What is the difference between a 2235 verses 2235A. As far as I
can tell the straight 2235 has red cal knobs. Which one is newer?
Thanks for the info/trivia .... upgrading from a 2225 to a 2235A.

edit:
I was able to find production and support dates:
2235 Manufactured 1984-1988 supported 1995
2235A Manufactured 1990-1994 supported 2000

2235A is newer by 2 to 10 yrs, but what changes did they make if any? Are there any known problems with the 2235/A?

I am upgrading from 2225 to the 2235A. I am very happy with the
2225 but it's 50 Mhz. The 2225 could measure 80 Mhz with out a
problem. I am sure the 100Mhz 2235A can handle 108 Mhz (top of FM band).

My question is how far over-rated Bandwidth can you push a Tek
2XXX series scope? Any thoughts on Bandwidth. What happens
when you go over. From my simple test, the scope just quits, fades out.

The rule is buy as much BW as you can afford; however I read
when you get into higher bandwidth, than 150 Mhz, scopes get
way more complex (more finicky and difficult to calibrate and repair).

I have a Tek 2236, from the same family as your 2235. IIRC, the primary difference between the 2236 and the 2236A was an improved power supply.

Mark

Yea that might apply to the 2235/A, power supply difference.

I understand the 2236/A has on screen measurements, nice. I just stole a 2235 (got a good price). Love my 2225, so I am sure I will enjoy the 2235. I work on FM radio and it would be nice to have something to go to 108 Mhz. I am looking forward to the upgrade.

Mark how does the 2236/A measurement functions work. Do you
put it to use. It's not a 'storage scope', right?

The 2235's 100 MHz will cover enough above and beyond 108 MHz if you have probes that will go well above 100 MHz- you probably would need 150 MHz probes to be safe. You likely recall a lot of Dean's postings on that subject.

You also get delayed sweep with the 2235, but it's something you probably won't end up using much. In a sense you bought a very similar car with a little more horsepower and air conditioning

-Mark-

The 2236 is not a storage scope, but I don't really have a use for one. The only DMM feature of my 2236 that I typically use is the frequency counter function, to be sure I'm on frequency when adjusting radio IF coils. I do have to spend a little time figuring out which combination of little square buttons I have to push to get the function I want. The other DMM features work, but it's usually easier to pull out a real DMM if you want to measure a few resistors... As Mark P noted, be sure to get a good set of probes. I lucked into a pair of Tek P6109 150 MHz probes for cheap.

Mark

I don't want to hope to much, I think it comes with the manual and probes... the little blue storage bag on top is full in the picture. Even if it's only the machine, what I paid (with a warranty) I'll be happy. I have 100 Mhz probes, but they're el cheapo china specials. They work great, but I'd like some 150 Mhz Tek probes for cheap. I have to read Deans post on probes. I read some stuff on the web and have to admit, it was over my head with out more reading and study.

As far as a car with more HP, I think I doubled HP? I just got tired of not being able to look at my Sencore SG-165's FM band RF output. The HP 8640B of course goes to 512Mhz. The poor little 2225 was struggling over 80 Mhz, but it would display 110 Mhz, it just started to look funky. Being a FM radio fan I justify the upgrade, doubling the BW. This will be a keeper I hope. Reading the web I found all the manuals, Op, Service and "Fold outs", with board layouts.

Reading some of the few repairs and trouble shooting it seems to be a reliable scope and easy to repair. The few complaints on the web had typical repairs, new caps or cleaning connectors, that fixed misbehaving 2235's. The 2235A is only 16-20 yrs old. It was made till 1994 and supported to 2000. I never had any test gear this new. All the gear I have stopped being built or supported more many decades ago.

The delay sweep might be fun to play with. I am sure it has some use or they would not put the feature on the machine. Some on on ARF explained the use, but I'd have to see it let it sink in. Every feature on the 2225 I needed and used: two channels, X-Y mode, Z-input, external trigger, line sync... I did not get into all the trigger modes, but it did all I needed, but ran out of horse power above 80 Mhz.

SCORE! Got the Tek 2235A and it works and it came with:

Power cord
Operator manual
BNC to SMA connector cable
Two 150 Mhz Tektronix probes (yea!)

(Was not expecting all these goodies)

First good thing about going from 50 Mhz to 100 Mhz bandwidth scope is I can check my Sencore SG-165's signal Gen that has a FM band of Freq 80-108 Mhz. On the 50 Mhz scope couldn't really read those higher freqs, with out it getting a little weird. I did not know if it was the SG-165 or Scope. I know now. It looks good on the 2235A.

The other thing I noticed is the 2235A does not have a multiplier. The 2225 had a X5 and X10 mode, which would expand the wave. The 2235A does not have that (I think?). There is a X10 DC trigger, but that does not affect the scale (I think?). The controls are quite different on the 2235A and will take some getting use to. The 2225 is still a great scope and kind of think I just might keep it as a spare.

Question should I sell my old 100 Mhz Chinese probes with my 2225 scope? The new probes are 10X only. Do I need a 1X Probe?

I would hang on to at least one 1X probe, there are just times you'll find you want it.

-Mark-

Yea I was just playing with them and I agree. The new old scope, the Tek 2235 seems way more sensative. Must be associalted with the bandwidth and also the vertical voltage goes down to 2m volt. The 2225 was only 5m volt. If I only had 10X I would be limited to 20m volt.

BTW the Tek 2235A has this cool back lighting of the screens graticule's.... Now I am going to work in the dark, just so I can the back light.

Nice catch on the Tek probes. I've got my eye out for a set of 150MHz Tek probes.

Now that you have the new scope, it's your chance to really compare the $8 Chinese probes with the Tek probes as far as their specified range. Let us know how they do at the top of the range.

I accepted your assignment and spend an hour playing with two
scopes, four probes and two HP signal gens. I'm dizzy.

The Tek's are 10X fixed, China made 1X and 10X.
The Tek's are bigger and more heavy duty
The Tek's have the BNC with the plastic grip
The Tek's have a spring loaded ground pin at the BNC end
(the Tek 2235 has a ground surface around the BNC, why the
extra ground don't know.)

Performance testing, I got dizzy from all my testing, but the big
difference is when the China made probe is in 10X, it read less
amplitude than the Tek. When the China made is in 1X and the
scale adjusted on the scope to match the Tek's 10X scale, the two
probes were very close to dead on amplitude and Freq. I used
5Mhz mostly. Went back and tried higher Freqs, 100 to 125 Mhz,
which is over the scopes rating. The China probes hung in there
but they were reading less. Both showed some shift moving the
cables around. Freq and phase matched close enough. They all
calibrate nicely.

I'm sure they are better test I could do. The proof will be using
them. I'm convinced a 1X is worthy to have. The China made traces
seemed clean and the Tek a little fatter trace? I noticed amplitude
changed as I dialed up the HP 8640B, went up than down and up?
Signal gen or probe responce? Both makes of probe did it.

More on the 2235A. There are more controls to get trouble
with. I saw some weird stuff going on with the display, I had never
seen before. I thought the scope was screwed up. However t was
how I had it set. The more features, the more settings to screw
up. It has separate sweep rates for A and B and the delay sweep
feature and a cool vernier control on the front. I have to say the
2225 has a slightly sharper display? I don't know may be not, but
they have same size displays. The difference is the 2225 runs out
of steam at 80 Mhz and the 2235 soldiers on into the 130 Mhz
range and higher.

I found the 10X magnification switch on the 2235, its a center pull
deal on the sweep rate control. Overall its a nice upgrade. Most of
the advantage for me is the wider bandwidth. All the fancy sweep
controls, delays are over my head and need right now. I see how
they can be used for signal response timing, but have no need for
that right now.

Good job on the testing. I love Tek scopes but there are a lot of buttons. I'm no expert by any means but I think doing comparisons like this are one of the best ways to become one with your new scope.

I think I will try to keep away from probes with switches for now. As I said in another post, I think that's what caused most of the import probe failures I saw.



Does this include voltage measurements? Two 10X probes reading different amplitude could be a problem. You will need to figure out which probe is correct.



I would also be a little concerned about the signal falling then rising again. Is it the generator or the scope? I generally don't use a sweep when signal tracing but I would want to know if it's the scope or the signal generator. If I had to guess, my bet would be the generator.

FYI,

The spring loaded pin on the Tek probe contacts a ring on the scope. This pin is connected to a resistor in the probe. The resistance is different for x1, x10, x100. This way the scope knows what type probe you've connected. Here's some more info on the subject. http://www.electronics-related.com/usen ... 6046-1.php

The China probes don't have this pin, so the scope thinks it's a x1 no matter what. So when you put the China probe in the x10 position, you'll have to multiply the amplitude of the trace by 10.

OK I read the link, thanks. That explains why the China probe in X10 reads lower? The Tek scope is looking for that resistor (11k in this case) to signal it to get the voltage divider right. In X1 and the scale adjusted to match the Tek X1 scale, it matches amplitude.

QUESTION/PROBLEM????

I am still shaking down this new scope to make sure it is working. This is a minor or non issue but, the A and B intensity control - has two separate controls, outer ring A and center knob B intensity. It seems only A works (outer ring) and controls both traces A and B? Which is fine, but wondering what the B control is for. Seems to have no affect? May be it's how I set it?



I agree. WELL I go back and check this and now it seems to work? (EDIT I FOUND THE CONDITION AND IT's NOT GOOD?) I must have it set wrong? Weird operator error? I recall when I went from 1, 2, 10, 20, 50 v/div Vert at 10 the displayed signal amplitude increased, 20 was same as 2 and 50 went down to what looks like the right scale. Now that I think about it, I am using the other signal Gen. I want to make sure this scope is good while in my 7 day warranty. It doesn't do it with a 9 volt battery either. So either it's an intermittent switch issue (on both channels unlikely?), I had some setting that caused it or I'm seeing things? I have 6 more days to figure it out.

Edit: Using the Probes on the signal Gen was confusing things. I went to straight coaxial Sig Gen to Scope.... Found the issue, Channel B gets wacky above 250 Khz or 500 Khz, than it starts it reversal on the Vertical Scale / Div select at 5, 10 and than back down at 20 volts (or .5, 1 and 2). I noticed B is kind of Jumpy and the higher the freq the worse the amplitude issue gets. Channel B is OK at 2 volts/vert div or less. Any ideas. Channel A is fine.

I believe with the intensity controls, the A and B correspond to the timebases rather than the channels. The A will be for the regular timebase, B is for the delayed portion if you are using delayed sweep.

It sounds like you might have an issue with the channel 2 vertical amplifier. As far as what it is would be anyone's guess.

-Mark-