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HP 5335A Timer / Counter - Anything i should know?
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Orange:

--- Quote from: Dr. Frank on May 26, 2014, 06:11:52 pm ---
And what is the "MK 36000 time bomb"?

--- End quote ---
My unit had a MK36xxx ROMs. They are notorious for sudden failure. Lots of units of HP and Tektronix have them. If you ever have a unit with them, and the unit does not work while everything else is OK, it might be the dreaded ROM syndrome. Mostek did a bad job with these suckers.
They basically loose their content, also known as ROM rot :)

 
Dr. Frank:
Yes sorry, I'm a bit late.
I had to study all the change history in manual 05335-90044, up to Serial Prefix 3154.

V1.1 had been introduced in June 1984, for all instrument with 2424A06001 and above.

V1.1  has one decimal point in the HP-IB string, as shown with my instrument.
V1.0 shows no decimal point in the GP IB string at all.

I already have the newer prescaler  in the C-channel (05335-60034), which divides by 64.
The old prescaler (05335-60009) divided by 20 only, therefore the firmware has to match.

It's not clear, if there exists an intermediate firmware which corrects all the bugs of V1.0, but is made for the old prescaler, i.e. multiplies the result by 20 instead of 64.

The difference may be inside the EPROM A4U22, as 05335-80012 (as in my unit) refers to the new /64  prescaler, and 05335-80006 refers to the old /20 prescaler.
That's change 7 in this manual, and affects prefix 2820, exactly my counter, and also for retrofitting the newer C-channel option 030.


Obviously, I have an intermediate A4 version, 2 EPROMs - but V1.1 and the newer prescaler. Perhaps my instrument had been updated, or the C - Input had been replaced.

I could not find a comprehensive table, which EPROM code refers to which firmware version, and/or to which prescaler.
Frank
Dr. Frank:
Well, my instrument also needed a new fan, but I bought one from papst again.

In my version, the 110V type had been replaced by a 24VDC / 36CFM one, as shown in the photographs.
It is fed by the unregulated + or - 25V. Got no schematic for that change.

I chose an 8414NGM, 80x80x25mm,58m3/h, and it has 26dB(A) only.

Frank
Orange:
My unit also has a Papst DC fan, its rated for 18 Volts, but it runs from 24 Volts !

Strange that official diagrams do not include this change. For sure it was build by HP like this.

I could change it for a Sunon Maglev, that should kill the noise  :)
Dr. Frank:

--- Quote from: Orange on May 26, 2014, 09:48:00 pm ---My unit also has a Papst DC fan, its rated for 18 Volts, but it runs from 24 Volts !

Strange that official diagrams do not include this change. For sure it was build by HP like this.

I could change it for a Sunon Maglev, that should kill the noise  :)

--- End quote ---

This change from 110V to 24V is described in words, but I'm lacking the schematics.
So it was an official change, definitely.

The fan operates from 18 to 28V.
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