Re: sencore cr70 repair

David -

The schematics and test procedure are on
ftp://ttl.arcadetech.org/TTL/Test_Equipment/ under sencore / cr-70.

Although I don't understand the purpose of those pots yet, they definitely
do not adjust voltage range. I think the problem was that the test
procedure had me measuring from G1 to G2 which would include the bias
voltage, but it did not specify a setting. It looks like you need the knob
on -20 to see the expected voltage range. Otherwise the range will be
offset, like I was seeing.

The two pots R23/R24 are basically on the output to the gauge, and I think
they calibrate where the needle is placed for a given cutoff current or
emission current. But I still don't fully understand the circuit or how I
should perform a calibration.

-joey

On Wed, Feb 27, 2013 at 11:02 PM, David Shoemaker <davids@oz.net> wrote:

> At a guess (without having schematic access) I would say one is low range
> limit and the other high.****
>
> ** **
>
> Use a fine sharpie to mark the existing positions of the two pots.****
>
> ** **
>
> I would turn on the unit, let it sit a few minutes to warm then set the
> G1/G2 to minimum. Then slowly tweak the R24 pot up / down and see if it
> does anything to the low end range. If not try R23. I bet one or the
> other will adjust the minimum swing point.****
>
> ** **
>
> Then adjust it to max and tweak the other to see if that pulls the high
> end max down to where it should be.****
>
> ** **
>
> David****
>
> ** **
>
> *From:* owner-vectorlist@vectorlist.org [mailto:
> owner-vectorlist@vectorlist.org] *On Behalf Of *Darren Finck
> *Sent:* Wednesday, February 27, 2013 7:27 PM
> *To:* vectorlist@vectorlist.org
>
> *Subject:* Re: VECTOR: sencore cr70 repair****
>
> ** **
>
> The problem is that after replacing IC4 it's no longer calibrated and it's
> failing the test procedure. The voltage on G1/G2 is supposed to swing from
> 20 to 400 volts but it's actually swinging from 80 to about 460 volts
>
>
> Can anybody help explain the purpose of pots R24, R23, and how I might
> want to adjust them to recalibrate the unit properly? It looks like I need
> to adjust both of these but I don't know how.****
>
> ** **
>
> -joey****
>
> On Tue, Jan 15, 2013 at 10:45 AM, Joey Oravec <joeyoravec_at_gmail.com<http://mc/compose?to=joeyoravec@gmail.com>>
> wrote:****
>
> I already have the schematics, parts list, and manual but there are
> various pots that surely need adjustment after changing out components.***
> *
>
>
> Have you scanned the schematics? If so, send a copy (or a link to them)
> and I'll be glad to look at them and try explaining the purpose of the pots
> you're asking about. I have a CR31, and had to dig pretty deep into it to
> repair it, so I became pretty familiar with its schematics & operation. So
> with the expectation that the CR70 is similar to the CR31, I should be able
> to follow it pretty well.****
>
> ** **
>

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Received on Wed Mar 6 10:40:59 2013