eBay score: HP 8904A -- crazy waveforms

[fivefish]

I got an HP8904 and this little boy can do some neat tricks.... like adding output of multiple channels together and coming up with crazy waveforms. I also like that it has capability for floating outputs. It only goes up to 600khz, but that's plenty enough for audio testing (which I think this function generator was specifically designed for).

BTW, on the scope display is the "summed" output from (3) different waveforms coming from a single output channel of the 8904A (i.e. scope is not showing 2 channels).

 

[rf-loop]

Nice generator (also have one, with internal 4 channels activated ("serial number trick"))

Using this generator need carefully understand how its outputs work! (RTFM)

There is two modes.  Other is floating differential. Other is grounded.

You have connected cable to 1 "Low" output. 
(I do not know what are exactly options your unit have)

[fivefish]

I just assumed the arrangement was HIGH then LOW.  (I have 8903B and this was the order.) I just downloaded the manual.

I have option 01, 02, 04 according to HP stickers on back.

Have you replaced the Lithium battery on yours?

The backlight looks weak. I'm tempted to replace it with a white LED.

[rf-loop]

Have you replaced the Lithium battery on yours?

Years ago. (mod for different battery, if I remember right Tadiran SL-700 series some model)

[Grigioresine]

Hello everybody, I've one HP 8904A and I'm recording a random frequency shift on its output. It's more evident if you generate a square wave. I easily got the two service manuals that are available in the Keysigth web site but the "A2" board scheme is missing. The A2 board is the one where are located: the CPU, the clocks and all the digital part of the system. I'm reconstructing the scheme by using the DMM but it's quite long to do and I'd prefer to have the A2 board scheme if available.
From what I see all the clocks have a really bad waveform and the 6.7MHz, in addition, shows the frequency shift that I recorded on the output waveform.
I hope that you can help me.
Many thanks in advance.
Regards,

[LazyJack]

HP did not publish the shematics for the A2 board, so it is not available.