Author Topic: Test Equipment Anonymous (TEA) group therapy thread (Read 18607079 times)

tggzzz · « **Reply #47825 on:** January 25, 2020, 10:10:16 am »

Quote from: fredman12 on January 24, 2020, 10:03:03 pm

I have a Tektronix 2235 that has a distoration in the right lower quadrant. Any ideas how to repair?

I would suspect a distorted mesh in the CRT. So, check that the CRT does have a mesh. If it does, you would have to replace the CRT.

VK5RC · « **Reply #47826 on:** January 25, 2020, 10:23:21 am »

A really dumb question (from a dumb guy) re the distorted Tek, there's nothing magnetic on/under the bench /big transformer nearby?

For sick dragons, I liked the controlled trial of steroids/oral/inhaled for a post viral cough vs honey and lemon - guess which was the best! 👍

bd139 · « **Reply #47827 on:** January 25, 2020, 10:28:12 am »

Good call. That got me a couple of times.

Also take the graticule cover off and clean it. Sometimes it holds a bit of static which can distort things.

Martin.M · « **Reply #47828 on:** January 25, 2020, 10:49:29 am »

Quote from: med6753 on January 22, 2020, 07:06:09 pm

Ripped into the 535A to try to find the source of the arc and bang. As usual it turned into a marathon.

First, looked over the Trigger A section and the only thing I found suspicious was two flying leads that were real close to each other. But no marks indicating an arc. I separated them anyway. Sorry for the poor focus. Camera doesn't like going that close. They are the 2 bare leads going across the center of the pix.

Next I powered up and checked the ref V and all the B+ voltages. They are all OK. This PSU is damn stout to put up with those arc bangs. They were LOUD. And so far there have been no further snaps and bangs.

Next determine why no free running trace in “Auto” mode on Time Base A. Turns out the “Trigger Preset” adjust is off. This is where things went down hill. The pot is hopelessly jammed. I took it out and apart. Tried to free it up and the resistive element fell apart. It's a 200K linear miniature pot. No gots so I have to order one. It's the pot on the stand off. BTW, this Trigger Preset pot does NOT appear on my 535A schematics. Nothing new, see this all the time with Tek equipment. So many revisions and the manuals can't keep up.

In the meantime Time Base B does work fine. I'll order a new pot and at the same time I might as well start ordering replacement capacitors for the PSU. And in other news.....I found a “parts unit” 485 on Ebay for a reasonable price. Coming next week. I may FINALLY fix the trigger issue with the one sitting in the closet.

----------------------------------------------------

med6753 · « **Reply #47829 on:** January 25, 2020, 11:23:54 am »

Swapping over the Trigger board from the 485 parts unit.

The old board removed. Good riddance.

Replacement board installed. It's all modular and plug in except for 2 soldered wires in the far upper corner left.

At last! After all these months of fighting with it. It triggers!

But all is not well. There is some noise on the trace. The gain on both channels is extremely low. And worst of all the 50 ohm inputs on both channels no worky. Apparently some Gorilla blew them up. No worries...we'll work through it.

Specmaster · « **Reply #47830 on:** January 25, 2020, 11:44:29 am »

Quote from: bd139 on January 25, 2020, 10:28:12 am

Good call. That got me a couple of times.

Also take the graticule cover off and clean it. Sometimes it holds a bit of static which can distort things.

Things like a linear PSU close will cause it distort as well. Scopes are always susceptible to stray magnetic fields as be seen with the need to re-adjust the trace rotation almost every time you relocate the scope.

tggzzz · « **Reply #47831 on:** January 25, 2020, 11:49:03 am »

Quote from: med6753 on January 25, 2020, 11:23:54 am

But all is not well. There is some noise on the trace. The gain on both channels is extremely low. And worst of all the 50 ohm inputs on both channels no worky. Apparently some Gorilla blew them up. No worries...we'll work through it.

The noise may be due simply to the bandwidth; try BW limit.

The 50ohm issue might be a problem with the input relay and/or overvoltage protection. From a recent posting on TekScopes:

Quote

Tektronix had an inductive collapse transient problem from the coil of K151 which, over a period of time, tended to wipe out U80, the 155-0076 input protection IC. After SN B155789 a PNP transistor was installed as the relay driver which stopped this problem. Get two 155-0076 IC's from Sphere, this will probably clear up these problems, If your serial number is B155789 or below it would be smart to add the relay driver circuit shown on sheet 1 in your manual.

med6753 · « **Reply #47832 on:** January 25, 2020, 11:54:22 am »

Quote from: tggzzz on January 25, 2020, 11:49:03 am

Quote from: med6753 on January 25, 2020, 11:23:54 am
But all is not well. There is some noise on the trace. The gain on both channels is extremely low. And worst of all the 50 ohm inputs on both channels no worky. Apparently some Gorilla blew them up. No worries...we'll work through it.

The noise may be due simply to the bandwidth; try BW limit.

The 50ohm issue might be a problem with the input relay and/or overvoltage protection.

It's not the BW limit. I have my other 485 powered up and there's definitely a difference in trace quality between them. I haven't yet checked the PSU for voltage/ripple so that's the obvious place to start and go from there.

Edit....the S/N of this unit is B177847 so it has the input protection fix.

xrunner · « **Reply #47833 on:** January 25, 2020, 02:03:01 pm »

Here's my collection of victims from the Netgear board. Setting was 380 C and medium air. Most went smoothly even the BGA chip wasn't too bad. After I got comfortable, I used it for a real repair (or at least the start of one). I was easily able to remove the MOSFET from the 220 MHz mobile radio. Really glad I finally got this station.

How about a 3D print bed as a pre-heater LOL.

bd139 · « **Reply #47834 on:** January 25, 2020, 02:09:45 pm »

The important bit is sticking them all back on again

More seriously that’s a pretty good job. I want one now

Martin.M · « **Reply #47835 on:** January 25, 2020, 02:15:59 pm »

Specmaster · « **Reply #47836 on:** January 25, 2020, 02:37:12 pm »

Quote from: bd139 on January 25, 2020, 02:09:45 pm

The important bit is sticking them all back on again

More seriously that’s a pretty good job. I want one now

Yep, I don't use mine all that much, but when you need it, its worth its weight in gold, same as a desoldering tool. I got one of those 858 clones with the fan in the handle that mnem hates so much, but it is more than capable in the right hands for the occasional use they get.

xrunner · « **Reply #47837 on:** January 25, 2020, 02:41:26 pm »

Quote from: Specmaster on January 25, 2020, 02:37:12 pm

Quote from: bd139 on January 25, 2020, 02:09:45 pm
The important bit is sticking them all back on again

More seriously that’s a pretty good job. I want one now
Yep, I don't use mine all that much, but when you need it, its worth its weight in gold, same as a desoldering tool. I got one of those 858 clones with the fan in the handle that mnem hates so much, but it is more than capable in the right hands for the occasional use they get.

Which reminds me - now I need to buy soldering paste ...

The manual gives other uses for it such as "heat shrink, drying, remove lacquer, thaw, ... and disinfecting". Now I want to disinfect something.

Cerebus · « **Reply #47838 on:** January 25, 2020, 02:47:27 pm »

Quote from: med6753 on January 25, 2020, 07:27:32 am

Are you having a Discord meeting today at 1900 hours UTC? I haven't seen any recent mention of this.

Firstly, I thought 21:00 UTC (I think y'all getting 9 O'Clock and 9-teen hundred confused) - which by the way is just the wrong time for me here in London on a Saturday night which is why my quietude on Discord.

Secondly, don't know. The world has gone quiet on us. Anybody?

Cerebus · « **Reply #47839 on:** January 25, 2020, 02:49:21 pm »

Quote from: xrunner on January 25, 2020, 02:41:26 pm

The manual gives other uses for it such as "heat shrink, drying, remove lacquer, thaw, ... and disinfecting". Now I want to disinfect something.

Much good flame disinfection did Mnem!

med6753 · « **Reply #47840 on:** January 25, 2020, 03:13:36 pm »

I put the 485 back in the case to give a quick run in to see if any other issues crop up. Turns out the noise on the trace was hash getting into the scope since it was out of the case. The trace is now much improved.

Issues:

Both channel 1 and 2 have gain issues. Those traces should be 0.5V p-p. They are 0.4V p-p. The gain adjustment cannot achieve 0.5V p-p.

As mentioned both 50 ohm inputs are dead.

Need to check the PSU.

The knobs on the volts/div are from a 465 junker. The originals were cracked. But the parts mule has good knobs and they will be transferred over.

I fully expect that compensation adjustments will be necessary once the channel issues are resolved.

Specmaster · « **Reply #47841 on:** January 25, 2020, 03:15:55 pm »

Oh dear, thats sure to give mnem a poke in the ribs now, and he will retaliate with as much of his firepower as he can muster unless the medication has dampened his coals, so they won't burn any more

, How you're doing our friendly little dwagon

.

I wonder if the reason you're all doing so badly at the moment is because of the stark contrast from the big suck the icy blast? Give it a couple of years and you'll all be hardened to it all.

Martin.M · « **Reply #47842 on:** January 25, 2020, 03:34:43 pm »

Quote from: Cerebus on January 25, 2020, 02:47:27 pm

The world has gone quiet on us. Anybody?

I am watching always in the uited kingdom to catch a nice Solartron 6 1/2 or more, with orange display.
now washing the dirty boy here on the table, 427A.. (90% of the hobby is domestic)

mansaxel · « **Reply #47843 on:** January 25, 2020, 03:37:13 pm »

Quote from: Martin.M on January 25, 2020, 02:15:59 pm

(Attachment Link)

A wonderful instrument. Fully agree. I want a 410c. Or 410b. And then a Labor W Gerät. And a Simpson 260.

tggzzz · « **Reply #47844 on:** January 25, 2020, 04:04:19 pm »

Quote from: Martin.M on January 25, 2020, 03:34:43 pm

I am watching always in the uited kingdom to catch a nice Solartron 6 1/2 or more, with orange display.

About 2 lots of 6 Solartron 7075s were sold here recently. I didn't bid because I already have a spare 7075 frankenmachine including a cable

Yes, the panaplex displays are restful and generally delightful. I also have a working front 7075 panel that I need to find a use for.

Neomys Sapiens · « **Reply #47845 on:** January 25, 2020, 04:15:14 pm »

Quote from: Martin.M on January 25, 2020, 06:35:28 am

Quote from: edavid on January 24, 2020, 11:45:20 pm
Do not buy a 7844 with the P11 (eyehurt blue) CRT.
correct. Bring it directly to me.

this is my 7844, opt 21 (dedicated slots) + opt.78 (P11, blue beams)
(Attachment Link)

The only what is not so amazing is the readout system:
Some segments are "thin" displayed, by example:
a 8 looks like H. Also 6 and 9 the vertical bow is thin.
This may be better with a phosphor what have a longer delay then P11.
The little problem is not to see with simply vertical plugins bec. they use almost 1,5,0 , no 6,8,9
but counters, DMM read out results , so they do that.
P11 looks best with a sunglas filter (smoke grey, not blue), you see that here. The blue P11 was made for using the large Polaroid cameras, the films was very sensitive for the color.
A lot of digital cameras are also very sensitive for that, so the intensity must be low to get fine pictures.

Closest thing to Cherenkov blue that I have ever seen from a CRT or other electronic display. Eyehurt blue? Naw - soo good! Stop making me reconsider, I have no space!

mnementh · « **Reply #47846 on:** January 25, 2020, 04:24:03 pm »

Quote from: Specmaster on January 25, 2020, 03:15:55 pm

Oh dear, thats sure to give mnem a poke in the ribs now, and he will retaliate with as much of his firepower as he can muster unless the medication has dampened his coals, so they won't burn any more , How you're doing our friendly little dwagon .

I wonder if the reason you're all doing so badly at the moment is because of the stark contrast from the big suck the icy blast? Give it a couple of years and you'll all be hardened to it all.

I'm still alive... mostly just puttering on my bench at about half-speed. Right now taking a break to eat some leftover breakfast and check in here. Pretty sure my son brought the flu home from his basketball meet, so really nothing unusual in the chain of events that followed. I knew I was probably going to catch it from him when I decided to keep him company; these are the choices a parent makes.

We could pass the hat for tickets and send xrunner to Wuhan City with his 957DW+; he can disinfect everything there to his heart's content...

mnem
I think I hear a bed calling my name...

tautech · « **Reply #47847 on:** January 25, 2020, 04:40:36 pm »

Nah, I heard you've just gotta not drink Corona and you won't get the lurgy.

Martin.M · « **Reply #47848 on:** January 25, 2020, 04:41:10 pm »

Quote from: tggzzz on January 25, 2020, 09:59:20 am

Quote from: 0culus on January 25, 2020, 01:33:56 am
Dual beam does have one huge use case: looking at two signals of widely different frequency. Unless you do this a lot, it's probably not needed other from the cool factor.

example --> https://www.wellenkino.de/video/emg-1.mp4

Martin.M · « **Reply #47849 on:** January 25, 2020, 04:45:09 pm »


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Author Topic: Test Equipment Anonymous (TEA) group therapy thread (Read 18607079 times)

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