HP 8904A Restoration and Lab Checkin

Рет қаралды 1,753

3 ай бұрын

A huge thank you again for all that continue to Join us in the lab for repairs and alignments. The channel would not exist with out all of you so thank you again for dropping by.
Ways to support the channel:
Patreon - / zenwizard_studios
Paypal - Zenwizard@Zenwizardstudios.com
In this video we take a look at an HP 8904A Synthesized function generator. I have been looking to grab a few of these for the lab to assist with alignment and calibration of FM tuners. This was also an incredibly stable function generator for the time and still to this day. With some of the built in modulation abilities it will be a welcome addition to the bench….. Once we fix the display issues.
** Repair exposes the Tech to mains electric and should only be done by trained personnel. Errors can be fatal. **

Пікірлер: 19

@davidv1289 3 ай бұрын

Nice unit! I use one to modulate an HP 8657B for FM tuner alignment - works perfectly. As others have suggested, you should consider replacing the Rifa caps in the SMPS. Also, all software options can be easily turned on, info is available on the web and uses the programming info in the dead battery recovery service note. The display uses an ELP and many of these units have dim displays. Fortunately it uses a standard 2-line LCD display and one with an LED backlight will fit - I seem to remember it needing some different standoffs. I added a small interface board with a pot for backlight brightness control. Regards, David

@apollorobb 3 ай бұрын

I have a Kenwood SG-5150 nice to have a dedicated Stereo generator but i do tuners all the time . Didnt know the 8904 had all those goodies .

@szapcsika 3 ай бұрын

Sync out in is an option when you can connect several of these units so all of their output is in phase. Can be useful. It is a software option but of course you need the bnc connectors.

@Wil_Bloodworth 2 ай бұрын

Great to know!

@solodolo6018 3 ай бұрын

Love the vids Zen! I've been learning a lot from you

@roymercer6967 3 ай бұрын

Why are the four outputs required? This is the first I have heard that the four outputs are required. Thank you for another well done video.

@ZenwizardStudios 3 ай бұрын

The 4 outputs are for the floating option. Like a SMU when the output is set to floating there is Signal high and Signal Low. I might have mentioned this is for differential signaling but that is NOT the case with this unit. There is another video on the way that will go a bit deeper in to this.

@roymercer6967 3 ай бұрын

I should have paid closer attention. Thanks so much for taking the time and responding.

@vk5fe943 2 ай бұрын

Nice video, thanks. Apparently the AutoDigits in the 53230A setting is Off - if so, probably all the digits after the nineth or tenth digit after the decimal point is just garbage.

@ZenwizardStudios 2 ай бұрын

I will check on the auto digits. I have the 53230A set up for testing some 10 Mhz lab references (videos will be out shortly) if the gate time is not long enough things will bounce around but the 53230A only needs a gate time of about 0.1 Sec to settle down quite a bit.

@brianst.pierre6566 3 ай бұрын

Careful with the battery. If it dies I’ve heard the unit can be bricked. Also, see Defpom’s video on how to turn on all the software options.

@szapcsika 3 ай бұрын

There is a service note from HP on how to reconfigure it if the battery goes flat. So battery replacement is not an issue.

@stephenbell9257 3 ай бұрын

That battery also backs up configuration info like serial number, S/W option keys etc. If the battery goes flat you will lose these and it is quite difficult to restore them.

@ZenwizardStudios 3 ай бұрын

The S/W Option key is very easy to restore. I need to look in to the serial number what that entails.

@szapcsika 3 ай бұрын

@@ZenwizardStudios Search for HP Service Note 8904A-05. It details how to recover from battery loss by entering some magic parameters. After that you can use the service manual to reenter the serial no, and the options.

@ZenwizardStudios 3 ай бұрын

Do you by any chance have a PDF of the complete service manual? Most of what I am finding on line is missing section 4 which is the alignment procedure. I do have that service note but I also need the complete service manual. Would like to do a full alignment after I get the appropriate power meters. I will need those for my spectrum analyzers as well.

@andywlala 3 ай бұрын

You gonna swap out those three RIFAs too ? Being a 110V country probably not real high priority, but since you had it open …

@Runco990 3 ай бұрын

I've had plenty of RIFA's smoke in a 110V country. I always change them. 😁

@Wil_Bloodworth 2 ай бұрын

Thank you. I just bought this very same model with the same options. Can you please tell me which capacitor series you used and which series you chose for the low-ESR capacitor. Much appreciated sir!