I've got a couple of TV's that I'd like to work on this year. I'm in no hurry and am taking my time digesting how to best work on them. In the Sam's photofacts they typically display a waveform that you will need to check for and I'd like to know what you guys would recommend for an oscilloscope. I don't know how to use one but I have an old Heathkit course entitled "How to Understand and Use Your Ocilloscope" and it walks you through its uses. The scope they use is a Heathkit IO-12. Is this a good scope for TV servicing (B&W sets from the late 40's to early 60's)? Does anyone have any other recommendations? I'd prefer something that is not solid state since I don't know how to troubleshoot SS equipment but I'd still be interested in suggestions. Also, I'm looking in the < $100- range.

Thanks!
Geoff

I like the old Tektronix 500 series scopes. You can find them quite inexpensive at electronic flea markets. They are quite large and heavy but the knobs are big and it makes it easy to see the markings.

I have several scopes,I like my Tek 547, it uses tubes and some solid state components. I also have a B&K 1472 solid state scope I've used since the 70's for TV servicing. It's small, all solid state, but very useful. I would recommend a scope with at least 20 Mhz bandwidth.

Eddie

I

I agree Eddie, the 547 is a very accurate and precise 50MHz band width scope, and, with the right plug-in, you can do just about anything, except put wheels on a miscarriage, or weld the crack of dawn. A real work horse.

For TV work though most any of the so called "service" grade scopes with at least a 5MHz band width would do. Keep in mind that they were used primarily for displaying composite envelopes and a few wave shapes, not for any precise measurements.

I have a RCA model 825 which is the same as a Heathkit IO-12. PM if interested.

I use a BK 1474, which I presume is similar to the 1472 mentioned earlier. It seems adequate for TV work and it's small enough to put on the bench next to what you're working on. Some of the older scopes you run across are pretty gargantuan by comparison.

If you're using the scope as a tool, I'd go for something solid state and as new as you can afford. I see no advantage to using an old scope full of tubes, which may need as much servicing as the TVs you're fixing.

I'm sure there are fancier scopes out there. I use mine primarily to display waveforms, not make precision measurements.

Just my $0.02.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

If I got a 547 what about calibration? Does the calibration drift over time? The reason I was thinking of a Heathkit oscilloscope is that I think I would be more comfortable restoring and then calibrating it. I know very little about solid state equipment.

- Geoff

The 547 is is an incredible heat generator, it draws 510W even with quite a few oldie type transistors and unless you must have a tube type and enjoy replacing pricey tubes and SS Id suggest getting any of the better 30-50mc SS ones so at least you can see whats coming out of the tuner at roughly 21 or 41mc.

Leader makes some good ones that are in the $20-30 range on the used market and the Tek 453/453A not much more. The 453 uses nuvistors in the front end which arent cheap and the 453A is all SS.

Carl

The point of buying a newer s-s scope is that it's far less likely to need restoration or calibration. I bought my BK 1474 at a garage sale ages ago, never serviced it other than brushing dust off the front. It has worked well through many projects. I happened to check the vertical calibration last week and that looks fine.

Phil Nelson

a Tek 515A is not so large then other 500 series scopes, but it have the 5 inches screen and the lowest price of all.
515A is a full warm scope, easy to repair.

a 422 is nice, smaller and inexpensive.

the 453 is oversized for TV service and more expensive.

greetings
Martin

I like the Tektronix 7603.
Big screen, solid state reliability.
Uses 7xx plugin modules - lots of them and modules are cheap.
If the Scope stops working, higher probability its a module
that you can find to fix the issue.
100Mhz bandwidth.
Fully functional with 2 or 3 modules.
On screen display shows the horizontal and vertical settings.

I own two of these and the only thing I've done to them
is to clean them and spray paint the blue cabinet to freshen it up.


Carl

Its a small portable scope and if $40-50 with probes and bag is expensive I dont know what you consider reasonable in Germany.

While a 5mc scope is OK for the video and sound stages it doesnt help at the output of the tuner or the IF stages. Might as well get a scope that is really usefull.

I cant even give a 500 series scope away and wind up parting out rather than let audiophools grab the tubes to sell. The latest one was a working 545

Carl

hello Carl,

, for 50 you will not get a 453 here in germany, and when, it comes without anything and mostly some problem like a bad intensity pot.

greetings
Martin

How about the Elenco S-1325...

http://www.tequipment.net/ElencoS-1325.html

I've got the opportunity to get one of these with probes and manual at a fraction of the cost listed on this site.

- Geoff

Actually, the one I am looking at is a 25 MHz. Strange since it is the same model as the 30 MHz in the link above. Will a 25 MHz work well for TV servicing? I believe I would only be using it to view the wave forms shown in the schematics of Sam's Photofacts. Any advice would be appreciated.

- Geoff

It all depends if you just want to look at pretty waveforms in SAMS for final alignment or bring a completely dead set back from the grave. The actual cost of the scope wont differ by much if at all. SAMS were based upon actual test equipment used in shops at the time the set was built....it wasnt very much or very good and the better lab gear was unaffordable to most.

I suggest studying an old TV block diagram and understand what goes on from the antenna connection to the CRT. The older B&W TV's had a 21mc IF but that was changed in the 60's I believe to around 42mc.

Carl

Well that's just it. I know nothing about vintage TV's but want to learn. I have an old Philco set from 1952 that in all likelihood will be my next project so I'm try to learn as much as possible about servicing it. My plan is to replace all the caps and any out of tolerance resistors and test the tubes, including the CRT. I got the photofact and saw all the pictures of the wave forms and understand that I need to get these wave forms at various points, and if I don't I need to make the necessary adjustments. In preparation for this I wanted to get a fairly cheap scope and then use my Heathkit book "How to Understand and Use Your Oscilloscope" which has a bunch of experiments in it that are designed to help you learn how to use a scope.

My only plans right now are to work on tv's from the late 40's to late 50's. Maybe a Predicta if I get brave .. So, knowing nothing about TV servicing, I just wanted to know if the Elenco at 25 MHz will suffice as a first scope for a tv newbie since I have an opportunity to get one dirt cheap. If the advice here is that it is not a worthy candidate then I will pass and look for something else.

Thanks,
Geoff

If the IF is at 21mc then your OK but Ive never been near an Elenco anything so have no comment as to quality.

Carl

Looks like the IF is higher:





- Geoff

There was no IF standard so that general area was used. A 25mc scope will work fine at that IF for alignment purposes and be sure to use a 10X probe to minimize loading.

Carl

Thanks Carl. I found a YouTube series by bandersentv that goes through the alignment process of both the IF and RF sections of an Admiral 24A12:

http://www.youtube.com/watch?v=g2y8C32i088&feature=plcp

Based on that and based on the alignment information for my set it looks like a 100MHz scope is the way to go. What are your thoughts on an HP 1743A? I have a chance to get one of those for a reasonable price.

- Geoff