Testing resistors and capacitors in-circuit on vintage Hammond A-100 organ with multimeter

I recently purchased a vintage Hammond A-100 organ, which is based on tubes, no solid state (imagine that!), the 'percussion' feature (inside pre-amp) does not work so I ordered a new set of tubes thinking that it would solve the problem.Well, it didn't, so now I need to do a more in-depth troubleshooting to find out what's wrong. By reading online I found a lot of people replacing resistors and capacitors due to their age. In order for me to test a resistor or a capacitor, do I really need to disconnect it from the circuit? Are there any 'tricks' someone in the field is aware of? It sounds like a daunting job since there are hundreds of them in this beast. I'm also probably gonna have to get creative because I only have a multimeter. thanks.

The hard way ascertain where the fault is first and where about in the schematic isolate in blocks Inject signals and then break this down into smaller sections
Then yes unfortunately there is no easy method

See the following for a nice little diy LCR bridge project software based

http://www.sillanumsoft.org/ZRLC.htm

Or even on this site nice little project
http://www.eeweb.com/blog/circuit_projects/pic-based-portable-lcr-meter

Or if you are into music which I also like (Music not wrap) then

http://home.comcast.net/~joegwinn/ about a third of the way down the page

Its take them out and test them statically with LCR BRIDGE IF NEED BE or blanket change

You will also need a function generator to inject various signals I should have mentioned this as well (Must have usefull tool )

Analogue version for you here (easily made)
http://www.ecs.umass.edu/ece212/ECE212_lab6.pdf

Here is another project you can build as well
http://www.microsyl.com/index.php/2010/03/24/function-generator/

Do you have access to the schematic diagram for this organ, or access to a working one? If so, there are analog signature analysis techniques that can help.

That's a lot of information! I'll look thru everything as soon as I get a chance, thank you for the ideas.

I do have access to the schematics; this analog signature analysis techniques sounds very promising, I'll need to look into that since I'm not familiar with it. Thanks.

I haven't tried this myself, but it's been advertised in Nuts and Volts for years (even decades), and they claim that it is used by Panasonic, Pioneer, NBC, ABC, Ford, JVC, NASA... and they give you a 60 day trial period:

* http://www.eds-inc.com/cap.html

BUT, this will only be good for testing any electrolytic capacitors in circuit.

This might prove useful, as well:

* http://www.eds-inc.com/leak.html

I’ve tried this out myself but its not all that accurate it works on occasions but you still truthfully have to remove the cap out of circuit (A pain when it comes to surface mount components) especially with this lead free solder

Higher temperatures render the surface mount device inoperative and damages by the time you get this off the board

(Useless idea, this was hasn’t saved anyone or anything at all ) never mind the product or the PCB or saved bussiness or for that matter assisted or reduced enviroment polution

(lead free solder ) Biggest load of rubbish they ever came out with this story in fact all this has done is cost people money and industry and has lead to an even bigger rise in illegal dumping ( Reasons obvious the companies cant afford to pay for all the dumped throw away goods down the local tip ) Thier enormmous idea of the throw away world , I know

I knew this would backfire in the end as well but they do try it on with this and as usual refuse to accept engineers advise when we say “THIS WONT WORK” , a 1000 times worse than ever before (never listen to anyone at all this lot ) Always have to wait for this to backfire in thier faces and then all of sudden Its , "Oh I should have listened " by which stage of course yes as usual damage is done and of course NO answers No replies couldnt care less and resign Typical this attitude you get ( Total numb nuts heel bent on destrying the electronics service sector and industry totally)

Everey few years we go though this row now

Hence I still continue to use leaded resin cored solder

PS if you wnat a good supplier this is where to get this from

Its excellent solder flows beautifully ( From Hard experience and plenty of searching ) Wouldn’t recommend it otherwise


http://translate.googleusercontent.com/transl...gn.htm&usg=ALkJrhgjD5cSB9FG-VpZDtdVQjBMzm3zcg

in my opinion as an amateur technician, when I want to do measurements on 2 components, I had to remove it from the pcb Circuit, why? because it is associated with other components, and indeed that is not the precision capacitor must be replaced, though still new, probably because dry so that it works is not optimal. I've proved it on a PLC circuit as dry capacitor can hinder the performance of data communication. Thank you.

You are dead right with respect to this you can gain a fair idea by connecting a dvm across this using diode check charging the capacitor one way and then the other way but you can never ever really gain an accurate result unless you remove from the PCB as you said because you have more than one component in series or in parallel with the cap you are checking Low values are practically impossible to test anyway except possible for leaky or short Other than this it is remove from the PCB

Hammond organs are not rubbish. The designers surely foresaw the potential problems & Knew that capacitors would likely eventually fail.
So how did they deal with the future service/repair issues?
I'd guess that they modularised the design & took great care to indicate test point values on the circuit board.
So the key may be to get the service info which may be available only through an accredited service agent. Even then I'd suggest this is a repair job for a specialist - if one such can be found.
I would great;y appreciate comment on this as I am sure would the OP.

Depends on your own personal taste I suppose but id agree with what your saying except the fact that you have to go through a specialist

If you can read a schematic and know how oscillators work and have fundamentals in electronics plus few years good overall experience then there’s nothing stopping you apart from schematics as you say that is advisable but then that applies to any electronic appliance Great Shame we don’t see more co operation in this request wed have far more decent engineers and companies wouldn’t you agree

Thats all that counts at the end of the day wether you can do the job or not

That simple if you worked hard didnt shirk in your working carrer in electronics you will be able to undertake most jobs as such you reap the rewards

Mark H
May I ask you to estimate the likely time it might take you to check out & repair such a circuit, & lets assume there are several faults.
I think we can readily assume you have the skills, experience & Know how.
So it might be very instructive for the OP to hear your take on the possible time frame which I am guessing will be " several days" at least.
Thanks

To troubleshoot resistor and capacitor in circuit just open one side of the terminal then check the resistance and capacitance using multimeter for an accurate readings.

time is very influential on the work component, but likely also affect the characteristics of the components and the environment, such as space heat or intense vibrations from the Circuit board. thanx