Help I'm new  - Page 1
Forum section: electronics / beginners

author: Charlie C
author_rank: Newbie
timestamp: December 28, 2013, 02:20:38 am
content: I’m new, and need to learn quick, haven’t touched a tube in 20 years, capacitors, transistors, diodes, AC, DC, Help do I need a Fluke 87v, working on two old Hammond Organs from the late 60’s, tubes, transformers, high voltage, tonewheel, leslies.

author: Rerouter
author_rank: Super Contributor
timestamp: December 28, 2013, 03:10:55 am
content: Lets Break this down a bit for the people to follow:" I'm working on two old hammond tube organs from the late 60's and am working to repair them"" I'll need to test tubes, transformers, high voltage tube supplies, tonewheels and leslies"" Will a 87V Fluke multimeter be sufficient for this? "" I need a bit of reminder on the basics such as capacitors and transistors"Please specify in what ball park the high voltage your playing with is, if its over 1000V you will either need a divider probe for your multimeter or a HV multimeterFor the multimeter, i would strongly recommend getting a multimeter with capacitance and if possible one that can measure higher than 100uF, as any wet cell caps will be dead in that thing, and those that are not could probably do with a replacement, which the 87V does not have, equally frequency will be invaluable for tracing signals without a scopeFor a place to brush up on the basics, have a look here,http://www.allaboutcircuits.com/

author: ampdoctor
author_rank: Frequent Contributor
timestamp: December 28, 2013, 06:38:11 am
content: Charlie;You're probably not going to like what I'm about to say but the way you phrased your questions here appears to indicate a significant lack of experience working on this type of equipment. If you even need to ask about whether a certain meter fits the bill for this type of service you're not qualified. To work on these pieces of equipment you're going to need a fair bit more equipment than a meter and access to a tube tester. Just sayin'First off Hammond organs are notoriously tricky to work on even for seasoned professionals. While the power amp probably isn't particularly high powered by modern standards, you're going to find a veritable forest of preamp tubes. You're also going to have to deal with a mix of point to point, eyelet, terminal strip construction and maybe even some rudimentary pcb's depending on the model and year of mfg. Second, you're going to be dealing with a LOT of tubes and a LOT of current and high voltage. If you make a mistake, at best you're going to let a lot of magic smoke out and at worst you're going to wind up being one crispy critter!Working on old Fender and Marshall tube amps or old table radios and such are one thing, but this is a whole different ballgame! Either bite the bullet and take it to a pro or proceed very slowly and show extreme caution! If you do decide to tackle them yourself, you'll want to become intimately acquainted with antique electronics supply. They're a great one-stop for not only tubes but a lot of other NOS and reproduction parts you may need.http://www.tubesandmore.com

author: AG6QR
author_rank: Frequent Contributor
timestamp: December 28, 2013, 06:55:40 am
content: Quote from: Charlie C on December 28, 2013, 02:20:38 amI can guarantee that the people who designed, prototyped, built, and serviced that equipment in the 1960s did so without a Fluke 87V. Maybe they were lucky to use some variant of a Simpson 260?Of course, that doesn't mean the old meter is the best choice for you today, but I'm just pointing out that the choice of meter isn't the most important decision you'll be making here...You may want some gear besides a multimeter. A scope could be very useful for some functions. It wouldn't need to be very high bandwidth. An audio generator might sometimes be a handy companion to the scope. A simple ESR meter can be a timesaver when checking which caps need to be replaced. A good LCR meter might also come in handy.And I'll echo ampdoctor's general advice.And then you need the knowledge to use it all. Some of it is theoretical, and some of it comes with experience, knowing which particular parts on which particular units tend to fail in which ways.But

author: Charlie C
author_rank: Newbie
timestamp: December 28, 2013, 11:43:42 am
content: Hi, Thanks for replying to my post, I first joined the hammond organ forum, some of the best there are the old hammond repair men, the top two have the same model as I do, they throw so much of their knowledge and experience at me so fast, they tell what I will need to replace and why down to every nut and bolt that must come out just to get to the electronics, the learning curve is high for me without the basics, thanks for the all about circuits webpage, I’m going slow, not in the learning, but in the practice, there’s 70+ capacitors to replace, the two in the main power supply are 50 uf 450 VDC, my field is mechanical engineering never got close to electrical design, I’m not looking forward to getting knocked on my ass by a capacitor, my budget for test equipment right now is only about $1000.00, that’s more than the Hammond will ever be worth, I’m also a musician, and the old hammonds are hard to give up on, I’m here to learn electronics from scratch, please point me in that direction, Thanks Charlie. P.S. found the page on education, I feel like an old dog trying on new tricks, thanks charlie

author: Charlie C
author_rank: Newbie
timestamp: December 30, 2013, 02:00:36 am
content: Hi, Found so much here, it’s all good, will learn quickly, that model Hammond of mine, are the ones most challenging to work on, I’ll learn a whole new set of skills, and if the world goes into survival mode, maybe I can survive longer than a few days knowing a little more about electronics, I think you may have saved me, thanks Charlie