I recently acquired a Canberra 35+ MCA. The good news is
that it powers up. The bad news is that is about all it does.
Well, if I press the RESET? button on the display card I get it
to say Canberra on the top line of the CRT, and display two
lines of >>> on bottom of the CRT. The good news is that I
got a copy of the manual and schematics with it. The bad
news is that not all the schematics are legible.
Does anyone else here have experience with this unit? I
might want to bounce a few questions off you as I start to
troubleshoot it. I'll do it by private email, so as to not clutter up
the forum (unless folks think the thread would be useful to
others).
Canberra 35+ MCA Help Needed
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ChrisSmolinski
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Richard Hester
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Re: Canberra 35+ MCA Help Needed
I have a 35+ that is a little under the weather, too. I suspect either a faulty power supply or a blown preamp. When I start a scan, the on-screen dead time meter maxes out, and no spectrum appears. I haven't peeked under the hood yet due to lack of time. If it is anything like its near ancestor the Series 30, it has a mess of teardrop tantalum bypass caps that spontaneously go short and pull down a crucial supply. I have a Series 30 with just that problem, and some day I'm going to need to go through the whole thing and swap out the bad tantalums for something more enduring. I would choose Oscons, but a mess of those would cost a king's ransom, and they don't go any higher than 20-25 volts. When I get around to it, I'll probably use 1uF film caps, with a few electrolytics for damping. No tantalums for sure...
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ChrisSmolinski
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Re: Canberra 35+ MCA Help Needed
I've not started to look through the circuits yet, but did they
use improperly rated tantalums? I've used these caps myself
(in real production jobs not just at home) without problem.
Well, except for when someone decided to install them
backwards. They will blow up, the bad news is that they won't
do it right away but will wait several weeks, so the product
has safely left the factory.
Anyway, I guess I will start with checking out the various
supplies. Is there any easy way to gain access to the boards
while they are installed? I'm thinking that making up some
sort of extender card might make troubleshooting much
easier.
use improperly rated tantalums? I've used these caps myself
(in real production jobs not just at home) without problem.
Well, except for when someone decided to install them
backwards. They will blow up, the bad news is that they won't
do it right away but will wait several weeks, so the product
has safely left the factory.
Anyway, I guess I will start with checking out the various
supplies. Is there any easy way to gain access to the boards
while they are installed? I'm thinking that making up some
sort of extender card might make troubleshooting much
easier.
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Richard Hester
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Re: Canberra 35+ MCA Help Needed
I have had bad luck with teardrop style tantalums, even with proper voltage derating. By this, I mean using a 4.7uF, 35V cap for a 15V supply. The older caps (70's and early 80's) are not even as good as ones of recent manufacture. They have a tendancy to, in the industry term, "scintillate", or break down intermittently, even when used with proper derating. If the breakdown is large enough, it doesn't heal, and a shorted cap is the result. I just finished debugging a line driver assembly where I had used 3.3 uF, 35V teardrop caps to bypass the supply rails on some high speed op amps. Out of 8 total caps, I had one short right at the get-go. This is on top of other experiences with initial cap failure. Never again, - I will use anything but tantalums these days for supply bypassing - it's too much of a crap shoot. The system 30 analyzer I have has had two of the little bastards go short. When I have time, I intend to clean house...
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Richard Hull
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Re: Canberra 35+ MCA Help Needed
Richard is correct! I find that tantalums are really a superb capacitor. However, they hate heat; even moderate heat. They can dry up a bit over years of use or inaction and "twinkle" the supply rails, (not good). In the old 8100's that I have, it is all 74XX TTL chips with hundreds of tants on a board and 7 huge boards. Heat comes out of these densely populated boards in the machine like a running clothes dryer.
The solution is not to isolate and replace problem caps, but to gut the lot of 'em. This will effectively place the machine in "as delivered", new condition so far as the supply rails are concerned. Anything less than a "gutting" will have you back in the machine before long.
IMPORTANT!
I have traced a couple of real tough intermittents to DIRTY TRIM POTS on boards!!! Solution....
1. Hopefully, have the machine in its intermittent working state.
2. Find the arm or wiper pin of the pot on the underside of the board and measure the DC potential very accurately or, if a waveform, its amplitude.
3. Mark with a pen or scratching needle the position of the adjustment screw on the pot.
4. Now turn the pot's adjustment screw violently from side to side many times over a full 270 degrees or more with 10 turn pots. This scrubs the wiper and resistance element of oxide, grease and dust.
5. Return the pot to its original position by the mark first, then, fine tune with re-establishing the proper amplitude on the wiper. NOTE. Do this one pot at a time and, hopefully, in the offending or suspect area of the circuit.
Naturally, if you really know you have located a flakey pot, REPLACE IT!
Remember, all of these old MCAs were purchased as work horses. They all had the piss worked out of them over many years. Most, ultimately went bad and were either too old or costly to have reaired. The new replacement unit came in and the old unit went into a closet for another 5 or 10 years to have the dielectric in the electrolytics dry up or depolarize. Finally, the "Assets and Property" dept. disposed to a surplus dealer where it sat again for a while often in hot and cold and damp environments.
What you have is a very dead critter.
A lot of TLC, creativity, perseverence and, often, no small amount of treasure will be required to drag it back amongst the living.
My venerable old 8100 has a real "campfire tale" associated with its checkered career coming back from the dead due to the ministrations of 5 owners following its original surplus purchase on E-bay over 6 years ago! A true resurrection! But that's another story.
Richard Hull
The solution is not to isolate and replace problem caps, but to gut the lot of 'em. This will effectively place the machine in "as delivered", new condition so far as the supply rails are concerned. Anything less than a "gutting" will have you back in the machine before long.
IMPORTANT!
I have traced a couple of real tough intermittents to DIRTY TRIM POTS on boards!!! Solution....
1. Hopefully, have the machine in its intermittent working state.
2. Find the arm or wiper pin of the pot on the underside of the board and measure the DC potential very accurately or, if a waveform, its amplitude.
3. Mark with a pen or scratching needle the position of the adjustment screw on the pot.
4. Now turn the pot's adjustment screw violently from side to side many times over a full 270 degrees or more with 10 turn pots. This scrubs the wiper and resistance element of oxide, grease and dust.
5. Return the pot to its original position by the mark first, then, fine tune with re-establishing the proper amplitude on the wiper. NOTE. Do this one pot at a time and, hopefully, in the offending or suspect area of the circuit.
Naturally, if you really know you have located a flakey pot, REPLACE IT!
Remember, all of these old MCAs were purchased as work horses. They all had the piss worked out of them over many years. Most, ultimately went bad and were either too old or costly to have reaired. The new replacement unit came in and the old unit went into a closet for another 5 or 10 years to have the dielectric in the electrolytics dry up or depolarize. Finally, the "Assets and Property" dept. disposed to a surplus dealer where it sat again for a while often in hot and cold and damp environments.
What you have is a very dead critter.
A lot of TLC, creativity, perseverence and, often, no small amount of treasure will be required to drag it back amongst the living.
My venerable old 8100 has a real "campfire tale" associated with its checkered career coming back from the dead due to the ministrations of 5 owners following its original surplus purchase on E-bay over 6 years ago! A true resurrection! But that's another story.
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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ChrisSmolinski
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Re: Canberra 35+ MCA Help Needed
I'm going to try a new angle with the 35+ I'm pouring over the
schematics to see if I can extract the ADC ouputs from that
card. It looks like the important front panel controls go directly
to the ADC card. If the uP is needed to control it, I hope I can
tap off it, and feed the ADC readings into a computer, which is
really what I want to do anyway. Then I can do all the
processing and binning I want.
We'll see.
schematics to see if I can extract the ADC ouputs from that
card. It looks like the important front panel controls go directly
to the ADC card. If the uP is needed to control it, I hope I can
tap off it, and feed the ADC readings into a computer, which is
really what I want to do anyway. Then I can do all the
processing and binning I want.
We'll see.
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ChrisSmolinski
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Re: Canberra 35+ MCA Help Needed
Canberra has a service manual for the 35+ available for (gulp) $65. Does anyone have experience with these? Will it be worthwhile in addition to the operators manual and schematics that I already have? I have an email into OETech to see if he has one, no reply yet. I still want to see if I can grab the ADC readings off the stabilizer port and ignore the rest of the MCA hardware.
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Jon Rosenstiel
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Re: Canberra 35+ MCA Help Needed
I recently acquired another 35+, (e-bay), to go along with the functioning one I already have. (OE Tech)
I put in a low-ball bid, not really expecting to “win” it, but when time ran out it was mine! I figured it probably wouldn’t work, (correct), but just maybe, just maybe, I could fix it. And if I couldn’t fix it I’d use it for spare parts. Either way, I wasn’t out a bunch of $$, and I’d learn something along the way.
When I powered it up it acted similar to Richard Hester’s sick mca. The dead time indicator didn’t max out, but it did go up to around 75%. And it would display a partial spectrum, but the last quarter of the memory was non-functional. I checked the power supply voltages, (no problem there), and looked over all of the boards with a magnifier. (Again, no problems).
I plugged the boards back in, fired it up, and it was worse than before! Now the dead time indicator maxed out, it wouldn’t display a spectrum, and it “locked up” when the collect button was pushed!
I waited for the weekend to tackle it again. I removed all of the boards and checked them over for the second time. (Found nothing obviously wrong). While I had it apart I cleaned off the years of dust using a soft brush followed by several blasts of compressed air. I also applied some cleaner/lube to the front panel rotary switches to smooth out their action. I reinstalled the boards taking extra care to be sure they were fully seated. I also replaced the leaking batteries, (three 1.2V Ni-cads), on the cpu board.
When I powered it up I was floored….IT WORKED! It functioned just the same as my “good” mca. For the remainder of the weekend I was a spectrum takin’ fool! One pmt, two mca’s!
If I had to guess what “fixed” it I’d have to say it was removing and reinserting the boards a couple of times. (And making certain they were fully seated). I suspect the board edge contacts had become oxidized over the years, and required a little “pushing and shoving” to break through the oxidation.
Chris, I don’t know if I can be of any help with your dead 35+, but you’re more than welcome to e-mail me.
Jon Rosenstiel
I put in a low-ball bid, not really expecting to “win” it, but when time ran out it was mine! I figured it probably wouldn’t work, (correct), but just maybe, just maybe, I could fix it. And if I couldn’t fix it I’d use it for spare parts. Either way, I wasn’t out a bunch of $$, and I’d learn something along the way.
When I powered it up it acted similar to Richard Hester’s sick mca. The dead time indicator didn’t max out, but it did go up to around 75%. And it would display a partial spectrum, but the last quarter of the memory was non-functional. I checked the power supply voltages, (no problem there), and looked over all of the boards with a magnifier. (Again, no problems).
I plugged the boards back in, fired it up, and it was worse than before! Now the dead time indicator maxed out, it wouldn’t display a spectrum, and it “locked up” when the collect button was pushed!
I waited for the weekend to tackle it again. I removed all of the boards and checked them over for the second time. (Found nothing obviously wrong). While I had it apart I cleaned off the years of dust using a soft brush followed by several blasts of compressed air. I also applied some cleaner/lube to the front panel rotary switches to smooth out their action. I reinstalled the boards taking extra care to be sure they were fully seated. I also replaced the leaking batteries, (three 1.2V Ni-cads), on the cpu board.
When I powered it up I was floored….IT WORKED! It functioned just the same as my “good” mca. For the remainder of the weekend I was a spectrum takin’ fool! One pmt, two mca’s!
If I had to guess what “fixed” it I’d have to say it was removing and reinserting the boards a couple of times. (And making certain they were fully seated). I suspect the board edge contacts had become oxidized over the years, and required a little “pushing and shoving” to break through the oxidation.
Chris, I don’t know if I can be of any help with your dead 35+, but you’re more than welcome to e-mail me.
Jon Rosenstiel
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ChrisSmolinski
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Re: Canberra 35+ MCA Help Needed
Jon,
Glad to hear you got it up and running! My 35+ doesn't get even as far as yours initially did. Cleaning board contacts is on the to-do this.
My CPU board has no batteries on it, looking at the [poor copy quality] schematics I have, it looks like a jumper is installed bypassing them and feeding 5VDC to the memory power supply pins. I'm not sure if this is kosher, not being that familiar with the unit. There's evidence of a little PCB rework on the board as well.
One thought I have had is to bypass the CPU of the 35+ if possible, and just run the ADC board, grabbing the 12 bit conversions, and feeding them into a PC via the serial port with a little PIC circuit. That way I can write my own software to do data capture/display/analysis. I haven't figured out yet how tightly integrated the CPU is into the sampling/ADC circuitry, and whether the ADC/etc can be made to "free run" without a CPU controlling it.
While I have the poor quality schematics for the unit, I don't have any functional block diagrams or circuit descriptions, so it is a bit time consuming reverse engineering how everything is supposed to work.
I'll do the much needed cleaning up of the contacts and see how things go from there. It would be slick to get this up and running.
Glad to hear you got it up and running! My 35+ doesn't get even as far as yours initially did. Cleaning board contacts is on the to-do this.
My CPU board has no batteries on it, looking at the [poor copy quality] schematics I have, it looks like a jumper is installed bypassing them and feeding 5VDC to the memory power supply pins. I'm not sure if this is kosher, not being that familiar with the unit. There's evidence of a little PCB rework on the board as well.
One thought I have had is to bypass the CPU of the 35+ if possible, and just run the ADC board, grabbing the 12 bit conversions, and feeding them into a PC via the serial port with a little PIC circuit. That way I can write my own software to do data capture/display/analysis. I haven't figured out yet how tightly integrated the CPU is into the sampling/ADC circuitry, and whether the ADC/etc can be made to "free run" without a CPU controlling it.
While I have the poor quality schematics for the unit, I don't have any functional block diagrams or circuit descriptions, so it is a bit time consuming reverse engineering how everything is supposed to work.
I'll do the much needed cleaning up of the contacts and see how things go from there. It would be slick to get this up and running.
Re: Canberra 35+ MCA Help Needed
I've finally fired up my Canberra 35+. It looks like it is in good shape until I try to get a spectrum. The dead time meter seems to work properly when it is getting signals from the scintillator(it fluctuates slightly, and responds to gain and SCA level changes), but I get no spectrum. The only time I can get any signal to appear on the screen is if I put it in a -PHA, then it fills up the low end bins with full counts, nothing in-between. So All I see is the first few hundred channels full of max counts. I can increase the SCA LLD, and it will cause the channels to fill slowly, but still goes from 0 counts to 130000 with one pulse. The channel #1 bin acts strange and fills about 1 count every second or two, with out any input at all.
I haven't hooked up a pulser to check one channel, but would suspect it would fill the entire channel with one pulse. Any idea as to what might be wrong? I put in an order for an operations manual from Don Orie. Maybe I don't have something in the software set up right? Any insight would be great.
Thanks,
Mike Amann
I haven't hooked up a pulser to check one channel, but would suspect it would fill the entire channel with one pulse. Any idea as to what might be wrong? I put in an order for an operations manual from Don Orie. Maybe I don't have something in the software set up right? Any insight would be great.
Thanks,
Mike Amann
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Jon Rosenstiel
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Re: Canberra 35+ MCA Help Needed
Mike,
The reason bin #1 acts strange is that the 35+ uses channel #0 to record live time and channel #1 to record true time.
Something else you might check, on the ADC board there's jumper for selecting either charge sensitive or voltage sensitive input. (V/C jumper) It's located just to the right of center near the top of the board. If you're not using a preamp select charge, with preamp select voltage.
Needless to say, the manual will be a big help.
Jon Rosensitel
The reason bin #1 acts strange is that the 35+ uses channel #0 to record live time and channel #1 to record true time.
Something else you might check, on the ADC board there's jumper for selecting either charge sensitive or voltage sensitive input. (V/C jumper) It's located just to the right of center near the top of the board. If you're not using a preamp select charge, with preamp select voltage.
Needless to say, the manual will be a big help.
Jon Rosensitel
Re: Canberra 35+ MCA Help Needed
Thanks Jon,
I ended up getting it working. I found three open traces on two different boards. I found one open trace on the backplane board, where a screw from one of the rubber feet had severed a trace during shipping(the person I bought it from sent the MCA in a box with no padding). I also found two open traces on the memory bd. These were caused by someone who had tried to pull the board out on one side with pliers, and on the other side where they used a hammer to pound in the board. Both these actions opened traces on the board.
After I put it back together, everything seems to function great. I can now get spectrums, and all the memory and ADC channels seem to work fine.
I do have a couple questions. Is the battery on the CPU bd needed? The one on my board is corroded, but still has 1.5V across it. Can I just remove it, or do I need to replace it? If so with a rechargeable or a regular battery?
Also, What is the best way to remove the boards from the unit? I took a lot of work to get them out of their card slots, it was like they were stuck in them really good. I ended up squirting isopropal alcohol into the connectors to try and loosen them up. It felt like I was going to break the backplane board with every board I removed. My thumbs are still sore from removing them.
Now it's time to learn how to take and read spectrums.
Thanks,
Mike Amann
I ended up getting it working. I found three open traces on two different boards. I found one open trace on the backplane board, where a screw from one of the rubber feet had severed a trace during shipping(the person I bought it from sent the MCA in a box with no padding). I also found two open traces on the memory bd. These were caused by someone who had tried to pull the board out on one side with pliers, and on the other side where they used a hammer to pound in the board. Both these actions opened traces on the board.
After I put it back together, everything seems to function great. I can now get spectrums, and all the memory and ADC channels seem to work fine.
I do have a couple questions. Is the battery on the CPU bd needed? The one on my board is corroded, but still has 1.5V across it. Can I just remove it, or do I need to replace it? If so with a rechargeable or a regular battery?
Also, What is the best way to remove the boards from the unit? I took a lot of work to get them out of their card slots, it was like they were stuck in them really good. I ended up squirting isopropal alcohol into the connectors to try and loosen them up. It felt like I was going to break the backplane board with every board I removed. My thumbs are still sore from removing them.
Now it's time to learn how to take and read spectrums.
Thanks,
Mike Amann
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Jon Rosenstiel
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Re: Canberra 35+ MCA Help Needed
Mike,
Great, you got it working!
The battery, (three AAA 1.2V Ni-cads in series) is not really needed for the mca to work, but without it one does lose the ability to store spectrums or energy calibration values while the machine is powered off.
It sounds like the small plastic removal levers are missing on your boards. Even with the levers in place the boards are quite difficult to remove. My experience was the same as yours, sore fingers and concern for the motherboard.
Jon Rosenstiel
Great, you got it working!
The battery, (three AAA 1.2V Ni-cads in series) is not really needed for the mca to work, but without it one does lose the ability to store spectrums or energy calibration values while the machine is powered off.
It sounds like the small plastic removal levers are missing on your boards. Even with the levers in place the boards are quite difficult to remove. My experience was the same as yours, sore fingers and concern for the motherboard.
Jon Rosenstiel
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Richard Hester
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Re: Canberra 35+ MCA Help Needed
From the symptoms displayed by my 35+, it sounds like it might respond nicely to a general cleaning. Cramolin and/or Pro Gold are a good investment for cleaning up PCB edge card fingers and connectors. You would not believe the green crud that can come off of even gold plated fingers. However, I don't think I'll be messing with my machine until after I move, as I just got myself a new (to me) house. A full basement - bliss!
Re: Canberra 35+ MCA Help Needed
Jon,
Do they need to be Ni-cads(do they get charged by the power supply)?
I do have the removal levers on the cards, but even with them, I felt like the levers would break before the card would come out.
Thanks,
Mike
Do they need to be Ni-cads(do they get charged by the power supply)?
I do have the removal levers on the cards, but even with them, I felt like the levers would break before the card would come out.
Thanks,
Mike
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Jon Rosenstiel
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Re: Canberra 35+ MCA Help Needed
Mike,
The dead ones I removed from my 35+ were 1.2V Ni-cads so I replaced them with the same. I assume they're charged by the power supply.
Jon Rosenstiel
The dead ones I removed from my 35+ were 1.2V Ni-cads so I replaced them with the same. I assume they're charged by the power supply.
Jon Rosenstiel
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ChrisSmolinski
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Re: Canberra 35+ MCA Help Needed
I've given the PCB edge connectors a good cleaning, and checked the PCBs for any obvious track damage - none found. Some evidence of re-work on the CPU board (bottom center near the edge connector), as well as some very slight corrosion on the PCB itself from a leaking battery? Cleaned that up, all the PCB connections buzz out ok.
Next step might be to take the chassis apart and check the motherboard out, as well as the ribbon cables.
Here is what happens:
On power up - nothing on the CRT. Most/all of the LEDs on the front panel (behind buttons, etc) light up (or actually seem to be flickering very fast, but this might be an artifact of a multiplexed driver?)
If I press a button, I hear a relay click, but nothing on the CRT.
If I press the pushbutton on the display board (reset?) I get a display on the CRT. It says Canberra on the top line, and I get two lines of question marks at the bottom. Sometimes those two lines are instead random characters.
Once, just once, I got something that looked like a reasonable display. Can't repeat that.
Does anyone know where I could get some S100 bus style extender cards on the cheap? If I could get each card up in the air out of the chassis where I could get at it (one at a time) I might have a fighting chance. Actually I guess I'd need two S100 extenders for some cards. I think I saw them at DigiKey, but at $75 ea that kinda blows the budget.
Next step might be to take the chassis apart and check the motherboard out, as well as the ribbon cables.
Here is what happens:
On power up - nothing on the CRT. Most/all of the LEDs on the front panel (behind buttons, etc) light up (or actually seem to be flickering very fast, but this might be an artifact of a multiplexed driver?)
If I press a button, I hear a relay click, but nothing on the CRT.
If I press the pushbutton on the display board (reset?) I get a display on the CRT. It says Canberra on the top line, and I get two lines of question marks at the bottom. Sometimes those two lines are instead random characters.
Once, just once, I got something that looked like a reasonable display. Can't repeat that.
Does anyone know where I could get some S100 bus style extender cards on the cheap? If I could get each card up in the air out of the chassis where I could get at it (one at a time) I might have a fighting chance. Actually I guess I'd need two S100 extenders for some cards. I think I saw them at DigiKey, but at $75 ea that kinda blows the budget.
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Richard Hester
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Re: Canberra 35+ MCA Help Needed
There's an S-100 card extender up for grabs on Ebay right now, no bids. I found it by searching for " S-100 card".
Re: Canberra 35+ MCA Help Needed
Hi Chris,
My CPU board has the same kynar wires on the board(looks like they couldn't route those traces on the board). I ended up buying a cordless phone battery pack rated at 3.6V and 650 mA Hrs and used this for the cpu battery. I also found a couple wires in the ribon cable from the fron pannel to the ADC board crushed and severed(or hanging on by a thread). The lighting up of all the led's on the front pannel is not normal. The relay click is good, that should click every time you press a button(originally with mine the relay wasn't clicking(didn't know it existed) then found the broken trace on the bottom of the mother board that fixed that problem). The pushbutton on the display board can be held down by pushing it in and turning it a 1/4 or half turn, apparently that causes the display to display a matrix of dots across the screen to check the display lineararity.
The operations manual from OE tech gives a description of all the jumpers on the boards and pinouts and such, which is definitely very useful for undersatnding what supposed to happpen with the unit.
Mike Amann
My CPU board has the same kynar wires on the board(looks like they couldn't route those traces on the board). I ended up buying a cordless phone battery pack rated at 3.6V and 650 mA Hrs and used this for the cpu battery. I also found a couple wires in the ribon cable from the fron pannel to the ADC board crushed and severed(or hanging on by a thread). The lighting up of all the led's on the front pannel is not normal. The relay click is good, that should click every time you press a button(originally with mine the relay wasn't clicking(didn't know it existed) then found the broken trace on the bottom of the mother board that fixed that problem). The pushbutton on the display board can be held down by pushing it in and turning it a 1/4 or half turn, apparently that causes the display to display a matrix of dots across the screen to check the display lineararity.
The operations manual from OE tech gives a description of all the jumpers on the boards and pinouts and such, which is definitely very useful for undersatnding what supposed to happpen with the unit.
Mike Amann
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ChrisSmolinski
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Re: Canberra 35+ MCA Help Needed
Thanks for the ebay heads up Richard, I've checked several times in the past and nothing came up. Of course it's there when I don't look!
Mike: I get one click when I press a button, then that's it. So it's possible the CPU board is flaking out, that might explain the odd CRT display.
I have a copy of the op manual, as well as schematics (poor copies, but I can make most of it out). I contacted Canberra, and asked if they had a service manual. They said yes, $70, but I am not sure what it would give me over an above what I have now. Has anyone seen one of these?
If I manage to snag the S100 extender I might be able to figure out what on the CPU board isn't working, I don't have my docs handy but as I recall it uses a standard cpu.
My end goal is to just get the ADC stuff working, so it spits out a 12 bit parallel word with each pulse. Then I can feed that into a PC and write my own software to handle it from there on.
Mike: I get one click when I press a button, then that's it. So it's possible the CPU board is flaking out, that might explain the odd CRT display.
I have a copy of the op manual, as well as schematics (poor copies, but I can make most of it out). I contacted Canberra, and asked if they had a service manual. They said yes, $70, but I am not sure what it would give me over an above what I have now. Has anyone seen one of these?
If I manage to snag the S100 extender I might be able to figure out what on the CPU board isn't working, I don't have my docs handy but as I recall it uses a standard cpu.
My end goal is to just get the ADC stuff working, so it spits out a 12 bit parallel word with each pulse. Then I can feed that into a PC and write my own software to handle it from there on.
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Richard Hester
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Re: Canberra 35+ MCA Help Needed
If you want to use just an ADC, why not grab hold of a Canberra 8075 or 8076 NIM module? They are more likely to be working correctly, as there isn't the extra garbage associated with the MCA. Once you get the raw data into the computer somehow, the computer can do the binning and display functions. One of Richard Hull's colleagues has come up with a simple hardware interface and acquisition program for the 8075, so we know it can be done. If I remember correctly, there is an 8076 currently lurking on Ebay...
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Richard Hull
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Re: Canberra 35+ MCA Help Needed
It turns out that the 8076 is not so user friendly and the 8075 (rarer item) turns out to be the best bet and easiest to interface.
Richard Hull
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Richard Hester
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Re: Canberra 35+ MCA Help Needed
That's good to know obout the 8075 vs. 8076. I see both units pop up regularly on Ebay. The Tracor A-Ds show up quite often, too. I know nothing about interfacing to those, though. I got a 100 MHz Tracor in a lot of NIM modules and decided it was entirely too pretty to gut for the case. I may change my mind later, though....
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Jon Rosenstiel
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Re: Canberra 35+ MCA Help Needed
Richard Hull wrote:
> Richard is correct! I find that tantalums are really a superb capacitor. However, they hate heat; even moderate heat. They can dry up a bit over years of use or inaction and "twinkle" the supply rails, (not good). In the old 8100's that I have, it is all 74XX TTL chips with hundreds of tants on a board and 7 huge boards. Heat comes out of these densely populated boards in the machine like a running clothes dryer.
Richard,
What do you mean by "twinkle"?
Jon Rosenstiel
> Richard is correct! I find that tantalums are really a superb capacitor. However, they hate heat; even moderate heat. They can dry up a bit over years of use or inaction and "twinkle" the supply rails, (not good). In the old 8100's that I have, it is all 74XX TTL chips with hundreds of tants on a board and 7 huge boards. Heat comes out of these densely populated boards in the machine like a running clothes dryer.
Richard,
What do you mean by "twinkle"?
Jon Rosenstiel
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Richard Hester
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Re: Canberra 35+ MCA Help Needed
Tantalum capacitors (especially the older ones) would "scintillate", or suffer a transient breakdown in their tantalum oxide dielectric. If the scintillation was small enough, it healed. If not, the capacitor would short, or burn, or explode. People really had no business using tantalums directly across power supply rails, but there really weren't many alternatives 30 years ago, as electrolytics weren't all that great, and film caps were way too big and expensive. Ceramics in large values were also expensive. It was standard practice (if you were a cautious designer) to put a current limiting resistor of a certain amount of ohms per microfarad (I forget how many) in series with tantalum capacitors to prevent them from self destructing.
The only advantage I see with tantalums is that they have a low self-inductance, along with a respectable ESR. They can be used in conjunction with ceramic capacitors to bypass and damp power supply rails. Given their expense and unreliability, I would rather use a low value switcher grade electrolytic capacitor instead. A couple of months ago, I refurbished a Tennelec SCA module that was pulling down the +12V supply of a newly acquired NIM bin. I stripped out all the tantalum bypass capacitors and replaced them with either electrolytics or ceramics, depending on the value. At least two of the tantalums I pulled were shorted. I have several MCAs awaiting the same treatment.
The only advantage I see with tantalums is that they have a low self-inductance, along with a respectable ESR. They can be used in conjunction with ceramic capacitors to bypass and damp power supply rails. Given their expense and unreliability, I would rather use a low value switcher grade electrolytic capacitor instead. A couple of months ago, I refurbished a Tennelec SCA module that was pulling down the +12V supply of a newly acquired NIM bin. I stripped out all the tantalum bypass capacitors and replaced them with either electrolytics or ceramics, depending on the value. At least two of the tantalums I pulled were shorted. I have several MCAs awaiting the same treatment.