Author Topic: Very nice HP1745A with little problems.  (Read 18340 times)

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Offline David Hess

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Re: Very nice HP1745A with little problems.
« Reply #75 on: October 18, 2014, 01:48:49 pm »
For example, I realized TIP142 has reverse pin order compared to that don't-know-what-is-it-darlington.

Which means that the TIP140 series was not the original transistor.  I forgot to mention the pinout issue which shows up a lot in these old instruments.  Old transistors in the TO-127 package are ECB so TO-126 or TO-225 replacements are needed if you want to keep the same pinout but these packages are limited to about 40 watts which should be sufficient in this case.  I might use a 2N6039 or similar.

Quote
At MAGx5 there is nothing to do with that precious 2.37V zener with special thermal coefficients.
Because in this setting it is shunted by MAGx5 switch!

Yes, the zener diode only matters in normal mode.

I think I have got it!
What do you think, David?

Sorry for blurred picture.

I have made worse pictures.

I looks great.  Like I said earlier, the shape is not critical for proper operation.
 

Offline TGyuri

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Re: Very nice HP1745A with little problems.
« Reply #76 on: October 22, 2014, 09:45:32 am »
TIP142 is perfect at this position I think.

I've made some progress.
I've performed calibration 5-31 vertical amplifier balance adjustment and 5-32 position and sync balance adjustment.
Annoying trace shift, when changing Volts/Div almost has gone.
I think there are much more things what need to be calibrated.
I don't have a sine generator to about 100 MHz.
Bradley 192 has only fixed outputs at 20 MHz, 50MHz and 100MHz.

 

Offline TGyuri

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Re: Very nice HP1745A with little problems.
« Reply #77 on: October 29, 2014, 12:54:07 pm »
The postman, who is usually ringing twice, now only once. :)
He haven't had more time.
So I have got the original service manual now for HP1745A.
I have ordered it from ebay seller teoutlet.
It is in very good condition.
It is much better to read, than crappy .pdf, which is downloadable.
I'm wondering I'm going to make a better copy about it,
and I will send it to Keystone, to put it up to their website.
Regards,

Gyuri
 

Offline David Hess

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Re: Very nice HP1745A with little problems.
« Reply #78 on: October 29, 2014, 07:07:42 pm »
So I have got the original service manual now for HP1745A.
I have ordered it from ebay seller teoutlet.
It is in very good condition.
It is much better to read, than crappy .pdf, which is downloadable.
I'm wondering I'm going to make a better copy about it,
and I will send it to Keystone, to put it up to their website.

I often end up extracting pages from PDF scans, cleaning them up, and then printing them out so I can mark them up with colored pens as I work.  For paper manuals that I have, I sometimes scan in pages so I can print them out and mark up the copies as well.
 

Offline TGyuri

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Re: Very nice HP1745A with little problems.
« Reply #79 on: April 07, 2019, 12:34:03 pm »
I wasn't here for some time.
Lately I've purchased a Leo Bodnar 40ps pulser.
It is a very useful little gem, I like it very much!
Of course I've tested my HP1745A scope with it.
I've got about 130MHz bandwith on CH1, it is quite good I think.
However, I've got only 70MHz on CH2.
You can say, don't worry about it, then there is a 100MHz average.
Yet, I think I will check some things at CH2, someday.

Kind regards,
Gyuri
 


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