Forgot to mention that the HP P/N is 2100-1736.

Thanks again,
Barry - N4BUQ

The balance pots in my 334A have gotten pretty erratic. Am I correct to assume these are carbon-track types and not wire-wound? I presume that this application would demand carbon-track but in my search for a replacement, I've seen references to wire-wound so it made me curious.

If these are carbon-track, then I'm hesitant to attempt to clean them so wanted to confirm.

Also, if anyone knows where some good replacements are, I'd be interested. These are 3000 ohm/100 ohm dual concentric pots.

Thanks,
Barry - N4BUQ

Wally
Depends on largely on
1) The size of the castors ( wheels), bigger wheels are generally easier to deal with and actually less likely catch and tip
2) The floor surface they are rolling on

Weight? can be a factor, put? heavier on the bottom -Lighter on the top ) think low center of gravity
Though things have changed in my current set up and I have long since abandoned the racks, you used to be able to find racks that were 36"? high. I really like these if you have the room as the make great rolling "table tops" with a power supply in the bottom

Dave
NR1DX

--
This email has been checked for viruses by Avast antivirus software.

There are plenty of 34401A displays on ebay for under $30. I assume they're clones since there are so many but have no reason to think they're bad. I'm hoping the prices on 53131A displays will also continue to fall.
?

I have a bunch of old HP and other equipment and am using a Tek scope stand for some of it. I was wondering if anyone had any suggestions about rolling stands for TE, Do the rolling racks?that musicians use for their audio equipment work well enough? They are 19 inch racks.
Any suggestions would be helpful.

Wally KC9INK

Just recently, I was working on my Marconi 2380 Spectrum Analyzer and realized there was a need for a decent anti gravity device. However my inquiries to the government about their gravity wave program were not met with any degree of sincerity. Apparently they have some sort of very large device that can measure gravity "waves".
I would think the dollar value of these HP and other old test equipment units would be much higher if someone would just come up with an anti-gravity device.

Wally KC9INK

Hi Askild,

thanks a lot for the clear and detailed pointer.
With "nonvolatile trace memory" mentioned in the manual, I thought of something
more durable (EEPROM, FlashROM) than a battery back-up SRAM :-) Would have
been nice, if the programmers had added some CRC or at least a checksum to the
data compression throwing an error message if something fails. At least they had
time for the famous "Tetris game" :-P
As the price tag for the M48Z128Y replacement from Maxim is in the $30 range,
(and then you dont't know how old it is already) I'm thinking of setting up a
"discrete" solution with a $3 128kSRAM, a coincell and 2 Schottky-Diodes
(or a DS1210).

Cheers??? Andreas

So I looked up this HexaWave HWF1681RA - definitely a MESFET. If it turns out they're shot, you may be able to find NEC brand equivalents. I vaguely recall that I have some amplifiers that have NEC-something-something-8001 or 8002 types that have similar Idss specs. I don't recall the exact part numbers, but you may find a bunch searching NEC/CEL (California Eastern Laboratories - their US distributor way back when).

Ed

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Hi Jeff,

Thanks for the info, very interesting.

Both devices test good on the diode range of the 34401A, next test is to see what I can do with them

I have a Tek ext mixer on its way to me and I should be able to put that on the 8566B and see something, I hope so anyway.

cheers

Tim

Tim,

The other device was made by ADTECH as you noted, later ECI, which was bought by Alpha Microwave (when Control Data owned them) and became the basis for their MMW mixer line. My first boss at Westinghouse Defense was one of the principles at ADTEC (all came from Johns Hopkins, including Merrill Skolnik and other notables). Really innovative MMW company in the early 60's.

IIRC, uses a MMW flat cartridge crystal, point contact type with a hand pointed Tungsten whisker (using HF) made by Frank Trageser (only guy who could do them right...).

If the diode tests good with a ohm-meter for some sort of front to back ratio then you are in business. Use typical precautions.? Mostly used in the harmonic mode with LO & IF diplexed together on the N connector, IF in the DC-several GHz (10 ?) range. If both ends open, you can use in fundamental mode mixing. NF ranged in the 15-20 dB area.

Should get you close.

BTW, if you decide to get rid of the ADTEC device, let me know, would like it for the collection.

Regards,

Jeff Kruth

In a message dated 4/7/2020 10:07:18 AM Eastern Standard Time, Brucekareen@... writes:

Tim,

Demornai-Bonardi 633 devices were directional couplers that coupled to a crystal detector on one coupled side and a flange on the other.? They were generally used with a reflecting cavity wavemeter on the flanged port to measure frequency.? The W version would have covered 90 to 140 GHz (WR-8).? These are fairly early designs and yours is probably at least fifty years old.? I am not familiar with the other device.

Bruce, KG6OJI

Sounds like you don't have a manual/schematic, but if you can look at the actual circuit and poke around for measurements, look for how the MESFETs are biased. If the sources are grounded, then there should be a negative gate bias supply somewhere, going into the circuit (it's also possibly generated locally, like with an ICL7660). If this bias supply is lost, the MESFETS (depletion-mode devices) will be full-on, and have very low resistance, which can be self-destructive, depending on the design. Good designs should include protection against this event, by disconnecting the drain DC supply or having some sort of intrinsic current limiting at a non-destructive level.

If the sources are degenerated and self-biased, there's no need for a negative gate bias supply. You should be able to find the source resistors and bypass caps, which will be adjacent the MESFETs, to tell if this is the case.

I'm not familiar with the parts you mentioned, but if you can find a datasheet, you can at least figure out how they should be set up. There are some enhancement-mode RF MOSFET types, but I don't know if any go to multi-GHz. I found some of these inside a power amplifier (+30 dBm 1 GHz) in my noise generator.

So anyway, measuring very low MESFET channel resistance in an unpowered circuit doesn't necessarily mean they're shot - they need to be properly biased first. If it turns out they are some kind of enhancement-mode parts, then that's a different story.

Good luck.

Ed

On 3/30/20 12:56 AM, saipan59 (Pete) wrote:

Maybe the rack was originally for HP computer systems, they had
deeper SCSI storage cabinets.

An anecdote: The last few years of my career with HP/HPE Storage, I was
the EE for a SAS-3 JBOD shelf. The main PCB is primarily a SAS expander
chip with SAS etch going to the front of the box for the drives, and to
the back of the box for the SAS cable connectors. The folks who decide
the "physical" aspects of the product insisted that the box had to be
rather deep, so that when mounted in a rack with servers, it would be a
similar depth, for ease of access to the SAS connectors and such. But
that Requirement meant that the main PCB had to be quite long, creating
signal integrity issues. As a result, we had to use an expensive PCB
material that added significant cost to the box. Nobody (of importance)
wanted to consider different cable design or chassis design options that
would have allowed a shorter board.

Wow Pete, I didn't know you were involved with that stuff. Very cool.
I just brought up an MSA50 not long ago, was that the model you worked on?

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

?
OT:? ? question? ?Aeroflex 3416 6 GHz Signal Generator,? ?No RF output? ? ?& Service Man. for 3410 - 3416 series

? ?Apologies, I will post this on the Marconi group,?
? ? ? ? but thought I might ask here, for the moment.

hi Dave, Nigel, & others who might know something about Aeroflex or its IRF /Marconi version ?

I have an Aerolflex IFR 3416 (digital) Signal Generator ?( of the 3410 Series ) that has No RF output, and I'd like to try to repair it.

b)? Trying to find the Service & Maintenance manuals P/N: 4680/111 (or 468880/111 ?)? & P/N: 46882/500.
? ? ? ? ? ?Cobham wanted ~ $200 for the Service Man., but can't afford anything close to that.
I do have the Op Man, but that has little hardware info in it (" replace the main PCB... ").

Anyone ?

thank you,
rick

I'd like to see $US150.00 for the 5363B Time Interval Probes and $US100.00 for the 8002A Pulse Gen. Manuals for both are available.

I've had the probes for some time and they were fine the last time I used them. Not that they needed it but, puttering one evening, I pulled them apart and cleaned them, no issues were seen.

The 8002A is a U of Calgary shelf queen I've had running into a 'scope the last about week and everything responds in the expected manner.

I pack -well- and haven't a shipping issue in 20-25 years.

PayPal is good.

Best,
Bill Perkins
PEARL, Inc.
3020a Erlton St. SW
Calgary, AB
T2S 2Y6

+ 587 578 4434 Cell' and text

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For precision nothing beats a 3458A, 8.5 digit, but it’s expensive. The 3456 is the better of the 3455/3456 pair. ?Our standard bench meter is a 3478A. Should be relatively cheap and they seem to be accurate and hold cal well. Downside is a 300V max input.?

I'd vote for the HP3455A and HP3456A. I have about three of each, and I did have to repair some of them initially (which is why they were quite cheap) - mostly the usual bad power supply cap replacement. I prefer the 3455A user interface, even though the 3456A is supposedly a little newer and better.

If you're moving from 4.5 to 6.5 digits, it will be like a breath of fresh air. You? may be able to just not worry about calibration yet, since even if old, they will likely still be much better than your old gear. During a design, you can probably get by with less than ideal equipment, and no standards to compare. For the time being, it appears you mostly need more resolution, not necessarily absolute accuracy. As you get to the end, then you can worry about the exactness.

BTW I have one old DMM that's very cool, I think, because of its exceptional resistance measurement capability. It's a DANA 5900, which at first glance is just another old 1970s lab grade DMM, with 5 digits plus 60% over-range. What's cool is that it utilizes those digits well - it includes 100 meg and 10 ohm FS ranges, which are outside those of typical DMMs. Indeed, they're out of its own auto-ranging capability, and have to be selected manually. At the high end, it tops out at 160 megs with 1 k ohm resolution. At the bottom, it can read to 16 ohms with 100 micro-ohm resolution.

I picked this up years ago at a flea market for somewhere around free to five bucks, as I recall, and it worked when I checked it out. I was considering junking it out, since it's old and beat up, and I have plenty of DMMs, until I discovered the ohms ranges. I saved it set it aside just for high megohm use. I recently had need to use it, and found it had crapped out. I've been working on it on and off over the last couple of months, trying to save it. It's almost OK now. If not for those ohms, it would be long gone.

This goes to show that even if you have good, working stuff, it can still let you down, resulting in repair or replacement projects. This will of course tend happen when you need it the most.

Anyway, I'd recommend not looking for "a" new DMM, but "some" new DMMs, if it's for a mission-critical need. I keep the HPs on the shelf in reserve or for high grade measurements, my bench DMMs are old Fluke 8400As (5+ digits), but mostly I use my pile of Harbor Freight freebie DMMs.

Ed

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But you can buy 34401A displays fairly readily and for not too much cost, whereas the Keithley ones are like hens teeth and very many show which segments have been lit longer than others.

I have a 3456A, 3465A, 34401A, Datron 1271 and a Keithley 2000 and have to say I prefer the Datron and Keithley displays the best - apart from the 3465A (lower class of DMM) there isn’t much to choose from the others for what I need.

---

The?HP34401A DVM is a very good choice, and I have see them go for very reasonable prices. I bought three of them locally a couple of years ago for a low price. They are very stable and small. The don't contain much magic, so they still can be serviced. Documentation is excellent.
I have a very stable 10.000000 volt test source, that I bought new on eBay and had rechecked after a year. I also have a Fluke AC calibrator and a couple of DC calibrators, so I can test with good confidence. My reality check is a pair of Fluke 8506A DMMs. These can often be found at very low prices, along with their near twin, the Fluke 8505A. They however are much larger meters.

Stuart K6YAZ
Los Angeles

On 2020-04-09, at 20:24, Bruce <bruce@...> wrote:

I recmmend the HP 3457. Good voltmeter and relatively inexpensive -
less expensive to ship (lighter) - and more reliable than the 3456.

Yes. Needs good front lighting though, as the display is an unilluminated LCD.
But then, it doesn’t degrade like the VFDs on newer instruments.
(This is all mostly moot if you collect the measurements on a PC via HPIB.)

As long as you have reasonable lighting and no vision problem, the 3457A is a slam dunk.
(Like all meters, it does have some weak points, but it is exceptionally long-term stable; a 20-year-old calibration may still be < 10 ppm off.)

One more problem with this vintage of HP equipment: The Schaffner IEC inlet with the famous RIFA madness (actually WIMA in this case).
Some assembly required if you don’t like things in your lab to explode at night.
(Explosion more likely in 230-V-land.)
This is true of a lot of instruments from the late 1980s.

3456A is a bit on the upward curve of the reliability bathtub by now; if you have 20 meters, it makes a good 21st, but I wouldn’t use it as one out of two.
I love the LED display on it; it does drift about way more than the 3457A though.
(I don’t have experience with the 3455A, but that seems to have left the bathtub already.)

If you don’t need 3000000 counts of the 3457A, the 3478A also is a nice meter.
Outside the HP range, but cheap and 6 digits+, look for Solartron 7150 (incidentally, same Schaffner issue) or Philips PM2534/2535 (now, that display is actually a bad example for LCD).

Grü?e, Carsten