[Coco] CoCo Cassette Relay (Remote)

[Chad H]

Ok, problem solved.  It was the contact on the pivot arm in the relay.  I
took a jeweler screwdriver tip and 'scrubbed' the contact area between the 2
points and now its working :)  

For posterity, I will note the following:

*  You CAN pop off the transparent cover of the relay while the board is in
the case and without any unsoldering to test.  With a small pointed object
you MAY be able to press the pivot arm down manually and complete the
circuit causing the cassette motor to run.  This actually works well when
the relay is working properly.  If the points are dirty, put a little
side-to-side pressure on the contacts or try cleaning between them

* For potential replacement, note this:

The underside of the relay is 5 pins  (rough diagram is this)..

		1		2	3
		4			5

Pins 4 & 5 are the Coil points  (Supply 5 volts DC across these and it
latches)

Pins 1 & 3 are Normally closed  (not used)

Pins 1 & 2 are Normally open  (Open circuit leaves cassette motor off)
These are bridged when the 5V latches the relay and causes the motor to run.
This can also be shown by bridging the first and list pin of a cassette
cable while its unplugged from the back of the CoCo, same thing.

If this relay has trouble again, I will probably just go ahead and get a
cheap 5VDC relay from Jameco and be done with it.  I think all of theirs are
electronic, no more of this mechanical latching stuff.

-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
Behalf Of Chad H
Sent: Saturday, October 19, 2013 8:42 PM
To: 'CoCoList for Color Computer Enthusiasts'
Subject: Re: [Coco] CoCo Cassette Relay (Remote)

Ok a search of this relay seems to say that it's an "obsolete" part.  I
can't really find any real information on it.  Looking at the bottom side of
the relay though I'm pretty sure I've identified which pins are doing what.
The 2 coil pins are obvious.  Of the other 3, 2 pins seem to be normally
closed according to my multimeter, then OPEN when the latch drops.  Looking
at the pin-holes in the CoCo board, there are traces from these 2 pins back
to the CoCo din at different pins, which makes sense.  I also popped the
transparent cover off the top of the relay, perhaps I can clean some
contacts.

Worse case scenario, the operation of this parts seems VERY simple.  A
simple 5V relay wired to the correct pin points would substitute this one.
If the pins don't line up to the mounting location (which they probably
wouldn't)  I'll just 'improvise" :)

I will post my findings in case anyone else becomes interested in the future
(i.e. faces similar problem)

-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
Behalf Of Chad H
Sent: Saturday, October 19, 2013 8:13 PM
To: 'CoCoList for Color Computer Enthusiasts'
Subject: Re: [Coco] CoCo Cassette Relay (Remote)

Well I just finished de-soldering the relay a few seconds ago.  I have to
figure out how to test it and where I can get a replacement if its bad.
Here is the relay in question ...
http://www.mediafire.com/view/v0fc475uu1cohiu/Coco_2_Cassette_Relay.JPG


-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
Behalf Of Gene Heskett
Sent: Saturday, October 19, 2013 8:03 PM
To: coco at maltedmedia.com
Subject: Re: [Coco] CoCo Cassette Relay (Remote)

On Saturday 19 October 2013 20:47:48 Chad H did opine:

> I was testing the functions on a newly acquired CoCo 2 and everything 
> seemed flawless until I got to testing the Cassette operations.  It 
> does pass audio in/out but the Remote on/off (i.e. MOTOR ON/OFF etc) 
> does not function.  I do hear the relay clicking and can see the 
> contacts dip under the clear top of the relay.  I moved the cable back 
> to another CoCo 2 and  everything's fine.  It's definitely in this new 
> CoCo 2.  I suspect dirty contacts in the relay.  Is there a way to 
> make sure?  If it is the relay, what kind can I replace it with?
> 
Very little to no wonder at its age.  You could put in a fresh one of
course.

But I expect its very easily fixed too.  You may have to remove it in order
to gain access to get the cover off, which is probably a snap on variety
though.

Once the cover is off, find some clean newsprint, no ink, like from the edge
of the daily fish-wrap, and carefully cut some strips about 1/8" wide &
perhaps an inch & a half long.  Put one strip between the open contacts,
press them closed gently, and pull the paper thru the contact until the end
of the paper is about to come thru, then release the contact so that no
fibers from the end or edges are torn off & stuck to the contact.
It will likely be fairly well blackened as it removes the decades of
oxidation from the contact.  Repeat once more with that strip, then replace
it with a fresh one and check for the mark again.  Repeat until you are not
putting any more dark marks on the paper.

That relay is IIRC a dpdt, but could be a spdt.  If dpdt, clean the other
contacts by the same method.  Using a decent air pressure, 40 or 60 psi,
blow through the contacts as you exercise them, then snap the cover back on
and re-install.  S/B good for another 20 years, at no cost unless you had to
go buy the newspaper & scissors.
> 
> Thanks for any  "input".
> 
> 
> 
> 
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Cheers, Gene
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