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Test equipment repair/replacement What was THIS genius thinking!

#1 User is offline   othman11 

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Posted 08 May 2011 - 10:08 AM

I'm having a bit of an issue with some test equipment I'm trying to replace. This is for testing nuero-stimulator. It is two bread boards with three resistors and one capacitor for each board. My issue is that the three reistors appear to be different wattage...I don't know how to determine the wattage of each.

http://img52.imageshack.us/img52/3517/img20110504153010.jpg

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#2 User is offline   Reign 

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Posted 08 May 2011 - 12:46 PM

Unless you are using very discrete equipment the wattage ratting is needed to dissipate the heat going through the component for various voltage and amperage needs.
If the equipment is not needed to be "exact" to the numbers of the original wattage or the original was put together on the premise of what parts were available you can usually get away with using a medium wattage resistor for all general use such as a 1/2 watt.

if in doubt here is a sizing chart.
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#3 User is offline   othman11 

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Posted 08 May 2011 - 01:01 PM

View PostReign, on 08 May 2011 - 12:46 PM, said:

Unless you are using very discrete equipment the wattage ratting is needed to dissipate the heat going through the component for various voltage and amperage needs.
If the equipment is not needed to be "exact" to the numbers of the original wattage or the original was put together on the premise of what parts were available you can usually get away with using a medium wattage resistor for all general use such as a 1/2 watt.

if in doubt here is a sizing chart.



Thanks for the link, it does make it easier for me. At least I got the 1/2 watt resistor correct. In this case, is it more of a size (Ohms) need?
I don't know why they used three different wattage resistors. We didn't buy these boards, some "enganeer" made these over 25 years ago.

These bards also have an "orange drop" capacitor on them. Can I change from the "orange drop" to some thing different (easier to find and a bit cheaper)type of capacitor, as long as I keep all the same voltages, tolorances, and what not?
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#4 User is offline   Kelemvor 

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Posted 08 May 2011 - 01:48 PM

View Postothman11, on 08 May 2011 - 01:01 PM, said:

Thanks for the link, it does make it easier for me. At least I got the 1/2 watt resistor correct. In this case, is it more of a size (Ohms) need?
I don't know why they used three different wattage resistors. We didn't buy these boards, some "engineer" made these over 25 years ago.

These bards also have an "orange drop" capacitor on them. Can I change from the "orange drop" to some thing different (easier to find and a bit cheaper)type of capacitor, as long as I keep all the same voltages, tolerances, and what not?

By orange drop I assume you're referring to the usually orange ceramic disc capacitors? If so, those could be replaced by similarly rated non polarized capacitors. Here's some info on caps: http://encyclobeamia.../capacitor.html
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#5 User is offline   othman11 

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Posted 08 May 2011 - 02:18 PM

View PostKelemvor, on 08 May 2011 - 01:48 PM, said:

By orange drop I assume you're referring to the usually orange ceramic disc capacitors? If so, those could be replaced by similarly rated non polarized capacitors. Here's some info on caps: http://encyclobeamia.../capacitor.html


Thanks!!!! I don't mind paying for caps, but not at .65 a pop.
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#6 User is offline   kzaske 

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Posted 09 May 2011 - 09:17 AM

If it were me, I would diagram the boards first to see how much variance I have to play with. It is possible that the caps are serving more than one function within the circuit. It ia more probable that the "orange caps" and the various wattage resisters are just what he had laying around when he built the boards.
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#7 User is offline   othman11 

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Posted 10 May 2011 - 05:26 PM

View Postkzaske, on 09 May 2011 - 09:17 AM, said:

If it were me, I would diagram the boards first to see how much variance I have to play with. It is possible that the caps are serving more than one function within the circuit. It ia more probable that the "orange caps" and the various wattage resisters are just what he had laying around when he built the boards.


That's the issue, they were made from stuff lying around. I could buy new boards...at $500 each and I need a minimum of 2. But the company isn't going to put out that kind of money.
These are for testing Transdermal electronic neuro-stimulators, both analog and digital. They have three settings to test; burst, constant, and modulate.
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#8 User is offline   kzaske 

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Posted 11 May 2011 - 12:10 AM

View Postothman11, on 10 May 2011 - 05:26 PM, said:

That's the issue, they were made from stuff lying around. I could buy new boards...at $500 each and I need a minimum of 2. But the company isn't going to put out that kind of money.
These are for testing Transdermal electronic neuro-stimulators, both analog and digital. They have three settings to test; burst, constant, and modulate.


There was a time a few years ago I had one of those for blocking pain. I doubt it was the same thing but simular in principle.
Given the need I think I would grab what I can get as far as the resisters are concerned, 1/4 watt should do nicely for all of them as long as they are creminic (not wire wrap). I noted that two are wire wrap and one of the resisters in the photo is creminic (I bet I mis-spelled it). Back in the 70's body color noted the type of resiter (creminic film or resistance wire wrap). Not so sure you want the inductance from the wire wrap resisters as I doubt these circuits are LC frequence filters.
As for the cap, if you can find a wireing diagram of the base unit on the web it should tell you if you need a polorized cap or not. If you don't any cap will work. If the base unit is from the seventies, I will bet that these are for the contact pads (probes). If so memory tells me that polorized caps are required, or you might be able to sub a diod into the circuit.
I feel like Shermin just used the way-back machine on me.

Ken /|\
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#9 User is offline   othman11 

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Posted 11 May 2011 - 07:07 AM

Thanks for the info. I'll stick with the 1/2 Watt route for now. I guess I'll use a new capacitor (orange drop). I am using the carbon film resistors. Those wire wound things are a pain, I've had to repair the solder joints twice!

Sent from my LS670 using Tapatalk
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#10 User is offline   kzaske 

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Posted 11 May 2011 - 09:00 PM

View Postothman11, on 11 May 2011 - 07:07 AM, said:

Thanks for the info. I'll stick with the 1/2 Watt route for now. I guess I'll use a new capacitor (orange drop). I am using the carbon film resistors. Those wire wound things are a pain, I've had to repair the solder joints twice!

Sent from my LS670 using Tapatalk


That would be the safe route. Good luck.

Ken /|\
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#11 User is offline   othman11 

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Posted 19 May 2011 - 08:36 PM

View Postkzaske, on 11 May 2011 - 09:00 PM, said:

That would be the safe route. Good luck.

Ken /|\
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I have received the resistors and the capacitors (went with ceramic). I soldered up 3 new boards and still have one to go. Everything is ROHS compliant (boss likes this). Now to test the new boards...I'll let you know how that goes.
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#12 User is offline   kzaske 

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Posted 20 May 2011 - 12:42 PM

View Postothman11, on 19 May 2011 - 08:36 PM, said:

I have received the resistors and the capacitors (went with ceramic). I soldered up 3 new boards and still have one to go. Everything is ROHS compliant (boss likes this). Now to test the new boards...I'll let you know how that goes.


Looking forward to an update.

Ken /|\
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#13 User is offline   othman11 

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Posted 23 May 2011 - 06:06 PM

UPDATE!!!! I have builded and tested three boards. Well what do you know, no "cold" solder joints. Everything works better than those antique boards. :teeth: :tada:
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#14 User is offline   Agent51 

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Posted 23 May 2011 - 06:55 PM

What exactly are you building or is it top secret?
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#15 User is offline   othman11 

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Posted 23 May 2011 - 07:50 PM

They are for testing; Transdermal Electronic neuro-stimulators. I use an "o" scope to test Frequency, Burst time, Voltage, Burst length. The old boards have sime quality issues... Like old age.

The FDA requires that we test functionality on all Class 1 and 2 medical devices.

This post has been edited by othman11: 23 May 2011 - 07:58 PM

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#16 User is offline   Agent51 

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Posted 23 May 2011 - 08:39 PM

Ahhh
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