Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old May 28th 16, 10:07 PM posted to sci.electronics.repair
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Default Scopes, Horizontal Deflection

Now dammit, I know how a ramp generator works and I know how a relaxation oscillator works, which is what the ramp generator sometimes becomes in a scope. I wish Jim Yanik was around.

I got two. One is a Tek 465B that works but B sweep does not. the waveform that the plates indicates that when switched it IS switching to B sweep but not starting.

The other is a 204, and the main sweep seems to have the same problem. the final amps are fine in both units.

The problem I have with these is actually following the schematics. Seriously, I think if I could print them out on HUGE paper I might be able to follow it. But that is not practical at this time nor is it practical with these schematics the way they are split up.

I hae already got TWO copies of the PDFs so I can have two instances open, because with the new and improved Acrobat Reader it won't open the same copy twice and I haven't been able to find a way to open two pages at the same time in one instance. Having to go from page 250 to page 146 is a bunch of bull****.

But anyway, we got two scopes, kinda similar in design, with the same problem. What is the common problem when the sweep doesn't start ?

I understand the principles of operation, it is just that I can't run their gauntlet. From the time base part go to this board for the triggering, and then this board for the switching of the triggering and then way the out in bum****t Egypt somewhere to trace the signal.

It is just so much of a bitch to follow.

The Hameg is a 204. It works fine in XY mode. There is a slight DC shift when you change the time/div setting, pretty much at the lower ranges.

The Tek is a 465B and actually woks but B sweep does not. It IS switching to B sweep but B sweep never starts no matter what you do. On page 267 of the service manual, Q6036 has the same voltage on all three terminals but does no check shorted. That makes it somewhat suspect but doubtful it causes this problem. I supplies a calibrated voltage to the ramp generator. Generally if you give it a little more voltage you get more ramp. This gets no ramp, just sits there. In fact if the circuit is entirely open somewhere that is pretty much what would happen.

Maybe I should rethink this Q6036.

Any pointers welcome on either scope. I know they ain't the cat's ass but I would like to see them work.

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Old May 28th 16, 10:54 PM posted to sci.electronics.repair
tom tom is offline
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Default Scopes, Horizontal Deflection


wrote in message
...
Now dammit, I know how a ramp generator works and I know how a relaxation
oscillator works, which is what the ramp generator sometimes becomes in a
scope. I wish Jim Yanik was around.

I got two. One is a Tek 465B that works but B sweep does not. the waveform
that the plates indicates that when switched it IS switching to B sweep but
not starting.

The other is a 204, and the main sweep seems to have the same problem. the
final amps are fine in both units.

The problem I have with these is actually following the schematics.
Seriously, I think if I could print them out on HUGE paper I might be able
to follow it. But that is not practical at this time nor is it practical
with these schematics the way they are split up.

I hae already got TWO copies of the PDFs so I can have two instances open,
because with the new and improved Acrobat Reader it won't open the same copy
twice and I haven't been able to find a way to open two pages at the same
time in one instance. Having to go from page 250 to page 146 is a bunch of
bull****.

But anyway, we got two scopes, kinda similar in design, with the same
problem. What is the common problem when the sweep doesn't start ?

I understand the principles of operation, it is just that I can't run their
gauntlet. From the time base part go to this board for the triggering, and
then this board for the switching of the triggering and then way the out in
bum****t Egypt somewhere to trace the signal.

It is just so much of a bitch to follow.

The Hameg is a 204. It works fine in XY mode. There is a slight DC shift
when you change the time/div setting, pretty much at the lower ranges.

The Tek is a 465B and actually woks but B sweep does not. It IS switching to
B sweep but B sweep never starts no matter what you do. On page 267 of the
service manual, Q6036 has the same voltage on all three terminals but does
no check shorted. That makes it somewhat suspect but doubtful it causes this
problem. I supplies a calibrated voltage to the ramp generator. Generally if
you give it a little more voltage you get more ramp. This gets no ramp, just
sits there. In fact if the circuit is entirely open somewhere that is pretty
much what would happen.

Maybe I should rethink this Q6036.

Any pointers welcome on either scope. I know they ain't the cat's ass but I
would like to see them work.


+++++++++++++++++++++++++++++++++++++++++=


Do you have waveform 73 on schematic 8? That is the B start gate. Start
there.



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Old May 28th 16, 11:46 PM posted to sci.electronics.repair
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Default Scopes, Horizontal Deflection

On 29/05/2016 7:07 AM, wrote:
Now dammit, I know how a ramp generator works and I know how a
relaxation oscillator works, which is what the ramp generator
sometimes becomes in a scope. I wish Jim Yanik was around.

I got two. One is a Tek 465B that works but B sweep does not. the
waveform that the plates indicates that when switched it IS switching
to B sweep but not starting.

The other is a 204, and the main sweep seems to have the same
problem. the final amps are fine in both units.

The problem I have with these is actually following the schematics.
Seriously, I think if I could print them out on HUGE paper I might be
able to follow it. But that is not practical at this time nor is it
practical with these schematics the way they are split up.

I hae already got TWO copies of the PDFs so I can have two instances
open, because with the new and improved Acrobat Reader it won't open
the same copy twice and I haven't been able to find a way to open two
pages at the same time in one instance. Having to go from page 250 to
page 146 is a bunch of bull****.

But anyway, we got two scopes, kinda similar in design, with the same
problem. What is the common problem when the sweep doesn't start ?

I understand the principles of operation, it is just that I can't run
their gauntlet. From the time base part go to this board for the
triggering, and then this board for the switching of the triggering
and then way the out in bum****t Egypt somewhere to trace the signal.


It is just so much of a bitch to follow.

The Hameg is a 204. It works fine in XY mode. There is a slight DC
shift when you change the time/div setting, pretty much at the lower
ranges.

The Tek is a 465B and actually woks but B sweep does not. It IS
switching to B sweep but B sweep never starts no matter what you do.
On page 267 of the service manual, Q6036 has the same voltage on all
three terminals but does no check shorted. That makes it somewhat
suspect but doubtful it causes this problem. I supplies a calibrated
voltage to the ramp generator. Generally if you give it a little more
voltage you get more ramp. This gets no ramp, just sits there. In
fact if the circuit is entirely open somewhere that is pretty much
what would happen.

Maybe I should rethink this Q6036.

Any pointers welcome on either scope. I know they ain't the cat's ass
but I would like to see them work.


**The 465B is a great old 'scope, BUT, like many Tektronix 'scopes of
the time, tunnel diodes are used in the sweep systems. The tunnel diodes
used are VERY hard to source.



--
Trevor Wilson
www.rageaudio.com.au

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https://www.avast.com/antivirus

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Old May 29th 16, 10:33 AM posted to sci.electronics.repair
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Default Scopes, Horizontal Deflection

On 28/05/2016 22:07, wrote:
Now dammit, I know how a ramp generator works and I know how a relaxation oscillator works, which is what the ramp generator sometimes becomes in a scope. I wish Jim Yanik was around.

I got two. One is a Tek 465B that works but B sweep does not. the waveform that the plates indicates that when switched it IS switching to B sweep but not starting.

The other is a 204, and the main sweep seems to have the same problem. the final amps are fine in both units.

The problem I have with these is actually following the schematics. Seriously, I think if I could print them out on HUGE paper I might be able to follow it. But that is not practical at this time nor is it practical with these schematics the way they are split up.

I hae already got TWO copies of the PDFs so I can have two instances open, because with the new and improved Acrobat Reader it won't open the same copy twice and I haven't been able to find a way to open two pages at the same time in one instance. Having to go from page 250 to page 146 is a bunch of bull****.

But anyway, we got two scopes, kinda similar in design, with the same problem. What is the common problem when the sweep doesn't start ?

I understand the principles of operation, it is just that I can't run their gauntlet. From the time base part go to this board for the triggering, and then this board for the switching of the triggering and then way the out in bum****t Egypt somewhere to trace the signal.

It is just so much of a bitch to follow.

The Hameg is a 204. It works fine in XY mode. There is a slight DC shift when you change the time/div setting, pretty much at the lower ranges.

The Tek is a 465B and actually woks but B sweep does not. It IS switching to B sweep but B sweep never starts no matter what you do. On page 267 of the service manual, Q6036 has the same voltage on all three terminals but does no check shorted. That makes it somewhat suspect but doubtful it causes this problem. I supplies a calibrated voltage to the ramp generator. Generally if you give it a little more voltage you get more ramp. This gets no ramp, just sits there. In fact if the circuit is entirely open somewhere that is pretty much what would happen.

Maybe I should rethink this Q6036.

Any pointers welcome on either scope. I know they ain't the cat's ass but I would like to see them work.


With any old-school-scope repair, it is sensible to check out all switch
and header contacts for corrossion problems, before getting bogged down
in circuit minutei.
The "well it was working fine, before I left it on the shelf for a year"
scenario.
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Old May 31st 16, 01:36 PM posted to sci.electronics.repair
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Default Scopes, Horizontal Deflection

"tom" wrote in message
...

wrote in message
...
I wish Jim Yanik was around.




Uh-Oh. Something happen to Yanik?


Mark Z.



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Old June 1st 16, 07:03 AM posted to sci.electronics.repair
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Default Scopes, Horizontal Deflection

"Do you have waveform 73 on schematic 8? That is the B start gate. Start there."

I have a square wave there that tracks the A sweep speed. However I see a flat line on the collector and emitter of Q4565. That makes it highly suspect.

I have to set it aside for a minute because I have a custom customer in tomorrow. But in the meantime I can figure out a decent replacement for Q4565. It is not that critical but I do have a little bit of respect for people who are that anal about designing.

Anyway, since the intensify function works off the ten turn pot pretty much correctly, but the intensified part never ends of course because B sweep doesn't start, that localizes the problem. Like I said, Q4565.

Thanks...

Now I just hope that ****er ain't germanium !
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Old June 1st 16, 07:12 AM posted to sci.electronics.repair
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Default Scopes, Horizontal Deflection

"**The 465B is a great old 'scope, BUT, like many Tektronix 'scopes of the time, tunnel diodes are used in the sweep systems. The tunnel diodes used are VERY hard to source. "

True, and tunnel diode triggering was the best. The thing would almost sync to white noise. My old 422 was that way. And played guitars and organs n **** into it and it always synced up, no problem. Even the human voice. Even most integrated program material (songs already recorded for those who do not know the phrase).

So, when I find something looks right for Q4565 I'll let you all know if it worked.
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Old June 1st 16, 07:20 AM posted to sci.electronics.repair
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Default Scopes, Horizontal Deflection



Uh-Oh. Something happen to Yanik?


Mark Z.


I think so, life. I think if he is alive now he is probably about 98 years old.

I would have liked to have met him and had a couple brewskis. I mean really, and you might as well know that I have no desire to meet any President of the US within my lifetime, and then some.

Yanik was super sharp with scopes. You ask a question and he says "that is a 100K ceramic, R401 which is on the left side behind the big blue thing in the middle of the board". Some **** like that.

I got that good with TVs but they don't go for ten grand.
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Old June 1st 16, 08:13 AM posted to sci.electronics.repair
tom tom is offline
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Default Scopes, Horizontal Deflection


wrote in message
...
"Do you have waveform 73 on schematic 8? That is the B start gate. Start
there."


I have a square wave there that tracks the A sweep speed. However I see a
flat line on the collector and emitter of Q4565. That makes it highly
suspect.

I have to set it aside for a minute because I have a custom customer in
tomorrow. But in the meantime I can figure out a decent replacement for
Q4565. It is not that critical but I do have a little bit of respect for
people who are that anal about designing.

Anyway, since the intensify function works off the ten turn pot pretty much
correctly, but the intensified part never ends of course because B sweep
doesn't start, that localizes the problem. Like I said, Q4565.

Thanks...

Now I just hope that ****er ain't germanium !
+++++++++++++++++++++++++++++++++++++++++++

No Ge transistors in the 465. It's late. I'll look at it tomorrow and
suggest a next step sans you fixing it.





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Old June 1st 16, 08:30 AM posted to sci.electronics.repair
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Default Scopes, Horizontal Deflection

Thanks. I actually just checked it real quick with the scope but did not pay alot of attention to the DC levels. I actually don't even know the pinout yet.

But I got square waves on one pin the the on/off time varies with the ten turn pot on the front panel for delay. That puts the problem right there, I should be able to smell it.

If the circuit works they way I think, which is they are feeding the emitter of Q4565, I do not like that. I mean I think it is bad because of the readings, but I think it went bad because of the way they used it.

But really, they probably had no other choice. I have seen it before, I have done failure mode analysis. And I have found that at times, they simply had no other choice and their circuit was going to beat on this certain part.

So anyway, what to put in there. I am not going to pay eBay $37 for a 11132-0002-1005 transistor, even if it is in original packaging. (I made the number up so don't bother)

It is pretty much a common base amp, but not really used linear, I THINK. No, I am pretty sure. You see the base hard biased by the two 1K resistors making the base voltage -4 volts. And it says right there that -3 volts starts B sweep.


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