Help With HP-3336B - Page 1
Forum section: electronics / testgear

author: George_Race
author_rank: Regular Contributor
timestamp: October 18, 2014, 12:26:12 pm
content: I recently picked up an HP3336B.When you turn it on it flashes 10 000.0 and then display the message OSC. FAILI do have the schematic and have spent a lot of time looking for the problem.It has Option 04 and 05 and I do have the TCXO Jumper in place, going to the EXT Input on the back, and it is right on at 10 MHz. The EXT LED is on in the panel.I have checked all the signals on the boards and everything seems to be there. The 30 MHz Xtal Oscillator is right on, the 1 MHz signal is coming from the rear connector as well. There is no output from the output amplifier system, but I think that the default level is set to maximum attenuation when first turned on. I can see a nice clean 10 KHz signal at the input of the amplifier section. So it appears that everything is working up until that point.I can even store and recall the message "OSC. FAIL" in any of the memory slots.Would appreciate some help getting this going.Thanks,George Race

author: George_Race
author_rank: Regular Contributor
timestamp: October 19, 2014, 12:54:37 am
content: A lot of progress was made today!The reason the OSC. FAIL message was coming on at startup was that the PLL high and low voltage ranges were way out of calibration. Once I got them calibrated, the error at turn on went away.Everything now works, and I have competed all the service procedures for calibration. The exception is the output calibration to set the levels at the three sets of outputs.I can't do that because the precision attenuator is not switching levels as it should. I exercised all the relays in the precision attenuator, and everything works as it should. So, the 8 relay drivers are not getting the proper pulse signals to operate the 4 relays as the output levels call for change. Actually, one of the 4 relays is switching in and out as I change output jack selection.Tomorrow I hope to get into that piece of the puzzle, that switches the attenuator relays as you select the output levels. If anyone has any ideas how to troubleshoot this area I would be interested in hearing.George

author: programguy
author_rank: Newbie
timestamp: April 05, 2015, 09:55:58 pm
content: I just picked up a HP-3336B recently and I'm curious how you go about exercising the relays? When you select each output (i.e., 75, 124, 135, 600), should you hear the relays engage?

author: George_Race
author_rank: Regular Contributor
timestamp: April 07, 2015, 12:06:18 am
content: As I remember, after taking apart and checking out everything in the attenuator assembly, the reason for mine not working properly, on nothing but the 75 ohm output, was that I was not in the right frequency range for the other outputs to come into operation.I guess that is what you call operator error! Initially I did not realize that there was a narrow band of frequencies that were expected as output connectors were selected. On mine, when the output frequency is within the range of the output connector, everything works just great.Not sure that is your problem, but it may lead you in the right direction.George