repairs of HP 8594A spectrum analyser

[kenramesh]

hello all ,
I have been facing problem with HP 8594A spectrum analyser.

1.As the instrument is switched on , FREQ UNCAL is displayed which is a permanent fixture.
2.When i try  to calibrate using CAL OUT the result is  SIGNAL NOT FOUND & SRQ110.
3. The trace line is slow in movement , data entry response also appears to be slow.

I couldn,t find service manual for 8594 series , but tried using 8590 series one.

As per that manual either A7 analog pcb, A16 processor , counter lock , or YTO may be faulty but not able to zero-on by using this manual.

I observed the following:

1.on A7 analog interface board Q1 is getting warm
  but if  cable running to YTO removed from the PCB, heat is normal.

2. FREQ UNCAL disappears & trace line moves fast when Counterlock board flat cable is removed

waiting for ur help  Pls suggest how do proceed.

Thanx in advance

Locked due to duplicate thread: https://www.eevblog.com/forum/repair/help-needed-to-repair-hp-spectrum-analyser/msg1494742/#msg1494742