Change A4C36 from 10µ/10V to 22..47µ/10V. Correct value depends on tolerances in the circuitry, and on the capacitors leakage current.
This will increase "Gate Mode NORM" time from (20ms..4s) to ca. (50ms..12s), delivering max. 10 digits instead of max. 9 only.
Well I tweaked one electrolytic, which controls the manual gate time, so that I could measure up to 12.5secs, (instead of only 1s), to get 10 digits from the front panel.
Otherwise, GPIB control would do the job, up to 11 digits.
FrankCan you go into detail on this.
You can do this also by hand, use the manual open/close push button, under gate mode.
if you leave the gate open for hundreds of seconds you get more digits.
And what is the "MK 36000 time bomb"?
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
OK, so I changed the EPROMS from V1.0 to V1.1. Initially done some tests on Channel A and B, and all seems fine...
Later today I checked Channel C With a 100MHz signal it displays 320MHz !, 1200MHZ gives 3840MHz on the display !
I presume that the later units have a different division factor for the Channel C board which is compatible with V1.1
I could not find this in the documentation.
So its back to V1.0
Well that's certainly worth a try.
I find it peculiar that HP never mentioned something about it. It's also a thing to remember if you want to upgrade your counter with a Channel C board.
This is turning into quite an interesting thread! ;-)
Yes, my unit is V1.1 and displays decimal point on boot. I'll try and upload the proms when i get a second
I think i will install the fan mod too. Mine is running from the DC bus, but boy is it noisy! It's like someone doing the hoovering in the room
Also, i notice the GPIB board "A7" is completely seperate from the logic board "A4" and consists of a GPIB driver, driven by some parallel data lines for address and data etc. A nice little project would be to replace this pcb with a modern microcontroller with a direct USB output, to a USB socket on the front panel (probably on the right hand side) That would neatly avoid all the messing around with GPIB->USB convertors etc!
If i find the time i might scope out some of the signals, however, assuming the driver IC on A7 is "dumb" then we should have TTL level GPIB protocol on the A7xA4 connector?
Ok, so if the GPIB board does have it's own intelligence driver, that means the interface between it and the main processor on A4 is even more likely to be fairly simple?
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
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.
I got mine 5335a very cheap, because it was totally dead, but cosmetic very good condition
After lot of research, all of the tantal C's on the input board were totally short circuit. The blue bulbs in the picture.
The power supply is short protected, so replaced all tantals, and the unit was up and running, and in good condition.
I got mine 5335a very cheap, because it was totally dead, but cosmetic very good condition
After lot of research, all of the tantal C's on the input board were totally short circuit. The blue bulbs in the picture.
The power supply is short protected, so replaced all tantals, and the unit was up and running, and in good condition.
Thanks for the tip, my 5335A is similarly dead (well the fan comes on and that's it), all the main PSU outputs read close to 0V with the regulator inputs are at +/- 12V and +/- 24V. I am used to shorted tants in IBM PCs, where due to the high current available the results are a little more spectacular
Regards,
John
After lot of research, all of the tantal C's on the input board were totally short circuit. The blue bulbs in the picture.
The power supply is short protected, so replaced all tantals, and the unit was up and running, and in good condition.
Thanks for the tip, my 5335A is similarly dead (well the fan comes on and that's it), all the main PSU outputs read close to 0V with the regulator inputs are at +/- 12V and +/- 24V.
If you have the DC fan, it's likely that the contacts on the relay socket have opened up. See the service note in my post above. The relay socket is a 27E213, Digikey part number PB806-ND. If it is the relay socket and you do the modification in the service note, you probably don't need a new relay; I'm still using my original relay. Anyone with a 5335A should make sure that this modification is done and switch to a DC fan. The 5V supply relay socket contacts get hot, fatigue and eventually, when they cool down, don't make contact with the relay any more.