Author Topic: HP 1741A oscilloscope - restoration project (Read 98447 times)

tekfan · « **Reply #50 on:** January 19, 2012, 03:13:05 pm »

Almost finished:

When I got the oscilloscope it didn't have the HV power supply cover as someone was obviously trying to troubleshoot it.
I used the cover of an old ATX power supply. It fits very nicely.

This is what the step response looks like.
I am feeding a fast risetime square wave from a Tek 106 generator (<1ns risetime) into the scope input terminated to 50 ohms at 50ns/div.
There is a lot of overshoot. This can be compensated out by adjusting the HF response of the vertical output amplifier.

Vertical amplifier compensated. The step looks much cleaner now.

And the end result is another nice oscilloscope from the 70's

krivx · « **Reply #51 on:** January 19, 2012, 04:08:32 pm »

This is really impressive!

What are you using to clean the front panels? I have a Philips scope from this period that is more-or-less functional but is a bit grimy.

firewalker · « **Reply #52 on:** January 19, 2012, 04:19:06 pm »

Excellent job! Look like new.

Alexander.

HLA-27b · « **Reply #53 on:** January 19, 2012, 04:33:36 pm »

Beauty!
and nice photography too.

tekfan · « **Reply #54 on:** January 19, 2012, 05:16:48 pm »

Quote from: krivx on January 19, 2012, 04:08:32 pm

What are you using to clean the front panels? I have a Philips scope from this period that is more-or-less functional but is a bit grimy.

I almos always use window cleaner, a cloth, toothbrush with bristles cut short, cotton swabs and that's about it.

wkb · « **Reply #55 on:** January 19, 2012, 05:49:35 pm »

My compliments! Beautiful job!

Kilroy · « **Reply #56 on:** January 19, 2012, 10:40:14 pm »

Awesome.

I find it particularly fascinating that the finished scope is now a 1740A instead of the original 1741A.

ilikepez · « **Reply #57 on:** January 20, 2012, 01:22:57 am »

Quote from: Kilroy on January 19, 2012, 10:40:14 pm

Awesome.

I find it particularly fascinating that the finished scope is now a 1740A instead of the original 1741A.

He got a second one to restore.

You did an amazing job tekfan. I hope to be that good with electronics someday. I don't know what it is about electronics from the 1970's but they all look gorgeous.

Teknotronix · « **Reply #58 on:** January 20, 2012, 02:29:28 am »

Great work!

snoopen · « **Reply #59 on:** January 20, 2012, 03:18:26 am »

Great work mate! Nice hacks with the IC transistor and ATX PSU case!

siliconmix · « **Reply #60 on:** January 23, 2012, 09:47:00 pm »

nice job

bsgd · « **Reply #61 on:** January 24, 2012, 01:06:40 am »

I just love the looks of old instruments!

Too bad they cost a fortune here and Im stuck with cheap chinese stuff.

wkb · « **Reply #62 on:** January 24, 2012, 03:51:48 pm »

Quote from: bsgd on January 24, 2012, 01:06:40 am

I just love the looks of old instruments!

Agreed! And the build quality of the older stuff is just so much nicer. OK.. the prices are another matter. I think the list price of my Tek 2465CTS was something like US$ 6800 in its day... Ouch

calin · « **Reply #63 on:** January 24, 2012, 09:22:58 pm »

I just grabbed one of these in a much much better condition of an craigslist ad .. if you can believe it .... for 50$ cash !!! insane !!

I can't wait to see how is working cause right now is resting in the trunk of my car as I am @ work

.

bsgd · « **Reply #64 on:** January 24, 2012, 10:45:01 pm »

Quote from: wkb on January 24, 2012, 03:51:48 pm

Quote from: bsgd on January 24, 2012, 01:06:40 am
I just love the looks of old instruments!

Agreed! And the build quality of the older stuff is just so much nicer. OK.. the prices are another matter. I think the list price of my Tek 2465CTS was something like US$ 6800 in its day... Ouch

Well agreed again! The quality on this stuff is really nice. Much better than any other electronics most of us can afford. And thats probably because these were very expensive on the past and we can glance at how well something could be engineered if price was not the single most important factor in manufacturing.

bsgd · « **Reply #65 on:** January 24, 2012, 10:45:52 pm »

Quote from: calin on January 24, 2012, 09:22:58 pm

I just grabbed one of these in a much much better condition of an craigslist ad .. if you can believe it .... for 50$ cash !!! insane !! I can't wait to see how is working cause right now is resting in the trunk of my car as I am @ work .

Can you post some pics? Please please please

mayeri · « **Reply #66 on:** December 09, 2012, 06:17:37 pm »

Hi all, I has recently been registered in this site because I saw the HP 1741A restoration project. The published images reveal a very impressive professional knowledge about oscilloscopes.
Not long ago I received a similar device from my acquaintance who has not used this about five years.

Let us breathe life into the topic…

mayeri · « **Reply #67 on:** December 09, 2012, 06:20:06 pm »

The storage mode seems ok…

mayeri · « **Reply #68 on:** December 09, 2012, 06:23:46 pm »

These two problems with conventional mode. How do I get rid of them? Please, TekFan...

tekfan · « **Reply #69 on:** December 09, 2012, 07:38:04 pm »

Quote from: mayeri on December 09, 2012, 06:17:37 pm

Hi all, I has recently been registered in this site because I saw the HP 1741A restoration project. The published images reveal a very impressive professional knowledge about oscilloscopes.
Not long ago I received a similar device from my acquaintance who has not used this about five years.

Let us breathe life into the topic…

Welcome to the forum! Hope you find some useful stuff on the forum.

So, looking at the storage controls (PERSISTENCE and BRIGHTNESS) they are almost fully counterclockwise. In this case when the scope is in storage mode you should get a screen that is completely green. The trace should fade out very fast since the persistence control is almost at its minimum.

In STORAGE mode the you should get the following displays with the control settings:
PERSISTANCE min., BRIGHTNESS min. ---> CRT looks completely green
PERSISTANCE min., BRIGHTNESS max. ---> CRT looks completely green, slightly brighter trace and screen
PERSISTANCE max., BRIGHTNESS min. ---> CRT no longer green, trace is stored on the screen
PERSISTANCE max., BRIGHTNESS max. ---> CRT no longer green, stored trace is slightly brighter

Pressing the ERASE button causes the screen to flash brightly and erase the stored image

When the scope is in CONVENTIONAL mode, the screen shouldn't be green anymore and the trace should fade out almost instantly. The storage controls should have absolutely no effect in CONV mode.

What may be happening is that one of the logic ICs on the storage board is defective, causing the flood guns and storage functions to be operatied in the CONV mode. This may also be caused by leaky transistors driving the flood gun control grids, collimator plates, collector mesh, and storage mesh.

Check if the storage controls (PERSISTENCE and BRIGHTNESS) have any effect when the scope is in STORAGE and CONV mode.

Those are all the ideas I've got at the moment.

You may want to read the Theory of operation section of the service manual (onward from page 94):
http://cp.literature.agilent.com/litweb/pdf/01741-90911.pdf

mayeri · « **Reply #70 on:** December 09, 2012, 10:36:54 pm »

Hi TekFan,
Thanks for the quick response. I thought it will not be too easy…
In storage mode I get a good picture in only one position: PERSISTANCE min., BRIGHTNESS min.
The storage controls (PERSISTENCE and BRIGHTNESS) do absolutely no effect in CONV mode. That’s ok.

mayeri · « **Reply #71 on:** December 09, 2012, 10:39:31 pm »

I show the rest:

mayeri · « **Reply #72 on:** December 09, 2012, 10:59:40 pm »

PERSISTANCE

SeanB · « **Reply #73 on:** December 10, 2012, 04:53:58 am »

I have a dead storage scope mainframe somewhere....... Think the tube still works.

mayeri · « **Reply #74 on:** December 10, 2012, 09:05:08 pm »

Does this phenomenon show an obviously defective tube? I would trust in the TekFan’s experience firstly…
Tube replacement would be? Then the spot remains…
Despite the spot it could be used in conventional mode.


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Author Topic: HP 1741A oscilloscope - restoration project (Read 98447 times)

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