2465B Error 05 44 Trouble Tracing Down Issue

[radiofreak313]

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.

[Omicron]

The dots mean the calibration data is missing. I'd guess the original nvram was dead. You say you replaced it, but did you calibrate the scope afterwards? I'm pretty sure the error code you're seeing will go away after calibration as well.

If you don't have the equipment to do a calibration, I've seen images of the nvram floating around on the forum (search for other threads on 2465b). That will get rid of the errors, but your scope will off course not be calibrated.

[radiofreak313]

I replaced the A5 board with the borrowed unit.  I put my NVRAM into the borrowed board (socketed) and calibrated the scope.  It calibrated fine with no errors (I have all the modules to calibrate it, I purchased at time of scope purchase because I saw what companies were charging to calibrate one of these).

I removed the Dallas chip put it into my board and same problem.  It cannot be calibrated with the my A5 board since no trace is visible.  The dots are the trace or part of it anyway.  Thanks for the comments.

[casinada]

Are voltages correct when the defective A5 is on the scope?
Have you followed the troubleshooting steps in the service manual?
Do you see anything on the screen when you press beam find?
Have you joined the Yahoo Tekscopes group?

[BravoV]

Are voltages correct when the defective A5 is on the scope?
Have you followed the troubleshooting steps in the service manual?
Do you see anything on the screen when you press beam find?
Have you joined the Yahoo Tekscopes group?

I remembered as instructed by the service manual, the 1st thing to do is to measure all important voltage rails at J 119 header, infact that header was designed and made for this purpose, cmiiw.