Repair worklog : Old rusty HP 3458A - Page 1
Forum section: electronics / general

author: TiN
author_rank: Super Contributor
timestamp: September 16, 2015, 08:30:29 am
content: Received final item for volt-nut freaks - 3458A. It's old unit with chassis corrosion from seller in Philippines, which we already discussed in Buy/Sell section here..So far initial inspection:* U100 processor MC68HC000P8 had paper sticker BAD (A5 board manufactured 1990)* Missing button cap on power switch, guard switch and front/rear switch.* Missing fuse binding post for amps on front panel* Rust on steel chassis* Mark "X" on mains power transformer* Mark "X" on analog board 66501 (manufactured 1996)* Error message RAM 1 LOW* Missing voltage reference board (so calibration is meaningless, even if it's still intact in 1990 year DS1220)..* Missing fuse holder for mains* Damaged plastic rear panel* No legsSmell like lots of work, lots of debug folks.

author: krivx
author_rank: Frequent Contributor
timestamp: September 16, 2015, 08:46:53 am
content: What's the plan? DIY or OEM voltage reference assembly? Will you get this functioning and then refinish/repair the enclosure?

author: Vgkid
author_rank: Super Contributor
timestamp: September 16, 2015, 08:57:40 am
content: This will be interesting...Following.

author: Macbeth
author_rank: Super Contributor
timestamp: September 16, 2015, 09:46:28 am
content: Looking forward to this

author: TiN
author_rank: Super Contributor
timestamp: September 16, 2015, 12:01:21 pm
content: Ok, back home with unit now. Let's see what we are dealing with..Steel chassis is rusty on rear side. Not nice treatment for such an instrument.Removing covers...All analog stuff is contained in aluminum box, isolated from steel frame by plastic inserts. HP calls those boards inside as "inguard", rest boards are "outguard".View on both sides without covers. As we can see, no A9 voltage reference presentInguard PSU. Some PCB damage around CR12 visible.Outguard primary PSU. All seems ok.68000 CPU, RAM, ROM and digital logic, board A5. Dated 1990, while rest of analog PCBs dated 1996.Probably seller changed digital PCB afterwards?Removing inguard PSU for now, adding jumpwire instead of fuse (don't have suitable cap), turning on...Aha. Nice and bright VFD, which is cool. Now will remove Dallas NVRAMs , and solder sockets instead, so we can troubleshoot this RAM 1 LOW.

author: TiN
author_rank: Super Contributor
timestamp: September 16, 2015, 01:29:30 pm
content: Removed DS1235Y's, installed collect sockets.Installed DS1230Y into RAM LOW, now getting message RAM TEST 1 HIGH, which is a good sign.I don't have any more DS1230Y's, only 1245'sNeed to order some ebay DS1230Y's and 1220 as well

author: free_electron
author_rank: Super Contributor
timestamp: September 16, 2015, 02:54:53 pm
content: before you go on power cycling this thing (and cause more damage.)take it completely apart and wash the digital boards first in a mixture of 50% distilled water and 50% pure alcohol (ipa). let soak for a while .then wash in pure alcohol ( to displace water )do NOT blow on the boards to assist evaporating the alcohol ! evaporation cools down so it pulls moisture out of the air that then condensates ...use a hairdryer set to a low temperature to avoid this from happening.meanwhile : sandblast the chassis to get the rust off.it looks to me like these machines have been in a 'flood'. during a topical storm some building flooded and these have been dipped ...as for the precision analog sections : don;t wash those yet. inspect very carefully under a microscope to detect any residual water stains. if none can be found : leave alone. if you find water stains: wash them.

author: jlmoon
author_rank: Unknown
timestamp: September 16, 2015, 03:14:36 pm
content: +1 to FreeElectron. Very good advice!!!

author: MadTux
author_rank: Frequent Contributor
timestamp: September 16, 2015, 05:40:52 pm
content: Boards are looking better than I expected. So not everything is lost yet.I would contact the seller and ask him to give you a reference board for free, since it wasn't mentioned as missing.Apart from sand blasting, you can also treat the rusted steel parts with dilute phosphoric acid. It will convert the iron oxide to a thin, transparent, insoluble iron(III)phosphate layer that will also act as a rust protection layer, similar to the aluminum oxide layer on aluminum parts.https://en.wikipedia.org/wiki/Iron%28III%29_phosphateBadly rusted stuff is best cleaned by cathodic electrolysis (use the part to be cleaned as negative electrode) together with a non corrosive electrolyte (e.g. sodium carbonate, beware of any halide salts, since they will corrode stuff like crazy after treatment). The hydrogen that gets generated on the cathode will flake away larger oxide particles while protectig the remaining non corroded metal from further attack.Don't use it for too long however, because the (monoatomic) hydrogen might eventually lead to hydrogen embrittlementGood luck

author: TiN
author_rank: Super Contributor
timestamp: September 16, 2015, 06:44:00 pm
content: Thanks for advices.Only boards powered currently are A5, outguard supply and front panel.Already checked most analog boards, it does not look like anything was flooded at all, not even dust on PCBs.So I don't touch analog stuff just yet.First step would be fixing digital side (ordered memories already), and checking power supplies (transformer, outguard, inguard).Two zeners on inguard PSU (CR11,CR12) are shorted, so need replace those too.Transformer output to inguard seems real fishy, secondary resistances <0.5ohm (5-pin connector P1) and output only 7VAC.

author: free_electron
author_rank: Super Contributor
timestamp: September 16, 2015, 07:05:05 pm
content: i'd still clean those boards first. the problem is we dnot know what the machine was submerged in.. freshwater ? saltwater ? what is the salts content ? any salt deposit combined with humidity is a disaster waiting to happen. dendrite growth... one dendrite and it's game over for this beuatiful machinethat's why the 50/50 mix of distilled water and alcohol. alcohol cannot dissolve salts. water does.

author: Macbeth
author_rank: Super Contributor
timestamp: September 16, 2015, 07:54:11 pm
content: It does look like the seller gathered together all the worst boards from his other 3458's and shoved them into a single unit. I don't mean he diagnosed them as faulty but looked at the labels someone previously diagnosed and marked and pulled out those boards and put together a whole unit, then assumed all the boards and transformers not marked bad were good and parted them out to sell seperately? (and the good VREF too)The swine!Of course it is still repairable and the MCU is working and the VFD looks nice. The other unit on ebay looks in worse condition.But definitely clean at least the digital and power boards with IPA and distilled water, and of course don't even put a fingerprint (or voltage) on the analogue boards yet!But what do I know? I think I'm teaching a grandma to suck eggs here!

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: September 16, 2015, 07:59:46 pm
content: I actually quite surprise how clean the boards are, would have expected much more corrosion on those boards. Reason why I didn't make a offer and take it. Plus I had bad luck with that seller. Let just say signal generator I bought from them was suppose to be working and was missing parts and in worst condition then expected. To make matters worst someone was inside it strip most the screws, hook DC fan to AC fan port and mark the power supply board a XX, so they knew it was defective, even manage to hook the LCD front panel backwards, so it would have never work in it's condition. Don't get how they figure in working condition?. The only reason didn't leave a Negative, was due to they sent another one out and was able to repair the power supply off the first one, took the good RF board off the second one and case since it had no rust and still in good shape. Rebuilt the RF boards with new Philips modules and make a complete working and back within spec. Replaced all out of spec capacitors. Cost some money and time, won't buy from them again. Just wondering what they do over there in the Philippines? Leave this stuff pile outside?

author: TheSteve
author_rank: Unknown
timestamp: September 16, 2015, 08:03:18 pm
content: The Keithley 2001 was a restoration of glory, what will this one be? "glory squared" perhaps?Really looking forward to your progress.

author: Macbeth
author_rank: Super Contributor
timestamp: September 16, 2015, 08:09:56 pm
content: Quote from: OldSchoolTechCorner on September 16, 2015, 07:59:46 pmSome pretty bad natural disasters / acts-of-god for the heathens daring to copulate for reasons other than procreation, likehttps://en.wikipedia.org/wiki/Typhoon_HaiyanFaced with that kind of $billions damage, a lot is going to end up scrapped. There are a lot of very very poor people in the Phillipines who make a living literally scavenging the landfill rubbish tips this will have been dumped in. A child will have been given $1 tops for finding this and it has passed through many hands before it ends up with someone who has the nous and capital to flog it on ebay.

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: September 16, 2015, 08:53:02 pm
content: Quote from: TiN on September 16, 2015, 12:01:21 pmThey more likely kept most the good boards and swapped defective ones in and took voltage reference board.

author: MadTux
author_rank: Frequent Contributor
timestamp: September 16, 2015, 09:25:55 pm
content: Quote from: OldSchoolTechCorner on September 16, 2015, 08:53:02 pmDefective isn't a problem, since you can change broken chips and or replace them with sockets to have it easier in the future. Only a matter of time, equipment and skill.But if trace on PCB or vias are corroded away, then the PCB and thereby the instrument is usually done. It's dead Jim, nothing you can do. So I guess TiN was actually quite lucky, since that wasn't exactly clear from low res ebay photos. And I have seen and had far worse PCBs in my hands. Mostly salt water and battery damage that was neglected for years.

author: OldSchoolTechCorner
author_rank: Frequent Contributor
timestamp: September 16, 2015, 09:50:56 pm
content: Quote from: MadTux on September 16, 2015, 09:25:55 pmTrue...Shock how clean the PCB's are, would have expected a lot of corrosion damage. Looks like it was left outside, but not flooded. So water stay outside the case pretty much is what I suspect, otherwise damage would have been a lot worst. Have seen and dealt with the worst. Sucks when a battery or capacitors leak everywhere on the board eating away at traces and pads, or other components.

author: TiN
author_rank: Super Contributor
timestamp: September 16, 2015, 11:38:19 pm
content: To give little more coverage, here are closeup on PCBs, so you can see condition.Only visible residues are on outguard PSU board. A5 digital board looks much more dusty than any other board, so it's likely was swapped.Other boards are all within 1995-1996 year, I think they are original.What worry me a bit, is a transformer. Anybody have good one to measure windings resistance / voltage on P1 connector which goes to inguard PSU?Not sure if data postedhereis 100% valid.Also how about firmware? Mine is Rev.6, anyone have Rev.9 dumps for future update?3458-88860 Rev6 firmware ROM dump3458-88861 Rev6 firmware ROM dump3458-88862 Rev6 firmware ROM dump3458-88863 Rev6 firmware ROM dump3458-88864 Rev6 firmware ROM dump3458-88865 Rev6 firmware ROM dump

author: eas
author_rank: Frequent Contributor
timestamp: September 17, 2015, 12:16:59 am
content: Thanks for posting. I'm looking forward to seeing how this progresses.

author: Radio Tech
author_rank: Frequent Contributor
timestamp: September 17, 2015, 12:44:04 am
content: Hope you get this going and thanks for posting this.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: September 17, 2015, 03:10:24 am
content: I can make time tomorrow to measure the transformer windings. I will have to clear the bench to make some room.Rev 8 or 9 will be pretty much the same functionally. Maybe there is something available

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: September 17, 2015, 02:07:17 pm
content: I have verified that the measurements for the inguard transformer connector are correct. Mine are nearly identical to those posted on the web page. All measurements were made with no load.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: September 17, 2015, 02:20:17 pm
content: I forgot to mention that the large blue capacitor on the bottom looks like it is turned. I usually have to replace the rotted foam along its edge and I see that yours is rotated away from the cover.

author: TiN
author_rank: Super Contributor
timestamp: September 17, 2015, 03:11:08 pm
content: Thank you. Then it's safe to confirm that my transformer is busted.I tried to open it up, but it's all covered in lacquer, and my patience run out quickly.Front panel must be removed in order to remove mains transformer.Looking good, just minor cleaning required..Frontpanel PCBA label and front binding post terminals.Transformer have two winding sections, primary with secondary for outguard +5V rail (goes to digital board and front panel, that's why it's working).Second section for inguard supply is inner bobin with two secondary windings (one with center tap to generate +18/-18 and second for +5V analog).This windings in my transformer are shorted together!I would not trust repaired/rewinded transformer in such an instrument anyway, so going to make Agisight richer for $337 to get new transformer.