Re: 2235 Trigger on one channel

Kevin Clark

Hi Tom :-)

As Tom indicates I am in the UK. Thank you for the eBay links. How does one tell
if they are fake?



On 16 May 2017 at 21:06 "Tom Jobe tomjobe@... [TekScopes]"
<TekScopes@...> wrote:

There are some new CA3102E arrays on eBay.
I believe Kevin is in the UK.
Here's one from Switzerland:
Two of several from the US:
There are many available from China, some of which look like they might
not be fake.

On 5/16/2017 9:02 AM, David @DWH [TekScopes] wrote:
> On 16 May 2017 14:03:52 +0000, you wrote:
> >Hi David
> >
> > Been a little busy so took a while to get back to this. So today
> lunch time I started to measure some voltages with my DMM as
> suggested, results as follows, something a little amiss (I think?)
> >
> > U555B Output pin 6 ch1 = 0.139V (0.2V) (0.06V error)
> > U555B Output pin 6 ch2 = 1.476V (2.5V) (1.02V error)
> >
> > U310 Output pin 1 ch1 = -3.26V (-3.4V) (0.14V error)
> > U310 Output pin 1 ch2 = -2.443V (-2.1V) (0.34V error)
> You can check the values of R314, R315, R317, R318, and R319 around
> U310 but I think the answer is going to be that U310 is bad.
> The signal into pin 1/11 is suppose to be low when channel 1 is
> selected. When that happens, the output of U555B is disconnected
> (pins 1/11 of U310 should not draw any current) and should reach all
> the way to ground which is what we are seeing and U310 should be
> working but it is not.
> When the signal into pin 1/11 is high, channel 2 is selected but pin
> 1/11 draws more current from U555B. In this case, it is drawing too
> much current indicating that either U310 is damaged or R314 and/or
> R315 are open.
> The fact that U555B is not reaching its full output is irrelevant
> because under that condition, U310 should not be forwarding the
> trigger signal anyway.
> > I also looked at the feed from the A3 Board Connection as follows:-
> >
> > Pin 18 (6.2V) = 6.5V (0.3V error), this also shows (0V) for XY but
> can't see how to check this on front panel.
> > Pin 32 (0.0V) = 0V
> > Pin 33 (5.0V) = 4.996V
> > Pin 34 (5.0V) = 4.996V
> >
> > Some of the values are slightly higher / lower than they should be,
> is this the issue?
> No, nothing is wrong there.
> I wonder if there are any good sources for CA3102 transistor arrays. I
> do not see any so if you cannot find one, blast me an email with your
> mailing address and I should be able to mail one to you. I will have
> to pull it from a junked board but will test it somewhat.




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