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Re: PG506 calibrator generator voltage error

Gif Sim
 

hi bob
thanks for the tips I'll go check it out immediately!
as i wrote to eric i have a pg506a there are no relays ...
the thing I don't understand is that if I connect a battery powered oscilloscope everything works correctly ... all controls and values are normal
i noticed that q290 q190 and r190 are very very hot but taking them apart and trying them they are okk ... also vr210 is ok the 9v are present
I noticed that when I connect an oscilloscope that can be tds784d or 2465b, then powered by the mains
the voltage +120 volts (which I measure on cr291) rises to +125 volts .....
I'm going crazy !!!
thank you all
simon


Re: PG506 calibrator generator voltage error

Eric
 

Hey Simon,
Measured with a Keithly DMM6500 standard output jack to the aluminum frame. In a frame and out of a frame.
In frame, resistance that rapidly went up to overflow. I believe a cap was charging.
Out of a frame, Same behavior.

Once charged infinite resistance.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Gif Sim via groups.io
Sent: Sunday, December 27, 2020 2:10 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] PG506 calibrator generator voltage error

hi eric
yess..I did as you wrote ... the pg506a used it long ago and it was perfectly calibrated and working (I calibrated some 2465b and 2467b)

the strange thing is that if I connect an oscilloscope with 1Mohm input, battery powered, therefore not connected to the mains electricity, to the amplitude standard output, the levels are correct ... the variable out potentiometer works and the display indicates the value set with the pot ....

but if I connect an oscilloscope (such as a tds 784d) with 1Mohm input, powered by the mains electricity, the output voltage is wrong (for example if I set 2 v to the output or about 2.4 v) ... .the variable out potentiometer has no effect on the output voltage and the display indicates a fixed value

my calibrator is the PG506A and one of the latest revisions of the boards there are no relays you find in the first PG506

I checked q325-q365-q326-q320-q280-q290-q245-q255-q270-q190 by removing them from board A1 and trying them with a component test they are all okk...

i checked all diodes and zener on board A1 and they are all okk now i am trying and replacing some electrolytic and tantalum capacitors on board A1 (but so far i haven't found any wrong ones)

Eric can you do me a favor? ... with the PG506 off, set to standard ampl and the selector on 2volt, if you connect the cables of a multimeter between the mass of the standard out female bnc and the aluminum frame of the PG506, what a resistance read the multimeter?

thanks eric and thanks to all those who can give any suggestion to understand the problem!
simon


Re: PG506 calibrator generator voltage error

Gif Sim
 

hi eric
yess..I did as you wrote ... the pg506a used it long ago and it was perfectly calibrated and working (I calibrated some 2465b and 2467b)

the strange thing is that if I connect an oscilloscope with 1Mohm input, battery powered, therefore not connected to the mains electricity, to the amplitude standard output, the levels are correct ... the variable out potentiometer works and the display indicates the value set with the pot ....

but if I connect an oscilloscope (such as a tds 784d) with 1Mohm input, powered by the mains electricity, the output voltage is wrong (for example if I set 2 v to the output or about 2.4 v) ... .the variable out potentiometer has no effect on the output voltage and the display indicates a fixed value

my calibrator is the PG506A and one of the latest revisions of the boards there are no relays you find in the first PG506

I checked q325-q365-q326-q320-q280-q290-q245-q255-q270-q190 by removing them from board A1 and trying them with a component test they are all okk...

i checked all diodes and zener on board A1 and they are all okk
now i am trying and replacing some electrolytic and tantalum capacitors on board A1 (but so far i haven't found any wrong ones)

Eric can you do me a favor? ... with the PG506 off, set to standard ampl and the selector on 2volt, if you connect the cables of a multimeter between the mass of the standard out female bnc and the aluminum frame of the PG506, what a resistance read the multimeter?

thanks eric and thanks to all those who can give any suggestion to understand the problem!
simon


Re: PG506 calibrator generator voltage error

 

I have repaired a number of PG506's and these are the common problems:

Intermittent operation of the flat white relays at the back of the instrument
On older instruments, there are two small metal-cased relays near the front. These switch in a low-pass filter for some standard-amplitude settings to reduce noise from the switching power supply.
Cam switch contacts. To get to these, it is necessary to remove the DVM daughter board
The standard amplitude cal trimpots R340 and R205. I replace the single-turn pots with multi-turn trimmers

To clarify the 50-ohm vs 1 megohm load question, the Standard Amplitude output is intended to drive a 1 megohm load at all ranges. At 10 V and below, it can drive 50 ohms, in which case the output should be exactly half the 1 megohm load value. The High-Amplitude output can drive either a 1 meg or 50-ohm load. The output to a 50-ohm load will be about a tenth of the 1-meg value.

The fast-rise outputs must drive a 50-ohm load.


Bob Haas


Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Thomas Garson
 

This is very interesting to me, but the description of the device on the eBay sale page is very difficult to follow. They discuss spectrum analyzers as if this is one. I don't see how that can be.

However, even if it is only a "flat" white noise source, I can see the utility it offers. My normal MO for testing receivers is to use my Marconi generator swept over the required spectral range while observing the output of interest on my 7000 series 'scope. This works quite well, but can be somewhat cumbersome. I have considered trying to acquire a tracking generator for my 7L12, but those are relatively rare and have been somewhat expensive.

I never considered using a broadband noise source as an alternative to the tracking generator. From your post, it appears that you have done so, with at least acceptable results.

It's kind of funny, because I work more in audio than RF and for years, prior to the advent of low cost computer "sound card" based analyzers with tracking generator, used noise with an analyzer for sound system measurements. Duh.

Any comments, hints or suggestions welcome.

Thank you.

Thomas Garson
Aural Technology, Ashland, OR
By my calculation, the dynamic range of the universe is roughly 679dB,
which is approximately 225 bits, collected at a rate 1.714287514x10^23 sps.

On 12/27/20 7:50 AM, Nenad Filipovic wrote:
On Sun, Dec 27, 2020 at 05:31 AM, Attilio wrote:
Can you give an indication as to which source noise should I buy ?
I've got one very much like this:
https://www.ebay.com/itm/0-2-2000M-Noise-Signal-Generator-Simple-Spectrum-Tracking-Source-High-Flatness/174453557146
It's reasonably flat and worth the price. You might find it cheaper on Aliexpress. Do not buy the PCB only version (no metal box, unless you intend to put it in one) as it will pick up all sorts of RFI from your environment.

What can I do to reduce the possibility of damage the first 7L13 mixer using
an active probe?
Same as what Chuck already said, care and discipline during usage. 7L13 attenuator offers fair protection on its own at -20dB and higher settings. Insertion of clamping diodes will provide additional protection but it may also disrupt the complex impedance of the input, which may impair the accuracy of measurements on higher frequencies.
Best regards and Happy Holidays,
Nenad FIlipovic


Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Attilio
 

Thanks Nenad,
I think I will buy what you indicated, I find it difficult to find a Tektronix TR502.
I agree with everything you and Chuck have written.

Best regards and Happy Holidays
Attilio


Re: Rescuing 500s from tube snatchers/scavengers - how much is it worth

-
 

PS the owner just died a few months ago and no one is sure what's going
to happen to the business so if there's anything that you want, you'd
probably better get it now.

On Sun, Dec 27, 2020 at 10:59 AM - via groups.io <rrrr6789=
gmail.com@groups.io> wrote:

Try the tube dealer mentioned in the previous post. He has the largest
collection of vacuum tubes in the world.

On Sun, Dec 27, 2020 at 1:12 AM snapdiode via groups.io <snapdiode=
yahoo.com@groups.io> wrote:

Do you know where to get a set of new Bendix 6900's?










Re: Rescuing 500s from tube snatchers/scavengers - how much is it worth

-
 

Try the tube dealer mentioned in the previous post. He has the largest
collection of vacuum tubes in the world.

On Sun, Dec 27, 2020 at 1:12 AM snapdiode via groups.io <snapdiode=
yahoo.com@groups.io> wrote:

Do you know where to get a set of new Bendix 6900's?






Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Nenad Filipovic
 

On Sun, Dec 27, 2020 at 05:31 AM, Attilio wrote:
Can you give an indication as to which source noise should I buy ?
I've got one very much like this:
https://www.ebay.com/itm/0-2-2000M-Noise-Signal-Generator-Simple-Spectrum-Tracking-Source-High-Flatness/174453557146
It's reasonably flat and worth the price. You might find it cheaper on Aliexpress. Do not buy the PCB only version (no metal box, unless you intend to put it in one) as it will pick up all sorts of RFI from your environment.

What can I do to reduce the possibility of damage the first 7L13 mixer using
an active probe?
Same as what Chuck already said, care and discipline during usage. 7L13 attenuator offers fair protection on its own at -20dB and higher settings. Insertion of clamping diodes will provide additional protection but it may also disrupt the complex impedance of the input, which may impair the accuracy of measurements on higher frequencies.

Best regards and Happy Holidays,
Nenad FIlipovic


Re: Details on 015-0670-00 Feed-Through Adapter for AM503B?

Jared Cabot
 

Yep, that was me who added the detailed info, the photo of the DIY voltage adapter is mine. :)


Re: Tek 453A

Glenn Little
 

My first 453 had no trace.
The fault was a 500 pF filter capacitor on the HV line.
The capacitor was a red, possibly epoxy, encased capacitor.
When held up to the light you could see black arc marks inside the capacitor,
I replaced the capacitor with a ceramic one and have had no problems since.
I have found this to be the cause of no trace on a few scopes.

If the price is right, the repair may be simple.

Glenn

On 12/26/2020 11:57 PM, Maurice Smulders wrote:
I can obtain a Tek 453A locally, but it doesn't show a trace, so I have no idea yet what is broken. What would be a good offer for it, and is it usually repairable?

- Maurice



--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"


Re: 2465B calibration temp?

Chuck Harris <cfharris@...>
 

1) there is absolutely no need to cool anything in the
2465B while it is out of the case. Not U800, not anything.

The only caveat to that is don't leave the scope laying on
the bench with the front panel overhanging the bench.

2) calibration can be done over a very wide range of room
temperatures, see the manual.

If yours is outside of the specs published in the manual,
and, it was inside of the specs in the manual when you calibrated
it last, you have a bad part that needs replacing... likely a trimmer
pot... especially likely one of the 10K resistors on the A5 board,
if it is a late serial number 2465B.

Electrolyte from failed SMD electrolytic capacitors etches the
elements of the 10K reference resistors, and if they weren't
replaced, they will drift ever upward in value. Similarly, any
electrolyte left on the A5 board will be hygroscopic, and make
the circuits on the board drift.

-Chuck Harris

Jean-Paul wrote:

Raymond and Victor,

Many thanks! I have done full cals on these but some years ago. Am Aware of cooling of A1 PCB, U800 etc with case open.

I have TEK manuals printed originals, PG506 and TM501, attens, terms etc.

To précise the questions:

IF the scope was already full CALed but the V or H is still off 1-3 % (perhaps bad first attempt at CAL?) can the V/H CAL be done with case closed or it must be open to reach trimmers?

Best Wishes,

Jon







Re: Details on 015-0670-00 Feed-Through Adapter for AM503B?

Ed (SCSKITS)
 

On Sun, Dec 27, 2020 at 09:26 AM, Ed (SCSKITS) wrote:
Never mind, the voltage adapter is on tekwiki...

ed


Re: Details on 015-0670-00 Feed-Through Adapter for AM503B?

Ed (SCSKITS)
 

Might be worth wile to get the schematic for the 015-0598-00 voltage adapter also.


Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Attilio
 

Nenand,
thanks for the information.
At the moment I was able to recover a 7613 mainframe, I was satisfied.
Can you give an indication as to which source noise should I buy ?
What can I do to reduce the possibility of damage the first 7L13 mixer using an active probe?

Thanks a lot and greetings to all


Re: Tek 453A

Dale H. Cook
 

On 12/27/2020 12:18 AM, Bob Albert wrote:



It's repairable. But it could have serious problems and if you don't
know, pass on it.



I agree with Bob. Also bear in mind that for many oscilloscope repairs you need a working oscilloscope to troubleshoot the dead 'scope.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/


Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Attilio
 

tinkera123 which diodes did you use to protect your SA?
Thanks, bye
Attilio


Re: Rescuing 500s from tube snatchers/scavengers - how much is it worth

snapdiode <snapdiode@...>
 

Do you know where to get a set of new Bendix 6900's?


Re: Tek 453A

Bob Albert
 

It's repairable.  But it could have serious problems and if you don't know, pass on it.  They are pretty old; I have one and it's great but only 50 MHz or so.  I no longer use mine due to getting higher performance units.
If it doesn't work, forget it.
Bob

On Saturday, December 26, 2020, 08:57:58 PM PST, Maurice Smulders <maurice.smulders@gmail.com> wrote:

I can obtain a Tek 453A locally, but it doesn't show a trace, so I have no idea yet what is broken. What would be a good offer for it, and is it usually repairable?

- Maurice


Tek 453A

Maurice Smulders
 

I can obtain a Tek 453A locally, but it doesn't show a trace, so I have no idea yet what is broken. What would be a good offer for it, and is it usually repairable?

- Maurice

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