From my perspective, I'm learning so much more from the failures than if this had been just another easy fix.
I'm sure it's really frustrating for you, Dave, but it is certainly serving the purpose of producing a great series of videos on troubleshooting. It doesn't matter to me whether you get the damned thing fixed; it's learning about the troubleshooting process that's important to someone of my limited experience. And, a better understanding of the role of the components in the various circuits.
Keep on (at least for a while longer).
If the DAC is something like an R-2R, you could get this effect if all of the low-side drivers were disabled. Check the negative rail to the DAC!
Edit - or the high side, of course, you'd just have the inverse... but we've already been checking negatives.
Oh, you're absolutely spot on. If the DAC's not getting the right high or low side supply (who knows whether they choose to do the design "upside-down" from the schematics we're used to), then you could fully expect this behaviour.
Keep on (at least for a while longer).
I will, but likely won't do any more videos until I can beg/borrow/steal/make a DIN41612 extender card or cable.
One card socket, one plug and 3 pieces of veroboard. Solder rows of socket edge on to veroboard and to the cut off edge of the plug. Then place another on top and repeat. Did that to make an extender for a avionics computer so I could reach the test points they conveniently placed just too far inside, and this one had the only set of sockets that were not common to the other cards. Good enough for occasional use.
Hi Dave,
check your email...
Regards
Ronald
I think every op amp in that beast is dead. The question is - what else is dead? If it were me, I'd pull and replace every op-amp in the thing and see where I was. Fixing old stuff is my hobby. I can't speak for Dave.
Dave may feel differently. I have a Tek 453 I am working on. When it is fixed I have to find another old Tek to fix. Vicious cycle.
The fact that your V/- 6.2 volts are reversed from the silkscreen is a red flag. Check the service manual to see if they have a note about the silkscreen being wrong (if the silkscreen is wrong it should have the note, especially if it isn't the first edition). Fix that first, then trace down the other bugs. Shotgunning the op amps would be a waste of time since if all or even most of the op amps are blown, their are going to be other ICs that aren't as easily obtained blown as well.
Watching this repair series makes me re-think my strategy for power rails on my boards... If the HP engineers had only put a simple zener diode and a fuse (link or thermal) as overvoltage protection on the rails, perhaps it would have survived and fewer components (ultimately NO components) would have been damaged.
by the way, Sony has patented the use of a zener diode, a PTC resistor and a thermal fuse for overvoltage protection.
I didn't know that.
http://www.google.com/patents/US6700766It's not clear to me if the patent only applies to battery packs, or if it applies whenever you use those 3 devices, or if it applies when the 3 devices are in close proximity so as to transfer thermal energy to each other thus decreasing the response time. They claim all 3 (among about 20 other variations too).
A zener and a thermal fuse can help protect against over-voltage, but a sustained overvoltage can overheat the zener, so they put a PTC in series with the zener, and that limits the zener current. Then they patented it.
Dear Dave:
--I recommend you get a used Hakko 470 or something like. It is a treat! I prefer the 470 over the 808, because it is much easier to use, since you are not carrying the weight of the motor, and, being smaller it can get into more places. I even use it to re-solder with if I only have one or two easy ones to do. When you no longer have to dick around with a spring operated solder sucker and braid, and can remove devices at the rate of one second per pin, with no destruction, your use of bad language will drop considerably. Many parts just fall out with no persuasion. Even if you do not use it on this particular project, I promise you, you will not be sorry!
"I see, Its a profit deal"
Steve Martin 1945 -
Best Regards
Clear Ether
by the way, Sony has patented the use of a zener diode, a PTC resistor and a thermal fuse for overvoltage protection.
I didn't know that.
http://www.google.com/patents/US6700766
It's not clear to me if the patent only applies to battery packs, or if it applies whenever you use those 3 devices, or if it applies when the 3 devices are in close proximity so as to transfer thermal energy to each other thus decreasing the response time. They claim all 3 (among about 20 other variations too).
A zener and a thermal fuse can help protect against over-voltage, but a sustained overvoltage can overheat the zener, so they put a PTC in series with the zener, and that limits the zener current. Then they patented it.
It's freaking pathetic that using three devices together for exactly their already existing intended applications can receive a patent.
I scoured google looking for the circuit diagram but no joy here either.
sometimes when I want something I can't find online I get lucky by emailing
people at say HP who might have access to data i am after and who would be willing to
do the favor. especially since this is somewhat outdated tech. just an idea to kick around.
--I recommend you get a used Hakko 470 or something like.
Quite rare to get one here in oz.
I've picked up a local cheapie, as new Hakko's in oz are very expensive, about to shoot a video on it right now...
forgive me if this is an incredibly dumb idea but I thought that an 8 pin dip socket used in a rather unusual way could be used to test those op-amps with out removing them from the board.
just put the socket down on top of the op-amp using the sockets legs like probes and connect the test circuit whatever you choose to the top of the socket, not sure how well this would work but sense the power for the part would come from the test circuit presumably on a bread board then you could test em without having the board in the dsa housing.
probably a dumb idea but it sounded better then soldering wires to every signal pin on every part and running all them out the side to test and get em all mixed up lol
anyway good luck getting this thing to work
Hi Dave. I have been following your blog for quite some time now. You were having a dilema about how to go about fixing the HP35670A and you were contemplating fixing it with some kind of extender card. Here in Toronto i found a couple of cards ( made by Sony, don't know what they are for) that have that 3 x 32 connector. I sent them in the mail for you to look at and hopefuly, you could use them to diagnose and test the A4 or A5 card on your DSA. I sent you a couple of e-mails in regards to this. Good luck with the repair.
Will
And the next episode will be when !!!!!!!!!!!!!!!!!
And the next episode will be when !!!!!!!!!!!!!!!!!
I know, right? I love to watch other people spend money.
And the next episode will be when !!!!!!!!!!!!!!!!!
I know, right? I love to watch other people spend money.
Ha ha ha , I just want to see him fix it, it used to work so it should work again, I'd find it a pride thing, perhaps that's why I'll never have my own business
.
I'm surprised the HP/Agilent or who ever owns the company haven't stepped in to help, I thought Dave had a strong bond with them.
I'm surprised the HP/Agilent or who ever owns the company haven't stepped in to help
Ten years ago: these companies in europe at least gave a huge discount on a new spectrum analyzer when the old one was swapped back.
They then destroyed the old equipment (at least what they told me).
So in fact they bought back their old spectrum analyzers for a huge amount of money just to keep these equipment off the second hand market so it would not cannibalize their new product portfolio for small companies.
It was a pain to see since in that time the company i worked for sold the old equipment for almost nothing to their own employees
So I think it is very tough to get any documentation, only hope is an old HP employee has his own document archive copy somewhere.
I'm surprised the HP/Agilent or who ever owns the company haven't stepped in to help
Ten years ago: these companies in europe at least gave a huge discount on a new spectrum analyzer when the old one was swapped back.
They then destroyed the old equipment (at least what they told me).
So in fact they bought back their old spectrum analyzers for a huge amount of money just to keep these equipment off the second hand market so it would not cannibalize their new product portfolio for small companies.
It was a pain to see since in that time the company i worked for sold the old equipment for almost nothing to their own employees
So I think it is very tough to get any documentation, only hope is an old HP employee has his own document archive copy somewhere.
Cricky is that what they used to do !!!!!!!! how strange, I have some old Black*Star equipment made quite locally to me not in the same league of course, Thurlby Thander bought black*star out and their sale team have been the most helpful people when I needed a schematic & user manual very impressive, so much so I would buy thurlby Thander known as TTL equipment in a heart beat now.
I'm surprised the HP/Agilent or who ever owns the company haven't stepped in to help
Ten years ago: these companies in europe at least gave a huge discount on a new spectrum analyzer when the old one was swapped back.
They then destroyed the old equipment (at least what they told me).
So in fact they bought back their old spectrum analyzers for a huge amount of money just to keep these equipment off the second hand market so it would not cannibalize their new product portfolio for small companies.
It was a pain to see since in that time the company i worked for sold the old equipment for almost nothing to their own employees
So I think it is very tough to get any documentation, only hope is an old HP employee has his own document archive copy somewhere.
Cricky is that what they used to do !!!!!!!! how strange, I have some old Black*Star equipment made quite locally to me not in the same league of course, Thurlby Thander bought black*star out and their sale team have been the most helpful people when I needed a schematic & user manual very impressive, so much so I would buy thurlby Thander known as TTL equipment in a heart beat now.
When I tried to contact Kenwood about an old Trio-Kenwood scope I was told that division of the company didn't exist any more and was given a phone number and address of a company that serviced them with the caveat that they went out of business a few years ago.
Dave check back the agilent forum you made. Someone apparetly want to send you the acquisition schematics!
Hi Dave,
I have the service manual. If you're interested, just send me an email, and I'll forward it.
afair Dave said on twatter he has schematics now
Dave I believe you have the schematics and I saw the bus extender cards in previous mailbag
Please don't give up ,continue when you have time. I love these videos its like watching an
Agata Christie murder mystery. "Ten little op amps"