Hello, I am new to this forum since I just purchased my first Tektronix 2465B to replace my aging HP 1707A.
I need some help tracking down the source of my problem with my 2465B (SN B055XXX). Here is the issues: No trace, needed to turn up Grid Bias to get display, Test Fail 05 44 (ADD LED On), after A/B TRIG is pressed read-out is present with flashing dots (2 rows) across top and bottom of screen (2 rows top and bottom). Readout is OK. No intensity control for either the main trace or readout.
Replaced A5 board from good scope (borrowed from a friend at work) and everything works fine. Problem is in A5 Board. All power supply voltages are correct (voltage & ripple as evident from the board swap).
-1.25V and 1.36V are very low. Jumping J504 to DIAG (Pins 2&3) causes Voltage to return and trace but no control. I previously replaced all Caps and Dallas Chip. U2101 - DAC pins 18 & 19 low output signal (should be over 1V, getting about .25), which feeds U2521 (CD4051). Also, TP9 low signal compared to good board. Since DAC output was low I replaced DAC with a DAC312. Problem still exists. All PCB traces checkout ok. Replaced U2521 & C2420 problem still exists. Checked (out of circuit) CR2422, CR2423 & Q2320 all good.
Any suggestions would be greatly appreciated. Thanks in advance.