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184 Time Mark Gen. - 2nS & 5nS not working


david
 

I put a 4.7pF MLCC in series with C11 and got the oscillator tuned. It is cycling between 10.000005MHz and 9.999994MHz. How bout that :) It was trial & error, it's kinda strange, I tried 2.5pF and then 5.6pF and neither one would increase the frequency much at all. I tried the 4.7pF last and it worked perfectly. C11 is in the middle of it's adjustment range now. Overkill? Yep.
David


Tom Gardner
 

Make sure you block any DC, and are very careful about the input power! If the DC block is a large capacitor (e.g. works to  kHz rather than MHz), consider whether any transients might be large.

Overkill? Possibly :)

On 08/04/20 03:17, Merchison Burke via groups.io wrote:
If you have a Spectrum Analyser, could that be used to check to 500 MHz output?


On 2020-04-07 9:22 a.m., david via groups.io wrote:
Thanks for the information guys, looks like I don't have the equipment or the knowledge to fix the 500MHz output. Not going to buy Nuvistors if I won't be able to check the results. My 465 is a 100MHz scope, it  shows 130mVpp signal at 200MHz output, so I believe that signal is OK. This 184 is working correctly except for the 500MHz. Only other issue is the 10MHz oscillator frequency does not have enough adjustment range. It is close enough, checking it with a GPSDO at 10MHz it is 9.999xxx, but it is at the limit of adjustment on C11. Any idea why the oscillator is beyond the range of C11 adjustment? Is it just the age of the crystal? Has anyone tried to reduce value of capacitor C11 by putting another cap in series with it? Only need to lower value of C11 a couple pF to fix it. I am amazed at how accurate this 184 is being all analog.
David



Melvin Gleep
 

Absolutely.

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Von: Merchison Burke via groups.io<mailto:merchison=yahoo.co.uk@groups.io>
Gesendet: Mittwoch, 8. April 2020 04:17
An: TekScopes@groups.io<mailto:TekScopes@groups.io>
Betreff: Re: [TekScopes] 184 Time Mark Gen. - 2nS & 5nS not working

If you have a Spectrum Analyser, could that be used to check to 500 MHz
output?


On 2020-04-07 9:22 a.m., david via groups.io wrote:
Thanks for the information guys, looks like I don't have the equipment or the knowledge to fix the 500MHz output. Not going to buy Nuvistors if I won't be able to check the results. My 465 is a 100MHz scope, it shows 130mVpp signal at 200MHz output, so I believe that signal is OK. This 184 is working correctly except for the 500MHz. Only other issue is the 10MHz oscillator frequency does not have enough adjustment range. It is close enough, checking it with a GPSDO at 10MHz it is 9.999xxx, but it is at the limit of adjustment on C11. Any idea why the oscillator is beyond the range of C11 adjustment? Is it just the age of the crystal? Has anyone tried to reduce value of capacitor C11 by putting another cap in series with it? Only need to lower value of C11 a couple pF to fix it. I am amazed at how accurate this 184 is being all analog.
David



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Merchison Burke
 

If you have a Spectrum Analyser, could that be used to check to 500 MHz output?

On 2020-04-07 9:22 a.m., david via groups.io wrote:
Thanks for the information guys, looks like I don't have the equipment or the knowledge to fix the 500MHz output. Not going to buy Nuvistors if I won't be able to check the results. My 465 is a 100MHz scope, it shows 130mVpp signal at 200MHz output, so I believe that signal is OK. This 184 is working correctly except for the 500MHz. Only other issue is the 10MHz oscillator frequency does not have enough adjustment range. It is close enough, checking it with a GPSDO at 10MHz it is 9.999xxx, but it is at the limit of adjustment on C11. Any idea why the oscillator is beyond the range of C11 adjustment? Is it just the age of the crystal? Has anyone tried to reduce value of capacitor C11 by putting another cap in series with it? Only need to lower value of C11 a couple pF to fix it. I am amazed at how accurate this 184 is being all analog.
David

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Melvin Gleep
 

I have not had the need, but I do not see any reason why putting a cap in series would not be worth trying.

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Von: david via groups.io<mailto:davide_us=yahoo.com@groups.io>
Gesendet: Dienstag, 7. April 2020 15:23
An: TekScopes@groups.io<mailto:TekScopes@groups.io>
Betreff: Re: [TekScopes] 184 Time Mark Gen. - 2nS & 5nS not working

Thanks for the information guys, looks like I don't have the equipment or the knowledge to fix the 500MHz output. Not going to buy Nuvistors if I won't be able to check the results. My 465 is a 100MHz scope, it shows 130mVpp signal at 200MHz output, so I believe that signal is OK. This 184 is working correctly except for the 500MHz. Only other issue is the 10MHz oscillator frequency does not have enough adjustment range. It is close enough, checking it with a GPSDO at 10MHz it is 9.999xxx, but it is at the limit of adjustment on C11. Any idea why the oscillator is beyond the range of C11 adjustment? Is it just the age of the crystal? Has anyone tried to reduce value of capacitor C11 by putting another cap in series with it? Only need to lower value of C11 a couple pF to fix it. I am amazed at how accurate this 184 is being all analog.
David


david
 

Thanks for the information guys, looks like I don't have the equipment or the knowledge to fix the 500MHz output. Not going to buy Nuvistors if I won't be able to check the results. My 465 is a 100MHz scope, it shows 130mVpp signal at 200MHz output, so I believe that signal is OK. This 184 is working correctly except for the 500MHz. Only other issue is the 10MHz oscillator frequency does not have enough adjustment range. It is close enough, checking it with a GPSDO at 10MHz it is 9.999xxx, but it is at the limit of adjustment on C11. Any idea why the oscillator is beyond the range of C11 adjustment? Is it just the age of the crystal? Has anyone tried to reduce value of capacitor C11 by putting another cap in series with it? Only need to lower value of C11 a couple pF to fix it. I am amazed at how accurate this 184 is being all analog.
David


robeughaas@...
 

It would take the bandwidth of at least a 485 (350MHz) to verify the level of the 5 or 2 nS outputs. At 500 MHz, a well-tweaked 485 has a response down about 40%, so the 2nS output would measure less than 200mV if it meets spec. The vintageTEK Museum recently restored and sold a number of 184's. To do so required going through our entire stock of nuvistors with a curve tracer and picking the best ones for the 5 and 2nS outputs. Even then, tuning is extremely critical,and changes with the instrument in and out of the case. Also, the stages leading up to the highest frequency need to be tuned well -- LILO! Low in, low out.

--
Bob Haas


Tom Gardner
 

On 04/04/20 00:28, david via groups.io wrote:
I don't have an oscilloscope with enough bandwidth to check the 200Mhz or the 500Mhz output. My 465 is 100Mhz and it doesn't have a trigger setting fast enough to trigger on the 200Mhz. My digital scope is 50Mhz but trigger goes to 5nS so I can see the 200Mhz. I think the bandwidth is why I'm only seeing 88mV peak to peak @ 200Mhz., If the 500Mhz is supposed to be 300mV peak to peak would I still be able to see it?
David
My 350MHz Tek 485 displays and triggers on a 1GHz signal. Naturally the trace's amplitude is significantly reduced.

The triggering continues to work, provided trace amplitude is >0.2 divisions.


david
 

I don't have an oscilloscope with enough bandwidth to check the 200Mhz or the 500Mhz output. My 465 is 100Mhz and it doesn't have a trigger setting fast enough to trigger on the 200Mhz. My digital scope is 50Mhz but trigger goes to 5nS so I can see the 200Mhz. I think the bandwidth is why I'm only seeing 88mV peak to peak @ 200Mhz., If the 500Mhz is supposed to be 300mV peak to peak would I still be able to see it?
David


Tom Gardner
 

ISTR I improved my 500MHz oscillator's output by modifying the coupling in the L69/L70 transformer.

Yup, I pushed the L70 wire so the two halves of the transformer were closer together :)

I also kept in mind that the purpose is to provide timing accuracy, not amplitude accuracy. Sometimes life is too short.

Oh, I did buy a NOS nuvistor for around £10.

On 03/04/20 21:24, Dave Seiter wrote:
I've had three 184s over the years, and I've never had one in which the 2 and 5nS sections worked correctly.  I gave up trying to fix the last one.  Maybe if you get some good leads I'll give mine another go (since I have so much time on my hands anyway!)
-Dave
On Friday, April 3, 2020, 01:06:15 PM PDT, david via groups.io <davide_us=yahoo.com@groups.io> wrote:
Only issue I have left to fix is the 5nS sine output is only 88mVpp. should be minimum of 0.3Vpp, and the 2nS sine output is not working at all. Have 100Mhz  3.7Vpp at input to 2nS board, no output. Have 2Vpp 100Mhz at input to 5nS board, only 88mVpp @ 50 ohm 200Mhz at output. Can any one help? I am wondering if either of the tubes V60 or V70 on 2nS board could be bad. Is there any way to check?  Is it possible that the 5nS output is only 88mV because of the low input of only 2Vpp ? Could the forward voltage drop on the diodes of the doubler  be that much?


Melvin Gleep
 

You can check for bad nuvistors by simply swapping positions with other nuvistors – just be sure to note which nuvistors you swap and insure you swap back to their original places, otherwise you will have to do a complete recalibration.

My 184 is working completely within specs, but I do remember I had to do some tweaking on the Position between L69 and L70 to get the proper Amplitude. The tuning of the 200 Mhz and 500 Mhz boards is very sensitive, but if your components are all OK, following the calibration instructions diligently should get you to good results.


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Von: david via groups.io<mailto:davide_us=yahoo.com@groups.io>
Gesendet: Freitag, 3. April 2020 22:06
An: TekScopes@groups.io<mailto:TekScopes@groups.io>
Betreff: [TekScopes] 184 Time Mark Gen. - 2nS & 5nS not working

Only issue I have left to fix is the 5nS sine output is only 88mVpp. should be minimum of 0.3Vpp, and the 2nS sine output is not working at all. Have 100Mhz 3.7Vpp at input to 2nS board, no output. Have 2Vpp 100Mhz at input to 5nS board, only 88mVpp @ 50 ohm 200Mhz at output. Can any one help? I am wondering if either of the tubes V60 or V70 on 2nS board could be bad. Is there any way to check? Is it possible that the 5nS output is only 88mV because of the low input of only 2Vpp ? Could the forward voltage drop on the diodes of the doubler be that much?


 

If your 2ns and 5ns outputs have low output it's worth checking the nuvistors.

D.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Seiter
Sent: 03 April 2020 21:24
To: TekScopes@groups.io
Subject: Re: [TekScopes] 184 Time Mark Gen. - 2nS & 5nS not working

I've had three 184s over the years, and I've never had one in which the 2 and 5nS sections worked correctly. I gave up trying to fix the last one. Maybe if you get some good leads I'll give mine another go (since I have so much time on my hands anyway!)
-Dave
On Friday, April 3, 2020, 01:06:15 PM PDT, david via groups.io <davide_us=yahoo.com@groups.io> wrote:

Only issue I have left to fix is the 5nS sine output is only 88mVpp. should be minimum of 0.3Vpp, and the 2nS sine output is not working at all. Have 100Mhz 3.7Vpp at input to 2nS board, no output. Have 2Vpp 100Mhz at input to 5nS board, only 88mVpp @ 50 ohm 200Mhz at output. Can any one help? I am wondering if either of the tubes V60 or V70 on 2nS board could be bad. Is there any way to check? Is it possible that the 5nS output is only 88mV because of the low input of only 2Vpp ? Could the forward voltage drop on the diodes of the doubler be that much?


Dave Seiter
 

I've had three 184s over the years, and I've never had one in which the 2 and 5nS sections worked correctly.  I gave up trying to fix the last one.  Maybe if you get some good leads I'll give mine another go (since I have so much time on my hands anyway!)
-Dave

On Friday, April 3, 2020, 01:06:15 PM PDT, david via groups.io <davide_us=yahoo.com@groups.io> wrote:

Only issue I have left to fix is the 5nS sine output is only 88mVpp. should be minimum of 0.3Vpp, and the 2nS sine output is not working at all. Have 100Mhz  3.7Vpp at input to 2nS board, no output. Have 2Vpp 100Mhz at input to 5nS board, only 88mVpp @ 50 ohm 200Mhz at output. Can any one help? I am wondering if either of the tubes V60 or V70 on 2nS board could be bad. Is there any way to check?  Is it possible that the 5nS output is only 88mV because of the low input of only 2Vpp ? Could the forward voltage drop on the diodes of the doubler  be that much?


david
 

Only issue I have left to fix is the 5nS sine output is only 88mVpp. should be minimum of 0.3Vpp, and the 2nS sine output is not working at all. Have 100Mhz 3.7Vpp at input to 2nS board, no output. Have 2Vpp 100Mhz at input to 5nS board, only 88mVpp @ 50 ohm 200Mhz at output. Can any one help? I am wondering if either of the tubes V60 or V70 on 2nS board could be bad. Is there any way to check? Is it possible that the 5nS output is only 88mV because of the low input of only 2Vpp ? Could the forward voltage drop on the diodes of the doubler be that much?