Re: 2246 Mod A main board overloading the SMPS

#85560

Completely agree. I ran the SMPS with just the fan for a whole afternoon before I was willing to go further.

With the 40W series bulb removed :), the SMPS starts up correctly with just the SMPS and the main board.  The voltages are a bit off but I don't want to adjust the +7.5V till all the boards are in and the SMPS is running under full load.

More to come.

Priya.

Show quoted text

--- In TekScopes@..., "chipbee40"  wrote:

--- In TekScopes@..., "Mover"  wrote:
 Indeed, the fan is not sufficient load to test the SMPS.

In my post in the original thread I was not implying that the fan alone was sufficient to "test" the power supply, merely that in order to fault find on a non working/tripping supply it was a convenient load/indicator of the power supply ability to function. Some switching supplies will not run without a certain load, this one will run with just the fan attached. Most faults can be rectified just with the fan as an indication. Unfortunately Tektronix omitted power supply expected load information, unlike Philips/Fluke for which scopes I have built full load test boards. JC

Re: Which would you pick? 454 or 475? -->the 475!!!

wshawlee2

#85559

realistically, the 475 is just a better scope in every way, and significantly newer and better desgined. and you have to love the 200+MHz bandwidth, and the ability to stop it down for lower frequency work. however, check the serial number, if low (below 20K), it may be a bit of a toss up. but power it up, see if it works, and check that the controls are not intermittent or noisy.  a bit of de-oxit will improve the pushbutton switches.  check the power supply caps, they are usually in need of replacements, and newer ordinary 105C radials work just fine there, as long as you remember to jumper the old style FP electrolytic ground pads together. the 454 will be much harder to get and keep running. the 475 custom ICs are generally available, the TD's not so much (in the trigger).

all the best,
walter
sphere research corp.

Show quoted text

--- In TekScopes@..., Matt Jodz  wrote:

Looking at getting either a 454 or a 475 and would appreciate any opinions as to reliability and ease of maintenance and repair for these two scopes.? The 454 is working fine and the 475 needs some (hopefully) minor repair.? I will be using them for hobby repair of older radio and test equipment.? Which would you prefer?? Thanks.

Re: Need help choosing a scope and some other RF capable equipment.

Don Black

#85558

开云体育

Hi jerry,
??? ??? ????? I'm in Australia, shipping costs here would be much more than the scope. It looks like a nice package, I'm sure it will sell.
I always enjoy your posts to the group, usually learn something from them.

Don Black.

On 05-Jan-13 10:24 AM, jerry massengale wrote:

Show quoted text

?

Thanks Don,

Yes it is 200MHZ. I will see if I can fix the listing. Where are you?

Jerry Massengale

-----Original Message-----
From: Don Black
To: TekScopes
Sent: Fri, Jan 4, 2013 4:08 pm
Subject: Re: [TekScopes] Need help choosing a scope and some other RF capable equipment.

?

Hi Jerry,
??? ??? ??? ??? Nice looking scope, too far away for me. However, you've listed it as a 200 MHz scope in the title but only 100 MHz in the description. I guess I could look it up but which is correct? I suspect 200 MHz.

Don Black.

On 05-Jan-13 5:03 AM, jerry massengale wrote:

?

Hi,

Sounds like Hybrid battery work. There are several nice 475s on ebay. Just search for tektronix 475. If you like, I have a 3 channel 7704A on ebay. See item 290839243077. It should serve well and other options can be added.

Jerry Massengale

-----Original Message-----
From: sknaugler
To: TekScopes
Sent: Fri, Jan 4, 2013 10:34 am
Subject: [TekScopes] Need help choosing a scope and some other RF capable equipment.

?

Sorry, this is long. Maybe you folks can help with our project, point us to sources of RF help, or at least help me find a scope. But because this is a scope forum I'll start with the scope part. I should add that a DSO would be nice, but an old fashioned CRT analog scope may be perfectly fine.

We need a scope to examine a waveform that we want to apply to a pair of electro-chemical cells wired in series. Currently we power the cells with 1.0 VDC, and they normally they draw between 3 and 5 A. It is thought that cell performance would improve if we can cause the chemicals in the cells to resonate, hence the desire to superimpose an AC signal on top of the DC. We have been able to explore frequencies up to 100 kHz for square waves and pulses and 300 kHz for sine waves, but not surprisingly those lowish frequencies did not help.

We now want to explore frequencies from about 1 MHz to as much as we can afford on a shoestring budget, but no less than 30 MHz for square waves and pulses and 50 MHz for sine waves. 100 MHz would be nice, but there's that budget issue.

The waveforms, at least initially, would be limited to 1 V maximum, and never going negative. We are thinking that the maximum AC amplitude would be 0.5 V peak, or 1.0 V peak to peak, and that would be superimposed on a 0.5 V DC bias voltage. A minimum AC amplitude would be 0.05 V peak, or 0.10 V peak to peak, and that would be superimposed on a 0.95 DC bias voltage.

We'd also like to monitor current if we can find a shunt that does not distort the waveform.

An issue is that I can't guarantee that the final wiring will give us a common ground point so we may need a scope and lead set up where can can measure two differential voltages. (Our Tek 222 with it's isolated inputs is nice in that regard, but at 10 MHz bandwidth won't work for these higher frequencies.)

So if you guys can point us in the right direction for what models of new or used scopes might work for us. Or even sell us one of your surplus working scopes.

Local Craiglist scopes available that appear to work from pics and description: (I know, buyer beware.)

Tek 2465 (not A or B) $350 firm. (Seems a little high)
Tek 2215A, $100 firm (Not quite enough bandwidth)
Tek TDS 3052B (No price given, and I don't know much about this other than labeled 500 MHz)
Anritsu MS2711D (I know nothing about this brand or model)

We're also going to need an arbitrary waveform generator, and the "superimposed RF on top of DC" power supply. These could be the subject of another posting if there's any interest, or we could keep those non scope subjects off forum.

If it makes any difference, our 3 person start up is in Seaford, Delaware.

Re: Need help choosing a scope and some other RF capable equipment.

#85557

Thanks Don,

Yes it is 200MHZ. I will see if I can fix the listing. Where are you?

Jerry Massengale

Show quoted text

-----Original Message-----
From: Don Black
To: TekScopes
Sent: Fri, Jan 4, 2013 4:08 pm
Subject: Re: [TekScopes] Need help choosing a scope and some other RF capable equipment.

Hi Jerry,
??? ??? ??? ??? Nice looking scope, too far away for me. However, you've listed it as a 200 MHz scope in the title but only 100 MHz in the description. I guess I could look it up but which is correct? I suspect 200 MHz.

Don Black.

On 05-Jan-13 5:03 AM, jerry massengale wrote:

?

Hi,

Sounds like Hybrid battery work. There are several nice 475s on ebay. Just search for tektronix 475. If you like, I have a 3 channel 7704A on ebay. See item 290839243077. It should serve well and other options can be added.

Jerry Massengale

-----Original Message-----
From: sknaugler
To: TekScopes
Sent: Fri, Jan 4, 2013 10:34 am
Subject: [TekScopes] Need help choosing a scope and some other RF capable equipment.

?

Sorry, this is long. Maybe you folks can help with our project, point us to sources of RF help, or at least help me find a scope. But because this is a scope forum I'll start with the scope part. I should add that a DSO would be nice, but an old fashioned CRT analog scope may be perfectly fine.

We need a scope to examine a waveform that we want to apply to a pair of electro-chemical cells wired in series. Currently we power the cells with 1.0 VDC, and they normally they draw between 3 and 5 A. It is thought that cell performance would improve if we can cause the chemicals in the cells to resonate, hence the desire to superimpose an AC signal on top of the DC. We have been able to explore frequencies up to 100 kHz for square waves and pulses and 300 kHz for sine waves, but not surprisingly those lowish frequencies did not help.

We now want to explore frequencies from about 1 MHz to as much as we can afford on a shoestring budget, but no less than 30 MHz for square waves and pulses and 50 MHz for sine waves. 100 MHz would be nice, but there's that budget issue.

The waveforms, at least initially, would be limited to 1 V maximum, and never going negative. We are thinking that the maximum AC amplitude would be 0.5 V peak, or 1.0 V peak to peak, and that would be superimposed on a 0.5 V DC bias voltage. A minimum AC amplitude would be 0.05 V peak, or 0.10 V peak to peak, and that would be superimposed on a 0.95 DC bias voltage.

We'd also like to monitor current if we can find a shunt that does not distort the waveform.

An issue is that I can't guarantee that the final wiring will give us a common ground point so we may need a scope and lead set up where can can measure two differential voltages. (Our Tek 222 with it's isolated inputs is nice in that regard, but at 10 MHz bandwidth won't work for these higher frequencies.)

So if you guys can point us in the right direction for what models of new or used scopes might work for us. Or even sell us one of your surplus working scopes.

Local Craiglist scopes available that appear to work from pics and description: (I know, buyer beware.)

Tek 2465 (not A or B) $350 firm. (Seems a little high)
Tek 2215A, $100 firm (Not quite enough bandwidth)
Tek TDS 3052B (No price given, and I don't know much about this other than labeled 500 MHz)
Anritsu MS2711D (I know nothing about this brand or model)

We're also going to need an arbitrary waveform generator, and the "superimposed RF on top of DC" power supply. These could be the subject of another posting if there's any interest, or we could keep those non scope subjects off forum.

If it makes any difference, our 3 person start up is in Seaford, Delaware.

Re: New old scope owner

John Griessen

#85556

On 01/04/2013 04:37 PM, Steve Purcell wrote:
Is there a way to search archives?Yes by logging into yahoogroups.com

Re: Need help choosing a scope and some other RF capable equipment.

Don Black

#85555

开云体育

You mean it really isn't flat???

Don Black.

On 05-Jan-13 9:24 AM, Jim wrote:

Show quoted text

?

History teaches us the unfortunate lessons and fates of people who believed that a flat Earth was the center of the Universe.

73

Jim N6OTQ

New old scope owner

Steve Purcell

#85554

Hi to everyone,

?

I've been reading the posts and researching the old analog Tek scopes. It's very exciting to see the interest shown even after all these years.

?

My 453 has arrived. I haven't been able to test it yet but it supposedly was working according to the ebay seller.

?

I'm sure I will have many questions and as an engineer who came into the field after all the basics were hidden inside IC's it's going to be exciting to see the textbooks come to life.

?

The Tek analog scopes are the perfect vehicle to learn analog design.

?

I'm not familiar with this type of format. There must be a lot of really interesting stuff that's been posted over the years. Is there a way to search archives?

?

Thanks

Steve

?

Re: High Voltage Probe to work on Scopes.

Don Black

#85553

开云体育

I guess this is the graph, found by Google search . It's valuable to know what's really happening.
Looking at the SA graph and comparing to the table, it seems to show a big falloff by 100 Hz, while the table only shows about 2% drop. Is this due to some artifact of the SA or am I misreading it (likely). The scale indicates start 0Hz, stop 1000 Hz which is 100 Hz per division.

Don Black.

On 05-Jan-13 6:31 AM, Neil Gruending wrote:

Show quoted text

???

I also use a 80K-40. I also sometimes use it as an oscilloscope probe for low frequency measurements. Somewhere I found a good frequency response graph for it.

Neil

On Fri, Jan 4, 2013 at 11:16 AM, Craig Sawyers <c.sawyers@...> wrote:

???

> I just have a Fluke 40K-6 6 kilovolt probe which is good for anything
except
> the CRT acceleration voltage. It is very accurate on all of my meters
*except*
> for my best one, an HP 3478A, because that one has a
> >10 gigohm input resistance on the two most sensitive ranges and high
> voltage attenuating probes are usually designed to work into 10 megohms.
>
> The 75 megohm input resistance of the 40K-6 is annoying though

I went for a Fluke 80K-40, which is 1000:1 and an input resistance of
1G-ohm. Goes to 40kV, so amply good enough for final acceleration voltages.

Craig

Re: Need help choosing a scope and some other RF capable equipment.

Jim

#85552

Hey, don't get in the way of research! ?:)

Either they achieve the results they seek, or they don't. ?It should never be our place to discourage pure research, nor to blindly challenge their postulates.

History teaches us the unfortunate lessons and fates of people who believed that a flat Earth was the center of the Universe.

73

Jim N6OTQ

Show quoted text

From: Miroslav Pokorni
To: TekScopes@...
Cc: David DiGiacomo
Sent: Friday, January 4, 2013 4:11 PM
Subject: Re: [TekScopes] Need help choosing a scope and some other RF capable equipment.

Chemicals can resonate no worse than Power/Ground plane on a multilayer board, as claimed by famous Howard Johnson of 'Black Magic' fame.

A bit off subject, but close enough to cold fusion.

Miroslav Pokorni

On 1/4/2013 12:40 PM, David DiGiacomo wrote:
?

Sounds more like cold fusion (or worse)! How could chemicals resonate?

On Fri, Jan 4, 2013 at 11:03 AM, jerry massengale j_massengale@...> wrote:
> Sounds like Hybrid battery work. There are several nice 475s on ebay. Just search for tektronix 475. If you like, I have a 3 channel 7704A on ebay. See item 290839243077. It should serve well and other options can be added.

Re: High Voltage Probe to work on Scopes.

Don Black

#85551

开云体育

Hi Alex, could you explain more on your modifications to the RCA probe for use with a DMM please. I guess you must have reduced the resistance because it originally was designed for use with VTVM with 11 meg input resistance while modern meters are usually 10 Meg (beware the cheap meters are usually only 1 Meg). I imagine any mods to the resistor would be best at the meter end away from high voltage.

Don Black.

On 05-Jan-13 5:33 AM, Alex wrote:

Show quoted text

?

Aren't these voltages mostly DC? Wouldn't a good old DC HV probe do the trick as well? No CFCs.

I got an old RCA HV probe, and once I replaced the shunt resistor with a home-made (filed down) "calibrated" resistor so it reads correctly on modern DMMs, it works fine.

--- In TekScopes@..., "fiftythreebuick" wrote:
>
> I would recommend a P6015 or P6015A. That's what I've used for decades. A P6013A would do it as well in most cases where the voltage is not above it's max rating.
>
>
> --- In TekScopes@..., "lazystrings" wrote:
> >
> > What High voltage probe/s do you recommend to work on Oscilloscopes?
> > The older scopes seem to have much higher voltages. The 7603 has 12KV and -2975V. Newer scopes have only 2KV :(
> > Thank you
> > Daniel
> >
>

Re: Need help choosing a scope and some other RF capable equipment.

#85550

开云体育

Chemicals can resonate no worse than Power/Ground plane on a multilayer board, as claimed by famous Howard Johnson of 'Black Magic' fame.

A bit off subject, but close enough to cold fusion.

Miroslav Pokorni

On 1/4/2013 12:40 PM, David DiGiacomo wrote:

Show quoted text

?

Sounds more like cold fusion (or worse)! How could chemicals resonate?

On Fri, Jan 4, 2013 at 11:03 AM, jerry massengale j_massengale@...> wrote:
> Sounds like Hybrid battery work. There are several nice 475s on ebay. Just search for tektronix 475. If you like, I have a 3 channel 7704A on ebay. See item 290839243077. It should serve well and other options can be added.

Re: Need help choosing a scope and some other RF capable equipment.

Don Black

#85549

开云体育

Hi Jerry,
??? ??? ??? ??? Nice looking scope, too far away for me. However, you've listed it as a 200 MHz scope in the title but only 100 MHz in the description. I guess I could look it up but which is correct? I suspect 200 MHz.

Don Black.

On 05-Jan-13 5:03 AM, jerry massengale wrote:

Show quoted text

?

Hi,

Sounds like Hybrid battery work. There are several nice 475s on ebay. Just search for tektronix 475. If you like, I have a 3 channel 7704A on ebay. See item 290839243077. It should serve well and other options can be added.

Jerry Massengale

-----Original Message-----
From: sknaugler
To: TekScopes
Sent: Fri, Jan 4, 2013 10:34 am
Subject: [TekScopes] Need help choosing a scope and some other RF capable equipment.

?

Sorry, this is long. Maybe you folks can help with our project, point us to sources of RF help, or at least help me find a scope. But because this is a scope forum I'll start with the scope part. I should add that a DSO would be nice, but an old fashioned CRT analog scope may be perfectly fine.

We need a scope to examine a waveform that we want to apply to a pair of electro-chemical cells wired in series. Currently we power the cells with 1.0 VDC, and they normally they draw between 3 and 5 A. It is thought that cell performance would improve if we can cause the chemicals in the cells to resonate, hence the desire to superimpose an AC signal on top of the DC. We have been able to explore frequencies up to 100 kHz for square waves and pulses and 300 kHz for sine waves, but not surprisingly those lowish frequencies did not help.

We now want to explore frequencies from about 1 MHz to as much as we can afford on a shoestring budget, but no less than 30 MHz for square waves and pulses and 50 MHz for sine waves. 100 MHz would be nice, but there's that budget issue.

The waveforms, at least initially, would be limited to 1 V maximum, and never going negative. We are thinking that the maximum AC amplitude would be 0.5 V peak, or 1.0 V peak to peak, and that would be superimposed on a 0.5 V DC bias voltage. A minimum AC amplitude would be 0.05 V peak, or 0.10 V peak to peak, and that would be superimposed on a 0.95 DC bias voltage.

We'd also like to monitor current if we can find a shunt that does not distort the waveform.

An issue is that I can't guarantee that the final wiring will give us a common ground point so we may need a scope and lead set up where can can measure two differential voltages. (Our Tek 222 with it's isolated inputs is nice in that regard, but at 10 MHz bandwidth won't work for these higher frequencies.)

So if you guys can point us in the right direction for what models of new or used scopes might work for us. Or even sell us one of your surplus working scopes.

Local Craiglist scopes available that appear to work from pics and description: (I know, buyer beware.)

Tek 2465 (not A or B) $350 firm. (Seems a little high)
Tek 2215A, $100 firm (Not quite enough bandwidth)
Tek TDS 3052B (No price given, and I don't know much about this other than labeled 500 MHz)
Anritsu MS2711D (I know nothing about this brand or model)

We're also going to need an arbitrary waveform generator, and the "superimposed RF on top of DC" power supply. These could be the subject of another posting if there's any interest, or we could keep those non scope subjects off forum.

If it makes any difference, our 3 person start up is in Seaford, Delaware.

Re: Need help choosing a scope and some other RF capable equipment.

sknaugler

#85548

No, nothing as impossible or profitable as cold fusion.? We're developing an electro-chemical compressor for refrigeration use, and there is water in our cells by design.

"Bound water and ice have critical frequencies (??_S) at about 10 MHz"

The above quote is from:? http://www.lsbu.ac.uk/water/microwave.html

We believe the water in our cells ins "bound" and not free, hence our desire for a DC biased RF power supply, but we need to test this.? We really hope that the water is not free because we really don't want to deal with DC biased microwave power supplies.

Steve N

--- In TekScopes@..., David DiGiacomo wrote:
>
> Sounds more like cold fusion (or worse)! How could chemicals resonate?

Cleaning Tek475A Attenuator Switches

#85547

开云体育

This post describes a procedure that I used to remove and clean the Ch1 and Ch 2 input assemblies for a Tek 475A scope.? My scope was showing intermittent and erratic traces even after switching ranges and tapping on the range switch.? What I discovered, and repaired, made the vertical display like new again.

I followed the procedure shown in the 475A Service Manual, pages 4-24, 4-25.? This manual is available on line.? The dis-assembly involves removing the Vertical Preamp Board and the Vertical Mode – Gain Switch Board and the associated Ch 1 and Ch 2 attenuator assemblies.? It sounds formidable but it can be done.? Take pictures with a digital camera or draw pictures in your own style to help you retrace your steps for re-assembly.

The input attenuators are mechanically operated by the range knobs (Volts/Div) which have cams that operate very small “switches” on the Gain Switch circuit board.? The attenuators are the little rectangular plastic assemblies which plug into the Vertical Mode – Gain Switch Boards (Ch 1 and Ch 2).? At first I tried using contact cleaner on the Attenuator module pins, sockets and board-mounted switch contacts (see photos) but that had almost no effect on the quality of the vertical displays.

Looking at the bottom of one of the Attenuator modules I noticed that some of the solder joints looked quite bad and had signs of corrosion.? The Service Manual calls for replacement of the Attenuator Modules.? They are available on line, but I decided to look further.? This is where you will want to have a somewhat steady hand, a good work light and an eye loupe or a head band magnifier.? I use one made by Donegan Optical, the OptiVisor model with 5 diopter optics.? I bought one at a local model / hobby store.? They are also available on line, new or used.

Before removing any of the Attenuator modules I marked them by Channel, and by location.? Then I removed the modules one at a time, and did a visual inspection of all of the solder joints on the bottom of the attenuator modules. I even opened up some of the modules being careful not to bump any of the variable elements (resistors or capacitors).? Where a solder joint looked bad I applied a small dot of liquid flux and carefully applied the soldering iron tip and a very slight amount of new solder if needed.? I did not use any flux remover (or alcohol).

When I reassembled everything I was very happy with the results.? In summary, I believe that the main cause of the erratic displays was the vibration sensitivity of the attenuator module cold solder joints.? You could pay for new / used attenuator modules but I found that it is possible to correct the problem first hand.

Photo 1: Vertical Preamp Board and Vertical Mode–Gain Switch Board.? Channel 1 attenuator cover removed to show attenuators.

Photo 2: Vertical Mode – Gain Switch Board with all attenuator modules removed to show switch contacts. (Mark the modules before removing them!)

Photo 3: Vertical Mode – Gain Switch Board close up showing board-mounted switch contacts. Carefully clean the little “forks” with good contact cleaner or alcohol and a small strip of paper.

Photo 4: Attaching Vertical Mode – Gain Switch Board to front panel.? Each input attenuator module attaches to the front panel with two nuts.? I used an Allen wrench to hold the nut and a cut up wooden stick to turn the nut onto the screw.

Photo 5: Use a nut driver to tighten the nuts to the front panel screws.

Re: 2246 Mod A main board overloading the SMPS

#85546

--- In TekScopes@..., "Mover"  wrote:
 Indeed, the fan is not sufficient load to test the SMPS.

In my post in the original thread I was not implying that the fan alone was sufficient to "test" the power supply, merely that in order to fault find on a non working/tripping supply it was a convenient load/indicator of the power supply ability to function. Some switching supplies will not run without a certain load, this one will run with just the fan attached. Most faults can be rectified just with the fan as an indication. Unfortunately Tektronix omitted power supply expected load information, unlike Philips/Fluke for which scopes I have built full load test boards. JC

Re: High Voltage Probe to work on Scopes.

#85545

Thank you for all the responses :)
I'll try to find a good deal on a Flule 80K-40 to add to the arsenal of rarely used tools :)

Show quoted text

--- In TekScopes@..., "J. L. Trantham"  wrote:

Just to measure HV DC, consider a Fluke 80K-6 (6 KV, 75 MOhm input
impedance) or a 80K-40 (40KV, 1000 MOhm input impedance) both designed for
10 MOhm input impedance DMM's.

Joe

From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of lazystrings
Sent: Friday, January 04, 2013 10:08 AM
To: TekScopes@...
Subject: [TekScopes] High Voltage Probe to work on Scopes.

What High voltage probe/s do you recommend to work on Oscilloscopes?
The older scopes seem to have much higher voltages. The 7603 has 12KV and
-2975V. Newer scopes have only 2KV :(
Thank you
Daniel

Re: Which would you pick? 454 or 475?

#85544

On one hand, the 454 has several Nuvistor tubes (the 454A replaced
them with JFETs) which can be difficult to find replacements for and
are not getting any younger.  In the worse cast, JFETs can be used if
the circuits are modified with the 454A design as a guide.

On the other hand, the 475 has custom Tektronix ICs which can fail and
are also difficult to find replacements for but I think many of those
ICs are shared with other 200 MHz and faster Tektronix instruments so
that may not be a big problem.

I would probably go with the 475 but someone else on the list may know
more about the ultimate reliability of these two instruments.

On Fri, 4 Jan 2013 12:49:57 -0800 (PST), Matt Jodz
<matt.inchina@...> wrote:

Looking at getting either a 454 or a 475 and would appreciate any opinions as to reliability and ease of maintenance and repair for these two scopes.? The 454 is working fine and the 475 needs some (hopefully) minor repair.? I will be using them for hobby repair of older radio and test equipment.? Which would you prefer?? Thanks.

Re: 2246 Mod A main board overloading the SMPS

Francis

#85543

Believe I am ready to put the SMPS back into the scope tonight.  I apologize to everyone who I misled with my earlier post on this and thanks as always for quick and thoughtful responses.  You guys are great!

Priya.You don't have to apologize for anything.
Everybody here is happy to help when possible.

Which would you pick? 454 or 475?

Matt Jodz

#85542

Looking at getting either a 454 or a 475 and would appreciate any opinions as to reliability and ease of maintenance and repair for these two scopes.? The 454 is working fine and the 475 needs some (hopefully) minor repair.? I will be using them for hobby repair of older radio and test equipment.? Which would you prefer?? Thanks.

Re: Need help choosing a scope and some other RF capable equipment.

#85541

Sounds more like cold fusion (or worse)!  How could chemicals resonate?

Show quoted text

On Fri, Jan 4, 2013 at 11:03 AM, jerry massengale <j_massengale@...> wrote:
Sounds like Hybrid battery work. There are several nice 475s on ebay. Just search for tektronix 475. If you like, I have a 3 channel 7704A on ebay. See item 290839243077. It should serve well and other options can be added.