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casdave
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casdave posted on Sat, Apr 28 2012 4:18 PM

I've been out of the repair game for some time now, so I'm out of date with the sort of stuff I need to start up again.

Last time I used a dual 40MHz scope, some generic function genny, and the usual hand tools - I don't imagine much has changed about the latter.

I reckon I need a scope, however its pretty much all gone digital storage, as for function generators - I've seen a few that can produce white noise and other custom waveforms - which is useful for load testing.

So what do you think, what would be good to find on EBAY, I don't really want to be going for new stuff, but equally I don't want to go for ancient stuff that is years out of spec either. I'm not expecting to do too much surface mount stuff - or at least I hope I won't.

I still have most of my hand tools, and anyway they are small enough that I can get what I need, when I need it.

Here is a list I might be thinking of

Scope

Variac

Function generator

Dual-rail tracking power supply

Decent soldering iron and desolder tools

Timer/Frequency counter?

Dummy loads

Isolating transformer

DVM

ESR Meter?

I suppose theres the matter of the various trade catalogues and datasheets to think of too, Towers Transitor book, CMOS & TTL data books?

How about linking to useful suppliers? Farnells and RS are very expensive and their range for discrete components seems to be reducing all the time, especially for non-preferred values of capacitors and resistors.

Feel free to add in your own essential resources and equipment recommends.

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tournedos
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I have the scope (100 MHz analog dual trace, delayed trigger Tek) and frankly I have needed it very rarely for any B&O repairs.

You'll need/want the Variac only if you intend to work with valve kit.

I wouldn't give up my ESR meter for the world. I have this one which has the nice property that you can measure most caps in circuit, the test signal is low enough amplitude that it won't bias semiconductors.

Somebody mentioned using a very simple signal injector "beeper" for troubleshooting amplifiers. I think I need to build me one.

What I'm sadly missing is an FM stereo test generator. Can't really align tuners without one.

--mika

sonavor
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Of course it all depends on how deep you are going to dive in.  If you are mainly refurbishing - doing recapping and refoaming then just a good soldering iron, de-soldering gun and maybe a capacitance (ESR) meter will do. I don't think I could live without my Hakko desoldering gun now that I have used it about a year.

A good DVM is something everyone should have even if you are not fixing vintage audio equipment.

If you think you will be taking on tasks like trouble-shooting circuit problems then you probably do need a scope. I use an Owon dual trace digital oscilloscope (25MHz) that was under $300 new (I wish I could afford a Tektronix). I don't have to use it that often but at some point you need it so I think that is something to put down as a must. I bought a dual-rail (30 VDC) power supply an a couple of function generators. They are pretty useful but like the scope, not something you have to use every day. At the end of last year I was lucky to find a good FM Stereo Signal Generator for an affordable price. I made good use of that on the Beomaster 6000 project (old Beoworld forum). I am looking at getting a good Audio Analyzer tester - a tester that can easily make distortion and S/N measurements.  I have gone after some on Ebay a few times but so far they have gone out of my price range.

I would say another must have item would be a dim bulb tester. When you really don't know the history of a new piece of equipment it is good to first turn it on using a dim bulb tester so you know if there are any ground shorts. I built my dim bulb tester with a variac attached to it so I could also bring the AC voltage up slowly. I have used that tester on every amplifier/receiver I have set on my bench.

casdave
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Hmm, not familiar with the term 'dim bulb tester' at all, I'd just use an inline ammeter and a variac.

I do expect to be looking at pretty much everything up to RF. I'm used to repairing videos, I don't expect to be taking those on again though, I don't have the gauges or the calibration tapes and I really don't want to get into the tv side of things again, so I will not be wanting a test card generator.

I would be interested in knowing a bit more about the non-crt scopes, they look to be very much smaller, as for storage scopes, what sort of sampling rate would be appropriate for signals up to say typical FM IF stages of around 10.7 MHz?

Apart from circuit drawings, what date sheets do you think will be useful?

sonavor
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Here is a picture of my variac, AC ammeter, AC voltmeter and (switch in/out) dim bulb tester.  The light bulb will take the current when you apply power to a device that has a short.  It (the bulb) acts as a current limiting device.  When it is in the circuit and there is no short, the bulb will briefly glow, then go dim ... indicating there isn't a short.  If the bulb glows bright and remains in that state, then there is a short.  It is a quick, easy test to indicate if there is a problem with a device you are testing.


Søren Mexico
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sonavor:

Here is a picture of my variac, AC ammeter, AC voltmeter and (switch in/out) dim bulb tester.  The light bulb will take the current when you apply power to a device that has a short.  It (the bulb) acts as a current limiting device.  When it is in the circuit and there is no short, the bulb will briefly glow, then go dim ... indicating there isn't a short.  If the bulb glows bright and remains in that state, then there is a short.  It is a quick, easy test to indicate if there is a problem with a device you are testing.

I like that one John, you posted in the old forum, still have your drawing, but never got around to get a Variac and build the dim bulb, it would have helped me a lot in my BM 2400 and BM 901, probably would have saved some transistors and diods

Here the drawing, hope you dont mind.

 

 


Collecting Vintage B&O is not a hobby, its a lifestyle.

Step1
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Step1 replied on Mon, Apr 30 2012 9:18 AM

Dave I have a Goldstar 40Mhz scope (with cursor display) which is not too bad at all - if you are interested you are welcome to view and make me an offer :) I also have a 20Mhz of the same model but am keeping this for audio. Folks on other audio restor forums seem to really like Tek scopes!

I have said this before - digital scopes don't really match analogues for analogue / audio and modulated signals IMO. They are superb for digital signals and very convenient to be able to press the 'setup' button and have the scope set up all the ranges itself - they are also nice and compact so free a lot of space if things are tight!

Soldering iron there is only one choice IMO - OKI Metcal :) Get an SP200 s/h off ebay I doubt you'll want to use anything else again! They are expensive though and only worth it if you do lots of work - or just want to treat yourself!!! Wellers are also super cool, but IMO not up to a Metcal. Forget about cheap stuff especially from Maplin etc they are no good really.

Thought I would sneak this in as an example of the versatility of the metcal - I used my 'normal' chisel tip on the (held my breath) without changing the temperature (you can't with these and don't ever need to anyway) I can go straight from that to a huge can and desolder almost immediately - It is not that the tip is hotter - The irons use RF tech. The tip is reactive and has the ability to heat on demand - just amazing! Oh and did I mention the 8 second heat up time :-D

Dual tracking PSU there are some interesting modern Chinese ones on the bay but of course many folk would rather have something they feel is better made - you pay your money! S/h off ebay?

Freq. Meter I can't remember my model it is a blackstar very accurate and small! I do want one of those nixie tube counters though just for the cool factor :)

Dummy loads I thought you would be ok with this subject ;-) - I personally think high powered resistors are ok for domestic amplifiers!

My isol transformer is a Maplin torroidal I very rarely use as I don't do valve or live chassis stuff. I use an RCD for personal protection. Variac I have two one is too small the other is one my grandfather used to control cine lighting for titling films. I saw a beefy s/h unit go on ebay for very little recently! I also think there is a place for mains bulbs too :)

Volt Meter Fluke / Metrix / Agilent? etc. etc. Check out EVE blog and mjlorton on youtube.

ESR meter there is only one and the company lives down the road from me - Peakelec.co.uk Lovely compact unit, hand assebled in Buxton and you can go along, pick up and talk to them :) You won't really use them for fault finding though, only to confirm what you already measure / suspect.

Suppliers there are good vintage suppliers listed on another vintage audio forum I won't mention one being in Canada I think. Generally you probably won't get a 50uF capacitor but the tolerance of old components will have left the value no where near the 50uf anyway so 47 would be absolutely fine! Obviously there may be instances where the tolerance is more important!

I like some of the American suppliers but you need to bulk order to make it worth it - normally over £50 gets free postage. Mouser send you a nice big paper catalogue which is rare these days!

 

Regards datasheets etc. Google is your friend here! I threw most of my books out tbh!

Oh DealExtreme sell some great solderwick that works well for half the price over here I will try to find the SKU hang on.... http://www.dealextreme.com/p/soldering-remover-3mm-x-1-5m-9159

Olly

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I have one of those Owon LCD scopes (PDS5022S) as well, and for most debugging and repair work they are a great asset. The scope has USB on the back so you can hook it to your computer, record waveforms and do analysis on the data later, which is very useful -- I used it to record all signals off the Datalink bus and successfully reverse engineer the protocol.

Owon also has some more expensive models (the MSO range) which have a logic analyzer and built-in spectrum analyzer, which are very handy when you want to debug more recent equipment. Rigol also has some very useful models in the same price range (about 1/2 the sticker stock of an entry level Tektronix).

As for the variac, I wouldn't recommend using that on newer gear which has an SMPS instead of a mains transformer and lineair power supply. Some SMPS designs can go runaway or crash completely when they are fed with a serious brown-out voltage (<80VAC for USA), but the bulb current limiting device will work fine there.

The bulb limiter will also save you a lot of fuses in case there is a line short and the device fuse blows *every single time* you want to do another test. ;)

 

casdave
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Looks like 20MHz scopes are very cheap at the moment and I have spotted one pretty close by for not very much at all.I'll maybe more on to something else when I reach its limitations - which will not be for a while yet.

My iron is a Weller with a temperature readout - I've not seen the type mentioned, except for a couple of new ones - they are quite expensive new so I'll have to wait until one comes up.

The ESR meter looks interesting.

Thanks for the bulb limiter drawing, I will get on to making a workstation using one.

hemenex
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casdave:
The ESR meter looks interesting

I have this one

I think Mika showed this once and I just had to get one of those. It was 84 EURs in Germany (but not from peak directly).

Have checked a lot of unsoldered caps since and indeed it showed the dark red ROE's as the worst.

BUT there are some of those still going strong; it's not an absolute must to change them. But while already havin' a device open why not; it can't hurt.

The other one I don't know but it might be as good as well...

 Gunther

EDIT: ok, looking at Mika's link above it probably wasn't him; anyway someone pointed that one out.

I never had the need for an ESR meter but now that I have it it's a really valuable toy - ahem - tool Big Smile

 

Step1
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Step1 replied on Tue, May 1 2012 5:01 PM

Like I said Gunther I live down the road from Peak and they are a superb bunch whom just for their service and helpful nature deserve custom! The meters are superb and show leakage too which is why you shouldn't use this model in circuit. You can also use it as a very low resistance meter (far lower than DVM's) and can calibrate the unit by shorting the leads and pressing a button.

I should also mention their transistor tester again a superb unit mine is battered but still going strong! I am popping round soon to get them to update the software and change the leads as they are getting a little tired now, and I am intrigued to know how well the unit measures transistor leakage!

Olly

sonavor
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I'll second that.  I started with the Peak ESR meter, really liked it and ended up buying their transistor/diode tester and their LCR meter. 

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