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Hello everyone!
Although this topic belongs to my 8350B restoration thread I did almost a year ago, I want to imprint some relevance. Shortly, my 8350B mainframe doesn’t have main transformer. Instead of that I feed it with three external sources.
These days I managed to get a 83592A plugin in two separated parts sets. I have put them together and after some power supply issues (classic shorted tantalum), there’s no errors displayed.?But no RF coming out.?Unleveled LED lits in the front panel.?Also no RF at the rear aux output, nor at the exit of YO itself (God shake! it’s tricky to access microcircuits!).
Following the signal path and troubleshooting notes on the manual, I check that the +5, +20, -40 supplies for the YO are present. Also the ON -10 volt signal and the M composite signal on scope. At first glance, G bias signal (which should be -2 volt) was almost 0. I check the associated components and after turning a pot, -2 volt come back.
Still no signal at the output of the oscillator :(?
Is there any other way to check the YO before officially declaring it dead?
Regards,
Ruben
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Hi Ruben,
Have you checked the current through the tuning coil? Probably best to set the 8350 to CW, and try a few different frequencies.
Regards, Askild
Hello everyone!
Although this topic belongs to my 8350B restoration thread I did almost a year ago, I want to imprint some relevance. Shortly, my 8350B mainframe doesn’t have main transformer. Instead of that I feed it with three external sources.
These days I managed to get a 83592A plugin in two separated parts sets. I have put them together and after some power supply issues (classic shorted tantalum), there’s no errors displayed.?But no RF coming out.?Unleveled LED lits in the front panel.?Also no RF at the rear aux output, nor at the exit of YO itself (God shake! it’s tricky to access microcircuits!).
Following the signal path and troubleshooting notes on the manual, I check that the +5, +20, -40 supplies for the YO are present. Also the ON -10 volt signal and the M composite signal on scope. At first glance, G bias signal (which should be -2 volt) was almost 0. I check the associated components and after turning a pot, -2 volt come back.
Still no signal at the output of the oscillator :(?
Is there any other way to check the YO before officially declaring it dead?
Regards,
Ruben
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Hi Askild
You mean the main coil or the FM coil??
Maybe I should do a test setup and measure de current drawing of both coils, heater and final stage FET amplifier…
Regards,
Ruben
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Hi Ruben,
I was thinking of the main coil. The FM coil can be ignored for now, as it only affect the frequency a little. Probably good to check the heater and FET drive as well.
Regards, Askild
Hi Askild
You mean the main coil or the FM coil??
Maybe I should do a test setup and measure de current drawing of both coils, heater and final stage FET amplifier…
Regards,
Ruben
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Rubin -
Two things to do:
1) Check ALL voltages to YIG sub assembly and check cable connections
2) Measure the YIG main coil current - you can ignore the FM coil - there will be a resistor used to sense the current somewhere in the circuit - measure the voltage across this resistor. Be sure the current is within expected values.
If no output, look for broken coac or measure output directly from the YIG
How is your 8660 coming ??
Cheers!
Bruce
Quoting RubenRubio <rubenrb2019@...>:
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Show quoted text
Hello everyone!
Although this topic belongs to my 8350B restoration thread I did almost a year ago, I want to imprint some relevance. Shortly, my 8350B mainframe doesn’t have main transformer. Instead of that I feed it with three external sources.
These days I managed to get a 83592A plugin in two separated parts sets. I have put them together and after some power supply issues (classic shorted tantalum), there’s no errors displayed. *But no RF coming out.* Unleveled LED lits in the front panel.?Also no RF at the rear aux output, nor at the exit of YO itself (God shake! it’s tricky to access microcircuits!).
Following the signal path and troubleshooting notes on the manual, I check that the +5, +20, -40 supplies for the YO are present. Also the ON -10 volt signal and the M composite signal on scope. At first glance, G bias signal (which should be -2 volt) was almost 0. I check the associated components and after turning a pot, -2 volt come back.
Still no signal at the output of the oscillator :(
Is there any other way to check the YO before officially declaring it dead?
Regards,
Ruben
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Ok, let’s do a test set up for current measurements. My plan: separate the oscillator board and make jumpers between both with wire to open them and put the ammeter.
Bruce - I’m measuring rf output directly from the YO, as you can see in the image.
8660 still waiting for pll alignment… coming soon
Askild - I will do heater, main coil and FET measurements. I need to be sure before tosh the YO…
Yesterday I got a little frustrated after seeing that there was no rf signal. So I replaced the YIG oscillator with a sweep signal from my 8341A. This way it proves that the ALC, amps, mixer and multiplier work reasonably well. It's hard to match the SYTM and the 8341A, but after doing a lot of free run sweeps and recording the maximums in the 8566B, I was able to observe a flat and stable amplitude response in all four freq bands of the 83592A. So I can say that the ‘frankenstein’ plugin seems to work except for YO. At least a good new for me to continue the project ;)
Regards,
Ruben
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QuotingRubin -
You should not need to break the main coil circuit to measure the current - that may affect the stability of the circuit.
Look at the main drive circuit. You will find a resistor (usually several in parallel) that the current control circuit uses to establish the YIG current. Simply measure the current across that resistor.
Cheers!
Bruce
RubenRubio <rubenrb2019@...>:
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Show quoted text
Ok, let’s do a test set up for current measurements. My plan: separate the oscillator board and make jumpers between both with wire to open them and put the ammeter.
Bruce - I’m measuring rf output directly from the YO, as you can see in the image.
8660 still waiting for pll alignment… coming soon
Askild - I will do heater, main coil and FET measurements. I need to be sure before tosh the YO…
Yesterday I got a little frustrated after seeing that there was no rf signal. So I replaced the YIG oscillator with a sweep signal from my 8341A. This way it proves that the ALC, amps, mixer and multiplier work reasonably well. It's hard to match the SYTM and the 8341A, but after doing a lot of free run sweeps and recording the maximums in the 8566B, I was able to observe a flat and stable amplitude response in all four freq bands of the 83592A. So I can say that the ‘frankenstein’ plugin seems to work except for YO. At least a good new for me to continue the project ;)
Regards,
Ruben
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Yup, you got point :)
I’ll search a resistor to apply that method, ohm law at it’s best.
Regards,
Ruben
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Hello there!
These days I have been thinking about the fate of this project. I am referring to the 83592A plugin and the 8350B mainframe, which have not turned out to be excellent investments (although they were at a didactic level, that’s for sure).
If finally it’s toasted, I don't feel like buying an YIG oscillator. What's more, I don't feel like putting more money into this project.?
I've been thinking of making a tracking generator for my 8566B out of it. Bands 0 and 1. I heard it’s fairly easy to do.?I imagine doing that on the other bands also need to align the SYTM of the plugin with the SA, and that’s impossible,?what you?think?
Regards,
Ruben
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Hi Ruben,
I don’t have a direct answer to your question. But, if you haven’t already seen it, this webpage may be helpful to you:
Matt
Hello there!
These days I have been thinking about the fate of this project. I am referring to the 83592A plugin and the 8350B mainframe, which have not turned out to be excellent investments (although they were at a didactic level, that’s for sure).
If finally it’s toasted, I don't feel like buying an YIG oscillator. What's more, I don't feel like putting more money into this project.?
I've been thinking of making a tracking generator for my 8566B out of it. Bands 0 and 1. I heard it’s fairly easy to do.?I imagine doing that on the other bands also need to align the SYTM of the plugin with the SA, and that’s impossible,?what you?think?
Regards,
Ruben
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Also I read about this on Kerry Wong blog and CuriousMarc video.
For the first harmonic band I need to place a mixer in the upper path. So the mod only be possible on band 0 (0 to 2.5 GHz)
Because the benefits of leveling circuitry, I'll give it a try for didactic and entertainment purposes, but still not happy with the project...
Regards,
Ruben
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Reading the schematics, I bring you some ideas, correct me if i'm wrong:
- I must measure the voltage drop across R1 (one of the power resistors in the plugin) and that will reveal the current sent to the YO coil, isn't it?
- The black heatsink on A9 board it's always hot. I think it is hotter than it should be, should check Q1 too? Maybe the transistor is shorted and it doesn't send sufficient current to drive the YO. What you think?
Regards,
Ruben
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Ruben -
Probably the easiest check is to see if the voltage across the resistor changes with frequency. Somewhere in the service manual, they should give you the ma/Hz number for this circuit. If that works out correctly, the YIG drive is OK. If the current is different than specified, the problem is with the YIG drive circuit. Also, be sure you are measuring the main YIG drive and not the FM coil. Bu be sure to check the current in the FM cil as it also can cause problems (usually less frequently).
Cheers!
Quoting RubenRubio <rubenrb2019@...>:
toggle quoted message
Show quoted text
Reading the schematics, I bring you some ideas, correct me if i'm wrong:
- I must measure the voltage drop across R1 (one of the power resistors in the plugin) and that will reveal the current sent to the YO coil, isn't it?
- The black heatsink on A9 board it's always hot. I think it is hotter than it should be, should check Q1 too? Maybe the transistor is shorted and it doesn't send sufficient current to drive the YO. What you think?
Regards,
Ruben
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If that test fails (I or V not changing) check the drive V to Q1.
If that is changing but the I does not (or the V across the R), suspect Q1.
Mark
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Ruben -
Probably the easiest check is to see if the voltage across the?
resistor changes with frequency.? Somewhere in the service manual,?
they should give you the ma/Hz number for this circuit.? If that works?
out correctly, the YIG drive is OK.? If the current is different than?
specified, the problem is with the YIG drive circuit.? Also, be sure?
you are measuring the main YIG drive and not the FM coil.? Bu be sure?
to check the current in the FM cil as it also can cause problems?
(usually less frequently).
Cheers!
Quoting RubenRubio <rubenrb2019@...>:
> Reading the schematics, I bring you some ideas, correct me if i'm wrong:
>
> - I must measure the voltage drop across R1 (one of the power?
> resistors in the plugin) and that will reveal the current sent to?
> the YO coil, isn't it?
>
> - The black heatsink on A9 board it's always hot. I think it is?
> hotter than it should be, should check Q1 too? Maybe the transistor?
> is shorted and it doesn't send sufficient current to drive the YO.?
> What you think?
>
> Regards,
> Ruben
>
>
>
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Following the service manual:
- Voltage across R1 is changing both in auto and manual sweeps, between 14 and 24 volts, from 10 meg to 20 gig, respectively.?
- Waveforms described in the figures are present at the test points given
- Also checked R1 and Q1 with DMM, both are ok.
So if you don't have any more ideas, I have a dead YIG oscillator :(
Regards,
Ruben
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just for clarification are you saying one yig can sweep from 10 meg to 20 gig ?
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From: [email protected] [mailto:[email protected]] On Behalf Of RubenRubio
Sent: 12 March 2023 13:29
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] 5086-7337 *Yig Oscillator issue* ? Following the service manual:
- Voltage across R1 is changing both in auto and manual sweeps, between 14 and 24 volts, from 10 meg to 20 gig, respectively.?
- Waveforms described in the figures are present at the test points given
- Also checked R1 and Q1 with DMM, both are ok.
So if you don't have any more ideas, I have a dead YIG oscillator :(
Regards,
Ruben
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Of course not
My mistake, those voltage values are present during mainframe command sweeps, in this case, from 10 meg to 20 gig. YO supose to do four sweeps at different freq spans to cover all bands.
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Actually from 2.3 to 7 gig, aprox.
In the general block diagram, there is a detail of those figures per band.?
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Hi Ruben? I do know that the 10 meg to 20 Ghx is in 4 bands I was just checking you hadn’t started looking at the fault wrongly ? If I am fault finding on the Multiplier plug ins ??I start at the fundamental? yig frequency once that works then the others start to play ?
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Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of RubenRubio
Sent: 12 March 2023 15:54
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] 5086-7337 *Yig Oscillator issue* ? Of course not
My mistake, those voltage values are present during mainframe command sweeps, in this case, from 10 meg to 20 gig. YO supose to do four sweeps at different freq spans to cover all bands.
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I got it
I will measure again using the first harmonic band. Will post here the exact results.
I am reluctant to think that the oscillator is dead, I hope that there is more ways to check it. The service manual don’t have any more. My knowledge is limited, but?I usually have intuition for these things.
Thanks Paul
Regards,
Ruben?
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RubenRubio
Paul Bicknell
