HP 8643A signal generator repair

[@LiquidAudio]

Great work repairing this, I appreciate your approach. I'm thinking of getting one of these, I have 2 x HP 8640Bs and they are becoming a pain to maintain!

[@tomking6006]

Look at those gorgeous VFD displays, none of that poxy impossible to read LCD rubbish. Great job on the troubleshooting, I'm so glad there are people rescuing equipment like this.

[@w1qg]

Those damn tantalum caps ! Great job troubleshooting.

[@cgeorge6786]

I have one of these. I wish the phase continuous sweep capability was greater but it is a beast and probably the most extreme piece of gear I have in my house. I think these were in the $20,000 range when they were new.

[@SpinStar1956]

Right now have a 8664A coming from eBay; sure hope it's OK. I did not know that they detailed schematics were not available (?). I mainly worry about esoteric unobtanium parts, so I really feel I stuck my neck out but needed the precision and sweep capability. Thanks for sharing this video and I think you did a great job of diagnosing and repair...

[@erin19030]

Suckkahh

[@carlosdanielmendozaperez6907]

Great Video, I came from EEVblog forum

[@tubeDude48]

Where can you *buy* a *schematic* from?

[@fenugrec5697]

I bit the bullet and bought the PDF service manuals from Artek.

[@tubeDude48]

@@fenugrec5697 - Don't know them...I'll search for them.

[@radiolabworks]

Didn't see it in the comments, but those front buttons are part of a larger rubberized membrane. So they can not be individually replaced. I had the same issue with a HP 8657B I bought and luckily found a used front panel to havest a replacement membrane from. On the 8657B it used two membranes. Most likely similar on your 8643A. BTW, I was able to still activate the switch using a insulated rod with a small bit of aluminum foil taped to its end. That worked fine until I found the replacement front panel.

[@fenugrec5697]

Thanks - yes, I eventually realized that it would most likely take a whole new membrane, that realistically would have to come from a complete front panel. Luckily I don't really need that particular button so it will probably remain unrepaired; I just taped over the hole so dust and debris doesn't get in.

[@Wil_Bloodworth]

Curious... why would you buy one of these with all of the modern options? Is it purely a "this could be fun" interest? I've had the option to buy one of these in working condition but I cannot think of any reason I would want a huge boat anchor like this in my room.

[@fenugrec5697]

Can you name a few of these "modern options" with equivalent specs that aren't 2k+ $ ? I wouldn't mind something smaller and lighter than this monster, but the modern alternatives are at least 4-5x more expensive than what I paid for this.

[@Wil_Bloodworth]

​@@fenugrec5697 I feel like you're not genuinely interested in a real response but are more interested in defending your purchase. And that's fine. I think your "out" to what would have been my next reply is going to be the "equivalent specs" wording. No matter how I reply or how close the specifications seem to be, I feel like your response is inevitably going take a contrary and argumentative stance which will ride on that phrase's proverbial back since your first response's tone is already rooted in that direction. My question as well as my interest was genuine and I do not have the desire or motivation to argue or validate your purchase. I was simply trying to understand the purchase logic as I am in the market myself.

[@fenugrec5697]

@@Wil_Bloodworth I don't mind discussing it - it would've been easy enough to simply ignore the comment. I would lie if the challenge of the repair wasn't part of the interest, but I think my point still stands - getting comparable specs, in a new model, is much, much more expensive. ( my research = 5 minutes of looking at rigol and siglent lineups). Some 50$ bargain-bin alternative might exist (I have in mind typical single-chip DDS bare boards that can be found on... "international shopping sites", but I don't expect the specs would compare favourably at all. I'm not aware of a middle ground, but would gladly be proven wrong. I don't even have space on my bench for this machine, I store it in a separate room and set it up on the floor when needed. But that inconvenience doesn't amount to 2k$ for me. So, 3 points : specs per dollar, total price, and repairability.

[@erin19030]

All that to generate a signal?

[@denis_w1wv131]

Enjoyed your video. I need to recap the power supply. The 5volt rail is low and causing an error. Where did you find replacement caps?

[@fenugrec5697]

Thanks. You're sure your low voltage condition is due to a bad PS and not an overload ? I just shop on the usual online suppliers (DK/mouser/newark) and find mechanically compatible parts with better temperature and endurance ratings if possible.

[@scottmorgan5370]

NO WONDER these things are so expensive. There is man/years of engineering in that machine.

[@jonka1]

When you replaced the battery did you apply a voltage to the circuit to maintain the memory?

[@fenugrec5697]

No : it was long dead, and the only thing you lose is the self-calibration. From the manual: " When the instrument is off and the Controller Board is removed from the motherboard connectors, the instrument calibration data located in the Controller Assembly RAM will be lost. At the next power-up, the instrument will sense a data lost condition and automatically activate the Recal routine. "

[@erin19030]

Are you gonna recap it?

[@fenugrec5697]

not systematically, beyond the known-problematic caps in the power supplies that I already replaced even if they looked good. A full recap would be wasteful IMO

[@n1ghtblur]

this is pretty badass

[@CraigPetersen12f36b]

I have the HP 8644A, at least I know what to expect if I need to replace the backup battery :)

[@fenugrec5697]

better look at that battery sooner than later... electrolyte corrosion damage is a huge pain to deal with !

[@tubeDude48]

*Allied Electronics* carries the Battery. Those connectors are called: *SMA*

[@fenugrec5697]

I'm fairly certain my unit uses the smaller SMC connector.

[@tubeDude48]

@@fenugrec5697 OK

[@ahmedgaafar5369]

I had very similar experience with my HP 8644B which pretty same unit like yours, but my unit was way much horrifying that i started to laugh after seeing what they sold me, 3 boards modules were loose not even plugged in slots, and two ALC boards duplicate and a missing Doubler board, and all the cables are loose ...not even one single cable was hooked.....!!!! so i ended up using it as spare parts for the other one that i have, took the power button and the covers. if you follow curiousmarc channel he called the technician who was working on a unit that he purchased from ebay...." THE TECHNICIAN FROM HELL" ....lol. probably he is same guy.