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Re: FG 504 problems

Colin Herbert
 

Has anyone ever tried cleaning the contacts on the "Frequency Multiplier" switch? They are (I'm sure) cam-type switches and are probably rather similar to the "Attenuator" switch contacts. The problem is access. While the "Attenuator" contacts are easy to get at and use the "paper soaked in isopropanol trapped between the contacts" technique, the "Frequency Multiplier" contacts can barely be seen. While I can't detect any higher-resistance situations, I'm wondering if (since these contacts are on a pcb, not like the attenuators in the 400-series scopes which are on a sensitive substrate) a few gentle and sparing squirts of Servisol would be a good or a bad idea?
Any opinions welcome.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via groups.io
Sent: 22 August 2020 10:32
To: TekScopes@groups.io
Subject: Re: [TekScopes] FG 504 problems

I am still puzzling over this. I have read the manual relating to the capacitance multiplier and have checked that C210, the resistors associated with it and switches 5, 6, 7 and 8 all look OK as far as I can tell. Also, R216 measures 10K and the slider is operating correctly (when U215 is out-of-circuit). I am left with the possibility that U215 is faulty, but I can't find a replacement. Does anyone have any better ideas, or maybe a replacement for U215 (Tektronix-made 156-0484-00)?
TIA, Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin Herbert via groups.io
Sent: 17 August 2020 13:53
To: TekScopes@groups.io
Subject: Re: [TekScopes] FG 504 problems


I still have some problems with the Function Generator (though I have fixed one) which relate to the symmetry adjustments.
All of the power-supply voltages and ripple levels are within spec. I have got through and ensured that items #6 and #7 in the adjustment procedures are correct. These relate to the "Top Dial Waveform Symmetry (R52)" and "Minimum Dial Waveform Symmetry (R155)". The problem comes in with the next procedure "Adjust Low Dial Waveform Symmetry (R215)". This requires a 10Hz square-wave to be generated and output, but my FG 504 stops oscillating at something like 90 Hz and just gives positive pulses of approximately 3.25 ms width. This cannot be corrected with R215, which has -15 VDC on its slider, but doesn't change the voltages on pins #1 and #5 of U215. At the other end of the "Frequency Start" dial, the square-wave is more symmetrical (but not completely so) and the positive pulses are about 1.75 ms wide. This is all with the "Frequency Multiplier" switch at 10. Could this be a failure of the timing capacitor at this setting, or is R215 or U215 at fault? I have tried reseating U215 with no improvement.
The +1V/-1V triangle waveform at the junction of R225 and R228 under the conditions stated in the manual is fine.

Any suggestions as to what is going on?

TIA, Colin.


Re: TDS684A freezing during boot (erratic behaviour)

Stephen Hanselman
 

If you have not done it already open it up and blow all the dust out of the unit. The fan sucks air through the PS andHV card. We have found virtually all of the units we’ve worked on had a serious reduction in air flow through the PS area

Regards,

Stephen Hanselman
Datagate Systems, LLC

On Aug 23, 2020, at 07:18, Rogerio O <rodd414@gmail.com> wrote:

Dear all,
I bought this scope from Ebay some time ago and it has been working very well.
However, since one month ago, it started to "freeze" during boot.
It does not happens all the time, but once every two or three power on attempts.
When it happens, I manage to make it run by powering on/off a couple of times, but that made me think I will run into trouble soon.
I suspected that I could have a capacitor leakage problem but I inspected the boards for corrosion but I could not find it.
Maybe the caps are just starting to fail so here comes the one million dollar question: Should I recap this scope?
Is this a common failure in this model?
Any other suggestions?
Thank you very much in advance for the help.



Re: TDS684A freezing during boot (erratic behaviour)

amirb
 

psu is a good starting point but it could be your NVRAM about to give up
at what stage during boot does it freeze?
I would suggest you build the debug port and see the debug console first. That will give you a better clue as to what the problem is


TDS684A freezing during boot (erratic behaviour)

Rogerio O
 

Dear all,
I bought this scope from Ebay some time ago and it has been working very well.
However, since one month ago, it started to "freeze" during boot.
It does not happens all the time, but once every two or three power on attempts.
When it happens, I manage to make it run by powering on/off a couple of times, but that made me think I will run into trouble soon.
I suspected that I could have a capacitor leakage problem but I inspected the boards for corrosion but I could not find it.
Maybe the caps are just starting to fail so here comes the one million dollar question: Should I recap this scope?
Is this a common failure in this model?
Any other suggestions?
Thank you very much in advance for the help.


TDS 68x Fan replacement

Rogerio O
 

Dear all,
I have a TDS 684A with a very noisy fan.
I searched this forum ( Google it) for a replacement and or mod but I could not find any information at all.
Any suggestions?


Re: Printing Tek knobs

 

Scott - how much did you pay to have the knobs printed? My son has a 3D
printer and might be interested in printing them. I don't know if he has
grey filiment but he probably can get some.

houdatto@gmail.com

On Sun, Aug 23, 2020, 7:06 AM <scott@myhappydestiny.com> wrote:

Hey Dave,

Perhaps you found the small knobs already, but for others as well:

I just printed a bunch of the small knobs Tek # 366-0636-00 using this
design file:

Tektronix 2225 Oscilloscope control knob by faultedlogic on Thingiverse:
https://www.thingiverse.com/thing:4111558

I used treatstock.com to find a printing service, and printed in Resin.
If you find someone with gray resin, that's great. Mine were clear, but
will paint them.

Scott




Re: Printing Tek knobs

Scott Gilson
 

Hey Dave,

Perhaps you found the small knobs already, but for others as well:

I just printed a bunch of the small knobs Tek # 366-0636-00 using this design file:

Tektronix 2225 Oscilloscope control knob by faultedlogic on Thingiverse: https://www.thingiverse.com/thing:4111558

I used treatstock.com to find a printing service, and printed in Resin. If you find someone with gray resin, that's great. Mine were clear, but will paint them.

Scott


Re: Graticle lighting

Scott Gilson
 

Dave,

I have a 2225 and am adding graticule lighting. It never came with it.

I'll likely go with LEDs, and use the +5.2V supply (non-critical digital logic) with an appropriate current limiting resistor.

You can still find these original parts online:

The plastic graticule reflector is Tek part # 378-0877-02, and is used on the Tek 2232 scope. It's just the plastic piece with white reflective tape along one edge. You could add two diffused LEDs, or regular bulbs. Note there are only two holes for lights, and the center portion is a screw hole for mounting.

The illumination board and reflector assembly with bulbs is Tek # 671-1463-00 or 671-0795-00. This has the plastic piece above, the PCB with two bulbs, and the wire and a connector. Not sure of the voltage it uses, but they are wired in series.

You may want to add a brightness adjust knob on the rear of the scope.

Have fun!
Scott


Re: 2246A Power supply failure turning on / off

Giuli Lauto
 

I d check also the on off switch, very common failure.


Re: Tek 465 Turns on, No Dot, No Trace

 

On Sun, Jul 12, 2020 at 06:29 PM, Stephen wrote:


The crackling sounds and the weird smell (not a burning smell), appeared for
the the first time when I depressed the Beam Finder. Almost the same happened
when I cranked the Intensity.
I didn’t exactly see a “trace”, but rather a blurry and unfocused glow.
But at least, it was finally somehow alive.
The crackling sounds and the weird smell could well be arcing, producing ozone, which you smell. It indicates that the PDA voltage is there (output of HV multiplier). The ordinary HV of a few kV usually isn't enough to produce this effect.
But is this about a 465 (the thread's subject) or about your 475A? I'm confused but have to admit I haven't read it all. If it's about your 475A, I suggest starting a thread about that.

Raymond


Re: 184 Schematics

Eric
 

I am as well

On Sat, Aug 22, 2020, 4:44 PM Raymond Domp Frank <hewpatek@gmail.com> wrote:

On Sat, Aug 22, 2020 at 10:39 PM, Raymond Domp Frank wrote:


Why not put them on TekWiki and make them available to everybody?
If you prefer, send them to me and I'll put them there.
FWIW: TekWiki is *the* reference site and repository for all things
classic Tek.

Raymond




Re: 184 Schematics

 

On Sat, Aug 22, 2020 at 10:39 PM, Raymond Domp Frank wrote:


Why not put them on TekWiki and make them available to everybody?
If you prefer, send them to me and I'll put them there.
FWIW: TekWiki is *the* reference site and repository for all things classic Tek.

Raymond


Re: 184 Schematics

 

On Sat, Aug 22, 2020 at 10:24 PM, david wrote:


I have taken all the schematics for a 184 that were in two pieces and
assembled each schematic into a single document. All PDF files. If anyone is
interested I can put the in a ZIP file and Email them to you. Much easier to
understand circuits when looking at complete schematic.
Why not put them on TekWiki and make them available to everybody?
If you prefer, send them to me and I'll put them there.

Raymond


Re: 184 Schematics

Peter Brown
 

I’m interested

Peter

On Sat, Aug 22, 2020 at 2:24 PM david via groups.io <davide_us=
yahoo.com@groups.io> wrote:

I have taken all the schematics for a 184 that were in two pieces and
assembled each schematic into a single document. All PDF files. If anyone
is interested I can put the in a ZIP file and Email them to you. Much
easier to understand circuits when looking at complete schematic.

David








Re: 184 Schematics

Stephen
 

On Sat, Aug 22, 2020 at 09:24 AM, david wrote:


I have taken all the schematics for a 184 that were in two pieces and
assembled each schematic into a single document. All PDF files. If anyone is
interested I can put the in a ZIP file and Email them to you. Much easier to
understand circuits when looking at complete schematic.
David
I’m interested.


184 Schematics

david
 

I have taken all the schematics for a 184 that were in two pieces and assembled each schematic into a single document. All PDF files. If anyone is interested I can put the in a ZIP file and Email them to you. Much easier to understand circuits when looking at complete schematic.
David


Re: Tek 465 Sweep Start Calibration

david
 

Yeah, I checked and R1112 is 49.9 ohm, R 1111 is 562 ohm, ordered 196 ohm 1% 50ppm resistor, I can replace R1113 without removing A7 board.I will let you know if it works. Thanks for help.
David


Re: PS503A Mod FF Photos?

 

On Sat, Aug 22, 2020 at 06:44 PM, Colin Herbert wrote:


Wouldn't another power-supply be a possibility? Perhaps another PS503A or
something simpler, even. What if you want four power-sources - basically then
you do need another power-supply.
Sure, definitely, I wouldn't want to modify a PS503 *today*. In the past, I may have but reason 2 wouldn't have applied...
In the past, I would have liked to use fewer slots in my TM50x.

Raymond


Re: PS503A Mod FF Photos?

Stephen
 

This is exactly what I was gonna say.
Use another power supply... 🤷‍♂️


Re: PS503A Mod FF Photos?

Colin Herbert
 

Wouldn't another power-supply be a possibility? Perhaps another PS503A or something simpler, even. What if you want four power-sources - basically then you do need another power-supply.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Raymond Domp Frank
Sent: 22 August 2020 17:41
To: TekScopes@groups.io
Subject: Re: [TekScopes] PS503A Mod FF Photos?

On Sat, Aug 22, 2020 at 04:17 PM, Stephen wrote:


May I ask why one would need to modify a PS503A?
Can’t you adjust and fine tune the 20V supply? That’s what i do on mine...
🤷‍♂️
A few reasons come to mind:
1. I may want to use the +/- 20V lines and supply my ECL logic as well (-5.2V nominal). It *is* a triple-voltage supply...
2. I may be using the +/- 20V lines, at the same time wanting to supply my Raspberry Pi 3B+, which doesn't like being fed less than 5.1V (or so).
3. I may want to supply my +/-15V OpAmp circuits while finding supply voltage limits for a connected 3.3V or (TTL) 5V circuit.
4. The reason I just stole from Colin: 5V at 1A from a TM504 (high power slot at the right) or the like.

Raymond

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