Re: Type 503 Oscilloscope Issues

Dave Casey
 

The lower right one is R692. Evan has listed the marked value, the allowed
range factoring in for tolerance, and the measured value in that order for
each resistor he's measured. However, he's mis-read R692 as 0.43 ohms
instead of 4.3 ohms, and he's accidentally marked it as 0.42 ohms even
though his tolerance range is correct for the incorrect value he's read off
the bands.

Dave Casey

On Mon, May 1, 2017 at 11:55 PM, 'Tom Miller' tmiller11147@...
[TekScopes] <TekScopes@...> wrote:



What is the one in the lower right 0.42 ohms? That is way out of range,
maybe open?

----- Original Message -----
From: enchanter464@... [TekScopes]
To: TekScopes@...
Sent: Tuesday, May 02, 2017 12:21 AM
Subject: [TekScopes] Re: Type 503 Oscilloscope Issues

It has been a while since last posting, but I have only gotten time
recently to work on the scope (in the midst of final exams).

Taking Dave's advice, I went ahead and measured the resistance of the
resistors surrounding V620 and V634 (basically everything on the ceramic
strips). I have a photo of my measurements here: https://goo.gl/photos/
JUFwEfmnyFAcYtp6A https://goo.gl/photos/JUFwEfmnyFAcYtp6A

I was unable to measure the resistor across V620, which is why there are
"???" for that value. Those values reported in red were the ones outside of
the tolerance range. Suffice to say, the majority of the resistors gave
values that were outside of their range. However, I am not sure if this is
due to how some are soldered together, which could affect the values (for
example, the resistor at V692 giving a resistance value of just the tube
itself, since its expected value is relatively small). In addition, only
one resistor (a 100 ohm) had values higher than its range, while the others
were all below their tolerance limit.

Before looking at getting a replacement tube for V620, would it be best to
replace these resistors? Or is there a better way I can test resistance to
confirm that the values I measured are accurate?

Also, a side note for Dave, but the schematic for wiring the 6.3 VAC
transformer did not get added to your posting. Would you be able to share
the image as a link (since the forums don't support attaching photos)?

- Evan

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