Author Topic: 3456A cover screw (Read 7274 times)

Vgkid · « **on:** January 09, 2015, 07:28:48 am »

Does anyone have the dimensions/ thread of the 1 screw that holds the cover on, or a place to buy them. I will upload a pic tomorrow if needed.

cncjerry · « **Reply #1 on:** January 09, 2015, 08:14:51 am »

I remember seeing a label that the screw is metric, I think. I have two such meters. Do you need the thread pitch and length?

Vgkid · « **Reply #2 on:** January 09, 2015, 03:32:07 pm »

I will take the pitch and diameter. I can measure the length. Whoever had it before me started to strip the heads of those 2 screws out. I further messed up the top one.

cncjerry · « **Reply #3 on:** January 11, 2015, 01:23:03 am »

I went down and measured it last night and it didn't make sense. The outside diameter was like 3.3mm and .8mm pitch according to the gauge. So I went looking for a 6-32 bolt because that would be around that size to check if it really is metric and couldn't find one. My shop is a mess right now as ? broke my arm before Christmas and left everything sit.

I'll go back down this evening.

Vgkid · « **Reply #4 on:** January 11, 2015, 02:09:26 am »

Take your time, just started giving me errors 3,4, and occasionally 10.

cncjerry · « **Reply #5 on:** January 11, 2015, 06:58:35 am »

I've had those same errors on three 3455 models. The 10 is something to do with the reference voltage but what it really means is that that node is loaded down. There are a pack of FETs on that node so finding the leaky one is a bitch. I have two open on my bench right now and I am trying to A / B them with a meter but the broken arm halted that as well. The error diagrams are pretty complete and it should be simple but for the life of me I can find the problem. I think it has something to do with the select which is driven by the ROM which when it goes bad you throw it out. Good luck.

Jerry

TerraHertz · « **Reply #6 on:** January 12, 2015, 04:13:05 am »

Unfortunately it's not a standard screw, as it has a shoulder and groove for a circlip. Which makes it a captive screw, and serves to pull the cover out as you unscrew that one screw.

The threaded part is definitely a UNF #6 thread - it fits a UNF #6 nut perfectly.
Also the head is Posidrive #2, not Philips. Hence why they get rounded out when you use a philips screwdriver.

Pic below, from my HP 3456A cover.

Vgkid · « **Reply #7 on:** January 12, 2015, 08:02:09 am »

Would that end up being a 6-40 screw?

TerraHertz · « **Reply #8 on:** January 12, 2015, 08:43:02 am »

Quote from: Vgkid on January 12, 2015, 08:02:09 am

Would that end up being a 6-40 screw?

Ha ha, I wouldn't know what that is, I use metric threads myself. I just happen to have some stock of various crazy Imperial thread screws for working on stuff made in the very few countries that haven't seen the metric light yet.
And that one, is a UNF #6.

Hmm...
http://en.wikipedia.org/wiki/Unified_Thread_Standard
I notice the UNF #6 is 40 tpi, so guess the answer is probably yes.

tautech · « **Reply #9 on:** January 12, 2015, 08:49:53 am »

Quote from: Vgkid on January 12, 2015, 08:02:09 am

Would that end up being a 6-40 screw?

Just checked my thread chart, yes UNF#6 is 40 TPI

Vgkid · « **Reply #10 on:** January 12, 2015, 03:49:29 pm »

Good, im used to metric as well.

free_electron · « **Reply #11 on:** January 12, 2015, 05:14:58 pm »

drat. i threw a whole bunch of covers in the recycling yesterday while i was digging for a frontpanel for Shahriar's meter.
I may still have some of those screws. lemme see tonite.

Vgkid · « **Reply #12 on:** January 13, 2015, 09:05:00 pm »

If you can find those screws that would be nice. At least i know the thread.
I would gladly accept broken a broken 3456a to go with those screws.

davorin · « **Reply #13 on:** January 15, 2015, 04:31:08 pm »

Quote from: Vgkid on January 11, 2015, 02:09:26 am

Take your time, just started giving me errors 3,4, and occasionally 10.

If yo ustill have those errors....hat something similar on one of my 3456A...think it was 3, 4 and 8...randomly...
Turned out the red CPU socket was bad...one contact was broken, which was the data line for communicating with the other boards...

Took me a looong time to find this ;-)

Always replace the CPU sockets (o;

cncjerry · « **Reply #14 on:** January 16, 2015, 06:02:08 pm »

I believe it is a 6-32 screw as I thought it was metric and measured it as .8 pitch. 25.4 divided by .8 is very close to 1/32 .

I looked in the parts list and can't find the reference. they do have a lot of 3.5 x .8 mm in the unit so it could still be metric.

Vgkid · « **Reply #15 on:** January 17, 2015, 03:52:19 am »

Here is the problem, this is a unusual looking ripple though.
using an external 5v power supply caused no errors.

davorin · « **Reply #16 on:** January 17, 2015, 06:15:58 am »

Ah right..had the same issues.....replacing the big electrolyt capacitor for the +5V rail solved it for me.....

Vgkid · « **Reply #17 on:** January 17, 2015, 07:01:46 am »

perfect, that is what I guessed as well.

Vgkid · « **Reply #18 on:** January 18, 2015, 04:45:48 am »

I will take the screw to my local hardware store, and see if they have a match; if not Fastenal.
the old capacitor measured at 110uF, with a DQ of 2.5.

free_electron · « **Reply #19 on:** January 18, 2015, 05:26:38 am »

My pith helmet is ready for tomorrow. i have to go dig in the pile of scrap/ donors...
there's a bunch of people waiting for parts .. displays, switch blades , screws ...

Vgkid · « **Reply #20 on:** January 18, 2015, 10:43:02 pm »

For those curious, the screw in question is a imperial flat-head screw 6-40usf of length 3/8 in, but .5in is close enough.

Vgkid · « **Reply #21 on:** January 26, 2015, 04:59:22 am »

Any luck on those screws?
Also, should I go ahead and recap the PSU?

lowimpedance · « **Reply #22 on:** January 28, 2015, 04:13:59 am »

Quote from: Vgkid on January 26, 2015, 04:59:22 am

Any luck on those screws?
Also, should I go ahead and recap the PSU?

There are a number of threads on here relating to this meter and generally errors are caused by the old electro's in the supply, so yes do a supply recap.
There are also some HP service notes that I uploaded some time ago ;

https://www.eevblog.com/forum/testgear/hp3456a-service-notes-for-owners-info!/msg144820/#msg144820


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Author Topic: 3456A cover screw (Read 7274 times)

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