I picked up a Tek 503 scope recently and decided to get it running. Found only one bad filter cap. But it appears the
HV transformer T620 (pn# 120-199) is bad, all the voltages out of it gradually drop after running for a couple of minutes.
The +500v supply voltage is solid, I changed the 6DQ6 oscillator and the 6BL8 control tube but no change.
I checked for shorts on all the outputs and nothing bad there.
Anyone have any ideas on what else I can check to rule out the transformer?
So does anyone have a parts 503 and be willing to sell the transformer?
ChuckA
--
See Early TV at:
www.myvintagetv.com
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Line filter failure in AN/USM 488
Perhaps this may help someone in the future. I was contacted by a woman in Delaware whose father was a collector. I was given a lot of 8 scopes. Nothing incredible, mostly 4xx series. There was a 485 and a cart and that's what I'm opting to keep. One I hadn't seen before was a 488, which from what I've read is a slightly modified US Military 2235. Very serviceable! The front panel is a bit of a PITA but the supply is very accessible. I replaced a good portion of the electrolytics. The bulk filter and Sangamos read extremely well so I left them in. But I still got burned. And so did the scope. A word of caution for anyone who comes across this series. Under the PSU cage, beneath the IEC line filter and behind the power button is a single RIFA 68nF filter cap. I missed it. But after the recap, I let it burn in. When I heard the pop and the current limit light up, I expected a tantalum. But after 30 minutes of searching, I can say it was pretty obvious once I found it. /g/TekScopes/album?id=294823
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Several Tek products on Pinterest
This showed up on my Pinterest feed and is from an NY Times Article:
The system the woman is using is a LINC-8. The original Laboratory Instrument Computer (LINC) was developed at the MIT Lincoln Laboratory. Digital Equipment Corporation integrated it with a PDP-8 and sold it as the LINC-8, later updated to the LINC-12. I used a LINC-8. It had a Tek monitor in it with a pair of amplifiers (derived, I think, from 500-series plug-ins). Ours had a 12-bit A to D converter in it and did not come with the Tek 560 series scope or external Tek module (not sure what that is in the photo). The Tek monitor was an X-Y display and one fun software that was included was called ¡°Spacewar¡± and each player used two knobs to maneuver and one of the buttons to fire.
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Re: Translating a post to English
I'd cut and paste the Spanish text into an online Spanish-to-English translator, or, if the text is on a website, as you indicate, use Google translator on that page.
DaveD
KC0WJN
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On May 2, 2024, at 12:11, spinroyd via groups.io <spinroyd@...> wrote:
?I have a 495 spec analyzer with a phase lock failure. Theres a post on this cite in spanish that was a fix. Is there a translator on this cite? I havent explored other apps yet.
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Re: Did I discover a manual error in my SC502?
I see what you mean. In that case, I won't cloud the issue with any more suppositions. I'd be interested in seeing if you find any clarification on it.
Thanks,
Barry - N4BUQ
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I added more photos. All the other positions match except ch1
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Re: Did I discover a manual error in my SC502?
I added more photos. All the other positions match except ch1
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Translating a post to English
I have a 495 spec analyzer with a phase lock failure. Theres a post on this cite in spanish that was a fix. Is there a translator on this cite? I havent explored other apps yet.
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Re: Did I discover a manual error in my SC502?
If that's the case, then it appears that agrees with CH1. The contacts are listed in 4123 order in the manual so it appears that is the position for CH1.
Barry - N4BUQ
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The one in the manual has 4 switch contacts because the first one is the power
contact that is omitted in the mode select section. The first contact appears
in the powersupply section. Ignore the 1st contact in the physical image. The
last 4 are the ones shown in the manual.
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Re: Did I discover a manual error in my SC502?
The one in the manual has 4 switch contacts because the first one is the power contact that is omitted in the mode select section. The first contact appears in the powersupply section. Ignore the 1st contact in the physical image. The last 4 are the ones shown in the manual.
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Re: Did I discover a manual error in my SC502?
The manual shows four switch contacts but the switch in the picture appears to have five. That seems incorrect.
Thanks,
Barry - N4BUQ
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So my SC502's mode contact switch positions doesn't 100% match the ones in the
manual.
Ch1 switch config should be 01100 according to the manual. But for me, the
actual switch contact is 01001.
Can someone else with an SC502 verify that mine or the manual is correct?
Images:
/g/TekScopes/albumid=294816
Thanks,
Benjamin
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Did I discover a manual error in my SC502?
So my SC502's mode contact switch positions doesn't 100% match the ones in the manual. Ch1 switch config should be 01100 according to the manual. But for me, the actual switch contact is 01001. Can someone else with an SC502 verify that mine or the manual is correct? Images: /g/TekScopes/albumid=294816Thanks, Benjamin
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Hi Glenn,
As to U241, the internal gates are just used as inverters by tying the inputs together, so NAND or NOR makes no difference here. Each is a drop-in replacement for the other in this case; no PCB layout changes required. I can't think of a good electrical reason to prefer one part to the other in mid-production -- they differ negligibly in prop delay, for example. Perhaps it was just what they could get at the time, or get at a good price, perhaps.
-- Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
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On 5/1/2024 9:54 AM, Glenn Little wrote: Another question is U241.
It is listed as 74S00 or 74S02 depending on serial number range.
Why would this part be changed?
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On Wed, May 1, 2024 at 06:54 PM, Glenn Little wrote:
Hi Glenn,
Unfortunately, replacing the "74S..." series logic gates is almost always a lottery win.
In circuit design, normally, the 74S series is used due to the higher speed of its logic gates and therefore a very fast step response, you can try with an equivalent code of the 74LS series (low consumption S series), but sometimes they are not fast enough (low consumption means greater slowness), if after replacement you should encounter operating defects or a degradation of the instrument's characteristics, you should search on eBay for a logic gate from the old 74S series.
kind regards... Loris IW4AJR
--
73 de IW4AJR Loris
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Re: Tektronix 760 trace issue (it's enormous)
For anyone wondering, it's fixed and the problem was caused by bad resistors in the focus circuit.
R3-R4-R5 were all significantly out of spec. I replaced R1 and R2 while I was there.
I added a couple more photos to the album. Thanks for the guidance everyone.
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On Wed, May 1, 2024 at 8:57?AM Clark Foley via groups.io <clarkfoley@...> wrote:
I did not check models but it is in your backyard.
This panned out, thanks! Still passively looking for a K217 for my DSA602.
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Re: FS: Tektronix 7613 w/Horizontal plug-in in, and vertical plug-in
If you're not in the area you can have it shipped, though if it is shipped, I cannot guarantee it's operation upon arrival. I will do my best to pack it.
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Re: WTB: Tek 500 Series Cover Latches
Try VintageTek Museum
Dave Wise
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On May 1, 2024, at 11:06 AM, Gordon, KJ6IKT <gfsmith@...> wrote:
?Hi All,
I have an old Tek Model 502 that is missing two of it's cover latches. These are the older latches that have a screw, anti-rotation washer, and plastic flat wingnut. One of them also needs a spacer washer but I can fabricate that. Would anyone have two of these animals out there? Willing to pay shipping and a nominal amount to get them.
73, Gordon KJ6IKT
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WTB: Tek 500 Series Cover Latches
Hi All,
I have an old Tek Model 502 that is missing two of it's cover latches. These are the older latches that have a screw, anti-rotation washer, and plastic flat wingnut. One of them also needs a spacer washer but I can fabricate that. Would anyone have two of these animals out there? Willing to pay shipping and a nominal amount to get them.
73, Gordon KJ6IKT
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I recently bought a FG503 at a hamfest that was in non working condition.
The serial number of this unit is in the high range.
The parts layout agrees with the low range parts layout.
The board does not appear to have been changed.
Would it be common to have this disagreement with serial numbers?
Another question is U241.
It is listed as 74S00 or 74S02 depending on serial number range.
Why would this part be changed?
The sockets are TI and I plan to change them to high quality sockets due to the problems reported with the TI sockets.
Any comments about the above before I dive into this unit?
Any words of wisdom?
Thanks
Glenn
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIVwb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA-LM ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
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Re: 11302A Enhanced Accuracy problem
I have put this on the back burner for now, thanks again for all the help!
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Benjamin Badrakh
Loris Bollina