[QuadList] Recortec timer issue

[LARRY]

Guy,

The one here stopped counting up, it would only count down. There are two infrared led/photoxistrs mounted under the roller, one for up count, one for down counting. The up counting led/xistr was open.
But, in the taking apart and repairing,I had to re-adjust the clock quadrature of the two (up/down) square waves. There are a couple pots on the back of the PC board and a couple test pins to scope onto, and then you adjust the pulse widths within a certain spec.
The circuit is a basic 74161 up/down register arrangement with dual clock steering.
I did notice that if the clock edges are out-of the spec, it will hang, or not count, or be an inaccurate count. It works very much like a counter on a Ampex VPR-80, if you are familiar with that one.
So maybe yours may just need a little tweak to allow for warm-up drift.

OK, hope this helps some,
larry

----- Original Message -----
From: "Guy Spiller" <quadruplex at verizon.net>
To: "Quad List" <quadlist at quadvideotapegroup.com>
Sent: Thursday, September 22, 2011 7:24:48 PM
Subject: Re: [QuadList] Recortec timer issue

Larry,
Did yours just suddenly quit counting completely, or was it somewhat 
intermittent...perhaps with temperature?
Guy

On 9/22/2011 6:30 PM, LARRY wrote:
> Hi Guy,
>
> If Ted can't find his manual, I got one.
> I just fixed the one on the TR-70c here a few months ago. One of the phototransistors went bad underneath the roller.
> Good luck finding a replacement! We were lucky to have another one in a non-fuctioning unit.
>
> Larry
>
> LE Odham
> Engr/Tech
> TAMIS Archive
> Knoxville, Tenn.
>
> ----- Original Message -----
> From: "Guy Spiller"<quadruplex at verizon.net>
> To: "Quad List"<quadlist at quadvideotapegroup.com>
> Sent: Thursday, September 22, 2011 4:30:44 PM
> Subject: [QuadList] Recortec timer issue
>
> The Recortec timer that was installed on my TR-70C suddenly stopped
> counting on machine powerup last night.  Just sits with all zeros.
> I have no documentation for this thing, as someone installed it after
> the fact, and no experience with Recortec timers at all. All my quads,
> "back in the day" had mechanical timer/counters.
> Do these things have a historically common failure mode?  Is there a
> lamp/photocell/slotted disc arrangement and possibly just a failed lamp?
> I haven't opened it up yet, but I thought I would check the vast
> knowledge here on the list and see if I can get some idea what I'm
> getting into before I take the machine offline to deal with it.
> thanks
> Guy
>

-- 
Guy Spiller
email: quadruplex at verizon.net
phone: (804) 379-2050
website: www.GuySpiller.com
Midlothian, VA


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