Date   

Re: FG 504 problems

Stephen
 

On Sat, Aug 22, 2020 at 04:08 AM, Colin Herbert wrote:


Yes, the cost was involved in my decision. The one from the US was cheaper and
the postage wasn't too bad. Also, the French vendor wasn't someone I had dealt
with before, so I was a bit reticent to throw a significant amount of cash at
an unknown, especially considering the plethora of fakes and dodgy electronic
bits that can come up on eBay from time-to-time. I thought that the US vendor
was a safer bet on that account, too.
Understandable.

Incidentally, I am an idiot; I had a copy of the document that Stephen posted,
but I didn't look it up and use it!
Colin.
Since someone here sent me a link to this document, it’s almost become my bedside book! 😂😂😂


Re: PS503A Mod FF Photos?

Stephen
 

On Sat, Aug 22, 2020 at 03:47 AM, Colin Herbert wrote:


You have a point, there. I just thought that the +5 VDC supply might give you
more current to play with, which is so, but using it in a high-power bay, you
have 1 A available to the 0-20 VDC supplies, rather than 400mA. I suppose
someone must have thought it a good idea for the folk without a high-power
bay.
Colin.
This might indeed be the reason. Because otherwise I don’t see what this mod would add to the table...
You’re probably right.


Re: FG 504 problems

Colin Herbert
 

Yes, the cost was involved in my decision. The one from the US was cheaper and the postage wasn't too bad. Also, the French vendor wasn't someone I had dealt with before, so I was a bit reticent to throw a significant amount of cash at an unknown, especially considering the plethora of fakes and dodgy electronic bits that can come up on eBay from time-to-time. I thought that the US vendor was a safer bet on that account, too.
Incidentally, I am an idiot; I had a copy of the document that Stephen posted, but I didn't look it up and use it!
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 22 August 2020 15:13
To: TekScopes@groups.io
Subject: Re: [TekScopes] FG 504 problems

On Sat, Aug 22, 2020 at 02:49 AM, <tenareze32@gmail.com> wrote:


That is a useful document, many thanks for the link.
My pleasure.

The LH0022CH is available in France and you might get it sooner from them.
https://www.ebay.fr/itm/ci-LH-0022-CH-ic-LH0022CH-pattes-dorees-de-chez-NS-boitier-TO99/201440559996?hash=item2ee6cb037c:g:KTcAAOSwU~FWDPBK
Simon
Whaoo! That’s an expensive little thing!!!


Re: Tek 465: CH1 No signal, CH2 signal reads a fraction of input, V Pos distorts signal

Roger Evans
 

Luis,

It is fairly convincing that R429 is broken and responsible for the vertical deflection errors, you can check by measuring for resistance from the ends of R427 and R428 to ground. It should be a single turn trimpot so the fact that it continues to rotate is an indication that the adjuster is not moving the wiper and possibly the wiper is completely detached leaving no connection to ground.

Either way you need to find a replacement for this 250R preset that has about the right spacing of its fixing pins. Did you make a note of the position of R455 before you tried adjusting it? If so then put it back to that position as a starting point for your adjustments after replacing R429.

Regards,

Roger


Re: Tek 465: CH1 No signal, CH2 signal reads a fraction of input, V Pos distorts signal

Greenpitu@...
 

Just wanted to add another observation:

If I calibrate V amplifier bias for maximum deflection (as per service manual), I no longer experience signal distortion and expansion or compression when operating the V pos dial. However the signal shown is 350mV, instead of the 300mV supposedly delivered by the onboard calibration.

I should be able to get hold of a second (and calibrated) scope in the upcoming weeks and make more accurate readings.

Regards


Re: PS503A Mod FF Photos?

Colin Herbert
 

You have a point, there. I just thought that the +5 VDC supply might give you more current to play with, which is so, but using it in a high-power bay, you have 1 A available to the 0-20 VDC supplies, rather than 400mA. I suppose someone must have thought it a good idea for the folk without a high-power bay.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 22 August 2020 15:18
To: TekScopes@groups.io
Subject: Re: [TekScopes] PS503A Mod FF Photos?

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... 🤷‍♂️


Re: PS503A Mod FF Photos?

Stephen
 

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... 🤷‍♂️


Re: FG 504 problems

Stephen
 

On Sat, Aug 22, 2020 at 02:49 AM, <tenareze32@gmail.com> wrote:


That is a useful document, many thanks for the link.
My pleasure.

The LH0022CH is available in France and you might get it sooner from them.
https://www.ebay.fr/itm/ci-LH-0022-CH-ic-LH0022CH-pattes-dorees-de-chez-NS-boitier-TO99/201440559996?hash=item2ee6cb037c:g:KTcAAOSwU~FWDPBK
Simon
Whaoo! That’s an expensive little thing!!!


Re: PS503A Mod FF Photos?

Colin Herbert
 

First off, my PS 503A doesn't have the FF Mod, but you can find text relating to the mod at http://w140.com/tekwiki/images/9/91/061-3171-00.pdf. There are no photos, I'm afraid.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jared Cabot via groups.io
Sent: 21 August 2020 02:12
To: TekScopes@groups.io
Subject: [TekScopes] PS503A Mod FF Photos?

Hi,
Does anyone have a PS503A Dual Power Supply module with the Mod FF (adjustable 5v output) installed?
I'm just looking for some photos to determine the difficulty of retrofitting this mod to my unit.


Thanks!
Jared


Re: FG 504 problems

Simon
 

That is a useful document, many thanks for the link.
The LH0022CH is available in France and you might get it sooner from them.
https://www.ebay.fr/itm/ci-LH-0022-CH-ic-LH0022CH-pattes-dorees-de-chez-NS-boitier-TO99/201440559996?hash=item2ee6cb037c:g:KTcAAOSwU~FWDPBK
Simon


Re: Tek 465: CH1 No signal, CH2 signal reads a fraction of input, V Pos distorts signal

Greenpitu@...
 

Hello!

I attempted some calibration adjustments today and as per service manual to adjust the V amplifier bias (R455) and output centering (R429).

*** Vertical Amplifier Bias ***
As in previous days, Ch1 AC div/pos 0.1V connected to onboard calibrator with 300mV square signal.

Before making any adjustments, and as per previous posts, the signal displayed is just 1/3 of the input calibrator signal i.e expands one vertical division only.

Adjusting the variable resistor R455 allowed me to increase the deflection x3. So in essence, I now was able to see the full 300mV signal, expanding across 3 divisions as expected.

If I turn the V Pos in either direction the signal no longer expands by 50%, it now compresses by approx 20%.

So I guess something still not quiet right here? Also, is this the correct way of calibrating the V amplifier? I ask because the service manual says "calibrate for maximum deflection", it doesn't say "calibrate until you see what you expect to see" which is essentially what I am doing?

** Adjust Output Centering **
No input signal, Ch1 on .2 volts/div as per manual

Connected TP322 and TP324 with DMM, and turned V Pos dial until I read 0mV on meter. At this stage, the trace was at +1.1 divisions over the center graticule line.

I then tried to adjust R429 as per manual so that trace line is exactly at the center of the graticule. But I was going nowhere! No matter how many turns I went on each direction, the trace simply didn't move, it stuck at +1.1 divisions.

Does it mean its fully open and needs replacement? Is this related somehow to the signal compression problem I mentioned above?

Many thanks and best regards
Luis


Re: FG 504 problems

Stephen
 

On Sat, Aug 22, 2020 at 01:10 AM, Colin Herbert wrote:

Interleaved.

I have no idea how you got that info, but many thanks.
I took the TEK parts number you provided and checked the reference from this document:

http://w140.com/tek_xref_free.pdf

You should download it. It will make your life a lot easier.

It wasn't available
from my usual sources like Sphere Research and Qservice.
I have now bought an LH0022CH from an eBay seller in the US. I found that the
writing around the can says LH0022CH - I was fooled by there being nothing
written on the top.
I suppose that your shops 20mins away in Paris sell these, do they?
Colin.
Since these are quite old shops, they may sometimes have some old stock stashed somewhere at the back.
But I’ve just checked; not this time.

Happy I could help.


Re: FG 504 problems

Colin Herbert
 

I have no idea how you got that info, but many thanks. It wasn't available from my usual sources like Sphere Research and Qservice.
I have now bought an LH0022CH from an eBay seller in the US. I found that the writing around the can says LH0022CH - I was fooled by there being nothing written on the top.
I suppose that your shops 20mins away in Paris sell these, do they?
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 22 August 2020 11:39
To: TekScopes@groups.io
Subject: Re: [TekScopes] FG 504 problems

Colin,
156-0484-00 is a LH0022CH, which you could replace with a more modern LF411MH/883 (same pinout), but check the data sheet, or with a TLE2141ACP and countless others (but not the same pinout).
Look here: https://www.datasheets360.com/part/detail/lh0022ch/-6869668862597770303/


Re: FG 504 problems

Stephen
 

Colin,
156-0484-00 is a LH0022CH, which you could replace with a more modern LF411MH/883 (same pinout), but check the data sheet, or with a TLE2141ACP and countless others (but not the same pinout).
Look here: https://www.datasheets360.com/part/detail/lh0022ch/-6869668862597770303/


Re: FG 504 problems

Colin Herbert
 

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: 7A26 CH2 Readout

Stephen
 

After using the penetrating oil, it didn’t need to hold the front end of the BNC. After removing it, I realized there is a flat on the chassis hole, and on the plug itself, to keep it from turning, and to be inserted the right way.
It just will not move when you turn the hex nut at the back. Provided the nut is snug or just a bit tighter, it’ll turn just fine with a bit of oil. This is my first and only personal experience with removing one.


Re: 7A26 CH2 Readout

Stephen
 

In my last post, read « torque », not « torn », at the end.


Re: 7A26 CH2 Readout

Bruce Atwood
 

Use a "BNC Wrench" to hold or tighten the BNC connector. There are many different ones available or you can make your own..just a hole and a slot. Here is one that looks well made but a bit pricey. I have not used this one and I'm not associated with them.
https://www.amazon.com/BNC-Tool-Connector-Tightening-Wrench/dp/B00MEW0SCM


Re: 7A26 CH2 Readout

Jim Ford
 

Stephen and Colin, there is another way to get the BNC out. I used long-nosed pliers on the nut on the back of the BNC with just enough grip on it to keep it from turning. Then I took a rag and wrapped it around the BNC connector sticking out of the front panel so as not to mar it and grabbed the rag with regular pliers opened just enough to grip the connector without crushing it. I applied the torque to the regular pliers, and I found that they were able to grip it just tight enough to turn it and loosen the nut on the back. The space on the back is too small to get enough torque with the long-nosed pliers to break the nut loose, but it wasn't too difficult to hold the nut.

Then I did the reverse to get the BNC firmly back in place on the front panel after I did my repairs.

Hope this helps somebody.

Jim Ford

------ Original Message ------
From: "Stephen" <stephen.nabet@gmail.com>
To: TekScopes@groups.io
Sent: 8/21/2020 9:33:53 AM
Subject: Re: [TekScopes] 7A26 CH2 Readout

Thanks for the tip and offer Colin. But it’s not going to be for this repair. I messed up the BNC front end quite a bit trying to remove it. The hex screw was extremely tight and firmly stuck. Probably due to age. I had to use a lot of penetrating oil, and quite a bit of torn to get it to finally turn.
I’m just going to change it.



Re: Oscilloscope Operator Training Kit - TNGTDS01

Harvey White
 

One good source for glitches is to use a 7490 counter to drive a 1 of 10 decoder,  I think a 7442.  The decoding logic does not have a time equivalent path, and the 7490 is not synchronous.

Harvey

On 8/19/2020 1:18 PM, ebrucehunter via groups.io wrote:
Thanks Brian.

Searching online for information on the Velleman boards, I see that Jameco https://www.jameco.com/z/EDU06-Velleman-Oscilloscope-Tutor-Kit_2175568.html offers them for $29.99 .  Although inexpensive, the signals these boards generate are generally available from instruments on the bench top.  My interest in the Tektronix board is for the glitched signals it offers as a way to demonstrate the capture and storage capabilities of these DSOs for catching transient waveforms.  I have never owned a storage scope before, but on several occasions could sure have used one.

Bruce, KG6OJI




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