Re: Buying replacement tubes
sometimes when you eke, you end up saying eek!? once you see prices, availability, and the like.
Harvey
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On 8/30/2019 6:08 PM, snapdiode via Groups.Io wrote: "eke", not "eek".
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Re: Buying replacement tubes
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Re: Buying replacement tubes
Hi Jamie,? You might also ask yourself, "do I need to replace it"?? ?I would only recommend replacing a tube if it is KNOWN to be bad.? ?Tek circuitry in particular is very conservatively designed, so it can operate just fine even as the tube is failing.? Frequently enough, when I'm troubleshooting a piece of equipment, I'll test tubes in part of the circuit that is working, and the tubes may test "bad" or "marginal".? ?I leave those in place so as not to add more problems.? ?If the circuit works, leave it be.? ?When you've got everything working, then you can go back and swap out the tubes that tested poorly so as to extend your time to the next service interval.
?Dan
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On Friday, August 30, 2019, 03:10:08 PM EDT, Jamie Ostrowski <jamie.ostrowski@...> wrote:
When a tube needs to be replaced in an oscilloscope, will matching the tube number be sufficient, or are there other items to consider about the tubes? For example, if I have a bad 12AX7, will any 12AX7 do, or do I have to get one with the matching D-getter, the right plate color, etc, etc. I look online for a 12AX7, and there are a multitude of variants listed.
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Re: Buying replacement tubes
One of the most important "criteria" used to justify the exorbitant price on E-Bay is the fact that the seller is offering them for sale, " I have it, therefore it is 'special'". My brother has literally thousands of tubes of all types, most of which were found at Flea markets and Estate sales. Yes, Some tubes in these lots turn out to be junk, but MANY are NOS or like new. He laughs every time he sees one of these $99 "matched" 12AX7 tubes sets. Sadly, this is the world we live in, where BS rules and $$$ have replaced common sense and real knowledge. Too many good old TEK scopes have been sacrificed to "perfect" a Guitar amp or an audio receiver or amplifier.
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Michael Lynch
Dardanelle, AR
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Re: Buying replacement tubes
Very well stated, Dave!
Especially the part I have highlighted.... ;-)
Tom
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On Fri, Aug 30, 2019 at 12:31 PM, Dave Casey wrote:
*Most of the criteria listed for tubes from online resellers is nonsense.**
The 12AX7 is a popular audio preamp tube, so anything people can imagine
makes a difference like the shape of the getter or the color of the plate
will be used to try to eek more value out of the sale.
When replacing tubes, especially in Tek scopes, any tube of the correct
type will do EXCEPT when specific matching criteria are prescribed by Tek.
Any tubes that need to be matched or "selected" for a given parameter will
be called out in the manual with a specific part number (the description
will say something like "Tube, 12AX7, selected". There is a document on the
tekwiki that will provide the selection criteria (e.g. that the two
sections of the tube are matched within x percent). If you're just trying
to get the scope running, selected tubes aren't as important. They matter
much more when you're trying to achieve calibration or meet the original
performance specs for the scope.
Dave Casey
On Fri, Aug 30, 2019, 2:10 PM Jamie Ostrowski <jamie.ostrowski@...>
wrote:
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Re: Buying replacement tubes
The document referred to on Tekwiki gives extensive information on the aging of tubes for use when the scopes were manufactured and for sale as replacements. That is done so that the scope will retain its calibration and not drift as the tubes age. Most of the tubes I use as replacements came from scopes I have parted out, mostly due to mechanical damage from shipping. When I do have to buy tubes, I get them from Radio Electric Supply at as they seem to provide an excellent product.
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Re: Buying replacement tubes
Most of the criteria listed for tubes from online resellers is nonsense. The 12AX7 is a popular audio preamp tube, so anything people can imagine makes a difference like the shape of the getter or the color of the plate will be used to try to eek more value out of the sale. When replacing tubes, especially in Tek scopes, any tube of the correct type will do EXCEPT when specific matching criteria are prescribed by Tek. Any tubes that need to be matched or "selected" for a given parameter will be called out in the manual with a specific part number (the description will say something like "Tube, 12AX7, selected". There is a document on the tekwiki that will provide the selection criteria (e.g. that the two sections of the tube are matched within x percent). If you're just trying to get the scope running, selected tubes aren't as important. They matter much more when you're trying to achieve calibration or meet the original performance specs for the scope. Dave Casey On Fri, Aug 30, 2019, 2:10 PM Jamie Ostrowski <jamie.ostrowski@...> wrote:
When a tube needs to be replaced in an oscilloscope, will matching the
tube number be sufficient, or are there other items to consider about the
tubes? For example, if I have a bad 12AX7, will any 12AX7 do, or do I have
to get one with the matching D-getter, the right plate color, etc, etc. I
look online for a 12AX7, and there are a multitude of variants listed.
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Jim,
I will post this picture in the archives. someone else may have the same issue with their 475.
--
Michael Lynch
Dardanelle, AR
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When a tube needs to be replaced in an oscilloscope, will matching the tube number be sufficient, or are there other items to consider about the tubes? For example, if I have a bad 12AX7, will any 12AX7 do, or do I have to get one with the matching D-getter, the right plate color, etc, etc. I look online for a 12AX7, and there are a multitude of variants listed.
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Re: Tek 576 Curve Tracer HV Transformer winding
Making High Voltage Transformer: Ideas to rewind a HV DIY transformer Regards! Miguel -----Mensaje original----- De: [email protected] [mailto: [email protected]] En nombre de atwood.1@... Enviado el: mi¨¦rcoles, 28 de agosto de 2019 20:25 Para: [email protected]Asunto: Re: [TekScopes] Tek 576 Curve Tracer HV Transformer winding I just took apart the HV XFMR from my 561. The core is a ferrite or powdered iron E-E type. After removing the wrap around the core, the two E's separated easily at room temperature. Still hoping someone has the winding data for a 120-225 or a 120-275 transformer. That data might confirm my reverse engineering of my 120-225.
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Ok Michael,
I admit it , I am as they say here a bit on the thick side.
Saw the red boxes on the photo but thought they were part of the schematic.
Did not realise that you had put them there.
Boy are they spread about the PCB.
Anyway I have done a quick check and on C963 it measures 1.7 ohms, NOT GOOD.
BUT hope spreads eternal..
I will lift one leg and put in a new R963 and see what happens.
At east I now know that the mystery resistor is R963.
If I lived closer I would treat you to a nice meal somewhere in ARZ
Never been there but have visited about 22 States in cluding the show at
Dayton.
Thank you again, Will let you know if there is any more magic smoke.
Regards
Jim
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On Fri, 30 Aug 2019 at 15:46, Mlynch001 <mlynch002@...> wrote: Jim,
You may have already done this, but double check your power supply
voltages. I found some of the LVPS resistors on my 475A had drifted badly
and my +110 rail was way over voltage. The scope worked fine, but that
would have surely led to some eventual problems. There is a thread
describing this repair within the group.
/g/TekScopes/message/156583
--
Michael Lynch
Dardanelle, AR
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Jim, You may have already done this, but double check your power supply voltages. I found some of the LVPS resistors on my 475A had drifted badly and my +110 rail was way over voltage. The scope worked fine, but that would have surely led to some eventual problems. There is a thread describing this repair within the group. /g/TekScopes/message/156583 -- Michael Lynch Dardanelle, AR
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Hi Michael, Have quite a collection of tee shirts, ots of coffee stains, !!!! The board I am looking at is A9. If you sent a scan or photo, nothing came through. Just got your other email, I did disconnect the mysterious 10 ohm and the +15 supply came up to about 13 volts. Will reply to your other email . Hope the photo comes through Thanks for all Regards Jim On Fri, 30 Aug 2019 at 15:17, Michael W. Lynch via Groups.Io <mlynch003= [email protected]> wrote: Jim,
Been there, done that and have the Tee Shirt. As chuck stated, TEK is not
always the best about these locations. Not sure how this comes about, but
even the best have shortcomings. I gave up on that 475 manual and went
back to my old 475A manual and this is what I found.
This is the LOWER front corner of the board on the 475A and this board
LOOKS like the same part as the 475.
I hope this is of some assistance.
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell
Phonemlynch001@[email protected]@...
On Friday, August 30, 2019, 3:53:51 AM CDT, James R. Bartlett <
james.r.bart@...> wrote:
Good morning Michael.
Many thanks for the info/link.
I downloaded it and it is slightly different to mine.
I found the 3, 10 ohm resistors in the +15 volt supply on page 216.
However none of them appear in the component list for that circuit.!!!!!
I have searched but cannot find R961,R963 and R965 and associated 2.2uf
capacitors anywhere except in the main component list.
Can you help and point me as to where they might be.
Sorry to be a pain but this has me puzzled.
Many thanks
Regards
Jim
On Thu, 29 Aug 2019 at 23:11, Mlynch001 <mlynch002@...> wrote:
Jim,
Page 216 of 293 in the version of the 475 manual that I am looking at.
TEKWiki has a couple of versions for that instrument.
here is the link:
< TEKWiki is a great resource.
Best of luck on your repair.
--
Michael Lynch
Dardanelle, AR
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Jim,
Evidently the photo I attempted to attach will not post here directly? Contact me off list at this e-mail and I can send the picture to you.
If there is a way to insert pictures in a post, I do not know how to make it happen.
All 3 filters are on the A9 board near the J6 and J4 connectors. The 475A manual is much more detailed. Maybe TEK felt they had to step up their game?
mlynch002@...
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Michael Lynch
Dardanelle, AR
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Jim, Been there, done that and have the Tee Shirt.? As chuck stated, TEK is not always the best about these locations.? Not sure how this comes about, but even the best have shortcomings.? I gave up on that 475 manual and went back to my old 475A manual and this is what I found.? This is the LOWER front corner of the board on the 475A and this board LOOKS like the same part as the 475. I hope this is of some assistance.? Michael Lynch?479-226-0126 Home Phone479-477-1115 Cell Phonemlynch001@ [email protected]@...
On Friday, August 30, 2019, 3:53:51 AM CDT, James R. Bartlett <james.r.bart@...> wrote: Good morning Michael. Many thanks for the info/link. I downloaded it and it is slightly different to mine. I found the 3, 10 ohm resistors in the +15 volt supply on page 216. However none of them appear in the component list for that circuit.!!!!! I have searched but cannot find R961,R963 and R965 and associated 2.2uf capacitors anywhere except in the main component list. Can you help and point me as to where they might be. Sorry to be a pain but this has me puzzled. Many thanks Regards Jim On Thu, 29 Aug 2019 at 23:11, Mlynch001 <mlynch002@...> wrote: Jim,
? Page 216 of 293 in the version of the 475 manual that I am looking at.
TEKWiki has a couple of versions for that instrument.
here is the link:
< TEKWiki is a great resource.
Best of luck on your repair.
--
Michael Lynch
Dardanelle, AR
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Hi Jim,
Tektronix has always been terrible about identifying
these little power filter circuits. I rarely can find
them on any part's layout in the manuals.
The schematic where the filters are located is on page
216 of my copy of the 475 manual... But I think you
already know that.
The schematic shows them to be in the Sweep Generator
area, which is schematic <8>,,, Then everything goes
to heck...
However, they can usually be found near the source of
the noise. In the case of power coming onto a circuit
board, that is where the filter will be. In the case
of a noise source like a EHT supply, that's where the
filter will be.
The resistor will always be pointing at the noise source.
-Chuck Harris
James R. Bartlett wrote:
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Good morning Michael.
Many thanks for the info/link.
I downloaded it and it is slightly different to mine.
I found the 3, 10 ohm resistors in the +15 volt supply on page 216.
However none of them appear in the component list for that circuit.!!!!!
I have searched but cannot find R961,R963 and R965 and associated 2.2uf
capacitors anywhere except in the main component list.
Can you help and point me as to where they might be.
Sorry to be a pain but this has me puzzled.
Many thanks
Regards
Jim
On Thu, 29 Aug 2019 at 23:11, Mlynch001 <mlynch002@...> wrote:
Jim,
Page 216 of 293 in the version of the 475 manual that I am looking at.
TEKWiki has a couple of versions for that instrument.
here is the link:
< TEKWiki is a great resource.
Best of luck on your repair.
--
Michael Lynch
Dardanelle, AR
|
Good morning Michael.
Many thanks for the info/link.
I downloaded it and it is slightly different to mine.
I found the 3, 10 ohm resistors in the +15 volt supply on page 216.
However none of them appear in the component list for that circuit.!!!!!
I have searched but cannot find R961,R963 and R965 and associated 2.2uf
capacitors anywhere except in the main component list.
Can you help and point me as to where they might be.
Sorry to be a pain but this has me puzzled.
Many thanks
Regards
Jim
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On Thu, 29 Aug 2019 at 23:11, Mlynch001 <mlynch002@...> wrote: Jim,
Page 216 of 293 in the version of the 475 manual that I am looking at.
TEKWiki has a couple of versions for that instrument.
here is the link:
< TEKWiki is a great resource.
Best of luck on your repair.
--
Michael Lynch
Dardanelle, AR
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Jim, Page 216 of 293 in the version of the 475 manual that I am looking at. TEKWiki has a couple of versions for that instrument. here is the link: < TEKWiki is a great resource. Best of luck on your repair. -- Michael Lynch Dardanelle, AR
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Thanks Michael,
I have a few higher voltage Tants so will use a 35 or 50 volt one.
Can you point me in the direction on the schematic where I can see that
resistor.
Will replace it as well.
Again thanks for help much appreciated,
Regards
Jim
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On Thu, 29 Aug 2019 at 19:57, Mlynch001 <mlynch002@...> wrote: Jim,
I found it in the 475 manual as well. Just in a different location on the
schematics. It just took a bit of searching. I have a 475A that I was
able to bring back from oblivion and I was more familiar with that
instrument, manual and the schematics. The two machines are very likely
identical in that area. I have a Type 576 CT that had about 15 ¡°bad¡± axial
Tantalum caps when I first received it, these things were quitting every
time I turned it on, after the 2nd or 3rd failure, I decided to replace
them all, with modern equivalents.
--
Michael Lynch
Dardanelle, AR
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Re: 502A - Anyone looking to part with one?
Now THAT would be an awesome story to hear! :-D If I ever get the opportunity, you know I will be posting about it!
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Mlynch001
John Williams
Michael W. Lynch
Jason A.