Improving older test equipment

[jackinnj]

Conrad -- is the Tek 545 the one that Jim Williams illustrates in his application notes?

I had a 535 which was ex-Grumman on Long Island. In the early 1980's Grumman, AIL, Fairchild etc. were upgrading there stuff so the scopes became available. There was a problem with arc-over on the ceramic strips -- and you didn't want to use any kind of abrasive cleanser on them.

Well, I have an HP6177B current source which has to go under the knife...

[1audio]

Jim Williams used a 547 for most of those pictures. A 50 MHz scope.

PMA- I don't buy the 20 MHz analog scope not seeing any of a 100 MHz tone at such a high level. It may be a furry line but not invisible. At the same time which audio opamp can deliver a -20 dBM 100 MHz signal?

[jackinnj]

CFB Opamps perhaps -- LME49713 is an audio CFB with GBW of 132MHz.

[destroyer X]

regards,

Carlos

[Joshua_G]

Pavel,
What's audio link stage?

[anatech]

Hi,
I do use an HP 339A, it's far better than anything else I have used to date. There must be some wiggle room to improve things a smidgen. Even going over the power supply shout help. The input BW of these things is just a bit over 1 MHz, so they do catch most of the harmonics at 100 KHz.

The older 65x oscillators could be improved. They do have a meter to read output, and those meters are deadly accurate. Also, not much wrong with a 331/2/3/4 THD meter either. They double as an accurate audio level meter, better than Leader or Kenwood and most DVMs (as mentioned). They are also better at reading THD than Leader or Kenwood. The HP does get all the harmonics, and you certainly can't say that about the newer low cost products. I feel these instruments still have a long, valuable service life, even if they can't read the lowest levels of distortion. At least the answer you get with these is the truth!

John, I may have the manual for you if you need. Probably on PDF ... I believe you can also download it from Agilent's site. The file is 7.9 M in size, so not really email friendly. Joshua, you should download the manual for normal service and alignment use.

I have repaired and restored some HP equipment over the years while working at my own shop, and also for Transcat calibration labs. The big thing is to be clean and careful, you need patience so that you don't damage the PCB. Fingerprints matter (also for Fluke and Tek). One thing you must understand is that parts suggested by the current audio fad often will degrade the performance. You need to be careful what part you use.

One thing to consider. These instruments are 30 yrs old + in many cases, at least 20 years. Often, just returning them to specification by replacing those parts that no longer work properly will buy you more than you might think. By anyone's standards, these are still excellent pieces.

Hi 1audio, Jack,
I don't know if you fellas have the time, but maybe a thread on the instruments you are familiar with to go through what you may know? I'm sure this would be a huge help to some members. Anything you can share would be helpful, but pace yourselves!

-Chris

[1audio]

I'm on vacation now. When I get back I'll document the tweaks I have done for the Boonton 1120. I need to get another one tuned up and its a good opportunity to record the details for posterity.

"Only wimps use tape backup: _real_ men just upload their important stuff on ftp, and let the rest of the world mirror it " - Linus Torvalds, about his failing hard drive on linux.cs.helsinki.fi

[PMA]

These instrument-list oriented battles are really funny.

[jackinnj]

Originally posted by PMA
These instrument-list oriented battles are really funny.

I have had a fascination with instrumentation since as long as I can remember. When, as a lab rat I was supposed to be working with my mentor on a physics experiments I found it more interesting to get everything to work, and work noiselessly.

[PMA]

I meant something else, like ... "mine is better, and you ... " etc., this is funny indeed