BTW, I'd strongly recommend to replace the Schaffner mains filter if that hasn't been done in the last 10 years as they tend to blow up and spread some corrosive gunk all over the mainboard. They are still made, usually not very expensive, and the new versions should be more reliable. Just make sure you don't buy "new - old stock" as that wouldn't really solve your problem.
So, I know that the NVRAM is bad (really the battery inside)
The mains filter is quite expensive, in europe at least. I did replace it, but it cost like 60 euro's. You could probavly find them cheaper on ebay.
So, I know that the NVRAM is bad (really the battery inside)
As to the bad NVRAM, I'd replace it with a FRAM IC instead another NVRAM module. Works the same and doesn't need a battery.The mains filter is quite expensive, in europe at least. I did replace it, but it cost like 60 euro's. You could probavly find them cheaper on ebay.
I paid around £20 (around 25EUR) for a brand new one a couple of years ago.
Users who are modifying existing designs to use FRAM
should examine the memory controller for
timing compatibility of address and control pins.
Each memory access must be qualified with a low
transition of /CE. In many cases, this is the only
change required. An example of the signal
relationships is shown in Figure 2 below. Also shown
is a common SRAM signal relationship that will not
work for the FM16W08.
The reason for /CE to strobe for each address is twofold:
it latches the new address and creates the
necessary precharge period while /CE is high.
So, I know that the NVRAM is bad (really the battery inside)
As to the bad NVRAM, I'd replace it with a FRAM IC instead another NVRAM module. Works the same and doesn't need a battery.
Do you know HP54xxx memory handling /CE signal pass for using FRAM
You can just replace the BNC with some random BNC connector, it's nothing fancy. Be carefull not to shorten the original cable to the connector though, it's quite short if I remember correctly.
I would recommend fastening the NVRAM module to the socket with a tie-wrap.
BTW, give it at least have an hour before selftest/selfcalibration. It will fail when the system havent had time to properly warm-up.
This is off to a good start, nice score by the way.
I am looking forward to seeing your progress.
Wow!
I always turn down the intensity when the scope is not in use.
Especially on gear that I used daily at work.
By the way - what's up with those front BNC nuts? I had to remove them all with long-nose pliers because I couldn't get any socket on them and an open end wrench kept slipping off. They appear to be 5/8" but the socket won't fit because of the space against the case, and a regular open end wrench seems to slip off. The flats on the nut are very small. Yuck.
I can't buy a new Schaffner filter like the old one. The only new part numbers available is this
FN 393-2.5-05-11
The original part is
FN 393-2.5-05-12
No supplier I went to had the original part number, they only sell the new part number (-11).
I eventually called the NA office of Schaffner, and the engineer said they changed the design in 1993. He gave me a copy of the change notice (please find attached). Here's the deal - the new one (the -11 model) would work when using it on 120 VAC, because those connections made by the removable switch block are the same (it connects windings in series). BUT - the 220 VAC connections are NOT the same as the old model. That's what the engineer alerted me to. Take a look at the PDF attached.
So, the question I want advice on is - do I buy the new model knowing that if somebody used it on 220 VAC something bad might happen, or do I get a used -12 model, knowing the connections are exactly the same but might have a lot of hours on it? What should I do?
It is an IEC socket type right?
It is an IEC socket type right?
Well yea but I'd rather get the new part and mod the socket somehow to prevent the 220 option from working than put in something that doesn't look original. I'm looking at some used original parts on Ebay also, there is a date code on the label at the bottom.
I'm also wondering if the switch block from an old model would fit in a new one and may lend itself to modification.
OK but show us an image, is it switchable too?
Whatever you do BE SAFE
Whatever you do BE SAFE
Thanks Sue - no problem. It looks hokey but it's very safe.
Well I'm still alive.
I had to move the PSU as shown (because I did not have the "extender cable" for this scope) to complete the Attenuator Compensation Adjustments - Section 4-15. It states to use a 100 Hz square wave, 300 mV pp, into a 50 ohm termination at the scope. However, using the given parameters of the square wave they stated, I found that adjusting the compensation caps produced absolutely Zero observable change in the response to the square wave on any of the four channels. I decided to change the freq. of the square wave to 10 kHz and that allowed me to see and make the adjustments. Don't know if the manual has a mistake, but it seems so.
So having completed that part of the cal, I put the PSU back the way it's supposed to be.
And what is your square wave rise time and other signal charateristics. Adjustments need do with equipments what are listed in service manual or comparable. In this case HP8116A programmable pulse fenerator. If not available, then need look carefully HP8116A specifications and use something what is as near as possible (because in service manual, text is valid for named equipments) There is quaranteed rise time and overshoot etc.
Every step in HP service manual is just perfectly right. This is not made in china.
Also it is good practice to follow paragraph 4 order starting from 1, every step in order. This is how it is designed to do. (if know exatly what is doing then also know where can do different and how to execute own procedure)
If on your board things do not go as in manual, there is two reasons, device is somehow failed or you do something wrong. One problem where things do not go as in manual may be wrong instruments used for job.
Usually (mostly) these models do not need readjust exept if example mobo is changed. Mostly they pass specs for cal without adjustment. Main principle for adjustment is that first need be sure that something need really adjust.
I also want to hear from Wuerstchenund because he said they were still available. I sent him a PM and I'd like to know if he knows of any new old stock somewhere becasue that original part is not available as new.
Keep in mind - I know of nothing wrong with the part that's in the unit right now. I was just advised that they blow out by Wuerstchenund. Maybe it's not a big deal, how many blow out, what percent blow out? Any given part can fail. I mean the thing's been around for 27 years and the part is still working just fine and I can get the actual part (used) on Ebay right now ...
Usually (mostly) these models do not need readjust exept if example mobo is changed. Mostly they pass specs for cal without adjustment. Main principle for adjustment is that first need be sure that something need really adjust.
Yea but I like to adjust things - even if they may not need it.
I paid for this ticket and I want the whole roller coaster ride. This is my entertainment don't you see?
Sorry for only replying now but I was down with a cold.
When I said that replacement for that Schaffner mains filter is available I did not mean the original part, which is no longer made (the whole line has been redesigned, also because of the tendency to explode). But Schaffner has other models that fit the cutout and allow 120V/240V switchover. I can't remember what the exact model was I used in my 54510A but I remember that I had to modify the mains voltage switching logic for the new module slightly. I decided against hard-wiring the mains voltage to 240V, which would have created some potential issues for people that owned the scope after me.
In any case, Schaffner should be able to tell you what the suitable replacement models are.
The question is not *if* your old filter will explode, the only question is *when*. All these old Schaffner filters will blow up eventually, as due to their age the caps in them become dry, heat up, and due some design issue this is pretty much guranteed to end up in a more or less violent disintegration ...
So, what I'd like to do is buy a brand new model - the FN 393-2.5-05-11,
and mark out or black out the lettering on the reversible switch block so there is no 220v option indicated to the user, and also label the rear so as to indicate it is only for 120V. As you can see from the second attachment, even if I put in a different model filter and re-wired the internal wiring, there is still lettering on the back that indicates 120V/230V in two places. I mean, unless I scrape that off also, I can't prevent a person from doing something dumb and connecting it to 220V, if it ever left the US. So do you think it's acceptable to replace with the new design and black out the lettering on the reversible block so that 220V is not indicated? Is that acceptable?
Frankly, I'd do it properly and keep the device 120V/240V switchable. ...
My recommendation is to do the work properly. Especially since we're talking about mains voltages here, which aren't exactly insignificant.
What about a big red honkin' label saying "For 120 V mains only!"
as a last resort on the unit itself on two or three places to get
you out of any liability.
What else can I do given only two options?
Keep a mod book for the unit that stays with it and add a sticker inside and outside explaining such.
Original and modded schematic too, then only an idiot will FUBAR it.
Another thought xrunner.....I've come across manuals that in the first page or so there's been a card overlay stuck in place containing country specific information, often it's the first thing you see when opening the manual.
3rd sentence 3rd paragraph.....HP will replace the mains filter free of charge.
Wonder if they'll honour that?
3rd sentence 3rd paragraph.....HP will replace the mains filter free of charge.
Wonder if they'll honour that?
My memory is fading a bit now. But I can remember that Intel still honors the guarantee for the Pentium I according to the German c't newspaper...
Got the brand new Schaffner line filter today. There was still one thing about it I couldn't tell from any pictures. The new switch block that it comes with - as labelled - is wrong for the 120V position. The 220V position, is the correct one for the old way the PSU was wired, back in the day.
So, I can easily make it work, but I will use the old switch block in the new filter. Welcome to restoring old equipment.
Also got the BNC connectors I need - so I should have all the parts now.
Quadruple check that, sketch it out and be sure.
Is there no way the wiring can be reconfigured to make the switching correct?
Is there no way the wiring can be reconfigured to make the switching correct?
It's done!
Works well, for me it's a nice unit for my collection too.
Got my eye on another used piece of test equipment, may have another thread coming ...
Nice work!
Also nice to see peoples want restore these old well designed and made beauties.
BTW, I'd strongly recommend to replace the Schaffner mains filter if that hasn't been done in the last 10 years as they tend to blow up and spread some corrosive gunk all over the mainboard. They are still made, usually not very expensive, and the new versions should be more reliable. Just make sure you don't buy "new - old stock" as that wouldn't really solve your problem.
Yea thanks - I've heard about that and I'm going to attempt to find a replacement that fits in the existing cut-out.
Here's a few more screen shots for today. I'm just posting these for anyone browsing the web looking for info that may need to see them.
So, I know that the NVRAM is bad (really the battery inside), so what happens when you run the self-test? On the back of the unit is a red switch that sets the calibration to either protected or unprotected. If that switch is in the unprotected mode, you see that it passes all the self tests (with a bad NVRAM). If it is in the protected setting, the self-tests do not pass the NVRAM, D/A converter, or A/D converter (with a bad NVRAM). And finally, you can see the screen at the completion of the self-calibration. However, once you turn it off it will all be lost with a bad NVRAM; but it does complete properly.
Only other thing I've done is to pull out the power supply to see if it can be jury-rigged in such a manner as to allow one to tweak the tweakable adjustments underneath it without using the "extender cable" the manual talks about - I think it will be possible.
More to follow ...
Man, sure am glad I stumbled across this post. I picked up a 54502A a while back that didn't want to power up. When probing for voltages, something sparked and it powered up. Was planning on eventually replacing it not knowing the darn thing can explode black gunk all over the place. Thanks!