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Re: 2246 Mod A main board overloading the SMPS

 

Tom & Francis,

I discovered what it is - the ultra cautious in me had left a 40W light bulb in series with the isolation transformer secondary providing AC line power to the scope. It was there originally to prevent further collateral damage to the scope through my repair and testing. With any load exceeding the load provided by the fan, the SMPS pulls enough current through the light bulb that the AC line power to the scope drops below the 80V required to keep the SMPS running. This shuts down the SMPS and the 40W bulb comes on as the SMPS restarts - absolutely normal behavior. I had completely forgotten about the light bulb till this afternoon when I chanced to glance at it cycling with the SMPS and then I had an AHA moment!

Regardless, I did measure resistances (with a Fluke 116 - don't own a meter recommended by TEK) and here they are:
+5:100 ?? - mine is 99 ohm
-5:50 ?? - mine is 41 ohm
-15:500 ?? - mine is 750 ohm
+15:400 ?? - mine is 583 ohm
+7.5:150 ?? - mine is 134 ohm
-7.5:180 ?? - mine is 143 ohm
+58: 7500 ?? - mine is almost open ( 8M ohm)
+130: 9000 ?? - mine is 10,000
Other than the 58V resistance probably becuase my meter can't drive the diodes, my measurements looks fine.

I ran it without the series light bulb and it happily drives a 10 ohm resistor from the 5V and regulation is excellent at 5.05 VDC. With the light bulb in series, it won't run anything more than the fan. Indeed, the fan is not sufficient load to test the SMPS.

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.

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

Hi,

several things:

as Tom Jobe suggested, you can do the following:
with the scope disconnected from the mains, check the resistances
between ground and each supply. As Tek says, use an ohmeter that is able to forward bias diodes, usually a low range.

Values are
+5:100 ??
-5:50 ??
-15:500 ??
+15:400 ??
+7.5:150 ??
-7.5:180 ??
+58: 7500 ??
+130: 9000 ??

these values are taken from a 2245A manual, but should not be
very different on your scope. If one is significantly lower,
check the related circuitry.

The fan is not a sufficient load for the SMPS. When I make
my trials, I use 2 4.7 ?? paralleled on the +5v.
If the supply still ticks, try to disconnect the crowbar protection,
or tie together the gate and the cathode of the SCR. Maybe some
overvoltage due to a dying cap can fire it. Same recommendation
about Q2208 (base tied to ground).

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

Alas - if only it were that simple ...

I finally fixed my SMPS and put it back into the chassis with only the main board. It runs in chirp mode - about every 1 sec there is a clicking sound - the secondary voltages rise and then something gets overloaded and the SMPS shuts down and then cycles again.

I quickly disconnected power, isolated the SMPS and again verified that the SMPS is fine on its own with just the cooling fan load with a steady internal 44 VDC. No new or collateral damage thankfully.

There are no obvious shorts on any of the supply lines on the main board. The issue may still very well be with the SMPS being unable to handle load even though the fan runs fine and the other voltages are fine.

I assume that chirp mode is a common issue with these SMPS supplies. What have others done to (1) find whether the issue is with the SMPS or with the main board and if the latter, (2) which supply line or lines is drawing too much current and how to isolate the problem further?

Thanks in advance.

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

 

¿ªÔÆÌåÓý

Hi Steve,
?
Then most definitely you should?take a look at Jerry's 7704A. It can take any number of different plug in vertical modules including differential input types. You could use one for the current and a two channel standard for the single ended stuff.
?
BTW, I can attest to the quality of Jerry's work. He stands behind the equipment and there is no risk of getting a "powers up" unit from the bey.
?
Good luck,
Tom
?

----- Original Message -----
From: sknaugler
Sent: Friday, January 04, 2013 2:54 PM
Subject: [TekScopes] Re: Need help choosing a scope and some other RF capable equipment.

?



Hi Tom,

Like Jerry you suggested a 475. The only issue I have with a 475 is the fact that it's a two channel scope that does not have isolated inputs, although that can be fixed with the right lead assemblies. (I may not really mean leads. External isolating hardware of some sort where I don't know the right lingo.)

If I choose to only monitor the waveform voltage a two channel scope set up for differential measurements is fine. If I try to measure current (voltage across a shunt) I'll need a second two channels set up for differential voltage measurements.

And I prefer not to do this with two scopes. I like to overlay the waveforms and look for phase changes between the voltage and current.

So the 475 is still a good candidate if I choose to forgo monitoring current.

Thanks,

Steve N.

--- In TekScopes@..., "Tom Miller" wrote:
>
> Look for a 475. 250 MHz BW and usually under $200. Less if you care to learn how to repair the known issues (capacitors).
>
> This is an excellent general purpose scope.
>
>
> Regards,
> Tom
Re: Need help choosing a scope and some other RF capable equipment.

sknaugler
 

Hi Tom,

Like Jerry you suggested a 475. The only issue I have with a 475 is the fact that it's a two channel scope that does not have isolated inputs, although that can be fixed with the right lead assemblies. (I may not really mean leads. External isolating hardware of some sort where I don't know the right lingo.)

If I choose to only monitor the waveform voltage a two channel scope set up for differential measurements is fine. If I try to measure current (voltage across a shunt) I'll need a second two channels set up for differential voltage measurements.

And I prefer not to do this with two scopes. I like to overlay the waveforms and look for phase changes between the voltage and current.

So the 475 is still a good candidate if I choose to forgo monitoring current.

Thanks,

Steve N.

--- In TekScopes@..., "Tom Miller" wrote:

Look for a 475. 250 MHz BW and usually under $200. Less if you care to learn how to repair the known issues (capacitors).

This is an excellent general purpose scope.


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

sknaugler
 

Hi Jerry,

No, not Hybrid battery work. We're developing an electro-chemical compressor for refrigeration use. We have a web site that needs redoing, but there's a bit about us on www.xergyinc.com

Unless any of these scopes have fully isolated inputs, like our 222 with non removable leads, or the Fluke Scopemeters, I think we want a four channel scope with two pairs of channels to be configured as two differential inputs.

Your 7704A might be suitable if the 7A19 module could be swapped for a second 7A26, assuming the mainframe will accept such a combination. (Now I've got some reading to do.)

I assume you mean a plain old 475, not the TAS 475. Although the TAS 475 (100 MHz) and the TAS 485 (200 MHz) are four channel scopes, so seem interesting.

Maybe someone can chime in on TAS reliability, repairability, and their ability to be configured for differential inputs.

Steve N


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
Re: High Voltage Probe to work on Scopes.

 

¿ªÔÆÌåÓý

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: High Voltage Probe to work on Scopes.

 

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: 7854 ROMs

 

To all interested, the images made by Pentti (downloaded from Bruce)are ver. -02. Maybe the name of the archive file can be modified accordingly?

Best regards,

Bogdan

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

Hello all (and Ha Happy New Year)

I am looking for the images of the version -02 of the 7854 scope. All I could find are either the -00 or the old ones from Pentti. Anybody have them?
I was able to read the FPLAs (82S107 ver -00 and -02), but the ROMs themselfs are bad...

Best regards,

Bogdan
Re: High Voltage Probe to work on Scopes.

Craig Sawyers
 

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: High Voltage Probe to work on Scopes.

 

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. It
does not affect measuring the CRT cathode voltage because that is
close loop regulated but the resistive loading is a problem for other
high voltage measurements. A 40K-15 (15 kilovolt) or 40K-40 (40
kilovolt) for example would be better because they have a 1000 megohm
input resistance.

On Fri, 04 Jan 2013 18:33:41 -0000, "Alex" <alexeisenhut@...>
wrote:

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: High Voltage Probe to work on Scopes.

Alex
 

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.

 

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: 2246 Mod A main board overloading the SMPS

Francis
 

Hi,

several things:

as Tom Jobe suggested, you can do the following:
with the scope disconnected from the mains, check the resistances
between ground and each supply. As Tek says, use an ohmeter that is able to forward bias diodes, usually a low range.

Values are
+5:100 ??
-5:50 ??
-15:500 ??
+15:400 ??
+7.5:150 ??
-7.5:180 ??
+58: 7500 ??
+130: 9000 ??

these values are taken from a 2245A manual, but should not be
very different on your scope. If one is significantly lower,
check the related circuitry.

The fan is not a sufficient load for the SMPS. When I make
my trials, I use 2 4.7 ?? paralleled on the +5v.
If the supply still ticks, try to disconnect the crowbar protection,
or tie together the gate and the cathode of the SCR. Maybe some
overvoltage due to a dying cap can fire it. Same recommendation
about Q2208 (base tied to ground).

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

Alas - if only it were that simple ...

I finally fixed my SMPS and put it back into the chassis with only the main board. It runs in chirp mode - about every 1 sec there is a clicking sound - the secondary voltages rise and then something gets overloaded and the SMPS shuts down and then cycles again.

I quickly disconnected power, isolated the SMPS and again verified that the SMPS is fine on its own with just the cooling fan load with a steady internal 44 VDC. No new or collateral damage thankfully.

There are no obvious shorts on any of the supply lines on the main board. The issue may still very well be with the SMPS being unable to handle load even though the fan runs fine and the other voltages are fine.

I assume that chirp mode is a common issue with these SMPS supplies. What have others done to (1) find whether the issue is with the SMPS or with the main board and if the latter, (2) which supply line or lines is drawing too much current and how to isolate the problem further?

Thanks in advance.

Priya.
Re: High Voltage Probe to work on Scopes.

fiftythreebuick
 

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: HP question (yeah I know, this is the TEK forum :-)

 

There is a pdf scanned manual for the later 608E/F on the Agilent manual archive site' if that's any help...the direct url is: -



the general index/search url is : -



Ray, G4LUA

--- In TekScopes@..., David Wise wrote:

No, there's no 608C manual there, only a Service Note. I have a photocopy of a 608C manual;
if you still need it, contact me off-list and I'll scan it as time permits.

Dave Wise

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Albert
Sent: Sunday, December 16, 2012 3:28 AM
To: TekScopes@...
Subject: [TekScopes] Re: HP question (yeah I know, this is the TEK forum :-)

Hallo Leonhard,

This one?



Albert


Guys I am about to buy an HP608C VHF Generator (real boat anchor).

First of all I am looking for the manual in pdf, it's not at the BAMA site. Anyone able to help? (send to tubes.leonard@)
---
Thanks Leonard
7k parts for sale

 

Hi,

I am offering some modules and boards I no longer want. I have described them as best I know. The actual shipping cost will be added to each. At these prices, no refund or return is offered. PLEASE RESPOND OFF-LIST.

1. 7704a io brd 670-1879-00 with switch boards. the horizontal sw board is good. the vertical is missing the left button and the retaining clips on the left and right sw are bad. $5.

2. 7704a horz amp works 670-1853-01 $10

3. 7704a horz amp works 670-1853-00? $10

4. 7704a hvps board? bad suspect multiplier 670-1855-?? $5

5. 7704a delay line no know problem 670-1831-?? $5

6. 7704a z-axis bd. works 670-1854-00 $10

7. 7704a vert amp works 670-1852-02 $10

8. 7d01 power supply board no known problem 670-4286-02 $5

9. 7612 clock buffer no known problem has good 200mhz xtal oscillator from vectron labs model co-238mehb 670-4961-02 $20

10. 7704a power supply parts only, start problem covers missing $10

11. 7603 rectifier module works??? np back panel $10

12. 7503?? rectifier module works $10

13. 7704a power supply works fine $25

14. p6451 probe,? harness damaged pin1, header connector shroud damaged. untested $20

15. p6451 probe no harness note says ch 4 & 7 bad $20

16. p6451 probe no harness untested $30

17. p6451 probe accessories,? 2 harnesses with a few grabbers, clips' manual $20

18. p6451 probe no harness untested $30

19. p6451 probe with harness untested $40

20. p6451 NOS in sealed bag. no harness $50

21. 1/2 of john's tek_7k flex board, female side. $10

Jerry Massengale
Re: Is it safe to power on a 2246 power supply over the bench to check the voltages?

Albert
 

Thanks Francis, that's also the answer to my 2232 question where the resistors are 33 Ohm / 0.2 W. Waveforms 65 and 66 in the 2232 manual leave about 4 V for Vce during conduction.

Albert

--- In TekScopes@..., "Francis" wrote:
---
On the 2235A, the -8.6 reference is regulated by the control
of the conduction of the switching transistors, which are not
working in their saturation aerea, as stated in the service
manual (theory of operation-inverter). This explains the much
higher value of the base resistor (47 Ohms), which has only
IC/?? flowing through.
Re: 7A19 vs. 7A29 Noise

 

On Fri, 4 Jan 2013 09:42:53 -0700, David DiGiacomo
<daviddigiacomo@...> wrote:

There is no fundamental connection between amplifier input impedance and noise. I've design preamplifiers with sub-300 pV/rtHz, and they could easily have GOhm input resistance. That's because the noise of the input bias resistor is shunted by the (much lower) source impedance.
In my lab (aka basement), the "noise" is mostly RFI pickup.

Did you try connecting a termination to the 7A26?
On my 7A18 that makes some difference but the noise level is still
noticeably higher at the highest sensitivity where the only difference
is removal of the last high impedance input attenuator. I usually
test this with the input set to GND anyway.

The 7A26 is more difficult to gauge since it uses a switched low
impedance gain stage at the highest sensitivity which adds a
confounding factor.

Both the 7A18 and 7A26 uses the same input arrangement and even the
same dual FET. Besides the bandwidth difference, the 7A26 uses
integrated instead of discrete gain stages and I would expect them to
be noisier anyway.
Re: Need help choosing a scope and some other RF capable equipment.

 

¿ªÔÆÌåÓý

Look for a 475. 250 MHz BW and usually under $200. Less if you care to learn how to repair the known issues (capacitors).
?
This is an excellent general purpose scope.
?
?
Regards,
Tom
?

----- Original Message -----
From: sknaugler
Sent: Friday, January 04, 2013 11:34 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: 7A19 vs. 7A29 Noise

 

There is no fundamental connection between amplifier input impedance and noise. I've design preamplifiers with sub-300 pV/rtHz, and they could easily have GOhm input resistance. That's because the noise of the input bias resistor is shunted by the (much lower) source impedance.
In my lab (aka basement), the "noise" is mostly RFI pickup.

Did you try connecting a termination to the 7A26?
Need help choosing a scope and some other RF capable equipment.

sknaugler
 

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.
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