I question whether replacing U800 on a 2445 is worth the labor and the cost of the device. I suppose if it's a beloved family heirloom would make it about the only reason to keep it working.
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--- In TekScopes@..., "Tom Miller" <tmiller11147@...> wrote:
Hi Patrick,
Seeing the waveform on the input along with the DC component of 60 mV on pin 18 leads me to believe the chip is bad. I didn't want him to go through changing the chip unless I was sure that was the problem. It's no trivial task for a beginner to remove the main board just to get access to U800.
There are other failure modes that can cause the same symptoms.
Of course you or I could have arrived at that diagnosis within minutes but we are dealing with a language barrier as well as a time delay of a day between replies.
Rob has found two sources for U800 from $117 to $135 so that is very helpful. Now to find out if he can get some experienced help to change the chip.
Regards,
Tom
----- Original Message -----
From: Patrick Wong
To: TekScopes@...
Sent: Saturday, July 07, 2012 11:00 PM
Subject: [TekScopes] Re: tektronix 2445 help
I believe the outcome is the OP found a good horizontal sweep signal being fed to the input of U800 (pin 18). Since the output (pins 4 & 9) is not correct, it is reasonable to assume that U800 has failed, especially since U800 is a known problem area.
The low voltage measured by the OP on pin 11 indicates the current flow to that pin is greater than normal (pin 11 receives voltage via a 330 ohm resistor connected to the +15V power supply.) I suppose that also is indicative of a failed U800.
Thanks,
Patrick Wong AK6C
--- In TekScopes@..., David DiGiacomo <daviddigiacomo@> wrote:
>
> I think a summary at the end would be much more helpful than following all the blind alleys.
>
> On Sat, Jul 7, 2012 at 5:57 PM, Tom Jobe <tomjobe@> wrote:
>
> > Hi Tom,
> > How could the discussion of this Tektronix 2445 repair be considered "clutter" to a Tektronix Scope Group?
