Re: DSA602 useful? too huge on a bench?
If you can get them cheap and local, and you have the space, the DSA is a decent scope (top of the line in its day).
A lot of the plug ins are 50 ohm, so check carefully if you need a 1M plug in.
The 1M plug ins come in 2 and 4 channel.
If I remember correctly, each channel has a 1GHz bandwidth, so a 2 channel plug in would top out at 500MHz.
The modern digital scopes are much better for most work and much lighter. but also more expensive.
The CSAs are a different animal, sampling scopes for high frequency work. Still use mine for TDR measurements on PCBs.
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I have 2 vectorscopes/waveform monitors, one 1740 not an A made around 1988 and one 1760 made around 1998.
Both units exibit the same problem, weak display. I did some quick tests and all voltages look good and functions I?
know how to use seem to work.
Most likley these both have weak tubes but I need to be positive any help on what to test next?
The 1760 manual is on tekwiki and I have the 1740 manual on order.
I do not have a tube checker or a HV probe of 1G resistance at this time.? ?
--
Jeffeelcr
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DSA602 useful? too huge on a bench?
I could get a a couple of these cheap locally, (one for parts), except they are not super repairable...and they are huge.
Anyone like their function? Skip to 11801 or CSA803?
John
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Update for all.
The culprit was C10. Not fully bad - kind of tricky, really - but enough to bring almost down one leg of the C1/C2 ladder. Once that was corrected (plus a couple of other caps already replaced, and likely onward looking at full LV PS recap) this is a perfectly running, accurate scope. Very sharp screen too!?
Yeah!!
Very keen and effusive thanks to Ozan, for being helpful both here and offline.
Radu.?
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Re: Problems with 465 - Looking for Help!
I am using low melt solder to remove such difficult solder joins, works great.
-vf-
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12.?9.?2022 v 16:10, Dave_G0WBX via groups.io <g8kbvdave@...>:
Hi.
Be very careful changing those large PCB mounted main electrolytic cap's. They are a "press fit" into the circuit board before they are soldered.
Removing them without damaging the multi layer PCB can be a very long frustrating job.
I'm sure others here will suggest proven methods they have used successfully, but just an iron and sucker doesn't really do the job.
Take care.
Dave G8KBV (Ex Tek UK.)
--
Created on and sent from a Unix like PC running and using free and open source software:
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Re: Problems with 465 - Looking for Help!
Thanks Dave!? The ripple frequency?is 2x the 60Hz line frequency at 120Hz.
?
I'm?proceeding with replacing the filter caps, waiting on caps and adapters as per earlier advice.??
?
Thanks to all for the help so far!
?
Ed
?
K9EDR?
?
Sent:?Monday, September 12, 2022 at 9:20 AM
From:?"Dave_G0WBX via groups.io" <g8kbvdave@...>
To:[email protected]
Subject:?Re: [TekScopes2] Problems with 465 - Looking for Help!
Another hint, to check the AC Line voltage settings on the back of the
'scope.
What is the ripple frequency??? Is it 1 x Line Frequency, or 2 x Line
Frequency?
If the first, you may have an easier job locating the failed rectifier
and replacing it.
(It was not unknown for one diode in a bridge package to fail open or
short.? If open, then you tend to get 1 x Line Frequency ripple, even if
the main cap's are OK.?? If failed Short, then the fuse should blow,
protecting the transformer.)
If you have 2 x Line Frequency ripple, then yes,? likely a bad cap', as
2 x Line Frequency ripple indicates that your are still getting full
wave rectification so all the Rectifier Bridges & Diodes are OK.
Regards.
??? Dave G8KBV (Ex Tek UK.)
--
Created on and sent from a Unix like PC running and using free and open source software:
?
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Re: Problems with 465 - Looking for Help!
Another hint, to check the AC Line voltage settings on the back of the 'scope.
What is the ripple frequency??? Is it 1 x Line Frequency, or 2 x Line Frequency?
If the first, you may have an easier job locating the failed rectifier and replacing it.
(It was not unknown for one diode in a bridge package to fail open or short.? If open, then you tend to get 1 x Line Frequency ripple, even if the main cap's are OK.?? If failed Short, then the fuse should blow, protecting the transformer.)
If you have 2 x Line Frequency ripple, then yes,? likely a bad cap', as 2 x Line Frequency ripple indicates that your are still getting full wave rectification so all the Rectifier Bridges & Diodes are OK.
Regards.
??? Dave G8KBV (Ex Tek UK.)
--
Created on and sent from a Unix like PC running and using free and open source software:
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Re: Problems with 465 - Looking for Help!
Hi.
Be very careful changing those large PCB mounted main electrolytic cap's.?? They are a "press fit" into the circuit board before they are soldered.
Removing them without damaging the multi layer PCB can be a very long frustrating job.
I'm sure others here will suggest proven methods they have used successfully, but just an iron and sucker doesn't really do the job.
Take care.
??? Dave G8KBV (Ex Tek UK.)
--
Created on and sent from a Unix like PC running and using free and open source software:
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AFG5101 Option 02, can someone check a part number on theirs?
Hi all,
I'm thinking of creating my own version of the Option 02 PCB for my AFG5101, but the service manual seems a bit lacking in parts lists... Only showing part details for PCB A1 (Option 02 is PCB A5)
The schematics seem to have the needed part details for all parts except Transistors Q900, Q901, Q902, Q903, IC's U905, U914, and Crystal XTAL900.
Here's a link to an image showing the locations of the parts:
Can someone who has this option in their AFG5101 pull the board out and let me know what the part numbers for these parts are?
Some photos of the parts and the entire board would be greatly appreciated too, if possible.
If I'm successful in replicating this option PCB, I'll release the gerbers and BOM for others to use too.
Thanks!
Jared.
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Re: Problems with 465 - Looking for Help!
Interleaved:
On 9/11/2022 1:23 PM, Ed Riley wrote:
Thanks for all of the input so far!
As suggested I checked the low voltages for ripple with a
multimeter and a scope.
Only the 110V and 15V rails showed significant ripple on the scope
and only the 110V had AC on my multimeter.? I've added photos
here:
Then those supplies are suspect.
/g/TekScopes2/album?id=278262
The 110V rail measures 104.9 VDC; the 15V rail measures 12.99V.?
Using the multimeter the AC ripple voltage on the 110V measured
10.21V!? The scope appears to indicate 10.4V.
Something is either pulling it down, or a capacitor has failed and
it can't go *up* far enough (story later).
The 15V rail did not show AC on the multimeter but appears to
indicate 1.32V on the scope.
Believe the scope.
Should I be looking at the main caps or are there other places to
check first?
Start to analyze the supply.?
The +15 volt supply has a bulk supply voltage of about 24.5.?
There is a troubleshooting chart for power supplies in the service
manual.? Look at the +24 volt bulk supply.? Is there 120 Hz ripple
(or 100) on it or 60 Hz (or 50).? That can indicate a bad CR1541.?
Is the supply being pulled down by an excessive load?? Check the
voltage across R1549.? That ought to tell you how much current is
being drawn.? (about 900 mv/amp).? Is the 55 volts exactly on??
That's the reference for this supply.? Check if C1549 is good or
leaky.
Read the power supply theory and see how this supply works.?
Don't feel bad about having to do so.? Most people, unless they do
this for a living (and a lot of it) will go to that section and
red it at least once.?
Check the voltages given in the circuit for normal operation.
Short story.? I have a 1000 volt (maximum) voltage reference.?
Rather nice, you can adjust to about 1 microvolt on the one volt
range and 1 millivolt on the thousand volt range.
I couldn't get it to go above about 200 volts.? I checked the
amplifier, I checked a lot of the resistors, but it was only on
the 1000 volt range that I had the problem.
Long story shortened, I finally looked at the supply that was to
produce the 1000 volt bulk.? It was way low.? Looked at the supply
with a scope (and high voltage probe).? Massive ripple.? The
filter capacitors were bad, nothing else.? There was not enough
sustained voltage to allow the circuit to produce 1000 volts, even
though it hit over 1000 volts at the peak of the AC cycle.?
Two capacitors later, I had a working 1000 volt calibrator.? (DC
only).?
Harvey
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Ozan,
Thank you for looking into that - well, I thought I have a smoking gun... Not so lucky. Back to the bench!
Radu.?
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On Sun, Sep 11, 2022 at 10:47 AM, Radu Bogdan Dicher wrote:
While waiting for my isolation power solution (a B&K 1655A), I started checking parts from the LV PS.
I have not had to check optocouplers before, but I gather the phototransistor should look like a CE: OL both ways on diode/resistor check, right??
In the case of the MOC304 optocoupler, with the positive lead of the DMM to pin 5 (negative to 4), I am shown a junction worth of drop (about .6V) in diode test and about 2.8Mohm resistance... This is obviously out of circuit. Is this optocoupler bad?
---- Hi Radu, I think it is a MOC3043. According to the datasheet pin 5 is triac substrate and should not be connected. You may want to check 4 & 6. Ozan
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While waiting for my isolation power solution (a B&K 1655A), I started checking parts from the LV PS.
I have not had to check optocouplers before, but I gather the phototransistor should look like a CE: OL both ways on diode/resistor check, right??
In the case of the MOC304 optocoupler, with the positive lead of the DMM to pin 5 (negative to 4), I am shown a junction worth of drop (about .6V) in diode test and about 2.8Mohm resistance... This is obviously out of circuit. Is this optocoupler bad?
Thank you,
Radu.?
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Re: Problems with 465 - Looking for Help!
And, when you replace them, be aware that Tek used the can as a jumper
and the 3 holes on the pcb need to be tied together. Use high quality
long life 105C caps and, for a nice repair, get some of the cap adapter
boards that mate a modern snap cap to the obsolete pattern of the old
can (and also take care of the jumper issue). You can get those off
ebay, find gerbers floating around the net or make your own easily enough.
Use good equipment, good technique and care when removing the old cans,
damage to the board is possible if you're not careful.
Sometimes the bridges go bad, but high ripple is a good sign that one or
more filter caps have dried out.
Paul
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On Sun, Sep 11, 2022 at 10:29:26AM -0700, Michael wrote: Start with the main filter caps. ?Those are the most problematic. ?Most people do a wholesale replacement of all these main filters, while others have replaced only those out of spec. ?I have done it both ways.
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows
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Well, IPA cleaning didn't change anything.?
Does anyone have any additional suggestions?
It doesn't look like an easy task to replace CRT on this scope, even if a new or working replacement can be obtained.
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Re: Problems with 465 - Looking for Help!
Start with the main filter caps. ?Those are the most problematic. ?Most people do a wholesale replacement of all these main filters, while others have replaced only those out of spec. ?I have done it both ways. ?
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Re: Problems with 465 - Looking for Help!
Thanks for all of the input so far! As suggested I checked the low voltages for ripple with a multimeter and a scope. Only the 110V and 15V rails showed significant ripple on the scope and only the 110V had AC on my multimeter.? I've added photos here: /g/TekScopes2/album?id=278262The 110V rail measures 104.9 VDC; the 15V rail measures 12.99V.? Using the multimeter the AC ripple voltage on the 110V measured 10.21V!? The scope appears to indicate 10.4V. The 15V rail did not show AC on the multimeter but appears to indicate 1.32V on the scope. Should I be looking at the main caps or are there other places to check first?
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Re: Problems with 465 - Looking for Help!
I had a similar, but not quite the same, problem with a 465M. It turned out the 90V supply was low caused by a 2uF cap near the 90V test point and the HV cover.
Good luck!
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Re: Problems with 465 - Looking for Help!
I'll add my +1 to this discussion regarding the need to get all the supplies within spec before you try anything else. I had a 465B that displayed a really distorted trace that slowly improved over a 20 minute warm up time. The issue was repeatable. The problem turned out to be a bad can cap in the power supply. The experience really made a believer out of me regarding how serious slight deviations in the power supply rails can be.
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Re: Problems with 465 - Looking for Help!
You can check AC ripple with a meter, set to ACV, but need to verify that the meter was designed correctly for that. Flukes, HPs, and even most Microntas work okay, but the newer breed of cheap DMMs don't.? The quick way to check is to measure the AC volts of a battery / cell. If it measures twice what the DC measurement is, don't use that meter for AC ripple checks. I was only bit once with this issue, after that, I check all meters with the battery test.
---------- Original Message ---------- From: "Ed Riley" <edriley@...> To: [email protected]Subject: Re: [TekScopes2] Problems with 465 - Looking for Help! Date: Sat, 10 Sep 2022 06:30:29 +0200
Thanks Harvey!
?
I have a digital scope and will check the power supply ripple with it, post what I find.?
Sent using the mobile mail app
On 9/9/22 at 11:11 PM, Harvey White wrote:
From: "Harvey White" <madyn@...> Date: September 9, 2022 To: [email protected]Cc: Subject: Re: [TekScopes2] Problems with 465 - Looking for Help! You'll find that, like everything else, you'll want another scope to help repair this one.? Not absolutely needed, but it makes a difference.?
Harvey
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On 9/9/2022 11:45 PM, Ed Riley wrote:
Thanks Harvey and Michael!
?
Exactly the?kind of guidance I was looking for!
?
It¡¯s my first scope repair but looks to be a great learning project.?
Sent using the mobile mail app
On 9/9/22 at 6:32 PM, Harvey White wrote:
From: "Harvey White" <madyn@...> Date: September 9, 2022 To: [email protected] Cc: Subject: Re: [TekScopes2] Problems with 465 - Looking for Help! What happens with out of tolerance power supply voltages varies according to the circuit, things that ought to adjust properly won't.? Ripple on a power supply can creep anywhere, and generally does.? It presents itself as an unwanted signal that is gleefully seized by properly operating circuitry and treated as something valid.
Harvey
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On 9/9/2022 6:28 PM, Michael wrote:
Your LV supply will cause this issue. ?I just repaired a 465 that had almost identical issues. ?Your reported ?LV voltages are not ideal, I would bet that there is excess ripple on one or more of the LV rails. ?
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Jared Cabot
Michael
DaveH52
Tom Phillips