Re: Tek 495P A54 Memory Board Repair
On Tue, 24 Jul 2018, Michael A. Terrell wrote: It is simply astonishing how helpless some people are :) If one wants to replace a DIP IC he doesn't need _ANY_ specialized desoldering equipment. Just cut all pins as close to the case as possible, throw away that brick and pull the remaining pin stubs one by one using soldering iron and tweezer. Then use desoldering braid to clean the holes from remaining solder and the board is as good as new ready for a replacement IC. No special desoldering tools needed and no such tools make better job. The only case when one would require such tools is removing an IC undamaged for further inspection or reuse. In his case it is totally unnecessary because replacement buffer IC cost pennies so it is not even worth bothering with checking a suspicious one -- just yank it out and replace with a new one. Where are you located? Someone on the group may live nearby. I would offer
to replace it for you, but I can't get to my workbench until I finish
disposing of the things my family stored in the building.
Michael A. Terrell
-----Original Message-----
From: Rick Boswell <frboswell@...>
Sent: Jul 24, 2018 1:38 PM
To: [email protected]
Subject: Re: [TekScopes] Tek 495P A54 Memory Board Repair
The switches are enabled to the data bus via tri-state buffer and an
enable signal that occurs just once during boot up. Challenging to
trouble shoot with my limited test equipment. And, if the buffer is bad,
I lack the desoldering gear necessary to change it. --- * * KSI@home KOI8 Net < > The impossible we do immediately. * * Las Vegas NV, USA < > Miracles require 24-hour notice. * *
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Re: Tek 495P A54 Memory Board Repair
Well ¡, I don't yet know that it needs to be replaced. The buffer IC may not be the problem and I don't want to begin changing parts until I have a more conclusive idea as to which part to change. Located NH. What I am looking for per first post is someone who can trouble shoot & repair, or supply a known good board.
RB
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Hi Leo,
I fixed a couple of 22XX SMSP. The one in my 2232 last summer, and the other day the one in my 2215.
The regulator is not too fussy as to what FET model you use to replace the old one.... AS LONG as it meets or exceed the specs of the old one, of course ! ;-P Obviously the FEt you used did not meet the specs, by a long shot, so no big surprised that it failed.
Typically you just pick whatever FET you can get from your favorite parts supplier, that meets the specs( voltage and current rating), and as for Rdson, typically modern FET have a much, much lower Rdson, in the order of tens of milli-ohms versus a few ohms for the old ones.
For my 2215, the old FET was an ancient IRF820, 3ohms, horrible. I ran a parametric search and ended picking up a FET made " Infineon ", part number : IPP60R280P7, which is 0.028ohms... yes, two orders of magnitude lower. Great because the FET is not mounted on a heat sink, there is zero airflow, not even still air around it (because it's trapped in ins plastic holder), and this particular scope has no cooling fan to top it all. So really, the much lower Rdson is welcome.
Anyway, this FET works just fine..
In my 2232 I used another FET model and brand, don't even remember what it was, but works just fine also. An IRF something maybe...
Your scope came with yet another FET model. Tek themselves used many different FET models, it's not critical, so don't lose sleep over it... as long, again, as the specs the replacement you choose, meet the voltage and current rating, and take that opportunity to use a modern FET with a much lower Rdson, rather than trying to find an obsolete FET with a higher RDson... "original" is not always better ;-)
HTH,
Vincent Trouilliez
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Re: Tek 495P A54 Memory Board Repair
Where are you located? Someone on the group may live nearby. I would offer to replace it for you, but I can't get to my workbench until I finish disposing of the things my family stored in the building.
Michael A. Terrell
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-----Original Message----- From: Rick Boswell <frboswell@...>
Sent: Jul 24, 2018 1:38 PM
To: [email protected]
Subject: Re: [TekScopes] Tek 495P A54 Memory Board Repair
The switches are enabled to the data bus via tri-state buffer and an enable signal that occurs just once during boot up. Challenging to trouble shoot with my limited test equipment. And, if the buffer is bad, I lack the desoldering gear necessary to change it.
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Re: Tek 495P A54 Memory Board Repair
The switches are enabled to the data bus via tri-state buffer and an enable signal that occurs just once during boot up. Challenging to trouble shoot with my limited test equipment. And, if the buffer is bad, I lack the desoldering gear necessary to change it.
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Re: Tek 495P A54 Memory Board Repair
I only have the user manual for that model, but the SA has to read the switches, usually through a latch that is polled at startup. That is where I would start troubleshooting.
Michael A. Terrell
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-----Original Message----- From: Rick Boswell <frboswell@...>
Sent: Jul 24, 2018 12:55 PM
To: [email protected]
Subject: [TekScopes] Tek 495P A54 Memory Board Repair
I have a nice high serial number (B030xxx) 495P spectrum analyzer with a defective A54 memory board P/N 671212401. I have determined that this board is defective by swapping in a known good board from another 495P I have replaced the usual electrolytics but no joy. With the defective board in the SA, it boots up as a 492AP instead of a 495P as shown via on-screen messages. The 49x series of SAs use a common base of microcomputer code, with the model no. (and corresponding firmware) determined via DIP switches on the A54 memory board. I have checked the DIP switches with an ohmmeter and these seem to be working as expected, and are set according to the service manual. The DIP switches are enabled to the data bus during boot up to allow these switch settings to be read. It appears that something in the circuit enabling these switches to the bus is not working correctly. I have reached the limit of my test equipment and diagnostic & repair skills and am looking for someone who might be able to diagnose and repair this A54 memory board, or, looking to purchase a known good A54 board with v9.7 firmware. Any guidance much appreciated.
Rick
K8EZB
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Re: Bringing up a Tek 555 dual-beam scope
Hey Mike, Ive done three 500 Series restorations recently - 549, 547 and a 535,not a 555 though Tried to document as much as possible below, I don't do magic smoke method, rather take a very cautious approach - time consuming, but saves from burning part. Typically 1. I clean the unit totally, and do a complete visual inspection - for damaged/shorted components, broken wiring etc. 2. Recap - I generally replace all electrolytic and Paper. Mica ones do survive - But they all Mica/Paper the same, best way to test few with a leak tester. 3. Test tubes - Shorted tubes can be a disaster - So generally I test almost all tubes and ensure they are not shorted. 4. Naked wiring - They do have a lot of naked wires, you need to verify they are not shorted to ground/chassis. I burned many tubes while restoring 549 because of this 5. Use variac & power up, I do heater first, (remove Time delay Tube) and then if all good, then put the Delay tube back to power up all DC rails. 6. Then its troubleshooting based on what is broken - HTH Regds Rajesh On Sun, Jul 22, 2018 at 10:48 AM, Michael Leslie Squires <mikes@...> wrote: Just bought a Tek 555 scope with cart and power supply. The scope
appeared to have been used until replaced by a couple of 4xx series scopes
but just shunted aside when replaced.
I owned and used a 555 40 years ago (warmed my basement quite well) but
that scope, a Frankenstein monster created by plugging the CRT unit from
one into the power supply from another, not only worked but was calibrated
when turned on. As a result I never had to do any work on the unit.
Are there any precautions I should take when powering up this unit? One
suggestion is to plug it in and turn it on; if the magic smoke escapes find
where it came from and fix it. I do have a Variac and am thinking about
building one of the devices which has a large incandescent in series with
the DUT.
I do note that the contacts on some of the plug-ins are quite dirty, so
I'm going to give the unit a good cleaning before firing it up. I will
also check the big electrolytics for signs of failure and possibly for high
ESR.
My first scope was a Tek 511; I had to rebuild the HV supply as the diodes
had failed. I currently have a 465B which is working well.
Mike Squires
wwww.siralan.org or www.smithgreensound.com
UN*X at home since 1986
-- /Rajesh
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Re: Homemade tunnel diodes
FWIW non-linear optical methods are used to compress the length of laser light pulses. Somewhat
analogous to NLTL's, but at 10^14Hz.
Craig
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-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Ed Breya via Groups.Io
Sent: 24 July 2018 17:32
To: [email protected]
Subject: Re: [TekScopes] Homemade tunnel diodes
Jose said:
"Not many people seem to have made DIY NLTL, let alone samplers based on it."
This is probably true, because NLTLs usually have lots of stages, so can get very big and
complicated
before you get remarkable compression. For simplicity and effectiveness, a single SRD/varactor of
the
right type, in the right circuit environment, is pretty hard to beat for straight up impulse
generation or
frequency multiplication. A whole bunch of them cascaded can form a NLTL, with its edge-
enhancement and wide BW. As always, it depends on the particulars of the application.
I don't think there's a need for a "modern" replacement for the SRD/varactor. It's a common RF
part -
not at all an obsolete technology. Nowadays there are alternatives for many applications, by using
fast
active devices capable of appropriate edge speeds.
Ed
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Tek 495P A54 Memory Board Repair
I have a nice high serial number (B030xxx) 495P spectrum analyzer with a defective A54 memory board P/N 671212401. I have determined that this board is defective by swapping in a known good board from another 495P I have replaced the usual electrolytics but no joy. With the defective board in the SA, it boots up as a 492AP instead of a 495P as shown via on-screen messages. The 49x series of SAs use a common base of microcomputer code, with the model no. (and corresponding firmware) determined via DIP switches on the A54 memory board. I have checked the DIP switches with an ohmmeter and these seem to be working as expected, and are set according to the service manual. The DIP switches are enabled to the data bus during boot up to allow these switch settings to be read. It appears that something in the circuit enabling these switches to the bus is not working correctly. I have reached the limit of my test equipment and diagnostic & repair skills and am looking for someone who might be able to diagnose and repair this A54 memory board, or, looking to purchase a known good A54 board with v9.7 firmware. Any guidance much appreciated.
Rick
K8EZB
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Re: Homemade tunnel diodes
John Larkin of Highland Technology has posted a lot of comments about doing this on the news:sci.electronics.design Usenet newsgroup. His company does a lot of high speed system designs for other high tech companies. You can access that group through Google Groups to contact him, or just to read his comments.
Michael A. Terrell
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-----Original Message----- From: "Ed Breya via Groups.Io" <edbreya@...>
Sent: Jul 24, 2018 12:31 PM
To: [email protected]
Subject: Re: [TekScopes] Homemade tunnel diodes
Jose said:
"Not many people seem to have made DIY NLTL, let alone samplers based on it."
This is probably true, because NLTLs usually have lots of stages, so can get very big and complicated before you get remarkable compression. For simplicity and effectiveness, a single SRD/varactor of the right type, in the right circuit environment, is pretty hard to beat for straight up impulse generation or frequency multiplication. A whole bunch of them cascaded can form a NLTL, with its edge-enhancement and wide BW. As always, it depends on the particulars of the application.
I don't think there's a need for a "modern" replacement for the SRD/varactor. It's a common RF part - not at all an obsolete technology. Nowadays there are alternatives for many applications, by using fast active devices capable of appropriate edge speeds.
Ed
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Re: Homemade tunnel diodes
Jose said:
"Not many people seem to have made DIY NLTL, let alone samplers based on it."
This is probably true, because NLTLs usually have lots of stages, so can get very big and complicated before you get remarkable compression. For simplicity and effectiveness, a single SRD/varactor of the right type, in the right circuit environment, is pretty hard to beat for straight up impulse generation or frequency multiplication. A whole bunch of them cascaded can form a NLTL, with its edge-enhancement and wide BW. As always, it depends on the particulars of the application.
I don't think there's a need for a "modern" replacement for the SRD/varactor. It's a common RF part - not at all an obsolete technology. Nowadays there are alternatives for many applications, by using fast active devices capable of appropriate edge speeds.
Ed
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Hi all, a cheap and broken 2215A found it's way to my home :-), so now I am in the process of getting it repaired. I used this document from H?kan that helped me a lot: The fuse would blow instantly, so I separated the main PS from the rest by removing Q9070. An inspection by the eye learned that there were several low voltage elco's leaking, C960/C962 (+8,6V) were leaking; C961/C963 (-8,6V) were leaking; C968/C970 (+5,2V) were bad; C956 (+30V) was leaking; Fortunately no real damage to the PCB. Also the Q9070 and CR907 were toast. According to the document the FET is a IRF730 (400V 5,5A 0,75Ohm 12ns) and the diode a BYD73G (400V 1A 50ns) I replaced all the capacitors first, and now the scope has trace(s) when applying 43VDC to TP940 (Pos) and TP950 (neg). Being the optimist, I replaced Q9070 with a FQPF4N90C (900V 4A 3,5Ohm 50ns) and CR907 with a PR1507 (1000V 1,5A 300ns) I harvested from a switching PS, but.... They last about 2 seconds... Based on H?kan's document I applied a test voltage to C925, and the signals at the chip U930 check out, and since I tested all surrounding components Q908, CR908, R909, CR920, I come to think it must be the speed of the Q9070 and CR907 that causes the sudden death of these replacement components. My question is: does anybody (recently) repaired a 2215A LVPS and replaced these 2 comonents? If so, what replacements were used ? The documents suggest a MTP6N55 for the FET and a BYD73G for the diode, but I would love to hear if there are other successful candidates. Pictures can be found in this album: /g/TekScopes/album?id=64919un saludo, Leo
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Re: Tektronix DM5010 NiCa 2.4V battery replacement
On Tue, 24 Jul 2018 00:26:58 -0700, you wrote: Hi everyone,
Please keep in mind that this DMM has been available since the very beginning of the eighties, if not late seventies.
It has been designed about ten or less years after man walked on moon.
We should now be able to replace the entire CPU board with a single $2-3 micro-controller. You can, within limits. The 488 bus is a difficulty, and may be more happily replaced with a chip or an FPGA, your choice, although there are 488 simulators. The front panel had a separate chip that did LED output scanning and keypad decoding. That can be replaced with a CPLD if you want. The rest of it is custom interface to the remainder of the boards and the EEPROM (the CMOS battery backed up RAM being the main source of the problems). I would design with an ARM processor (yes, overkill), and an FPGA (I'd prefer a Xilinx Spartan 6 in a 144 pin TQFP package, which can be done at home). Then you'd have to have a number of level converters, some to the 5 volt front panel, and the rest to the 5 volt system boards. I'd rather overengineer and have capability left over than to get 3/4 of the way through and not have the capability left. You'd probably do well with a MEGA 64 (64K flash, and I think 8K RAM, 2K EEPROM) which would do for the 5 volt processor (if you wanted), then you'd need an interface to the 3.3 volt FPGA. Alternative is the XMEGA series (runs on 3.3 volts) replacing the ARM processor. I ran out of capability in the MEGA/XMEGA lines a while back and switched to ARM. The main problem is not the circuit design, but the replication of the original program in C. Mostly you want to know what the interface to the existing hardware happens to be (program wise). The 488 stuff is better defined. Harvey
Best regards,
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Re: 7603 specifically and general refurbishment procedures of older oscilloscopes
IMHO only replace electrolytic caps that have failed, those big Sprague caps are normally OK except when they go open-circuit.
Dave
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of johnasolecki@... Sent: 24 July 2018 12:40 To: [email protected]Subject: Re: [TekScopes] 7603 specifically and general refurbishment procedures of older oscilloscopes Thanks for the suggestions. I'm pretty certain I had all the buttons pressed correctly but I'll recheck that (wouldn't be the first time...!) and I'll try to check the unblanking circuitry. What about capacitors and other aging components? As needed or change them all? John
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Re: Homemade tunnel diodes
I did not know about NLTLs, thanks Bruce for the heads up. For those in my case, I have found a few references on the net: All documents refer to simulations made using Spice/LTSPice/ADS Not many people seem to have made DIY NLTL, let alone samplers based on it. On Mon, Jul 23, 2018 at 10:26 PM Bruce Griffiths <bruce.griffiths@...> wrote: For the purposes of harmonic generation NLTLs have much lower PN than SRDs.
Bruce
On 24 July 2018 at 05:37 thespin@... wrote:
Modern mixer diodes are great but I have yet to find a good replacement for step recovery diodes.
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Hi all,
Looking for a volt/div knob for 485. It works fine and would like to use it more.
Steve
KG7HYG
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Re: 465B - Power Switch Mounting Nut Question
Ren¨¦ Rajesh,
Thanks for the replies and pics. I thought that was correct but just wanted to make sure.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Barry" <n4buq@...>
To: [email protected]
Sent: Monday, July 23, 2018 9:28:03 PM
Subject: 465B - Power Switch Mounting Nut Question
A few months ago, I removed the trigger board from my 465B to work on the
power supply caps. I started reassembling it and was left with a small
nylon(?) block with a hex nut holder and a small slot in it. See the album
below for pictures of it.
/g/TekScopes/album?id=64907
If I'm not mistaken, I think this is used behind the nut that holds the power
switch in place and I used it that way (last picture); however, I'm
wondering if I have it turned 180-degrees and the small slot is supposed to
align with the main board.
Is that where that part goes and, if so, is it supposed to align with the
other PC board? I've found one picture on the web that shows it and I think
that's correct but would like to know whether I have that right.
Thanks,
Barry - N4BUQ
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Hi Guys,
If there is too much for Craig, I would be interested to do a sharing-type
deal. I live in London, UK. Both Craig and I wouldn't have any import
problems, I think.
This is only if Craig can't take everything, he has first shout.
It would be useful to know in a bit more detail what is being offered, here.
I am guessing that these originally came from Tektronix, Guernsey as did my
7623A?
Regards, Colin.
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Craig Sawyers Sent: 24 July 2018 11:59 To: [email protected]Subject: Re: [TekScopes] Tek bits Hi Andre I'm near Oxford UK and would be very pleased to have these. Regards Craig -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Andre de guerin via Groups.Io
Sent: 24 July 2018 10:57
To: [email protected]
Subject: Re: [TekScopes] Tek bits
Tiny island near France, called Guernsey.
www.cwgsy.net/private/mandoline "Error 008472. Horrible bug encountered. $Deity knows what happened."
On Monday, 23 July 2018, 09:04:47 GMT+1, Craig Sawyers <c.sawyers@...> wrote:
> Hi, in my shed I have a lot of Tek bits including very hard-to-find
long pots.have a few flybacks but not
sure what state they are in.
Anyone have a use and want to pay postage only?
_A Where on planet earth are you?
Craig
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Re: 7603 specifically and general refurbishment procedures of older oscilloscopes
Thanks for the suggestions. I'm pretty certain I had all the buttons pressed correctly but I'll recheck that (wouldn't be the first time...!) and I'll try to check the unblanking circuitry.
What about capacitors and other aging components? As needed or change them all?
John
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Hi Folks
I am working on a tek 455 scope. managed get the trace up.
facing a trig problem. doesnt trig in auto/normal/single sweep.
trig view signal ok. suspect trig ic 155-0122-00
is this ic used in any other tek scope so that i can try to cannibalise and get this going
Thanks in advance
regards
Anand
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Sergey Kubushyn
Vince
Michael A. Terrell
satbeginner
David C. Partridge
Jose Luu