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Agilent 54835A scope (4 channel 1GHz / 4Gs/s) repair & uphack
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INFINIUM:
The connectors that I am investigating. 
INFINIUM:
https://www.circuitsonline.net/forum/view/94488/25
Here there are people  and in English photos : the most beautiful apparatus in my collection In Netherlands!
there are apparatus inside and outside beautiful and more with the red green display ON .
Nice people keeping care of the  :bullshit: :bullshit: :bullshit: :bullshit: :-BROKE :-BROKE :-BROKE
analogRF:

--- Quote from: INFINIUM on November 14, 2018, 01:21:18 pm ---Thanks ,
the OSD  was abandoned more than 15 years, almost now dead :'( in 2000 it was OK.
First  the CMOS ERROR asked me the bios FLOPPY  , last month..
I change the video card battery that was  with 3 Vols.
nothing  the same error , next week started to suddenly stop and start ,intermittent ..
now does not start at all  , the service manual said , put the resistor to inhibit the Power supply and replace it if does not start.
I guess is true   , trying to replace the PS , but there are to many signals in the control connector , I am busy in a small garage with cars ,etc. and I need the schematics to prevent putting wrong voltages in sensible circuits. :bullshit: :-BROKE :-/O.

--- End quote ---

could you explain what exactly happens when you push the power button?
INFINIUM:
When I push the On buttom the front relay  made a noise , the +15 volts  inhibit voltage change like the service manual said or going lower.    The PS gives only 15v for the starting inhibit circuit , nothing more now,
this 15 volts is only for the starting PS , is explain here in POWER SUPPLY WONT POWER ON  search
The signal to start is going in series with the PCB or cards that means that one is disconected is imposible to start the PC OSD ,
To test better the PS  the service manual said to put a 200 ohms  in the small connector PS  white cables  simulating the PC  and if the PS does not start to give the 5vols 12 v plus and minus  replace the power supply PS.
When I put the resistor the same I heard the relay click but any   ps voltages out , the H Voltage dc in the PS is present but later this 250 volts is not converted in 12 -5  volts is very difficult to check the vertical card in the PS ,somebody here  in the link  PS WONT POWER ON  put a 5 volts power supply extra in the original PS Connector and start the OSD like the cars in batery failure!
the PS vertical control card has to many components condensers chips, transistors, difficult to repair ,nothing is burnt  :rant:
the modele is HP54845A  Windows 95 ,
also in the Service manual said to check the resistencia to ground in the OSD , it seems ok.
I Have one PS from the old PC  chinese that gives all the voltages when one start cable is connected to ground ,only problem s  is the power only 200 wats ..and the conexion like a heart transplant :phew:
there are tips here for others hp  PS models  : the resistor x  330k , the fuse resistor in the power transistor , nothing for this PS ,
in resume I need to buy an expensive old PS , Change the condensers etc or  put a new PS WITH NOT MISTAKES!
Thanks
nctnico:
Did you check for shorts in the rest of the oscilloscope? Did you already try to disconnect only the acquisition board and then power on? Maybe the PSU is just fine but there is a short circuit somewhere else which makes the PSU shut down again.
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