Tube Amps / Music Electronics
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|2/16/2005 7:40 PM|
Are you in the Portland area loudthud?
I've got a couple Tek 2235 dual trace 100Mhz scopes that used to be local community college test equipment. I got them very reasonably used. They both work great...now I just need to figure out how to use them.... I still would like to get manuals for them but have no idea where to look.
I used to have a Ballantine 1066B solid state 20 Mhz dual trace scope that I sold to an Ampage member for $175. It worked very well also.
|2/16/2005 7:58 PM|
loudthud, if you are partial to Tektronix, how is it you are not on the Yahoo! Tek group? I knew about them before I had my first Tek scope. My best is a 453A, and it is sure nice. That I bought at the swap meet for $75 with the probes and manuals. Speaking of manuals, there is always someone on eBay (I can't recall who) that sells Tek manuals either as a CD or a high resolution reprint. Don't quote me, but I think the CD's are $9.95 and the reprints are $39.95 the last time I checked. The older tube Tek scope manuals are online for free. You may not like them, but my 316 seems to be built like a tank. And I've fixed many old Heathkit and Eico oscilloscopes. In fact, I was given a really old (40's?) GE oscilloscope that was maybe 500K in bandwidth. A handful of capacitors later, and it looks as good as any other tube oscilloscope. This thing had a regulated power supply (for both high and low voltages) and a really nice sweep and blanking circuit. Some oldies, like my RCA, you cannot get rid of the retrace lines. Who ever had the B&K; I am sorry. Those I cannot get excited about. They seem to have a weak trace, partially because the anode voltage is just not that high. I think even my 453A has a 12KVDC accelerating voltage, while the B&K manuals say something like 1600VDC. Or it usn't much more than 2KVDC. I just cannot remember right now. But I remember I don't buy any more B&K oscilloscopes.
|2/17/2005 8:21 AM|
I miss my 547 with the 1A4 module. It quit on me several years ago, and after years of not being able to find someone who knew scopes to fix it up, I finally ended up donating it.... :^(
|2/16/2005 11:29 PM|
'Ole bessy' will remain (in deference to her years of faultless service) ....unnamed!
|2/16/2005 6:42 PM|
I have a dumb B&K 35MHz on my bench at the moment. I have some fancier olf Tek scopes with plug ins at home. We had a nice enough Hitachi for a while.
Old tube scopes are swell, but they are generally MUCH larger than SS models, plus they will heat your shop in the winter for you. They get real warm.
I would look for a reasonable SS scope. One option is surplus. Look at Fair Radio Sales selection. A lot of them are military versions of existing commercial scopes. Sturdy. But ham fests and such are always cool. A Tek 465 is plenty of scope.
Frankly I don't look for a scope that goes down to microvolts, because I want the upper end high. Newer scopes often only go up to 5v/div. I want a scope that goes to 10v/div. That way with my X10 probe, I can display the whole B+. 500v covers 5 divisions. On a 5v/div machine, it is all you can do to get bias supply to fit on the screen.
Generally when I crank the gain up really high, I pick up the lighting in the room, the local AM radio station, and all manner of other noise.
|2/17/2005 5:08 PM|
I grew up in Portland but moved to Texas many years ago. Your best source for manuals is ebay. If you can't find exactly what you need, contact some of the sellers that have something close and lots of feedback.
The thing I dislike about the Yahoo groups is you can't see what the topics are unless you join the group. Might be a good resource for advice on fixing obscure problems though. When I say tube scopes, I'm talking about the old Tek 500 series with 30 to 50 tubes. One thing I wish I could have gotten when I worked there were these engineering power supplys that were the size of the old scopes, had many regulated voltages and lots of heater windings. Many low bandwidth scopes simply ground the anode and use minus 2 to 5 KV on the cathode for acceleration. Higher BW scopes use 10 to 25KV on the anode. Many high BW scopes use what is called a mesh CRT. It makes the display kind of fuzzy but allows for a much shorter CRT. The T900 series was an attempt to capture some of the low end scope market.
The 547 was a great scope. Bright sharp display. I like the 1A7 plugin, it went down to 5 or 10 microvolts per div.
Your advice is good. I would add though that many scope probes are only rated at 400V so they can and will be damaged when looking at high voltages, especially on output tube plates. Keep your eyes open for any 100X or 1000X probes at those Ham Fests. Looking at really low voltages is tricky but every once in a while, invaluable.
|2/17/2005 5:43 PM|
Holly crap, loudthud! It sounds like you know yer Tek scopes. I'd join (I did) if I were you. You get some real intense discussions of the circuits. I don't add anything because I feel like a kid there. But I sure read and try and learn. It's a lot of the newer stuff, but occasionally you get the old favorites. There is a pretty good thread right now on the 310, of all scopes. I have a 316, and as I say, it seems built like a tank.
I'll say it often, because I cannot see any reason to belong any any of the Yahoo! groups. They have a whole mess of tube audio groups. And there is a generic old oscilloscope group.
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