Nakamichi OMS-5

[s3tup]

Today i've fixed 5E - failed 7812 regulator.
Now i need to find a replacement belt to bring it to life.

[labjr]

I think this guy had the belts last year. But not sure now.

Home -

[s3tup]

Ok, the new belt is fitted (pretty tight fit i'd say), and...
Now i have another problem - it takes the disc, spins it for several seconds (10-12sec) and then spits it back.

How do i know whether the belt is too tight or there are other issues? (laser pickup gone)
Could the CD spin speed be too slow? I have to compare it with other player...

Hm... at least 3 failures in single unit

[labjr]

Not sure but may need alignment if it won't read the disc. I heard it's a bit involved.

[rlbuntin]

I am in need of a replacement power supply for my Nak OMS-5 CD player. Anyone have any leads on where I might find one?
-Rob

[stephensank]

Unless you actually mean you need a power transformer for the player, or the supply board got horribly damaged, there is no chance you need an entire power supply. On the original OMS-5/7, power supply issues ALWAYS, in my rather large amount of experience with them, come down to either cracked solder joints on the supply board, especially on the heatsink-mounted regulators, or failed regulator IC's, usually one of the 7805 type +5V regs. I've seen exactly nothing else go wrong in these supplies, and never a bad power transformer. If you do, somehow, have a bad transformer, your only chance is a cheap enough purchase of another OMS-5 with a bad laser, which is not that uncommon.

[rlbuntin]

Thanks stephensank, just saw your reply now, months later.

I am not a tech, so am just restating what the local audio shop told me (and wanted several hundred to replace - I didn't let them go ahead, 'natch).

The display on the unit does not light up when the power button is engaged. I'd be surprised if the power supply circuit board is damaged, as the unit worked fine one day and was DOA the next (no movement of unit, it was in the stereo rack the whole time). I'll check the solder joints for any that look suspect.

How do I go about checking the (7805) regulators ICs to find out if one or more are bad? Is this something I'd be able to do myself, or do I need to take this to a tech?

Thanks for any help you can give!

[stephensank]

Very simple. With the negative probe of a voltmeter connected to chassis, and the unit power on, use the positive probe to check voltage on the pin 3(on the right) of the 7805. Should get 5V DC. If you do get that, press down firmly on the board at the 7805 and see if the display comes on. If you do not get 5V, check voltage on pin 1, which should be(no schematic in front of me at the moment) somewhere in the 8-15V vicinity, more or less. Voltage there & not on pin 3 means the 7805 is dead. If you don't have pin 1 voltage, you more than likely have just very cracked solder connections to all three pins.

[rlbuntin]

Thanks again stephensank! I will post results when I get a chance to do this.

[mavallarino]

Hello Forum and Nak owners!

I was wondering if some lucky recipient of the OMS-5 service manual would like to send me/post a copy.

Background:
My friend has just brought me a few non-working CD players. I had told him I wasn't interested until I took a closer look to the OMS-5. Since it looked very well made I told him he could leave it. ;-)

The Issue:
The unit spins the disc, the tray opens and closes on demand but doesn't play the tracks. Could it be a malfunctioning laser unit?

Since everything is tight and "interleaved" I would like to reference a manual in order to get a better idea and before complicating my life even more.

Thanks in advance,
MV