Author Topic: HP 3435A Extreme Makeover (Read 23200 times)

xrunner · « **on:** February 12, 2015, 10:53:01 pm »

I thought I'd share an extreme makeover in this thread. I received a HP 3435A DMM which I won on an Ebay bid. What I'll be doing is taking it completely apart and cleaning it up to as like-new condition as possible. Assuming it's working for the most part, I'll be touching up the calibration also. Stay tuned for more pics as I take it apart and do the Extreme Makeover. Shots of the boards too - you know HP made some really nice boards don't you?

Be back soon ...

Here we have the unboxing. According to the rear label it has the battery option, but I won't be expecting the battery to be usable (if it's even installed), nor will I be getting a replacement for the battery. I'll leave the charging circuit in though (it should be a board on the top case).

Comparing it to the Rigol - it needs some touching up of the calibration, although it ain't too bad. AC and resistance work, so I got lucky on this one, i.e. no bad surprises.

EEVblog · « **Reply #1 on:** February 12, 2015, 11:06:19 pm »

Just remember that pornography is not allowed on this forum!

xrunner · « **Reply #2 on:** February 12, 2015, 11:15:24 pm »

Quote from: EEVblog on February 12, 2015, 11:06:19 pm

Just remember that pornography is not allowed on this forum!

Yes sir!

krivx · « **Reply #3 on:** February 12, 2015, 11:22:55 pm »

1 count off the Rigol? It is probably still within spec

EEVblog · « **Reply #4 on:** February 12, 2015, 11:24:49 pm »

BTW, I'm finally playing with that metal detector you sent! Better late than never?

xrunner · « **Reply #5 on:** February 12, 2015, 11:31:30 pm »

Quote from: EEVblog on February 12, 2015, 11:24:49 pm

BTW, I'm finally playing with that metal detector you sent! Better late than never?

LOL -wow I forgot about that. I really didn't ever open it so I have no idea what kind of circuit the Chinese came up with. Be looking for the teardown.

xrunner · « **Reply #6 on:** February 13, 2015, 11:45:48 pm »

Did some disassembly today. Here's the top and bottom, the battery and charging circuit is mounted on the top cover -

This is the charging circuit, which charges a lead acid battery to 7.2V. The board is really nice with all the gold traces.

This is what happens when you neglect lead acid batteries for many years -

And the battery used -

Battery charger circuit removed. Gotta have more gold!

MarkPalmer · « **Reply #7 on:** February 14, 2015, 04:16:13 am »

I have a 3435A that I have used as the "go to," on my service bench for what seems like forever. One thing I can say about them is this- they will withstand a LOT of abuse. I have inadvertently made every mistake one can think of when using a multimeter with my 3435A not really caring much if it gets ruined, but it just keeps coming back for more while remaining accurate all the time. It's the thing that will not die! Mine is in the bench style case rather than the plastic portable case, and it does not have the battery option.

-Mark-

SeanB · « **Reply #8 on:** February 14, 2015, 05:24:12 am »

Replacement battery ( not Gates but will likely fit there) is cheap, and those spade lugs are also cheap ( but not the same as those ones, which are the Hellerman aviation spec ones) as well. You will need to replace the whole wire to the board, as the corrosion will have wicked up it under the insulation.

As to the battery looking like that, they all eventually do that with time, some just came with a better seal than others and last longer before the green plague appears.

MarkPalmer · « **Reply #9 on:** February 14, 2015, 07:11:54 am »

If that's all the more the battery has leaked since 1979, I would be really happy

-Mark-

VK5RC · « **Reply #10 on:** February 14, 2015, 07:14:58 am »

Looks like a good example of the 3435. I am a fan of red LEDs.
It may be of use to your restoration , some links to others restoration efforts esp robrenz, Martin.M, ModemHead. robrenz had some good comments on plastic restorers I recall? Mothers Black.
https://www.eevblog.com/forum/repair/vintageclassic-renovation-techniques/

xrunner · « **Reply #11 on:** February 14, 2015, 01:42:32 pm »

Quote from: MarkPalmer on February 14, 2015, 04:16:13 am

Mine is in the bench style case rather than the plastic portable case, and it does not have the battery option.

Nice meter. I got a HP 3466 a while back from Ebay to restore (came with a coating of nicotine) also and it had the battery option, and the battery was also dead. I can't see using these meters again with a battery, when so many very good handheld DMMs are available. I photocopied the details of the batteries case and will place a small cut out of the paper inside the case where the battery goes, if anyone wants to know exactly what was in there.

Quote from: SeanB on February 14, 2015, 05:24:12 am

As to the battery looking like that, they all eventually do that with time, some just came with a better seal than others and last longer before the green plague appears.

Yea I think I'll replace the wire and connector to make it at least look good.

I'll have some more pics to post today. I'm about ready to do the cosmetic clean up. Then I'm going to touch up the calibration.

xrunner · « **Reply #12 on:** February 14, 2015, 11:48:30 pm »

The DMM is fully disassembled now. Here's some more naked ~~porn~~ pics for your entertainment -

Here you can see how they bent out some pins on the IC to reach a central connection point. The IC has a ceramic cover (heat sink?)

Another large package, and also a 10 kHz test point which I'll be checking once the cleanup is done.

dom0 · « **Reply #13 on:** February 15, 2015, 01:52:03 am »

The ceramic cover is just the way the case is made. IIRC these are LTCC packages where the die is glued in, bonded to the already finished ceramic carrier with the nice gold traces etc. and then the ceramic lid is put on top.

As I learned recently these central cooking-pot-like connections are essentially solder filled cups made of teflon. It's used to reduce leakage currents (makes sense with this kind of multi-slope converter. They don't do this however on the 3478A family of DMMs, which are a more "recent" design. Maybe they found a way to mathematically correct leakage errors).

The large white IC is probably the processor.

SeanB · « **Reply #14 on:** February 15, 2015, 04:40:11 am »

The more recent ones without the PTFE standoffs use a guard ring around each sensitive connection, with a low impedance ( compared to the input it protects) drive to keep leakage current down.

The case is glued down using a glass filled epoxy, which is cured to make a hermetic seal. You do have to be careful there, as touching the area or cleaning with a contaminated brush or alcohol solution will create a leakage path. In production those boards likely were cleaned with a Freon based cleaner in that area to make sure it was absolutely clean and grease free.

radiomog · « **Reply #15 on:** February 15, 2015, 04:43:05 am »

VERY similar to my 3438A

xrunner · « **Reply #16 on:** February 15, 2015, 03:26:07 pm »

Thanks for the comments (and on the previous page).

The clean up. First wash in warm soapy water - works wonders. Did not want to remove the paper label on the back so I was careful to not get any water on it. Any stains that did not come off were attacked with several other cleaning weapons on-hand.

Rub on some Armour-All - makes it look like new plastic -

All the case parts are clean and ready for re-assembly -

PaulAm · « **Reply #17 on:** February 15, 2015, 05:33:52 pm »

I have both a 3465a and 3466a (the autoranging version of the 65). I actually find that I liked the 65a better and that's my usual bench meter.

Be careful cleaning that plastic overlay on the front. Anything harsh will dissolve the legends.

xrunner · « **Reply #18 on:** February 15, 2015, 05:51:42 pm »

Quote from: PaulAm on February 15, 2015, 05:33:52 pm

I have both a 3465a and 3466a (the autoranging version of the 65). I actually find that I liked the 65a better and that's my usual bench meter.

I got a '66A off Ebay a few weeks ago. It was reeking of nicotine upon opening the box. Cosmetically - it was a lot worse than this one. However it looks like new now. I should have done this series on that one.

Quote

Be careful cleaning that plastic overlay on the front. Anything harsh will dissolve the legends.

Absolutely. It has emerged from the cleaning unscathed. I'm putting back together now, and I ran across an interesting thing when I got into replacing the corroded lead on the batt. charger circuit. I'll post the pic later and see if anyone knows the answer ...

xrunner · « **Reply #19 on:** February 16, 2015, 12:01:53 am »

I'm planning on keeping the battery charging board in the unit but I do not plan on using it. The battery board connects to the main board, and if it's disconnected, the DMM will not turn on. A sense line goes up to the battery board and then back down to the main board. However, it's possible to allow the unit to operate without having the battery board connected if a jumper wire is installed. You can see in the first pic where the jumper wire goes. It actually will cross over the connector to presumably indicate to service personnel that the connector is not to be connected.

It's interesting to note that there was a jumper on the board and it's been clipped off. I have an HP 3466A with the battery option and it's the same way. It looks like they manufactured them with the jumper by default, and the units that were to be shipped with the battery option have the wire clipped at the factory. As you an see in the second pic, it does now work without the battery board plugged in.

Take a look at the third pic. I repaired the corroded wire that plugs into the battery. On both the battery wires there is a very tiny plastic washer or grommet or

. I have no idea why that is on these wires. I've not seen these on any other wires in the unit. When I replace the wire I put it back on, but I don't know what it does. What purpose could they serve?

What purpose does the little plastic washer serve?

xrunner · « **Reply #20 on:** February 16, 2015, 05:37:41 pm »

One end of the ribbon cable going to the display had two of the metal strips separating from the plastic backing. It wasn't inserted straight into the connector - don't know why. May have been that way from day one. I fixed it by gluing the strips back to the plastic.

The glue I used is called Formula 560 Canopy glue. It's used a lot by model hobbyists but it really works well for attaching things to plastic - even vinyl.

PaulAm · « **Reply #21 on:** February 16, 2015, 06:04:24 pm »

I hate those cables; they fall apart all of the time.

I've used superglue to bond them; that seems to work reasonably well.

I've also pulled those connectors out and used regular headers.

xrunner · « **Reply #22 on:** February 16, 2015, 06:06:54 pm »

Quote from: PaulAm on February 16, 2015, 06:04:24 pm

I hate those cables; they fall apart all of the time.

I've used superglue to bond them; that seems to work reasonably well.

I've also pulled those connectors out and used regular headers.

Yea of all the things that are made so well in that meter, I wished they hadn't used that type of cable.

I tried CA glue first and it didn't seem to grab, this stuff is grabbing now.

xrunner · « **Reply #23 on:** February 17, 2015, 02:11:00 pm »

Went through most of the cal, still need to acquire an A/C source for a couple of required cal signals, but the rest are done.

Hey, on this meter you can even check and adjust the 10 kHz clock. I found it to be running at 9.380, so I tweaked it back up. The Rigol makes it easy to check. Maybe I should overclock it.

xrunner · « **Reply #24 on:** February 20, 2015, 03:16:57 pm »

Well might as well finish the thread with a pic. All done and looking/workin good.


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Author Topic: HP 3435A Extreme Makeover (Read 23200 times)

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