Hi,

?

I am currently working on my 8562A, which had this message at some point in the repair.

My main problem originally, was that I had to change the potentiometers of the amp LOG module A4 because of intermittence of these components and also those concerning the BLANKING (the screen was unreadable). I had measured precisely the values of all the adjustments before replacing them with pre-adjusted potentiometers...but it was not enough to avoid the problems.

I had mainly the error ERRxxx AMP LOG. When I decided after much testing and reading of the service manual, to align this LOG amp, I saw the message ERR 456 AMPL.

?

This message or others like it, not very precise, concern a global alignment of the module A5 to A3, but passing through A4. Modules A5 and A4 are the main modules subject to a large number of error messages.

?

The A5 module alone includes 24 DACs and 13 IOs for digital IF band adjustment controls...it's discouraging.

?

But if your spectrum seems to be working fine at first glance with this message, then here is an explanation based on the tests I completed: all of these alignments are in series, if one of them or a sum of several of them cause you to go out of a certain range, then error messages will appear, not necessarily caused by a faulty component. In my case for this particular message (ERRxxx AMP LOG), it was caused by a DAC that could not compensate the DC offset after the RF detector because of a bad alignment.

?

To get rid of all the messages related to A5 (after having fixed those of A4 for my specific problem), I simply did the alignment procedure #3 "IF Bandpass Adjustment" and alignment procedure #4 "IF Amplitude Adjustment".

?

So, in my case, it was not a hardware failure, but simply an alignment drift caused by a series of out of specification adjustments (aging, drift over time). Now everything is ok, for the moment I continue to check that everything is stable before closing the instrument.

?

?

?

Yves

?

?

Hi,

?

If there was no hardware failure, the problem is probably the following:

?

Errors appear when one of the DACs is at the limit of its range and can no longer correct, if the error is minimal, you don't see anything special on the screen but you wonder.

?

At the beginning of the repair of my 8562A, hot or cold I always had errors, it is a spectrum that I bought with this problem. After replacing several intermittent potentiometers, I started to redo the alignments. Then suddenly the error messages started to disappear one by one, others were intermittent (cold-hot). But I was able to measure the cause of one of the error messages on one of the DACs, it could not compensate for the DC offset at the detector (limit of the DAC 0 or 255). By realigning the circuit that preceded it, I could see that the DAC started to act and move away from the lower limit, and the error message disappeared.

?

Finally, apart from having replaced some potentiometers, there were no other problems, it was a matter of aligning the device properly...easy to say, but more difficult to do because of the complexity of the device.

?

?

Yves

?

?

Hi Yves,

Looks like my unit is thermal related as those ERR gone away after turn on for a while. I have it turned on for few hours now and feeding it?an FM modulated FM signal and everything sport on compare to another SA.

BRGds/Stanley