|
Try as I might, the 10Mhz crystal oscillator will not quite make it to 10MHz. The trimmer will get it to about 9.99987 (or something close to that) but I can't quite get 10MHz. I presume the crystal just can't be "pulled" enough and not sure if C11 is closer to 3pF or 12pF but I presume it's 3pF. Is there anything else that might be preventing the circuit from being set to either + or - with the cap? Is it possible the cap really isn't doing 3pF to 12pF anymore and, perhaps, needs to be disassembled and cleaned?
9.999x is really close enough but it's annoying to not be able to put it spot on (or, at least, closer to it).
Thanks,
Barry - N4BUQ
|
The advertised spec is +/- 0.001%, so (if my math is right) you are will within the advertised precision.
The circuit in which Y11 operates looks pretty simple, the only components around it are C11, R11, L18, and V10. I'd have a look at R11 to be sure it hadn't drifted (the parts list seems to indicate that it's an unremarkable carbon comp resistor, with 10% accuracy). You could also remove the Nuvistor and the crystal in order to check C11 in place. I expect that both V10 and Y11 are socketed, but I can't really tell about the crystal oven from the pictures in the service manual, so it might be easier to unsolder C11 than to remove Y11.
-- Jeff Dutky
|
How long a warmup time are you giving the crystal before trying to cal.
Also how is your probing set up? This circuit is incredably sensitive to
capacitance. Not enough heat in the crystal and or too much capacitance in
the probing set up will drag the crystal off to the low side of things.
Eric
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Show quoted text
On Tue, Dec 7, 2021, 12:41 AM Jeff Dutky <jeff.dutky@...> wrote: The advertised spec is +/- 0.001%, so (if my math is right) you are will
within the advertised precision.
The circuit in which Y11 operates looks pretty simple, the only components
around it are C11, R11, L18, and V10. I'd have a look at R11 to be sure it
hadn't drifted (the parts list seems to indicate that it's an unremarkable
carbon comp resistor, with 10% accuracy). You could also remove the
Nuvistor and the crystal in order to check C11 in place. I expect that both
V10 and Y11 are socketed, but I can't really tell about the crystal oven
from the pictures in the service manual, so it might be easier to unsolder
C11 than to remove Y11.
-- Jeff Dutky
|
Oh, I forgot to say: the trim cap looks like the same kind that was used in some 500-series scopes. With great care they can be disassembled and cleaned.
Here is a video showing the process
If you watch the video (it's a bit slow going) the video creator notes that one of the metallized disks is corroded which limits the upper range of the capacitor. You may have a similar problem.
-- Jeff Dutky
|
Hi Jeff,
Y11 is mounted in an an octal plug along with its heater so I can unplug that if need be. I have disassembled a trimmer similar to the one used for C11 and, as I recall, it did need some cleanup (I seem to recall the silver had migrated but that's a distant memory) so I was considering a cleanup for this on as well.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Jeff Dutky" <jeff.dutky@...>
To: "tekscopes" <[email protected]>
Sent: Monday, December 6, 2021 11:41:47 PM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator The advertised spec is +/- 0.001%, so (if my math is right) you are will within
the advertised precision.
The circuit in which Y11 operates looks pretty simple, the only components
around it are C11, R11, L18, and V10. I'd have a look at R11 to be sure it
hadn't drifted (the parts list seems to indicate that it's an unremarkable
carbon comp resistor, with 10% accuracy). You could also remove the Nuvistor
and the crystal in order to check C11 in place. I expect that both V10 and Y11
are socketed, but I can't really tell about the crystal oven from the pictures
in the service manual, so it might be easier to unsolder C11 than to remove
Y11.
-- Jeff Dutky
|
Hi Eric,
I probably did not perform a suitable warmup as I had considered that was more of a drift issue than anything. I presumed that if I can't get a +/- swing cold, then something may be wrong but that may not be correct. I'm letting it do a proper warmup and will recheck.
I'm pretty sure I was checking that via the output connector (per the manual) so that shouldn't have offset the oscillator with unnecessary capacitance (but thanks for the reminder about that).
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Eric" <ericsp@...>
To: "tekscopes" <[email protected]>
Sent: Monday, December 6, 2021 11:55:53 PM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator How long a warmup time are you giving the crystal before trying to cal.
Also how is your probing set up? This circuit is incredably sensitive to
capacitance. Not enough heat in the crystal and or too much capacitance in
the probing set up will drag the crystal off to the low side of things.
Eric
On Tue, Dec 7, 2021, 12:41 AM Jeff Dutky <jeff.dutky@...> wrote:
The advertised spec is +/- 0.001%, so (if my math is right) you are will
within the advertised precision.
The circuit in which Y11 operates looks pretty simple, the only components
around it are C11, R11, L18, and V10. I'd have a look at R11 to be sure it
hadn't drifted (the parts list seems to indicate that it's an unremarkable
carbon comp resistor, with 10% accuracy). You could also remove the
Nuvistor and the crystal in order to check C11 in place. I expect that both
V10 and Y11 are socketed, but I can't really tell about the crystal oven
from the pictures in the service manual, so it might be easier to unsolder
C11 than to remove Y11.
-- Jeff Dutky
|
Is the heater in the octal plug actually working? -- Mine was not.
(The thermostat was stuck open IIRC).
They don't run cool, so you can definitely tell...
David
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On Tue, Dec 7, 2021 at 8:45 AM n4buq <n4buq@...> wrote:
Hi Jeff,
Y11 is mounted in an an octal plug along with its heater so I can unplug that if need be. I have disassembled a trimmer similar to the one used for C11 and, as I recall, it did need some cleanup (I seem to recall the silver had migrated but that's a distant memory) so I was considering a cleanup for this on as well.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Jeff Dutky" <jeff.dutky@...>
To: "tekscopes" <[email protected]>
Sent: Monday, December 6, 2021 11:41:47 PM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator The advertised spec is +/- 0.001%, so (if my math is right) you are will within
the advertised precision.
The circuit in which Y11 operates looks pretty simple, the only components
around it are C11, R11, L18, and V10. I'd have a look at R11 to be sure it
hadn't drifted (the parts list seems to indicate that it's an unremarkable
carbon comp resistor, with 10% accuracy). You could also remove the Nuvistor
and the crystal in order to check C11 in place. I expect that both V10 and Y11
are socketed, but I can't really tell about the crystal oven from the pictures
in the service manual, so it might be easier to unsolder C11 than to remove
Y11.
-- Jeff Dutky
|
I can hear the thermostat cycling and see the lamp cycling as well. I'll check whether it's actually warm to the touch in a bit just to make sure.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "David Holland" <david.w.holland@...>
To: "tekscopes" <[email protected]>
Sent: Tuesday, December 7, 2021 7:48:41 AM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator Is the heater in the octal plug actually working? -- Mine was not.
(The thermostat was stuck open IIRC).
They don't run cool, so you can definitely tell...
David
On Tue, Dec 7, 2021 at 8:45 AM n4buq <n4buq@...> wrote:
Hi Jeff,
Y11 is mounted in an an octal plug along with its heater so I can unplug that if
need be. I have disassembled a trimmer similar to the one used for C11 and, as
I recall, it did need some cleanup (I seem to recall the silver had migrated
but that's a distant memory) so I was considering a cleanup for this on as
well.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Jeff Dutky" <jeff.dutky@...>
To: "tekscopes" <[email protected]>
Sent: Monday, December 6, 2021 11:41:47 PM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator The advertised spec is +/- 0.001%, so (if my math is right) you are will within
the advertised precision.
The circuit in which Y11 operates looks pretty simple, the only components
around it are C11, R11, L18, and V10. I'd have a look at R11 to be sure it
hadn't drifted (the parts list seems to indicate that it's an unremarkable
carbon comp resistor, with 10% accuracy). You could also remove the Nuvistor
and the crystal in order to check C11 in place. I expect that both V10 and Y11
are socketed, but I can't really tell about the crystal oven from the pictures
in the service manual, so it might be easier to unsolder C11 than to remove
Y11.
-- Jeff Dutky
|
If its cycling, its probably good. Mine wasn't heating, nor cycling
till I repaired it.
Just a thought, oh well....
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On Tue, Dec 7, 2021 at 8:55 AM n4buq <n4buq@...> wrote:
I can hear the thermostat cycling and see the lamp cycling as well. I'll check whether it's actually warm to the touch in a bit just to make sure.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "David Holland" <david.w.holland@...>
To: "tekscopes" <[email protected]>
Sent: Tuesday, December 7, 2021 7:48:41 AM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator Is the heater in the octal plug actually working? -- Mine was not.
(The thermostat was stuck open IIRC).
They don't run cool, so you can definitely tell...
David
On Tue, Dec 7, 2021 at 8:45 AM n4buq <n4buq@...> wrote:
Hi Jeff,
Y11 is mounted in an an octal plug along with its heater so I can unplug that if
need be. I have disassembled a trimmer similar to the one used for C11 and, as
I recall, it did need some cleanup (I seem to recall the silver had migrated
but that's a distant memory) so I was considering a cleanup for this on as
well.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Jeff Dutky" <jeff.dutky@...>
To: "tekscopes" <[email protected]>
Sent: Monday, December 6, 2021 11:41:47 PM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator The advertised spec is +/- 0.001%, so (if my math is right) you are will within
the advertised precision.
The circuit in which Y11 operates looks pretty simple, the only components
around it are C11, R11, L18, and V10. I'd have a look at R11 to be sure it
hadn't drifted (the parts list seems to indicate that it's an unremarkable
carbon comp resistor, with 10% accuracy). You could also remove the Nuvistor
and the crystal in order to check C11 in place. I expect that both V10 and Y11
are socketed, but I can't really tell about the crystal oven from the pictures
in the service manual, so it might be easier to unsolder C11 than to remove
Y11.
-- Jeff Dutky
|
In the Electro-Mechanical Catalog 4 the crystal frequency is specified at 75 C. The manual advocates 2(!) hours warming up before calibrating.
And also says that apart from C11 the "slug adjustment L18 ... will affect the oscillator frequency slightly".
Albert
|
At cold start, with 0.1us selected, the output checked 9.9981MHz. After about a 90 minute warmup, the crystal can is warm to the touch, cycle time is much longer, and the output still checks 9.9981MHz. I was going on memory that the output frequency was 9.999x and that's incorrect.
I'll have to check the components as well as the interaction of L9. I think I adjusted that for uniformity of the markers but I don't think I tried checking to see whether I can reach a compromise between L9 and C8 to get good results for both frequency and marker uniformity.
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "Eric" <ericsp@...>
To: "tekscopes" <[email protected]>
Sent: Monday, December 6, 2021 11:55:53 PM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator How long a warmup time are you giving the crystal before trying to cal.
Also how is your probing set up? This circuit is incredably sensitive to
capacitance. Not enough heat in the crystal and or too much capacitance in
the probing set up will drag the crystal off to the low side of things.
Eric
On Tue, Dec 7, 2021, 12:41 AM Jeff Dutky <jeff.dutky@...> wrote:
The advertised spec is +/- 0.001%, so (if my math is right) you are will
within the advertised precision.
The circuit in which Y11 operates looks pretty simple, the only components
around it are C11, R11, L18, and V10. I'd have a look at R11 to be sure it
hadn't drifted (the parts list seems to indicate that it's an unremarkable
carbon comp resistor, with 10% accuracy). You could also remove the
Nuvistor and the crystal in order to check C11 in place. I expect that both
V10 and Y11 are socketed, but I can't really tell about the crystal oven
from the pictures in the service manual, so it might be easier to unsolder
C11 than to remove Y11.
-- Jeff Dutky
|
Don't measure the frequency at the xtal - you will pull it down a load.
Measure at the output of the 1st gain stage (collector of Q94).
David
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of n4buq Sent: 07 December 2021 16:30 To: tekscopes < [email protected]> Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator At cold start, with 0.1us selected, the output checked 9.9981MHz. After about a 90 minute warmup, the crystal can is warm to the touch, cycle time is much longer, and the output still checks 9.9981MHz. I was going on memory that the output frequency was 9.999x and that's incorrect. I'll have to check the components as well as the interaction of L9. I think I adjusted that for uniformity of the markers but I don't think I tried checking to see whether I can reach a compromise between L9 and C8 to get good results for both frequency and marker uniformity. Thanks, Barry - N4BUQ
|
I'm checking the frequency at the output connector. I could also check it at Q94 but I think that either way, I can't quite squeeze 10.000MHz out of the oscillator.
Thanks,
Barry - N4BUQ
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Show quoted text
----- Original Message ----- From: "David C. Partridge" <david.partridge@...>
To: "tekscopes" <[email protected]>
Sent: Tuesday, December 7, 2021 11:58:36 AM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator Don't measure the frequency at the xtal - you will pull it down a load.
Measure at the output of the 1st gain stage (collector of Q94).
David
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of n4buq
Sent: 07 December 2021 16:30
To: tekscopes <[email protected]>
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator
At cold start, with 0.1us selected, the output checked 9.9981MHz. After about a
90 minute warmup, the crystal can is warm to the touch, cycle time is much
longer, and the output still checks 9.9981MHz. I was going on memory that the
output frequency was 9.999x and that's incorrect.
I'll have to check the components as well as the interaction of L9. I think I
adjusted that for uniformity of the markers but I don't think I tried checking
to see whether I can reach a compromise between L9 and C8 to get good results
for both frequency and marker uniformity.
Thanks,
Barry - N4BUQ
|
By the way, I wonder if someone could clarify one of the steps in Chapter 6. Paragraph 4.c. states:
"Adjust L18 (Fig. 6-7) midway between the two signal maximum amplitude points."
Does that mean that as the slug is moved through the coil, one should see two maximums and then set the the slug midway between those positions? I ask because I don't see two maximum values and, instead, the waveform changes somewhat as I move the slug but that's a bit erratic and not a smooth transition between two waveforms with maximums at both points.
If I'm misunderstanding this, then if someone could straighten me out on that, I would very much appreciate it.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "n4buq" <n4buq@...>
To: "tekscopes" <[email protected]>
Sent: Tuesday, December 7, 2021 12:11:47 PM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator I'm checking the frequency at the output connector. I could also check it at
Q94 but I think that either way, I can't quite squeeze 10.000MHz out of the
oscillator.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "David C. Partridge" <david.partridge@...>
To: "tekscopes" <[email protected]>
Sent: Tuesday, December 7, 2021 11:58:36 AM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator Don't measure the frequency at the xtal - you will pull it down a load.
Measure at the output of the 1st gain stage (collector of Q94).
David
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of n4buq
Sent: 07 December 2021 16:30
To: tekscopes <[email protected]>
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator
At cold start, with 0.1us selected, the output checked 9.9981MHz. After about a
90 minute warmup, the crystal can is warm to the touch, cycle time is much
longer, and the output still checks 9.9981MHz. I was going on memory that the
output frequency was 9.999x and that's incorrect.
I'll have to check the components as well as the interaction of L9. I think I
adjusted that for uniformity of the markers but I don't think I tried checking
to see whether I can reach a compromise between L9 and C8 to get good results
for both frequency and marker uniformity.
Thanks,
Barry - N4BUQ
|
On Tue, Dec 7, 2021 at 08:53 PM, n4buq wrote: By the way, I wonder if someone could clarify one of the steps in Chapter 6.
Paragraph 4.c. states:
"Adjust L18 (Fig. 6-7) midway between the two signal maximum amplitude points."
Does that mean that as the slug is moved through the coil, one should see two
maximums and then set the the slug midway between those positions? I ask
because I don't see two maximum values and, instead, the waveform changes
somewhat as I move the slug but that's a bit erratic and not a smooth
transition between two waveforms with maximums at both points. I don't like to put my 184 at risk to try this. As to the theory I can only think that the two peaks appear because the filter L18/L19 is double-tuned (as are all those filters between stages); I might be totally wrong. Suppose L19 is tune below the 10 MHz crystal frequency. Then I expect peaks when (very roughly) L18 is tuned to the crystal frequency and when L18 is tuned to the same frequency as L19. Perhaps the idea now is to tune L18 midway and then tune L19 (and C108?) again as prescribed. Repeated until the results are satisfactory. W.r.t. crystal temperature, in my 184 the crystal housing temperature stabilizes at about 38 C (measured with IR meter) while Tamb is 11 C. The crystal frequency goes up (light on) and down (light off) with 1.2 ppm between the limits. If the (average) oven temperature equals the crystal design temperature then I would expect a maximum frequency or a minimum frequency midway in each on and off traject (or at least a stationary point midway, not simply monotone increase or decrease). Of course the oven temperature can have drifted away due to aging of the bimetal (?) contacts. Albert
|
A funny coincidence and somewhat of topic. At the crystal housing I saw the name Bulova. Never heard of and sounded Eastern-European for me. Just a few hours later I saw a Dutch TV program like the The Antiques Roadshow on BBC. To my surprise one of the discussed objects was a watch made by ... Bulova, model Accutron, from the USA. Interesting internals with tuning fork, also shown at Wikipedia. The driving transistor for the magnet coils were produced by Philips here.
|
On Wed, Dec 8, 2021 at 10:36 PM, Albert Otten wrote:
A funny coincidence and somewhat of topic. At the crystal housing I saw the
name Bulova. Never heard of and sounded Eastern-European for me. Just a few
hours later I saw a Dutch TV program like the The Antiques Roadshow on BBC. To
my surprise one of the discussed objects was a watch made by ... Bulova, model
Accutron, from the USA. Interesting internals with tuning fork, also shown at
Wikipedia. The driving transistor for the magnet coils were produced by
Philips here.
Hi Albert, You probably remember that I am (actually: used to be) a watch collector, so you won't be surprised that I am familiar with Bulova. I still own one of their Accutron wristwatches. Bulova used to be in high esteem and at one time, competed only with Omega for supplying a moon watch in the Apollo age. Like Omega and Patek-Philippe (HP 5061A Caesium-beam clock!), Bulova made devices for scientific purposes as well. Their tuning fork resonates at 360Hz, which results in an audible buzzing. They are quite position-dependent, not a nice property for a wristwatch. Unfortunately, they run on a once ubiquitous (Hg) battery that is no longer in production. Alternatives probably exist but I never looked for them. They were a nice bridge between ticking escapement-driven mechanical watches and the later quartz watches. Raymond
|
Albert,
Thanks for the reply. I'll retry the procedure. I may have misaligned L19/C108 and need to get those set so that L18 can be adjusted to show those peaks.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Albert Otten" <aodiversen@...>
To: "tekscopes" <[email protected]>
Sent: Wednesday, December 8, 2021 2:33:51 PM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator On Tue, Dec 7, 2021 at 08:53 PM, n4buq wrote:
By the way, I wonder if someone could clarify one of the steps in Chapter 6.
Paragraph 4.c. states:
"Adjust L18 (Fig. 6-7) midway between the two signal maximum amplitude points."
Does that mean that as the slug is moved through the coil, one should see two
maximums and then set the the slug midway between those positions? I ask
because I don't see two maximum values and, instead, the waveform changes
somewhat as I move the slug but that's a bit erratic and not a smooth
transition between two waveforms with maximums at both points. I don't like to put my 184 at risk to try this. As to the theory I can only
think that the two peaks appear because the filter L18/L19 is double-tuned (as
are all those filters between stages); I might be totally wrong. Suppose L19 is
tune below the 10 MHz crystal frequency. Then I expect peaks when (very
roughly) L18 is tuned to the crystal frequency and when L18 is tuned to the
same frequency as L19. Perhaps the idea now is to tune L18 midway and then tune
L19 (and C108?) again as prescribed. Repeated until the results are
satisfactory.
W.r.t. crystal temperature, in my 184 the crystal housing temperature stabilizes
at about 38 C (measured with IR meter) while Tamb is 11 C.
The crystal frequency goes up (light on) and down (light off) with 1.2 ppm
between the limits. If the (average) oven temperature equals the crystal design
temperature then I would expect a maximum frequency or a minimum frequency
midway in each on and off traject (or at least a stationary point midway, not
simply monotone increase or decrease). Of course the oven temperature can have
drifted away due to aging of the bimetal (?) contacts.
Albert
|
David C. Partridge
Raymond Domp Frank