 80's equipment, you can try aluminum metallic paint, though for piano keys, they would wear out pretty early.

here is a knob that I repainted to match the faceplate finish (sorry, no before pictures, but the finish had worn away and started showing the copper underneath which had started corroding)

 

[Hiten]

1) Speed: The Deck if working perfectly for about 25 - 30 minutes, thereafter the motor becomes slow.

Are your cassettes free moving ? Sometimes unused cassette decks takeup wheel rubber pulley looses grip, when cassette tape spool gets heavy it turns slowly. Clean the mechanism with brush. With matchstick put one drop of oil on all moving parts, clean pinch roller, rubber belts and pulleys with alcohol. If problem persists there may be other problems.
regards

 

[greenhorn]

I wouldnt recommend the shotgun approach to applying oil on all the moving parts. I tried it once, and found that they started accumulating dust and that transport started to slow down even worse. - I think other than the capstan bearing and a few other places, you really dont need oil
And I believe you need something like light machine oil - whatever you use on sewing machines - any oil will not do.

 

[mbhangui]

And I believe you need something like light machine oil - whatever you use on sewing machines - any oil will not do.

Absolutely right. Most oil are organic in nature and will spoil plastic and rubber parts. Silicon oil should be used for such purpose. Philips used to sell silicon oil many years back. A desperate measure could be using the oil in condoms (which preserve the rubber for quite long and also is a general purpose lubricant)

 

[sureshkuranjalayil]

Thanks a lot to rubinsm, greenhorn, hiten and mbhangui for the inputs and suggestions.

As a first step, I had opened the deck yesterday night and cleaned it thoroughly using a soft painting brush. Pinch Roller, belt etc have been cleaned using IPA. Fortunately I am having a bottle of silicon oil (given by hiten bhai) and put the same in moving parts.

Today morning cancelled the morning walk and put the deck in use at 5:15 am. The deck is now working without any speed issues. Played till 7:30 am continuously. Will regularly use the same for a week and keep posted on the developments.

Now the pending issues are replacement of VU meter lamp and cleaning of face plate and keys. First I will try for the replacement bulbs. Hopefully, I may get the same from Lamington Road however, any pointers are welcome.

Regards,

Suresh

 

[Hiten]

Sureshbhai,
Do not put silicon oil on/in capstan wheel axle, pinch roller axle, two spools. take up or supply pulleys. just tiny amount of oil in these parts, otherwise as greenhorn has said it will attract dirt. for plastic moving parts or moving metal plates you can use silicon grease or for time being just minute qty. of silicon oil (Oil I have given you is little thick). However if you have already put silicon oil on spool, capstan, spool put one drop of IPA to clean it. Or just rew, ff few cassettes.
Regards

 

[sureshkuranjalayil]

Sureshbhai,
Do not put silicon oil on/in capstan wheel axle, pinch roller axle, two spools. take up or supply pulleys. just tiny amount of oil in these parts, otherwise as greenhorn has said it will attract dirt. for plastic moving parts or moving metal plates you can use silicon grease or for time being just minute qty. of silicon oil (Oil I have given you is little thick). However if you have already put silicon oil on spool, capstan, spool put one drop of IPA to clean it. Or just rew, ff few cassettes.
Regards

Thanks Hitenbhai. Will do so as mentioned.

Regards,
Suresh

 

[reubensm]

Gosh, once dirt accumulates, it would be difficult to clean, if the dirt-grease mix hardens, it would be as good as corrosion. Nevertheless, great going on the deck and nice to hear that it is working well. Always a special feeling when we fix something on our own and get it to work.