For Those Needing Test Equipment - My eBay Picks

This is where we talk about testing, measuring and repairing things. Sometimes we have to repair the equipment we use to test, measure and repair other things. It's an endless cycle of fixing the broken things we need to fix other broken things.
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mediatechnology
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For Those Needing Test Equipment - My eBay Picks

Post by mediatechnology »

While there is certainly the Soundcard option for performing a lot of tests there's a lot to be said for older knob-based instrumentation. I got the idea to start a thread series on the test equipment of yesteryear that can be bought today at low cost.

First up is Heathkit. There are three or four pieces of Heathkit gear I recommend that people here watch out for on eBay and CraigsList. They are usually very good values and useful tools if you have a bench to equip.

1) IP-2718 +/-20V +5V tracking PSU. Adjusts down to 0V.

2) IM-5238 AC Voltmeter. Has a -70 dB lowest range and a 30 dB meter scale range in dB mode. You can measure to about -90 on it. As good a value as an HP400E and more useful. Wished it had the bandwidth limiting filter of the HP400F though.

3) IP-2717 HV PSU. 0-400V, 0-100V and filament supplies using 6L6 series pass tubes. Unfortunately most eBay sellers know what these are worth but one can sometimes be scored <$100. The iron is worth that.

4) IG-18 Audio Oscillator and later IG-5218 models. These can be modified to reach THD levels as low as -90 2nd and -100 3rd. I think TAA had a series on modifying this back in the 70s also posted here. It's a switched Wein bridge.

When searching try using the SP-2718, SM-5238, SP-2717 or SG-5218 part numbers which are the assembled versions. These are often overlooked. I'll post more equipment picks later.
Gold
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Re: For Those Needing Test Equipment - My eBay Picks

Post by Gold »

I've been getting my test bench together too. No computers for me either. I'm not familiar with the Heathkit stuff.

I love the analog AC voltmeters. I have an HP 400E and a 400EL. I bought the 400EL calibrated and I love it. The scale is in .1dB and the ballistics are smooth. The 400EL has an output which I feed to my scope. I keep them on the L/R outputs of the equipment I'm testing. Very handy.

The best deal is a Fluke 8060A. They can be had for about $75 on eaby. In addition to the normal functions it is a frequency counter and can display in dB. It has a fast processor for continuity checks. It measures to four decimal places. I have a pair of those too. That is a desert island meter.
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JR.
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Re: For Those Needing Test Equipment - My eBay Picks

Post by JR. »

Back decades ago I had a pretty effective bench based around several Heathkit pieces. The scope (kit) was the only way to get a passable O'scope for $500 odd dollars.. I managed to resolve a respectable bench THD floor by feeding the product output of my Heathkit distortion analyzer into a old used spectrum analyzer I bought for $700 back in '70s. Neither was that useful alone, but together I could see distortion down into the dirt.

Unfortunately time and use hasn't been kind to this gear,,, I already have a pot handing outside of my scope faceplate (for the trigger) and I think that may have stopped working. A few years ago when I last fired up the THD analyzer it made some bad smells and quit. I didn't abuse this gear, but I did use it a lot.. so be aware that this gear may not hold up as well are professional test equipment.

That and the remarkable value available from a lot of new gear. I love my Tek digital scope that replaced my tired old Heathkit several years back.


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mediatechnology
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Post by mediatechnology »

Heathkit did make some very affordable 'scopes. Used, on eBay, they'd be my last choice these days the reason being that Tek, Leader etc are just so cheap.

With any used Heathkit the risk is how well it was assembled to begin with. My Dad built virtually all of mine - he enjoyed building them more than I did - and his work was very good. I usually just had to plug them in, check the calibration and use them. About the only repair I've had to do was re-capping the AC voltmeter and that was only a couple of years ago at its age 25. I built the IG-18 myself and later did the Morey mods. I did recall using a Heathkit scope at some clients studios and I do recall them being a little drifty. But, as John said, for about $500 there was nothing else available. I came pretty close to buying one until the Philips came into my life. Heathkit's credit programs made a lot of gear affordable to me.

I have done pretty well with used Leader Instrument scopes. I currently have an Tek 5000-series, Philips 3212 and a Leader LBO-518. Leader are an extremely good value used and available from $50 to $200 for a decent 20-100 MHz dual/quad trace.

The one problem I've had with 70-80s era Tek scopes over the years are the attenuator modules that are these small plastic plug-in networks in the 1, 2, 5 section. They go intermittent. Still the Tek 465 is my all-around favorite.

The Philips 3212 I paid a few hundred dollars for used in the early 1980s has traveled thousands of miles with me in the trunk of the car doing studio field maintenance. That has one of the most friendly well laid-out front panels I've ever seen. The tube is on the left. Any knob you reach for (at least if you're right-handed) isn't going to block the screen. I saw one on Craigslist the other day for around $50. The only thing I had to do with mine was replace the flyback* transformer. The newer ones were unpotted and the potted one I had developed internal arcing. *(The scope can be run on DC.)

Paul mentioned the Fluke 8060. I have one of those and after it was about 5-6 years old bought a new LCD for it. Several segments started going out. Turns out the common failure with those is the glass to zebra strip conductive plastic "connector" that jumps the LCD to the board. Cleaning the glass and re-installing it did the trick. It's a common failure in the 8050 and 8060. Fluke 8050s sometimes start out on bid around $10 or so. They have a really nice dB section. The other thing to watch out for on these is LCD aging. Most are OK but I did have one not make it through UPS during the summer.

Paul - the HP400EL that you have is one of the harder to find "log" dB scale meters. That one has a linear dB scale. I have both 400F and 400FL meters and the electronics are virtually identical. Apparently they do the logging internal to the meter movement which is very surprising. There are no internal calibrations for it. I checked with Ken Kuhn of the HP Museum http://www.kennethkuhn.com/hpmuseum/ and he confirmed that it was indeed internal to the movement. About the only difference between the "L" electronics are the capacitor across the meter and the series build-out. I have a manual if you need a copy for the "F" version. The E had BNC input IIRC, went to -70 dB FS and lacked the 100 kHz filter. But I think the electronics otherwise are very close.
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Re: For Those Needing Test Equipment - My eBay Picks

Post by Gold »

Another difference between the 400E and the 400F is that the E has a 600 ohm input impedance and the F has a 1? megaohm input impedance. It makes it less useful for in circuit measurements but good sitting at the output of the DUT. I would like to pick up an FL but before I finally sprung for a calibrated 400EL I bought three ones "in good condition". I sent one out to be calibrated and was told it couldn't be. I guess it goes to show that they will work even when they are broken. Now I have the moral dilemma of getting rid of them on ebay as "working".
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