No.081 - HP 34401A 6.5 digit Multimeter Repair - Part 1
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- čas přidán 11. 09. 2024
- In this video I begin repair of an HP 34401A 6.5 digit Multimeter including how to remove the front panel and troubleshooting the fault(s).
Part 2 is here:-
• No.082 - HP 34401A 6.5...
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Really enjoy these vids Ian. Not to dismiss your excellent fault-finding skills, but it surprises me how often folks and/or companies just throw something out as soon as fixing it requires component level fault-finding. It really emphasises how the throw-away culture has taken off. I've bought some really expensive kit for peanuts over the years with simple component-level faults costing pennies to repair.
It is all about cost. This power supply or its successor cost ~ 1-1.5k. A person with a skill level good enough to repair this power supply would cost ~ 120€/h here in Germany. For the repair you need at least some hours, waiting for a functioning tool etc.. all this costs time and money. But it is not bad. This way I can get those defective units from the bin
Thank you Ian for another interesting repair video. Looks like you have been busy! In part two you might include a quick explanation of why the "offset" power supply is used for those new to electronics. Regards, David.
Good idea, I'll give an overview of all the floating/offset supplies and sections and why they are there, and why HP at the time designed them as they did.......IMHO of course. Cheers.
I bought one of these meters off ebay about 6 years ago, the display looked bright in the photos. But when it arrived was very disappointed as was quite dim. So I took the risk of ordering a new display on ebay from China for about £30. It was perfect & is still bright today, thanks for video
They do go dim fairly quickly Nick.
@@SoddingaboutSi mine hasn't in 6 years use Simon. I guess I've been lucky
First! My mama is gonna be so proud!
I used to use multiple sets of glasses to work in the lab as you are doing. I saw the multiple sets on the bench in the video.
Now I use a set of custom made glass trifocals. The top is set for 26" (66 cm) for looking at the computer screen and instruments, the center is set for 12½" (32cm) for reading and soldering, and the bottom set for 7¾" (19.7cm) for inspection. I no longer need to change glasses in the lab. The close-up inspection section at the bottom means I need to use my stereo microscope much less. I had the lenses made from glass for scratch resistance. I have enjoyed working in the lab much more since I started using the trifocals.
Great idea!......yep, it's frustrating having to chop and change all the time. I'll see if my optometrist can do the same.
Q. Are your trifocals full width, or are the centre and bottom spot areas, and are yours quite tall glasses (large) or just normal more rectangular......am just trying to gather some info before going to the optometrist....... :)
@@IanScottJohnston I will email you a photo and measurements. The glass area is larger than all of my other frames.
I apologize for the delay in getting you the dimensions and photos. Life got in the way.
I texted you some photos last night.
Wow Ian!, that was a lot of work with the PDVs... but i need only one! nice job!
Recap before troubleshooting, or sort it out after?.............This is a question I got asked by a young fellow electronics friend.
The answer in my case comes from working in the offshore industry where Drilling downtime from broken electronics can cost 6 or 7 figures a day for the rig operators.
By powering up first and experiencing the customers problem/fault then when I do replace something and the fault disappears then I KNOW I have fixed it.
By replacing caps (or any other part) before power up and subsequently having it power up without ever seeing the customers problem then you never really know 100% whether you have fixed the problem, i.e. it could be intermittent, and so imagine sending that hardware back offshore only for it to fail immediately!
Of course, it's only safe to power up providing there are no holes in transistors or IC's etc. and thats why you see me go over the board before power up in the video's.
Hope that helps........and each to their own for sure.
100% First rule of troubleshooting is to replicate the customer complaint before touching anything!
Ian, really happy you've been able to make more videos! Always interesting.
Yeah, in some repairs may be multiple different faults.. Power rail is fixed, but then it appears, that display is faulty too.. Murphys law.. 😒
Great video, as always! 👍
Had the same capacitor issue a while back with my HP5385A counter...the bad electrolytic was venting underneath and you couldn't see the problem until you actually removed the cap. Hope you can find a nice VFD replacement, thanks for sharing the fix!
Excellent call on the caps!
This is great as I have one of these and it works fine but we all no cap's will fail so seeing how to get it apart is useful....cheers.
Nice repair. This is quite common fault actually. I fixed a lot of those with the same problem.
Saudações from Brazil! 👍
Thanks!
Ian. Nice workshop.
Excellent job =D Looking forward to part 2! Those red clips look painful to disconnect lol
Yep, when you first encounter them you stare and play with them forever before working out just how to remove them!
Excellent video thanks for sharing.
Great to see you again, Ian. Great meter! Will be interesting to see the follow-up videos. Always a pleasure. And Merry Christmas!
I would always run a wet finger over the contacts to see if the missing segment lights up.
Ian, if your after any spares contact me. I have a scrap unit . Also powering up with a button held down will give you a full power on diagnostic check. You will obviously need a display first!
Will do.....cheers.
Surprised nobody is making retrofit display pcb with bright green led segments. This would look a lot better than the aging vfd.
Thats true.....its a well known/used DMM. However, i have new VFD to hand so update video soon.
Nice one Ian I hope the PS2 minis are going well, I know a guy in Newzealand that loves it:-)
Glad to have you back doing repairs! You make this look easy. Would be interested to know what was on the other side of that discoloration in the end?
Small SMD bridge rectifier for the serial GPIB inteface at the back of the unit (electrically isolated from the main cpu). I'll have to test the GPIB interface once I get the unit back together again.
9:23 You have a broken solder joint, just above the "2" in the barcode label.
It looks like it in the video.....but it's not. It's just a stepped solder joint i.e. where it's been soldered, then been touched up by somebody and left a little step. It's not broken at all. Nice spot though.
Vary nice explanations Sir , need to know the secondary ac voltages of power transformer can you help me, waiting for your response
Second. good job Sir!
It's foud very nice explanations Sir, can you send me the details of power transformer secondary ac voltage, As my same transformer burnt, please help me,hope for your kind response, 🙏
Ian have you gotten around to making AR488 GPIB adapter yet? Seems like a neat alternative to a dead display would be to find a cheap laptop or tablet with USB ports and remote control the meter using computer or tablet display.
Has anyone ever changed out the VFD for LCD.. using some other microcontroller and what not that interfaces with the main board?
Hi Ian geat video, I have just picked one of these up that has been used in a car workshop so the front panel is a bit dirty, so planning to follow your helpful instructions on how to remove the front and take the display board out. Can you suggest a cleaning solution for the front panel that wont damage it, I was thinking of Isoproply alchol or servisol foaming cleaner?
I think I'd pop out the smoked screen and wash that with soap n water.
The front panel I'd wash first with soap and water to get most of the dirt n grime off (scrub it) then IPA after that.
Don't use acetone.
Looking forward to watching later, I'm in the market for an ESR meter(possibly not relevant to this video), I'm wondering when it tests with DC on the larger electrolytics - Would a multimeter be good enough to test these, I'm thinking the test voltage is lower on the ESR meter, perhaps this is why?
Depends on how much you want to spend. The problem with cheaper units and/or using a DMM is that they can run out of range i.e. when testing the likes of 2200uF and bigger caps etc. A dedicated unit will give you a lot more info also.
Sorry in advance for the dumb question, but at 8.33, you show the pushrod removed. How did you do that? I'm sure it's a simple procedure once you know what to do. Thanks
Yes, it's a bit of a fiddle. From memory you rotate is as you try to extract it and it'll find it's way out.
Those hold in clips look like a real pain in the arse!