Products > Test Equipment
HP 3325A , Need Repair help
(1/1)
GigaJoe:
HP 3325A:
errors on self test 2, 3 (seems misleading )
Output on display: 29mV P-P:
NOTE: Output not terminated to 50 Ohm
scope CH1 AC , and DC are present from generator output at lower peak of waves ( like DC offset , but it OFF)
output on display: 30mV P-P:
same DC offset "0" at bottom of sineway
Then I shorted ACD ,
all tests pass , 1V P-P , became 2.1V P-P unterminated , and everything works , but
no DC offset regulation
this test pass with +20mV off:
and im lost a bit , looking for direction ....
Found - LM311 , A14 board
Fixed , now it need adjustment ... calibration , at the level i can do ....
m k:
Since triangle is based on square and square is based on sine one can expect the problem is quite far back.
Since disabling Auto Cal removes the problem one can think that Auto Cal is the problem.
Top is still round, so offset is available.
Should peak detector find it during self test 1?
Maybe it's just a timing thing.
m k:
DAC to DC offset is controlled by HMD5 thru A14U29 as K5 to S/H latch A14U26 and strobed thru data decoder A14U27.
K5 is also setting Preset Up/Down Counters A14U6 and U8.
HMD5 is receiving level data thru A14U30.
Div 3 relay pad out is controlled by K5 thru A14U30, so is ramp reset thru A14U1.
Clearly K5 itself it most likely is not.
Function selector A14U28 uses K0-4.
After that actual "discrete" selector components are still many.
DC Offset Control has only function enablers and Offset Error.
Nothing that is directly ACD related.
ACD is outputted to HMD3 with level data.
So it is a digital info thing only and then is not controlling anything directly.
Navigation
[0] Message Index
Go to full version