[Test-Equipment] WTD: Help with old scope problem

Sun Oct 10 22:43:45 EDT 2010

A Simpson 260 appears to be 20,000 Ohms/volt, so on the 5000 V scale the
input impedance is:

5000 V x 20,000 Ohms/V = 100,000,000 or 100 Megs.

-John

==============

> Use a Digital Voltmeter with an impedance of 10 meg ohms or
> higher.                                             David
>
> --- On Sat, 10/9/10, Joseph Orgnero <josepho at shaw.ca> wrote:
>
>
> From: Joseph Orgnero <josepho at shaw.ca>
> Subject: Re: [Test-Equipment] WTD: Help with old scope problem
> To: "Discussion of Electronic Test Equipment"
> <test-equipment at mailman.qth.net>
> Date: Saturday, October 9, 2010, 11:41 AM
>
>
> Thank you Ed,
> I do have the original manual, so I'm OK that way.
> As for the HV, some other messages state that the 260 is not suitable due
> to
> loading, unfortunately, I don't have a VTVM for that purpose.
> I'll follow your advice and go over the scope again, hopefully, I shall be
> able to narrow down the problem.
> I'll keep you posted.
> Joe
> ----- Original Message -----
> From: <k4pf at juno.com>
> To: <test-equipment at mailman.qth.net>
> Sent: Friday, October 08, 2010 1:15 PM
> Subject: Re: [Test-Equipment] WTD: Help with old scope problem
>
>
>>
>> Hi, Joe
>>
>> If you don't have a manual, here is a free one on the 'net:
>> http://bama.edebris.com/manuals/tek/310a/
>> It is in  DejaVu format, so you may need an image viewer
>> like Irfan View or XnView, both available at download.com.
>>
>> You should follow the signal from the external horizontal
>> input, and see where it disappears.  It could be trouble
>> with the horizontal selector switch Sw-210 or the horiz
>> amplifier tubes V220 v240.  Did you remember to switch
>> the mode switch to ext horiz input?
>>
>> You an use a 6.3V line from the LV power supply
>> as a source of horiz input signal.  V220 and V440 should probably
>> be OK, since there is a controlled deflection using the horiz
>> position pot.  I assume the pot is near center of its rotation
>> for normal mid scale display.
>>
>> The Simpson 260 is excellent to check HV.
>> I'm surprised you get no reading with it
>> at the -1675V check point, even though
>> you see objects on the screen.  You can check the 5642 filaments
>> in a dark room this evening.  You can check the Simpson 5KV scale
>> by connecting to the +300V line.
>>
>> Have you another scope to work on the Tek?
>>
>> 73,
>> Ed Knobloch
>>
>>
>> ---------- Original Message ----------
>> From: "Joseph Orgnero" <josepho at shaw.ca>
>> To: "Discussion of Electronic Test Equipment"
>> <test-equipment at mailman.qth.net>
>> Subject: Re: [Test-Equipment] WTD: Help with old scope problem
>> Date: Fri, 8 Oct 2010 10:53:03 -0700
>>
>> Thank you Ed for the advice, re your comments. The -150 V is OK, I don't
>> see
>> light on the rectifiers but being sosmall is hard to tell, I don't get
>> any
>> deflection using the external horizontal input.
>> As for the HV measurement, I'm using a Simpson 260 on the 5 KV range. Is
>> this the right kind of meter>
>> I'll keep investigating.
>> 73's
>> Joe
>> ----- Original Message -----
>> From: <k4pf at juno.com>
>> To: <test-equipment at mailman.qth.net>
>> Sent: Thursday, October 07, 2010 1:51 PM
>> Subject: Re: [Test-Equipment] WTD: Help with old scope problem
>>
>>
>>>
>>>
>>> Hi, Joe
>>>
>>> Is the -150V correct?  Filaments lit on all 5642's?
>>>
>>> Using external horizontal input on rear panel, do you get
>>> any horizontal deflection?
>>>
>>> Do you have another 'scope to work on this Tek 310A scope?
>>>
>>> You need a very hi Z meter to look at the HV,
>>> like a 20K Ohms per volt VOM with a 5KV scale.
>>> (100 Meg Ohms resistance on that range)
>>>
>>> 73,
>>> Ed Knobloch
>>>
>>>
>>> "Joseph Orgnero" <josepho at shaw.ca> wrote
>>>>For a number of years Ihave been using a Tek 310A on my bench. I like
>>>> it
>>>>on spite of its age and limited BW because of its small size and sharp
>>>>trace. Recently,after not have been used for some months, presnted a
>>>>number of problems.
>>> - There is no horizontal trace, only a spot.
>>> - The spot can be moved in both directions (V&H).
>>> - The focus control has only limited effect on the spot.
>>> - The intensity control has no effect on it.
>>> - The tubes related to the horizontal and sweep sections check OK.
>>> - There are no broken, burnt or overheated components.
>>> - LV voltages are OK but I cannot get a reading on the HV test point
>>> (5642
>>> rectifiers).
>>> - If I apply a signal from the voltage calibrator, the spot splits on
>>> two.
>>>
>>>
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>>
>>
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