The next best-kept test equipment series [Archive]

N8YX

02-16-2013, 02:29 PM

(Don't worry, Jerry, I'm making my way to the HP stuff. But it'll be their network and spectrum analyzers. ;) )

We've discussed the scope/waveform measurement goodies elsewhere so now it's time to cover the signal source and metrics equipment. The gear I'll describe in this thread is modular in nature, fits into a variety of power compartments (also referred to as mainframes) and comes in many flavors.

Amongst them:

DC power supplies - manual and programmable
Voltmeters - manual, autoranging, autoranging precision, programmable
Frequency counters - manual, autoranging, programmable
AF signal generators - manually tuned analog, low and ultra-low distortion analog, ultra-low distortion synthesized programmable
RF signal generators - manually tuned analog, leveled output HF/VHF/UHF (used for scope calibration), programmable synthesized VHF/UHF
Function generators - arbitrary and fixed-mode - manually tuned analog, manually tuned analog with sweep, manually tuned analog with independent sweep (to 40+ MHz), programmable, programmable arbitrary
Pulse generators - manually tuned analog, HV (80+ Vout) manually tuned analog, independent-mode manually tuned analog, programmable synthesized
Television alignment equipment - raster generators, digital video probes, calibration generators (we'll go over these in depth elsewhere)
Calibration and tracking generators - manually tuned analog, programmable digital CalGens, ramp generators and spectrum analyzer tracking generators for use with the 7L1x series and 49x series were offered
Audio measurement, quantization equipment - distortion/SINAD/THD measurement, audio power level meters
Waveform measurement - a variety of oscilloscopes in 5/10/15/80MHz bandwidths were offered, as was a 2MHz B/W X-Y display
Logic analysis - A few options here, and each requires a scope (internal or external) for display of waveforms. At least one word recognizer was made available.
Miscellaneous plugins - prescalers, receivers, gates, delay lines, time bases and many other types were offered, both from Tektronix and from industry partners such as Tegam, Metrotek, Spectracom, Pulse Instruments, etc. Tektronix also offered a 'roll your own' plugin kit consisting of a case, breadboard and blank faceplate - in both single and double-wide format.

N8YX

02-16-2013, 02:47 PM

First off...to power and use any of these you're going to need a way to do so. Fortunately, Fred has spent (the equivalent of) millions of dollars on this stuff so you don't have to "trial and error" your bench.

A foreword about 500 (non-programmable) vs 5000 (programmable) series:

The 5000 series modules - being equipped with a GPIB I/O connector, in addition to multiple power headers - will NOT work in a 500-series mainframe without special modifications. The 500 series modules, however, WILL work in a 5000-series mainframe.

If the only type of equipment you'll be running is the 500 series stuff, you can use any of the TM500 mainframes. They come in 1, 2, 3, 4, 5 (portable) and 6-wide arrangements. The TM5000 frames were offered in 3 and 6-wide variants, along with a few specialty TM5003s which didn't have all power/communications slots populated. These are found as part of the DA4084 and AFG5501 packages; their usability with other 5000 series plugins varies depending on power and GPIB connector location.

So...if you're out scrounging the 'fests and want to run 5000-series equipment, be on the lookout for either of the following. In the case of the 5003, make sure all power slots are populated with connectors:

8894

N8YX

02-16-2013, 02:56 PM

This is one of the handiest TM-500 power compartments to have. Load it up, fasten the covers on the thing and take along as airliner luggage.

8896

N8YX

02-16-2013, 03:59 PM

Some thoughts on plugins, from a user's - not a collector's - point of view:

There are a number of modules which are classified as handy to have, and which weren't widely offered. Several examples are the TVC-501 (time to voltage converter; very useful with a scope plugin for trigger integration), the DA-4084 (incorporates a SINAD test, rather than the AA-501/AA-5001's THD+N test...ideal for communications receiver repair) and the word recognizer for the LA-501. A judicious shopper can still nab these for decent prices.

A little more up the pricing ladder but still fairly common are the SG505/WR/WQ audio oscillators, and the AF501 tunable filter/oscillator. A set of 505's (ideally, a Mod WQ/WR pair) is a must for audio power amplifier IMD testing and the asking price for these instruments reflects their demand. Even so...it's easy to find a stand-alone instrument whose performance meets or exceeds their claimed .002% THD. Thus, go for the better deal.

The synthesized variant is known as the SG-5010. Folks, there's no way in hell one of these is worth the $800-2000+ being asked by some equipment vendors...but we've only begun to scratch the surface of "ludicrous".

Presented for your consumption is the following:

http://www.ebay.com/itm/TEKTRONIX-TM-503-USED-MAIN-FRAME-W-SC504-OSCILLOSCOPE-PS503A-POWER-SUPPLY-TM503-/271093383491?pt=LH_DefaultDomain_0&hash=item3f1e6cc143

A "Best offer" of $300 is being damn generous, and the seller countered with a $550 offer.

FWIW, here's what one can get for that amount of money:

http://www.ebay.com/itm/Tektronix-2465B-Oscilloscope-400MHz-/390541944025?pt=BI_Oscilloscopes&hash=item5aee1d24d9

4 channels of 400MHz goodness and GPIB programmable to boot. The 2400 series is a fine array of equipment.

So...Rule #1 when shopping for TM-50xx stuff is to never pay more for a module than an equivalent piece of gear (which is most times functionally superior) will fetch.

N8YX

02-17-2013, 05:05 PM

And now a word about calibrators and generators.

First, NTSC analog-only stuff. Can anyone tell me why the following purveyor should put the pipe down?

http://www.ebay.com/itm/Tektronix-067-0916-00-Video-Calibration-Fixture-/300629125398?pt=LH_DefaultDomain_0&hash=item45fee46916

A few similar items are listed from time to time and I'll update this accordingly.

Next - WWVB changed formats in 2012; their new phase-modulation scheme means that equipment manufactured prior to the changeover - such as these examples from the 80s and 90s - will not decode the time data properly. In fact, they won't even go into phase lock:

http://www.ebay.com/itm/SPECTRACOM-MODEL-8163-NBS-FREQUENCY-STANDARD-RECEIVER-/221163122030?pt=LH_DefaultDomain_0&hash=item337e596d6e

http://www.ebay.com/itm/Tektronix-TM504-w-Spectracom-8163-8131-8150-/230650424332?pt=LH_DefaultDomain_0&hash=item35b3d62c0c

The last one is laughable. One wonders if the seller is aware of the fact it doesn't function as intended...

AE1PT

02-18-2013, 10:08 AM

Nice series of posts, Fred. I have been thinking about the Tek mainframe series as a replacement for my 465B--and rolling that over to monitor service in the OP section of the shack. And I agree that the prices are insane...

From practical knowledge, I know that these equipment recyclers pay nearly nothing for the used equipment. It is most often bought by the pallet from universities as 'surplus', and by lots in liquidation sales from corporations that are downsizing or have become defunct. I miss the surplus warehouse at the University of Kentucky--I built a whole research center from the ground up with 'discards' from other departments. Everything from furniture on up. There was a mass spec unit I wanted to carry away but could not rationalize who would maintain and operate it... Everything was free for internal university transfer to one's inventory list.

Pennies for things, literally--by the pound or shrink wrapped pallet--and then they tack outrageous prices running into thousands of dollars. Sometimes if one bids often enough on many things good deals are still had. My Gigatronics and Advantest gear are examples of that. But most of it? Do these guys actually sell this stuff at these prices or does most of it end up in foreign markets at half the price?

N8YX

02-18-2013, 06:48 PM

But most of it? Do these guys actually sell this stuff at these prices or does most of it end up in foreign markets at half the price?
I'm really beginning to think not, Pat. There's that whole "certification" bit: A lot of these so-called 'calibration labs' buy the stuff for pennies on the dollar, "calibrate" it then pass the savingsexorbitant lab fees onto prospective buyers.

One of the very first things I did when acquiring the Tek gear was to fork out the money for any required test fixtures, harnesses, extenders and calibration generators. The calibrators can be sent in for their yearly certification (if one gets overly anal about such matters) then used to repair anything else which makes its way across the bench.

Continuing the display of sheer eBay ludicrousness, the following is presented for consideration:

http://www.ebay.com/itm/Tektronix-SG504-/140912277334?pt=LH_DefaultDomain_0&hash=item20cf06b756

Did I mention that the unit requires a leveling head? They've been priced anywhere from $300-500. Whether or not they're actually being sold is another matter entirely.

You use a leveled signal generator to adjust gain compensation on a scope's vertical amplifier, and a '504 touts an output which is flat to within 1/2dB or so across the tuning range. Those scopes which offer bandwidth coverage into the GHz region must be checked with this type of a setup.

Back in December I managed to get hold of a like new '504 complete with head for $250. Due to miscommunication on delivery addressing, the seller and I chased the thing around for about a month. He even threw in a free Tek scope probe when it landed back at his shop.

The deals are out there - but unfortunately, so are the sellers.

N8YX

02-22-2013, 07:16 PM

Onto today's TM500 plugin. It's by far the most common one available - was made for many years - and shouldn't fetch more than a hundred bucks even in 'NIB' condition:

The AM503 current probe amplifier. You use this in conjunction with a 20A clamp-on probe (pricy) or a large, 100A clamp-on probe (pricy ^2) and an oscilloscope. The scope's vertical deflection becomes a representation of the current flowing through the connector around which the probe is clamped.

Handy for automotive wiring and automation control systems troubleshooting. Damned handy, but not $1000 worth of handy (probes not included) which some eBayers think they can get for one. Hamfests or general electronics fleamarkets along with government auctions are your best bet for snagging one of these.

N8YX

02-24-2013, 07:39 AM

Okay...let's put some measurement setups together. These are going to consist of both analog and digital arrangements, from the simplistic to the esoteric.

First is one which most communications electronics enthusiasts (ham, SWL, CB or scanner listener alike) will make immediate use of: A DMM/frequency counter combination. I am going to start by discussing counters in general and specifically mentioning a few wonderful counter modules which use the same (now unobtanium) Litronics DL-883A readout:

DC-503 (100MHz)
DC-508 (1GHz)
DC-508A (1.3 GHz)

All are great counters. Occasionally, a digit segment in the -883A (or the -882 2-digit devices used in the '503) will go bad. The original readouts are scarce but one can rob a working readout from an otherwise junk counter. Make sure to test a prospective unit before buying. When the counter is powered up, pressing its front panel 'Reset' switch will tell you everything you need to know about the entire display; should see a nice set of 8s.

(I would use a broken '503 to repair a display-defective '508x - not the other way around. The '508s are far too nice of a counter to relegate to the scrap heap. And a couple of us are working on a replacement readout for these units...IF we can find modern-day 3 digit readouts of a small enough form factor.)

That leaves us with a few remaining choices. My recommendations if using a TM500 series power module:

DC-502 (55MHz/550MHz pre-scaled)
DC-503A (125MHz)
DC-504A (100MHz, high-resolution)
DC-505A (225MHz)
DC-509 (135MHz) - can be used with /10 prescaler
DC-510 - same as the DC-5010 listed below but non-programmable; will work in a TM500 power module.

If using a TM5000 series module and space is limited, choose one of the following single-width programmable counters:

DC-5004A (100MHz)
DC-5009 (135MHz) - can be used with /10 prescaler

If, on the other hand, you aren't space constrained go straight for a DC5010. It's a two-channel, 350MHz counter which is adequate for almost every need the HF-focused ham/SWL can throw at it.

Should one need accuracy into the GHz region and want to keep things modular, you have a couple options. One is a DC508/508A unit. Another is the '509/'5009 unit with a DP-501 Prescaler ahead of it. Yet another approach (and one I would definitely consider) is to roll your own /10 prescaler and fit it into a defunct TM series module case.

(I'll cover "u-build-m" Tek TM constructs much later in this thread.)

8955

N8YX

02-24-2013, 08:22 AM

On to DMMs.

Almost all of these are single-width units and will work in both the TM500 and TM5000 series power units. A few have temperature measurement capabilities.

DM-501A (4 1/2 digit, voltage/current, resistance, temperature, dB-rms)
DM-502A (as above; 3 1/2 digit)
DM-504A (4 1/2 digit, voltage/current, resistance, dB-rms)
DM-511 (as above)

For TM5000 power units the following programmable multimeters are available:

DM-5110 (equivalent to a DM-511)
DM-5010 (as above, with Math functions; double width)
DM-5120 (6 1/2 digit high-precision; triple-width)

8956

N8YX

02-24-2013, 08:43 AM

Putting it all together - from the most simplistic to the most flexible.

If you're going to use just one single-width instrument at a time, it's entirely possible to do this with a TM501 (single width) power module then swap counter or DMM in as required. Do so with the power off, please. Otherwise, get hold of a TM502 or larger power module with which to run your accessories.

General-use:

DM-501A, DM-502A, DM-504A or DM-511 plus DC-503A, DC-504A or DC-505A

Communications service work:

DM-501A, DM-504A or DM-511 plus DC-501, DC-505A, DC-510 (with DP-501 Prescaler or an R-Y-O equivalent) or a DC-508/A.

Engineering and calibration lab work (requires TM5006 power module):

DC-5010, DP-501 Prescaler and DM-5120 DMM.

The combination listed immediately above can fetch north of $1200 if you're not a prudent shopper and south of $500 if you are. Make them an offer they won't refuse. I got all three modules for $450, albeit via separate sales.

N8YX

03-24-2013, 01:03 PM

Bump.

A couple weeks ago I made a heckuva score on the 'Bay:

SG5010 synthesized audio generator (ultra low distortion; does sine/sawtooth/square waves from 0.1Hz to 168KHz...and offers CCITT/SMPTE/burst functions)

AA5001 audio distortion analyzer - this one does THD and IMD testing, as compared to my DA4084 which is set up for SINAD tests

DC5009 Counter

DM501A 4 1/2 digit autoranging DMM

TM5006 mainframe

All for roughly the 'reasonable' price of an SG5010 by itself. At the higher end of the scale, these generators have been fetching upwards of $2100. Crazy, as I can buy a new stand-alone audio generator for less than half of that figure.

The SG5010 shows an Error 319 on powerup but this can be cleared and the instrument still functions. And the DC5009 has a digit with a burned-out segment but parts are inbound as I type this. Some day I'll get around to ordering the service manual for the '5010 and fix it but the instrument is fine for use as-is.

I have another DM501A in one of my TM506 mainframes. Swapping it into the '5006 in place of the DC5009, one now has an instrument capable of simultaneously measuring the performance of both channels of a stereo audio amplifier.

Just put one of these plus an SC502 in a TM515 case for a portable 16ch logic analyzer. Folks, if this is still available it's a very good deal:

http://jerseyshore.craigslist.org/ele/3661392080.html

N8YX

05-15-2013, 01:59 PM

Bump again.

Eddie graciously sent me a 1985 Tektronix Products catalog. Described therein are all the TM500 and 5000 series modules you could ever care to read about - with the exception of the discontinued stuff of the early 70s-early 80s and the modules of the 90s which had yet to be designed when the catalog was released. The AFG5101/5102, PFG5105, PG5110, CG5010/5011 and SG5030/SG5050 all come to mind.

What's really valuable is the accessories listing on each page: Which probes, leveling heads and other options went with each module.

We're going to study it intently so 'DSG knows what to look for at Dayton. :lol:

I noted in the Swap Meet area that I had a TM503 plus a few accompanying modules for sale. Will get pics of it posted when the weekend is settled.

X-Rated

05-15-2013, 02:22 PM

N8YX

05-15-2013, 04:05 PM

Lots of opportunity to find lots of test equipment there.
Fist full of dollars in hand, I'll be waiting.

I hope they have all of what I'm after. Tek 500/5000 stuff is hit-or-miss. Another area ham buddy of mine commented that there was a lot less of it available during the past two events than in past years.

Am going to start selling off a lot of my duplicate items. Occasionally I'll buy a loaded power module just to get that one piece I need and end up with multiples, so I'll pass them on.

N8YX

06-15-2013, 08:40 AM

Bump again.

Today we discuss the AM502 differential amplifier and what it can do for you:

9811

A differential amplifier allows one to examine the difference between two applied voltages or waveforms. This model has a usable bandwidth of DC to 1MHz...not much, right?

Wrong!

To stimulate groupthink, let's say that Pat ('MHZ) somehow coughed up half the contents of his garage to the Island membership and we all came into possession of items in various stages of repair, most of which are double or triple conversion superhets. Or maybe Pat himself decides to restore his collection en masse and address some of the design deficiencies inherent to a number of models of gear from the the 70s and 80s.

Two of the big bugaboos in vintage gear are aged/degraded electrolytic and tantalum capacitors, and (unless the equipment was built to mil-spec standards at the outset) filter blow-by due to improper layout and switching methods.

So...how's an AM502 with its measly 1MHz bandwidth going to help us here? Almost all rigs of that genre use a second IF in the 450-500KHz region and a few (Drake R7, etc) employ a 3rd at 50KHz.

We can connect a reference signal to one input of the '502, the pre- or post-filter signal to the other, adjust the DC offset control and get a good indication of how much IF energy is leaking through the switching circuits.

Moving on to post-detector AF...let's say some bypass caps in the AF stages have gone bad and are coupling hum or other unwanted signals into the audio chain. Supplying a reference audio signal to one input channel, the amplifier output to another and setting the filter adjustments appropriately will allow us to spot the culprit, as someone's not shunting low-frequency components as they should be.

A hysteresis squelch operates on a compare-and-hold principle and this module also makes for a decent tool by which to set the DC reference level of the comparator (if the circuit is equipped with such an adjustment means) or to verify operation in the presence of (you guessed it) suspect capacitors.

Basically, the AM502 is a useful tool for any circuit where you have an LF AC signal component superimposed on a DC voltage and are trying to pinpoint and quantify the source.

You'll need to hook the plugin's output to a scope of corresponding bandwidth. A combination consisting TM503 power module, AM502 and an SC502, 3 or 4 scope will make for a neat little benchtop troubleshooting outfit which doesn't take up a lot of room.

N8YX

08-10-2013, 09:02 AM

I got hold of a few Video Calibration Fixtures (067-0916-00) about a month or so back, along with the display chips required to fix the only one in the lot whose reference display wasn't fully operational:

10372

Does NTSC, PAL, SECAM. Perfect for restoration of old analog TVs, which I understand is becoming somewhat of a cottage industry.

Also scored one of the following. Yes, I had to pay a bit for it but considering this is the third one to be listed in 10 years...well, time is money:

10373

The 067-0938-00 Notch Filter is used to calibrate the SG505/SG-5010 series oscillators for lowest possible distortion products. It looks to be service-center-only issue, and since Tek quit supporting this stuff some time ago... I'm/we're it. I was lucky to find mine, after I let another one get away without realizing what it was.

N8YX

08-10-2013, 09:14 AM

There is another, somewhat rare video test fixture which I have that isn't listed on many of the Tek TM reference sites. It functions as a staircase, dot, comb and blanking generator and is a 2-wide form factor. I'll get it out of my storage area and take a few pics before placing it, a -0916- and a couple other related plugins into a dedicated video-test TM506 rack.

Got ahold of two of the following, an SC502 junker, an SC504 junker and two functioning 7B53A time bases for not much more than a single working SC503 fetches. More winter fixit fun; one's partially operative and the other shows no signs of life:

10374

Nuttin' fancy here - just a 2ch 10MHz storage scope. But it's all you need for working with lower IF and AF frequencies. Store a good (no distortion) input signal with the storage function, monitor the output of the device-under-test with one of the channels...overlay the stored and active traces then tune the D-U-T so the two waveforms match as closely as possible.

K7SGJ

08-10-2013, 02:17 PM

Some very nice scores. I have some fairly recent test gens for analog/digital tv/monitors and audio surround etc. Needless to say, I don't do a whole lot of that any more. Mostly buy/restore/sell radio equipment. I mostly use either the Marconi or IFR service monitor for that. I actually haven't been at the bench since my wife closed the business in Oct. and we moved everything out here. And we have been getting the building ready to sell, too. What a supreme pain in the ass that whole process has been. I plan to get the shop cleaned up and functional again in the next couple of weeks. I miss the smell of burning resistors, and the feel of hot solder rolling off my bare leg.

With all the TEK eq you are amassing, you are quickly becoming the MHZ version of the test eq crowd; but then you do use most of it and don't just stack it up in the garage. No offense Pat. :stickpoke:

N8YX

08-10-2013, 05:28 PM

I've got a lot of mine stacked at the moment, Eddie - though it's more of a space constraint issue than anything else. Many of my power mainframes are just doing duty as storage racks. I have a TM5006 and two TM506s along with a TM501, a '502 and a few assorted TM503s/504s which can be set up on the bench as required. I may not need a full complement of video or logic test hardware during any one given week but when I do it's fairly easy to swap the stuff around from its storage spot.

A dedicated service monitor, precision RF/sweep generators with a 2GHz or more upper frequency limit, LCR/ESR/Q meter and a network analyzer with a 1GHz or more upper limit are all on the Wanted list. There's just no space to put them at the moment so I'll sit on the cash instead and wait for better lab quarters.

suddenseer

08-10-2013, 07:45 PM

I don't even own a service monitor anymore, let alone "dedicated". You da man. I was a moocher. I always had a job at a facility with loads of lab equipment to work on my stuff. I even used my company's hot air soldering equipment, would hit a .032" dot without bridging. You could open up your own business with the hobby toys that I observed.

N8YX

10-19-2013, 10:03 AM

Though it's made for mechanical measurement signal conditioning, the AF501 Bandpass Filter/Amplifier also functions nicely for general purpose AF work. Of course, you'll need two of them (along with two -0938 Calibration Fixtures, featured on the previous page) if you wish to perform simultaneous L/R channel measurements of a stereo power amplifier. An evaluation of the input amplifiers/conditioning circuitry - specifically, quantifying channel leakage and cross-mixing - would be a typical application. To do this you'll need two signal sources (SG505s or equivalent), the pair of audio notch/peak filters we're discussing here, a dual-channel 'scope and a pair of DM501As for RMS measurements. Throw in an AA501 for distortion measurements and you've eaten up two TM506 mainframes worth of space.

http://www.barrytech.com/tektronix/tektm500/tekaf501.html

10850

KG4CGC

10-19-2013, 12:20 PM

MacGyver comes to you, for advice.

N8YX

10-19-2013, 01:26 PM

MacGyver comes to you, for advice.
My advice:

Don't pay eBay prices for this stuff...especially from those test-equipment resellers who think the equipment is still worth a considerable fraction of its new price.

I just grabbed another one of the AF501 units for $125 and even then I think I overpaid for a "very rare" (hah!) unit...considering there are several listed at the moment. Naturally, as soon as I won this unit two more were listed...for higher opening figures still.

And there are a pair of TM504 power modules listed as I type this. In addition to the other modules included with each (all four slots filled) is an AF501. $300 B-I-N or Best Offer. This is a realistic price for the equipment being auctioned.

N8YX

12-15-2013, 10:28 AM

Bump.

Going to put this one out there as a reference and tale of "how to fix".

The Tek PS-5004:

11205

A '5004 is a very useful gadget to have when you're doing such things as designing or servicing comparator or threshold-detection circuits and must employ a voltage/current source with greater than 1mV/1mA resolution.

They're NOT worth the $200-500+ prices which are being asked, especially for an "as is" unit.

I took a chance on a $99/shipped offering which read "32.740" upon power-up. A normally functioning '5004 should read "0.000". when initialized.

Replacement of all electrolytic capacitors in the -25.5v, 12V, 8V and 5V internal supply circuitry was necessary. Once this was done, the supply was plugged into a TM5006 mainframe using extender cables and powered up. It worked until three transistors in the 12V control supply section decided to go up in smoke.

Replacing them fixed the smoke issue but the display read "32.740" afterwards.

Here's the tricky bit:

The device is set up with a current DAC/current comparator and a voltage DAC/voltage comparator operating in bridged mode, and the supply itself either operates in a constant voltage or constant current manner. If the 8V supply which powers these comparators fails, the output follower device is driven to the supply rail...hence the high voltage reading.

That 8V supply is an MC78L08ACG - TO-39 package. Replacing it with a TO-92 version ( 78L08 ) works just fine.

Moral of the story: If you get one of these units and find the power-up readout doing what I've described, check all supply voltages. Additionally, check the TM9914 GPIB interface IC on the Programmer Board. If it's defective it'll draw the 5V supply low and the front panel will cease to function properly.

N8YX

12-25-2013, 11:08 AM

Finding myself with a bit of spare time over the past month, I dug a little deeper into the "to-do" pile. First off was replacing the display in a DC508 counter:

11289

The OEM readout uses three Siemens DL-883A 3-digit displays - which have long since become unobtanium. One of the guys on the Yahoo Tek500 Forum made a limited run, aftermarket readout board using discrete single-digit SMD LEDs which fits both the DC508 and DC508A counters.

I HIGHLY recommend this board if you have a '508 series counter. Installation took a couple hours, mostly due to the fact that my big fingers are a little challenged in small spaces - and there isn't a lot of room to work with in those smallish modules.

FWIW, if one can find a junker DC-503 (not the -'A' variant) and one has access to an ESD-safe vacuum desoldering station, the readout board may be removed and the center display can subsequently be desoldered and used to fix your '508.

As it stands, I now have a pair of readouts with which to fix my '503s should they ever go bad.

N8YX

12-25-2013, 11:50 AM

Next up was a DC-5010 counter.

Any of the xx-5xxx series of plugins will only work in a TM-5000 series power module, owing to both the device being GPIB programmable and having slightly different rear-panel power connections than the xx-5xx modules. An older (TM-500 specific) plugin will work in a TM-5000 power module - just not the other way around.

Maybe. The DC-510 counter appears to be identical to a DC-5010 with the exception of the latter's GPIB interface board.

I got hold of this counter as part of a package deal and only recently decided to test it out. With a 1.00000KHz reference signal applied to the Channel A input, the thing would consistently read 1.13xxxxxxxKHz - and no amount of tweaking the time base frequency adjustment would change this.

The 10MHz ovenized oscillator was verified as outputting the proper waveform, and a suspect pair of ICs (74LS90 and 74LS04) in the downstream divider chain was replaced. I now had a waveform at the 'R' input to the PLL chip (MC4044B) but was it the right one? Seemed to have a lot of ringing associated with it, and the measured amplitude was rather low.

Further, the filter/comparator circuit connected to the PLL - an MC1458 dual op amp - was being driven to the positive supply rail. Its output - normally -0.5 to -8.0v - is applied to a varicap diode which in turn controls the instrument's 320MHz master oscillator. (The MO output is divided by 80 then phase-compared by the MC4044B to the 1MHz time base reference; correction is by alteration of the error voltage. The 4MHz output is then used for a multiplicity of control functions.)

Since the service manual is a little vague on waveform data I had to make a SWAG and figured the MC1458 might be shorted high. Ordered replacement parts, exchanged...nope. Hmmm...maybe the PLL chip 'R' line is shorted low and is drawing the 1MHz reference down? A check with an ohmmeter showed 35 ohms resistance; that'll do it. Desolder the suspect part - an MC4044B - then remove it.

Path from 1MHz reference oscillator feed to 'R' pin foil still shows 35 ohms relative to ground. Damn.

I checked every trace associated with the signal path and could find nothing amiss, at which time a got a pointed soldering tool and scraped between the '1MHz' and 'GND' header pins which tie the timebase and auxiliary/input boards together.

Voila. Infinite resistance.

Plopped the removed PLL IC back into place, reassembled counter...and it worked.

Moral of story: Organic (carbon based) fluxes are hygroscopic...given sufficient time and moisture draw they will become conductive if a thick enough layer is present between adjoining pins or leads.

11290

It's not as compact as a DC-508 and only covers to 350MHz but the '510/'5010 is arguably one of the best modular counters that Tek produced.

Now...let's couple it to a previously mentioned plugin:

11291

If you wire your TM5xx/TM5xxx power module a certain way - providing rear-panel "Prescale Enable" signals from DP-501 to DC510/DC5010 (or DC509/DC-5009, for that matter) you now have a two or three bay instrument capable of counting to 1.3GHz in both frequency and events domain, and the counter will indicate normal or prescaled operation by virtue of the "GHz" LED. The '510/'5010 units also incorporate math functions which the other Tek counters don't.

I managed to get another DC-5010 at a fire-sale price, and once it's checked out I'm going to look into converting it into a DC-510 - which works in my older power modules.

N8YX

12-26-2013, 11:13 AM

Here's another neato plugin, albeit one made by a company other than Tek:

11295

It's a "programmable MOS/CCD pulse driver".

Sounds convoluted?

In simplistic terms, you apply a TTL (0/+5v) signal to the Input connector and the device converts that to a signal whose logic High and Low levels are set by the bottom two concentric controls. This allows you to control a variety of logic types, depending on how the states are set. Range is +/- 15v. Thus, all major families can be driven properly.

Of course, it makes for a neato RS-232/RS-485 level converter/transmission driver. Just apply your TTL-level ASCII signals to the Input connector and connect the Output to the device under test - after setting the levels.

Transition delay (slew rate) is also adjustable from the front panel. Helpful when playing with state timing and evaluating propagation delay through an array of gates.

These plugins were originally designed to drive charge-coupled device (CCD) imaging arrays hence the flexibility when it comes to setting output parameters - especially rise and fall times.

K7SGJ

12-26-2013, 11:32 AM

N8YX

12-26-2013, 12:00 PM

Just out of curiosity, where would you plan to use this? Are you doing some R&D, or do you see an application in your repair endeavors, beyond fixing other Tek modules?
I'm going to use it (actually, 'them') as a variable level driver in R&D work.

You see, I made a guy an offer he couldn't refuse - :snicker: - and ended up with several mainframes full of those, the PI-702 Programmable Bias Supply and a PI-451A MOS/CCD driver.

All of them got checked out and calibrated...I'll keep three or four and sell the rest. Likewise with the bias supplies.

I still do a bit of CMOS/TTL engineering work and find myself needing such a beast from time to time. Tek made several pulse generators - PG501/502/503/505/507/508/5110 - and as far as I know, none will allow dynamic level conversion. The PG5110 might, but I'm not paying $1300 for one to find out. Similarly, none allow post-conversion shaping of an outputted ASCII or Baudot data stream.

There are other uses for this thing but I can see it being very handy for working with logic circuitry. Unfortunately, Tek never did make a lot of that type of equipment in the TM5xx/5xxx format. A logic analyzer/word recognizer (which I have), a digital sweep generator (ditto) and a signature analyzer (which I'm looking for) were about it. They also offer a "Setup-Hold Time Calibration Plugin" which I need to get hold of...but not for the solid-gold prices they're currently fetching. Heck, I could design and build one from scratch if I really had to have that function in the lab.

K7SGJ

12-26-2013, 12:55 PM

I wasn't aware you were doing any R&D, and that particular piece is an odd one to have around just for service work. I'm sure it can be valuable in isolating logic application problems, but for the average repair bench, you don't usually see one in the mainframe. Glad you were able to resurrect a few. I think you have the right idea of buying several pieces of what you need, fixing them up, and selling off the repaired units you don't need. If done carefully, one can equip a very nice high end bench for a very modest overall investment. That's how I always equipped my benches in the past. Of course, there are times when you have to bite the bullet and buy new, but fortunately, they are few and far between. Thanks for making these posts on your progress with the test equipment. I find it interesting as it is an area in which I have spent a lot of my time, as well.

N8YX

12-26-2013, 01:30 PM

Thanks for making these posts on your progress with the test equipment. I find it interesting as it is an area in which I have spent a lot of my time, as well.

Eddie,

I'm glad to do so - both from an "interest" standpoint and a roadmap-to-repair perspective. Many folks I know have never heard of the various Tek equipment lines and it's always enjoyable to show them how to have champagne on a beer budget.

A lot of this gear - albeit used - is much better in its designated role than just about any 'hobbyist'-grade equivalent and can often be had for the same (or less) money.

This:

11296
Plus these:

11297

can be anything you want on a bench. Only have room for one power module? Swap plugins and it becomes a scope calibration center...a TTL/CMOS design center...RF/IF/AF signal source/measurement platform, audio distortion analyzer - the possibilities are endless.

Think of this equipment as the Legos of the E-E world. True, Tek/Tegam or the other gear manufacturers didn't make high-end signal or sweep generator, vector network analyzer, LCR/Q/ESR meter or service monitor plugins for the series (and in monolithic form, those are gonna co$t me dearly!) but for the average tinkerer/hobbyist the generally available TM stuff is perfect.

N8YX

03-15-2014, 09:33 AM

Bump.

I just scored a trio of these plus an RTM-506 mainframe:

11902

A Digital Audio Corp DSP unit, RCW-320T. Multiple filtering modes - I don't know if the unit incorporates an auto-notch function like my DSP-599s do but it'll be worth checking out.

Research 'round the 'Net shows these were built under contract for the NSA and were used to process COMINT audio for recording purposes. Upper audio B/W of 7KHz - perfect for ham-station or general communications audio work.

Plans are to mount the mainframe in one of my equipment racks then feed the line-level audio of both of the co-racked Mackay Marine receivers to the processors. Two SC501 scopes will handle post-processing monitoring.

This leaves one of the units free as a spare or for use in the lab.

K7SGJ

03-15-2014, 11:38 AM