Topics

TG501 Help

ArtekManuals
 

I am plodding through a pile of TM500 plug-ins that I have had in a box for over 15 years. a DM502A and FG503 now fully functional and CAL'd with relative minor repairs

Next up is a TG501. This one plays nearly flawlessly and seems to pass all but one test. I thought at one point when I was reading the manual that I might try to install the ability to set it up to use an external 10MHz standard ( I have a 10MHz GPSDO distribution in my lab) but the frequency was so close on ( less than .01% ) that I said why bother.

Now there is one problem. The is 5-2-1 ns output which runs separately from the the rest of the timing markers. The 2ns and 1ns behave normally, producing 500MHz and 1GHz sine waves of acceptable amplitude respectively. The 5ns (200MHz) output however is very low and the sine wave is very "lumpy". As near as I can tell this signal goes through U450B (switch) and an amplifier chip U455 . Also peaking C450, C465 and C467 per the manual C465 at the output of U455 reaches a peak at max C ( indicating not reaching an actual peak) . As near as I can tell U455 is only involved in amplifying the 5ns/200MHz signal. So the fact that the output cap doesn't peak and the output is not a very clean leads me to believe that U455 is bad???

Anyone been down this path and confirm my conclusions? Suitable modern day replacement? The part in the TG501 is an RCA CA3028A. All the data sheets I have seen so far rate this as only a 120MHz part and this is a 200MHz application?

--
Dave
Manuals@...
www.ArtekManuals.com

Dan Rae
 

On 11/14/2016 7:42 AM, Artek Manuals manuals@... [TekScopes] wrote:
. The 5ns (200MHz) output however is very low and the sine
wave is very "lumpy". As near as I can tell this signal goes through
U450B (switch) and an amplifier chip U455 . Also peaking C450, C465 and
C467 per the manual C465 at the output of U455 reaches a peak at max C (
indicating not reaching an actual peak) . As near as I can tell U455 is
only involved in amplifying the 5ns/200MHz signal. So the fact that the
output cap doesn't peak and the output is not a very clean leads me to
believe that U455 is bad???
Dave, U455 is actually a doubler. Can you confirm that it's input is seeing 100 MHz from the switch U450B? I don't remember having trouble here with mine once all the relays were working correctly. I don't think you'll find a substitute for the CA3028A though. And C467 is a sort of level control.

73 - Dan

johncharlesgord
 

Dave, It sure could be a bad CA3028A. Have you re-socketed it to check for bad contacts?
<<http://danssmallpartsandkits.net http://danssmallpartsandkits.net/>> has them for $3.50 each.
Its just a diff pair with a current sink on the emitters, so you could probably replace it with a couple of fast npn's (2N5179?) and a resistor pulling to the negative supply on their common emitter point.
--John Gord


---In TekScopes@..., <manuals@...> wrote :

I am plodding through a pile of TM500 plug-ins that I have had in a box
for over 15 years. a DM502A and FG503 now fully functional and CAL'd
with relative minor repairs

Next up is a TG501. This one plays nearly flawlessly and seems to pass
all but one test. I thought at one point when I was reading the manual
that I might try to install the ability to set it up to use an external
10MHz standard ( I have a 10MHz GPSDO distribution in my lab) but the
frequency was so close on ( less than .01% ) that I said why bother.

Now there is one problem. The is 5-2-1 ns output which runs separately
from the the rest of the timing markers. The 2ns and 1ns behave
normally, producing 500MHz and 1GHz sine waves of acceptable amplitude
respectively. The 5ns (200MHz) output however is very low and the sine
wave is very "lumpy". As near as I can tell this signal goes through
U450B (switch) and an amplifier chip U455 . Also peaking C450, C465 and
C467 per the manual C465 at the output of U455 reaches a peak at max C (
indicating not reaching an actual peak) . As near as I can tell U455 is
only involved in amplifying the 5ns/200MHz signal. So the fact that the
output cap doesn't peak and the output is not a very clean leads me to
believe that U455 is bad???

Anyone been down this path and confirm my conclusions? Suitable modern
day replacement? The part in the TG501 is an RCA CA3028A. All the data
sheets I have seen so far rate this as only a 120MHz part and this is a
200MHz application?

--
Dave
Manuals@... mailto:Manuals@...
www.ArtekManuals.com

Albert Otten
 

Could just as well be a bad contact in the 5ns push-button switch S450A, leaving pin 9 or 10 of U450B at +5V.
Albert

gmail
 

I installed the external ref option. But not with the TTL chip from the manual, but with a GAL. One of the BNCs is used to switch from internal to external ref (with a 50 Ohm terminator switching one of the GALs inputs). Another BNC on the TM502A is then used as external ref input. So i can switch. But it doesn't make much sense if you you are using it to calibrate scopes, you won't see it on the screen :)

On mine the voodoo output (1ns) doesn't work. I attempted to fix it, but i no luck so far. It is on the to-do list.

 

Guido:
On mine the voodoo output (1ns) doesn't work. I attempted to fix it, but
i no luck so far. It is on the to-do list.
What (scope) are you using to watch that 1 ns?

Raymond

ArtekManuals
 

Ray

I think your question was directed at Guido but in my case......

I have a 7904/7A29 ( I could drag out the 7103 ...ughhh what a beast)
While technically only rated to 500MHZ (2ns) .The combo7904/7A29 combo
doesnt start rolling off until about 750MHz and is down about 6db at
1GHz (1ns)

Dave

manuals@...



On 11/14/2016 5:58 PM, @Raymond [TekScopes] wrote:

Guido:
On mine the voodoo output (1ns) doesn't work. I attempted to fix it,
but
i no luck so far. It is on the to-do list.
What (scope) are you using to watch that 1 ns?

Raymond

[Non-text portions of this message have been removed]

--
Dave
Manuals@...
www.ArtekManuals.com



[Non-text portions of this message have been removed]

 

Hi Dave,
I think your question was directed at Guido but in
my case......
You are absolutely right: I was hijacking the thread and you know what I was thinking. Like you, I can see the 1ns "pulse" on a 7904 but we've seen on this forum that 'scopes like a 2465B (not surprisingly) couldn't, falsely giving the impression that the 1ns signal wasn't there.

Raymond

gmail
 

I'm using a 7704 with 7S11/S-4 and 7T11. I can see the 5 and 2ns signals, but not the 1ns signal.
Good to hear that it is fixed!

ArtekManuals
 

Once I cleaned up the signal I use a Boonton RF voltmeter to do the
adjustments of the variable caps


Dave



On 11/15/2016 1:35 PM, 'gmail' guidozonderspam@... [TekScopes] wrote:

I'm using a 7704 with 7S11/S-4 and 7T11. I can see the 5 and 2ns
signals, but not the 1ns signal.
Good to hear that it is fixed!

[Non-text portions of this message have been removed]

--
Dave
Manuals@...
www.ArtekManuals.com



[Non-text portions of this message have been removed]

 

Triggering of real time and especially sampling oscilloscopes can be
tricky if you try to trigger on the signal you want to adjust and it
is at the limit of the oscilloscope's capability.

In some cases for the initial adjustment you might get away with using
a free running sweep. Better though is to use external triggering
with the sync output from the time-mark generator.

On Tue, 15 Nov 2016 13:47:15 -0500, you wrote:

Once I cleaned up the signal I use a Boonton RF voltmeter to do the
adjustments of the variable caps

Dave

On 11/15/2016 1:35 PM, 'gmail' guidozonderspam@... [TekScopes] wrote:

I'm using a 7704 with 7S11/S-4 and 7T11. I can see the 5 and 2ns
signals, but not the 1ns signal.

Good to hear that it is fixed!

ArtekManuals
 

Just a FYI The "Sync out" on the TG501 stops at 100ns so from 50ns and
faster you only get 100ns external trigger out

Dave
manuals@...

On 11/15/2016 2:42 PM, David @DWH [TekScopes] wrote:

Triggering of real time and especially sampling oscilloscopes can be
tricky if you try to trigger on the signal you want to adjust and it
is at the limit of the oscilloscope's capability.

In some cases for the initial adjustment you might get away with using
a free running sweep. Better though is to use external triggering
with the sync output from the time-mark generator.

On Tue, 15 Nov 2016 13:47:15 -0500, you wrote:

Once I cleaned up the signal I use a Boonton RF voltmeter to do the
adjustments of the variable caps

Dave

On 11/15/2016 1:35 PM, 'gmail' guidozonderspam@... [TekScopes]
wrote:

I'm using a 7704 with 7S11/S-4 and 7T11. I can see the 5 and 2ns
signals, but not the 1ns signal.

Good to hear that it is fixed!
--
Dave
Manuals@...
www.ArtekManuals.com



[Non-text portions of this message have been removed]

Albert Otten
 

Perhaps external checks you didn't do:
At 5-2-1 and 1 ns pressed in, you still should get a small 2 ns signal at the 2 ns output connector. If not, the S450C contact to pin 13/14 U450C might be dirty.
At the 1 ns output connector you should see nearly the same amplitude 1 ns signal regardless whether you press 1 ns in or 2 ns in. So with 2 ns pressed in you should have both the 2 ns signal at the 2 ns connector and 1 ns signal at the 1 ns connector. You said the 2 ns works then, but please check this again and then look for the 1 ns signal. If 2 ns is present but 1 ns not present then you have pinpointed the fault in the path CR515-->output connector. Is the Peltola connector properly inserted in the output BNC? (Confirmed by near zero Ohm between center pin and ground of the BNC.). A bent center pin of the Peltola can happen ;=) .
NB In verifying the above statements I did not connect both outputs, 2 ns and 1 ns, at the same time.

Albert


---In TekScopes@..., <guidozonderspam@...> wrote :

I'm using a 7704 with 7S11/S-4 and 7T11. I can see the 5 and 2ns signals, but not the 1ns signal.

 

I actually doubled checked the TG501 manual to make sure it worked
like I expected it to. I found the front panel to be a little
ambiguous.

The sync or trigger output on most (all?) time-mark generators only
rises in frequency to a certain point but it is always synchronous to
the higher frequency outputs. This allows correct triggering no
matter how poorly the output is displayed.

On Tue, 15 Nov 2016 15:23:48 -0500, you wrote:

Just a FYI The "Sync out" on the TG501 stops at 100ns so from 50ns and
faster you only get 100ns external trigger out

Dave
manuals@...

On 11/15/2016 2:42 PM, David @DWH [TekScopes] wrote:

Triggering of real time and especially sampling oscilloscopes can be
tricky if you try to trigger on the signal you want to adjust and it
is at the limit of the oscilloscope's capability.

In some cases for the initial adjustment you might get away with using
a free running sweep. Better though is to use external triggering
with the sync output from the time-mark generator.

ArtekManuals
 

David et all

How "crisp" are your timing spikes in the 50, 20 and 10ns ranges? Mine
have a lot of ringing and one has a double peak. I an beginning to
wonder if I dont have other switching diodes problem in that chain as well?

You are correct about the sync of the external trigger out ..they all
trace themselves back to the same master oscillator. And you doubly
correct about the front panel being a bit ambiguous on the 5-2-1ns
switches and which outputs show up where

Dave

manuals@...




On 11/15/2016 8:41 PM, David @DWH [TekScopes] wrote:

I actually doubled checked the TG501 manual to make sure it worked
like I expected it to. I found the front panel to be a little
ambiguous.

The sync or trigger output on most (all?) time-mark generators only
rises in frequency to a certain point but it is always synchronous to
the higher frequency outputs. This allows correct triggering no
matter how poorly the output is displayed.
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--
Dave
Manuals@...
www.ArtekManuals.com



[Non-text portions of this message have been removed]

gmail
 

Hi all, Albert, thanks for the input.

Had to figure out where i stopped last time i worked on the unit. Turned out that CR515 was completely missing... I collected BA280 and MBD101 SMD diodes in the past. Tried both connected to the 2ns output and the BA280 looked most promissing, so i put that one in. Then after some tweaking i now have 1ns out :)

It is only about 120mV but i have no idea if the very good looking cable is really that good (RG142). It is also not completely stable, the whole sine jumps up and down a bit. Not sure if it is the TG501 or the sampling unit, but at least there is an output.

The offset out voltage of the 7T11 shows a lot of peaks (540mV peak-peak at 28kHz, so 35.7us apart). Zoom in and you see a dying out 23MHz sine for some 1.2us. My initial thought would be that the 7704A switching power supply causes this. It is all old stuff :) But it also seems to matter which TM i use for the TG502. One gives a more "jumpy" result than number two. Time for a recap.

The TG503 2ns is a whopping 1.5V peak to peak. Not the nicest sine but the higest amplitude to get most out of 1ns. 5ns is 1V and looks ok.
The 2465 sees also 1V with 5ns, 0.8V with 2ns and a few mV at 1ns. Not much, but it is a sine at one GHz :) Triggering of channel two, x10 mag on.

I don't have any other source or scope in the voodoo region, but it is good to have at least something to work with if needed. From what i read getting a trace on the 7S11/7T11 is already an achievement on its own.

Cheers
Guido

ArtekManuals
 

On 11/18/2016 6:52 PM, 'gmail' guidozonderspam@... [TekScopes] wrote:

Hi all, Albert, thanks for the input.

Had to figure out where i stopped last time i worked on the unit.
Turned out that CR515 was completely missing... I collected BA280 and
MBD101 SMD diodes in the past. Tried both connected to the 2ns output
and the BA280 looked most promissing, so i put that one in. Then after
some tweaking i now have 1ns out :)

It is only about 120mV
How are you measuring this? with the 7T11?

but i have no idea if the very good looking cable is really that good
(RG142). It is also not completely stable, the whole sine jumps up and
down a bit. Not sure if it is the TG501 or the sampling unit, but at
least there is an output.
Make sure the out put is terminated in 50 ohms, preferrably at the
output of the TG501 with one of those pass through BNC
terminations..lack of termination can result in all kinds of weird
ringing at this frequency (it is easy to forget that 1ns is really a
1GHz sine in this case. Use the trigger out from the TG501 to trigger
the scope and see if that helps

The offset out voltage of the 7T11 shows a lot of peaks (540mV
peak-peak at 28kHz, so 35.7us apart). Zoom in and you see a dying out
23MHz sine for some 1.2us. My initial thought would be that the 7704A
switching power supply causes this. It is all old stuff :) But it also
seems to matter which TM i use for the TG502. One gives a more "jumpy"
result than number two. Time for a recap.

The TG503 2ns is a whopping 1.5V peak to peak. Not the nicest sine but
the higest amplitude to get most out of 1ns. 5ns is 1V and looks ok.
The 2465 sees also 1V with 5ns, 0.8V with 2ns and a few mV at 1ns. Not
much, but it is a sine at one GHz :) Triggering of channel two, x10
mag on.
Again make sure you are terminated in 50 ohms this will clean things up
if your not. Also you should do all the tuning of the 5/2/1ns sections
terminated this can effect some of the tuning and the tuning interacts
so you have to go through it more than once


I don't have any other source or scope in the voodoo region, but it is
good to have at least something to work with if needed. From what i
read getting a trace on the 7S11/7T11 is already an achievement on its
own.
An RF voltmeter (Boonton or HP) is good at this frequency especially
for tuning the caps in the RF filters in the 5-2-1 sections


Cheers
Guido
--
Dave
Manuals@...
www.ArtekManuals.com

gmail
 

Hi,

The 120mV (p-p) is measured with the 7S11/S4/7T11 combo. The S4 is 50Ohms in. And yes, i used the trigger out as external trigger for the 7T11. And I did tweak the settings of the 1/2/5nS outputs more than once.

The whole sine jumps up and down on the screen; it really looks like the DC component is not stable. That's why i looked at the offset out of the 7S11. Which is not clean. (signal every 35.7us on the DC component; dying out 23MHz sine for some 1.2us). But i don't know if this is related. Also don't know if it is the TG or the sampler which is doing this (maybe it is even the 7704A mainframe, that i could test i guess by using another mainframe). i'll have a go at that, i have a 7623A to try.

The adjustment procedure for the TG501 says to use a sampling scope for adjusting the 5/2/1 signals (5S14). I used the 7S11/7T11. Don't have anything else at the moment.

Cheers,
Guido

mosaicmerc
 

What bandwidth is needed for this TG501 cal? I have an in-cal TDS694C, 3Ghz scope with 4Ghz probes for Hi imp sampling.

ArtekManuals
 

I think Tek suggested the sampling scope because when the TG501 was
first released they didn't have a scope that mere mortals could afford
that would go to 1 GHZ. Why they just didn't suggest peaking the 2ns and
1ns out with a RF voltmeter will always be a mystery I guess ??

Dacve

On 11/20/2016 6:13 PM, 'gmail' guidozonderspam@... [TekScopes] wrote:

Hi,

The 120mV (p-p) is measured with the 7S11/S4/7T11 combo. The S4 is
50Ohms in. And yes, i used the trigger out as external trigger for the
7T11. And I did tweak the settings of the 1/2/5nS outputs more than once.

The whole sine jumps up and down on the screen; it really looks like
the DC component is not stable. That's why i looked at the offset out
of the 7S11. Which is not clean. (signal every 35.7us on the DC
component; dying out 23MHz sine for some 1.2us). But i don't know if
this is related. Also don't know if it is the TG or the sampler which
is doing this (maybe it is even the 7704A mainframe, that i could test
i guess by using another mainframe). i'll have a go at that, i have a
7623A to try.

The adjustment procedure for the TG501 says to use a sampling scope
for adjusting the 5/2/1 signals (5S14). I used the 7S11/7T11. Don't
have anything else at the moment.

Cheers,
Guido

[Non-text portions of this message have been removed]

--
Dave
Manuals@...
www.ArtekManuals.com