HP 4194A Impedance Gain Phase Analyzer REPAIR, any other owners ?

[oz2cpu]

this one looks promissing, it boots and runs..

I really love this unit, so i really would like to get it running..

BUT it beeps, and display the famous "Bridge Unbalanced" hardware error say the manual.
I googled a million times, some posts talk about A4 module blown fuse, but there is no A4 module to find. (where should that be located ?)

service manual from keysight web is in a terrible compressed low resolution version,
so i cant read or understand most of the schematics.

Any one got a working unit ? please reply here ?
Any one got better schematics : my username at gmail dot com, please

I would love to perform some very simple versus measurements:
your working unit, to mine defective
lets take a scope, and see what goed in/out of the different BNC connectors, in the same modes, and same settings,

I see things i am unsure is right or wrong.

[jonpaul]

Bonjour cher Monsieur

Marvelous machine, similaires to 4195A and 4193A with impédance test set 41952A

We have used 4195A 30 years

These were designed at Hp and build in collaboration with Yokogawa Japan, uses HP custom  SOS CPU.

HP extender set and HP signature Analyzer may may be required to troubleshoot.

Suggested général  proceedure

1/ obtain hi res pdf or printed service manual for the serial number range

2/ check every power bus for voltage and ripple.

Failed lytics, PSU regulators and shorted bypass tantalum caps  are  common

3/In decades old instruments corrosion and oxidation can cause issues especially intermittent

PCB to cable and PCB card edge should be unplued and exercised

4/ may have built-in self test proceedure

5/ if you are located in Scandinavia our old friend Magnus D. might be of assistance, in Stockholm....

Further information may be on HP memory project.

Manuel might be at BAMA  archive
Artech may sell a pdf or printed copy.

Bon courage et bon  chance


Jon

[oz2cpu]

here is my latest video release
about this HP 4194A

https://youtu.be/X5wNRnbFRwk

[oz2cpu]

here is part 2
mostly main unit of HP 4194A

https://youtu.be/GsAZFcgaGAk

[jonpaul]

Rebonjour

visual inspection usually reveals little except blown tants or corrosion.

As mentioned suggest you find the complete service manual, ( not a bad PDF) and follow proceedure.

Extenders and HP signature Analyzer required

Finally check out the HP instruments forum on groups.io.

jon

jon

[oz2cpu]

so far :

found a lot of leaked caps , desoldered a few, and measured their values, most are close to ok values,
but leaked conductive puke over the boards, so they need deep clean.. and of course replacement.
i will wait with that, until the real error is found and fixed.

heard from previous owner, they do recall it was killed by wrong use, measuring audio amplifier gain-phase
where they forgot attenuators..

still no luck getting service manual / schematics in use full quality.
no one contacted me so far about that,
and also no other owners found.

[strawberry]

same as Dynacord sl1200 amp, no schematics available. how it works , how to test components and what to expect, recognize previous repair attempts..., after week/month it is fixed