Repair worklog : Old rusty HP 3458A

[Macbeth]

I think the most difficult in this repair would be finding DIP-packaged LM339 and LM393  I did not used DIP parts for many years, and resist urge of bodging in SO-versions in there 

http://www.donberg.ie/descript/l/lm_393.htm

http://www.donberg.ie/descript/l/lm_339n.htm

[TiN]

1 Euro for jellybean LM339? No, thank you, I'll keep feeding Digikey for 3.2$/10pcs and free shipping 

But actually I think I'll give another chance to local electronics stores, I bet some might have LM339 in DIP with date codes from 1970's 

[Macbeth]

Ah, yes. I figured the DIP packages were now rare and just remembered donberg sells loads of old stuff (for ridiculous prices). Looks like they are easily available 

[pelule]

In Germany they offered by Conrad @ 0.64€/pcs or @0.58€/25pcs (Conrad is not the cheapest seller)
http://www.conrad.de/ce/de/product/1253062/?gclid=CLuf5pbjssgCFUUOwwod7UQE7A&insert_kz=NA&hk=SEM&WT.srch=1&s_kwcid=AL!222!3!68417927961!p!!g!!lm339n&ef_id=U899gQAAAPVjv31F:20151008113105:s

[TiN]

Well, I meant not that its hard to buy DIP, it was more like "I did not used dip IC for like 7 years or so". SMT rule.

Lets not go flamewar, but I wish all stuff be SMT, so easier to deal with..

[pelule]

I am a bit old fashioned and prefer DIP during evaluation & circuit testing using a pinboard.
Hate to solder just to do a quich circuit test.
But it may caused by the vintage design of myself 

[Kleinstein]

LM339/393 schould be easy to get in DIP. Also LM2xx / LM1xx series will do - they are the higher quality series. Chances are good, even in a small loacl shop.

DIP version might might have the advantage that you can use a socket and thus easy change, just in case they really need to be sellected.

It should be possible to follow the signal and thus localize the defect better before unsoltering parts.

[Macbeth]

For the best of both worlds... get to solder SMT and DIP 



I think TiN was only joking about the DIP stuff, but maybe Ukranian-Taiwanese jokes in English text don't translate too well over the internet   

Now, let's get back to more interesting stuff... 

[ManateeMafia]

Agilent was using custom adapters for their A/D boards in the 3458A due to the lack of original Elantec parts.

I think TiN is passed out somewhere catching up on his sleep and the crowd is getting restless...

[Macbeth]

Agilent was using custom adapters for their A/D boards in the 3458A due to the lack of original Elantec parts.

I think TiN is passed out somewhere catching up on his sleep and the crowd is getting restless...

We have OldSchool for the inbetween hours... Where are you dude? Nothing in life could be more important   

[ManateeMafia]

I live in Florida and I am on vacation this week, so lots of time waiting for 3458A updates while working on my projects.

I agree about the importance. There is no info located anywhere else for these meters. Those that know how to repair them, have not posted any notes. It is good to see this meter get fixed and knowledge shared on its repair.

OldSchool will undoubtedly will have just as much fun with his meter.

[TiN]

Nah, I did not passed out, but will soon.

5:25 AM here...

You can bet your bottom dollar, I was desperate... Look at this contraption:

I'll post more details later after some good sleep, but here's the progress tonight:



Dodgy 4094 which controls LM339 to control low current ranges? Testing with LA on inputs and outputs.

So I removed 4094, installed collet sockets (it's not analog critical part anyway, don't want solder board too much)..

Then decided to replace RP200 (it was soldered by prev.owner, remember?)

Removed it..

And...WTF..



Missing pin on the bastard.. And yes, it's common pin for all 7 resistors in package to pullup LM339 output. No wonder JFETs were not working..

And since I did not have any MC14094 in DIP, but I really could not wait, used wrong sized DIP14-SMT adapter, desoldered 4094 from dead HP 33120A board, put some wiring, and...tada...:



 

Will it work? I gave some decoupling love too with pair of 1uF 16V X7Rs



Now my 3458A have 3 SMD components in it!



Bingo...

Was another issue tho, TR300 (yellow long thingy on A1 board near vishay resistors) is extremely sensitive, if I bend it just a little or touch it - ohms and current measurement go berserk and selftest failures all over it. I think bad contact inside of that thing.. So ManateeMafia's burnt board could be a handy donor, I believe. 

Did very rought CAL with 10V from Keithley 2400 and 10K from ESI DB52 (not even 4wire lol), passed without errors. So, almost done, perhaps?
Time to crash in bed now. 

[Vgkid]

Good Job 

[ManateeMafia]

Same here. Will have to go get some beer now...

That part looks like 10 TO-92 components connected together. Mine looks good so we can discuss later how to get that part to you.

It will be nice to see that bad part torn down but it feels like a ceramic coating. Chances of getting part numbers from those transistors could be difficult but it might be worth a future project.

[nidlaX]

Will it work? I gave some decoupling love too with pair of 1uF 16V X7Rs



Now my 3458A have 3 SMD components in it!

Holy shit! Welcome to bodge city!

[crispy_tofu]

Congratulations OP! Just a little more... 
Now for OldSchoolTechCorner's 3458A repair 

[VK5RC]

@TiN , Great story and outcome, well done, I note those Tek clips, I am also a fan of them, they hang on like crazy and don't short to the pin next door.
You have laid down the gauntlet for OldSchoolTechCorner, I would not dare to enter this arena !!!!
Well done guys.

[FlyingHacker]

@TiN , Great story and outcome, well done, I note those Tek clips, I am also a fan of them, they hang on like crazy and don't short to the pin next door.
You have laid down the gauntlet for OldSchoolTechCorner, I would not dare to enter this arena !!!!
Well done guys.

Well done on the HP! Congrats.

Good source for those Tek clips? Are they for probes only, or general connections?

[TiN]

Ebay on clips. They are sorta compatible with standard 2.54mm pins, but actually they need little smaller pin thickness. I use them for everything probing around often, not just LA.

And yes, I think I missed this photo somehow.



ManateeMafia, we can do a teardown on that yellow thingy, no problems. Perhaps even try order ceramic PCB for replacement copy

Option 1 works with DS1230's after jumper JM600 relocation.
Another question, people who have real opt002, does it report OPT 0,2 for OPT? query? Yea, I know it's pointless, but still 

[engiadina]

I am using those clips a lot:

http://de.farnell.com/hirschmann-testmeasurement/973972100/probe-clamp-2mm-60v-2a/dp/523410?CMP=os_Google-DE_ProductDetail_Redirect

At least their MSRP is much lower than the TEK ones and you can find cheaper sources than Farnell.

I have the TEK clips as well, I could not say which one I prefer. Well, I might slightly prefer the TEK just because of their color. This light grey helps much better to see where the clip is connected. Apart from that, I have no preference at all. Maybe the Hirschmann are available in red or something? Have to look.

[Dr. Frank]

ManateeMafia, we can do a teardown on that yellow thingy, no problems. Perhaps even try order ceramic PCB for replacement copy

Option 1 works with DS1230's after jumper JM600 relocation.
Another question, people who have real opt002, does it report OPT 0,2 for OPT? query? Yea, I know it's pointless, but still 

TiN, congratulations for that repair!

Welcome in the club of 3458A owners..

From all we know (volt-nuts), the 3458A does not report opt. 02 automatically, as there is evidently no hardware query, and the opt 02 PCB is obviously identical to the normal version.


For the defective yellow part, you mean for sure Z300? (designator TR300 does not exist)
That is the Ohm overvoltage protection circuit.

Have a look on the 34401A, there this circuit is done with discrete transistors, 10 EA MMBT6520L.

All the HP DMMs have a very similar Ohm circuit topology, so that may be copied.
3 pins only are needed, i.e. input, output, transistor chain bias. All other are n.c.

Frank

[Zucca]

He did it!

[krivx]

I'm very impressed. This took you less than a month. I'm thinking about all the repair jobs I have had lingering for several years and all of them are much simpler devices than a 3458a...

[Towger]

I'm thinking about all the repair jobs I have had lingering for several years

I am the same, but then I think of all of Dave's projects on the long finger and feel better

[Macbeth]

Tell me about it... My own Keithley 2000 I temporarily fixed with a bodge while waiting for the correct part from Vishay sample service. I've had them sitting in a drawer for a couple of weeks meaning to get round to it, but the bodge is working and it's the AC range I don't really use so procrastination sets in...