[Boatanchors] Review on the "Isolated" Variac I bought (another long ramble)

[Phil]

First, let me say that I wanted to purchase BOTH a variac & an isolation 
transformer.  My workbench is relatively small, 48" wide and 24" deep, 
with a pegboard back for tools and an overhead shelf (with fluorescent 
lamp on the under side) that is ideal for holding test equipment.  On 
that shelf left to right is a Heathkit LG-1 Sig Gen, Heath IM-21 AC 
VTVM, Heath V-7A VTVM, Heath IT-12 Sig Tracer, Leader LSG-17 Sig Gen and 
finally TWO metered "Tekpower TP-3005D" 0-30V 5 Amp regulated Power 
Supplies.  Those Power Supplies are the latest addition to the bench and 
let me say, they are ABSOLUTELY WONDERFUL!  Separate digital meters for 
Voltage/Current, they have adjustable current limiting.  Cooling fan 
comes on when you put enough load on it to heat it up a bit. You can 
hear relays switching transformer 'taps' as you vary the output Voltage 
across it's range (that reduces the workload heat stress on the series 
pass transistors.

On a separate cart next to the bench is the B&K O'scope, 2.4GHz 
Frequency Counter, Volteq SFG2002 Function Generator (to take care of 
stuff below the range of the Heath & Leader Sig Gens). And finally a 
RadioShack 13.6V 19 Amp supply to work on larger radios.

So my bench is (Finally) pretty well equipped, the only thing that was 
really lacking was a tube tester (some day down the road) and a 
variac/Isolation transformer.
************************************

But this is REALLY about the Variac I bought, both the good and the bad!

I needed both a Variac and an Isolation Xformer, but like I said, don't 
have a big bench.  I REALLY figured that a 500va unit would be MORE than 
large enough as I DON'T do tube transmitters and such now-a-days (can't 
man-handle them, not even a boatanchor like an R-390A etc

While shopping (for new, I don't do eBay) I ran across ONE unit that 
combined BOTH an isolation Xformer AND a Variac.  It was called an 
"Isolation Variac", BUT at about 1000va it was larger and heavier than I 
really needed.  But for convenience I decided to buy it anyway.  Reviews 
indicated that it IS a TRUE ISOLATION transformer.

This is the unit I bought. . .
http://www.amazon.com/Variac-Variable-Transformer-Isolation-1000va/dp/B006NGC6HU?ie=UTF8&redirect=true&ref_=ya_st_dp_summary 


I read the reviews, both good and bad and decided to buy it anyway, 
figuring if it DID have problems I could fix it or return it.  ONE of 
the things that repeatedly came up in reviews was a "wobbly shaft and 
excessive knob height". I figured I could probably take care of that IF 
mine had those bad 'features'.  It did. . .
********************************

When it arrived I was a bit surprised, the unit is larger and HEAVIER 
than I expected (about 21 lbs).  And like others said, it "STUNK" with a 
capital S.  That doesn't bother me, a lot of the Chinese stuff I've 
bought stunk when first opened but it dissipates fairly quickly.
**********************************

Examination showed that YES, it did have a 'WOBBLY SHAFT'.  After making 
SURE that the unit was fine electrically, no sparks, or bad/bouncing 
readings when adjusting the Voltage (in other words, good contact 
between wiper and transformer windings) I then checked to make SURE that 
it is truly an 'Isolated' variac.  IT IS, there is NO continuity between 
the primary and secondary windings.  ONLY the round ground pin from the 
AC line input is fed through to the outlet.  I feel that is a GOOD  
thing as it's only a safety ground, but important.

I used my DVM to compare the actual Voltage output against that which 
the analog meter showed.  I checked it at BOTH 50 & 110 Volts output.  
As close as I could read the small analog meter the readings were DEAD 
ON accurate.  That was a surprise!

NOTE:  Some reviewers have said that the Voltage output doesn't 
correspond to the knob reading.  DUH!!  First, the arrow on the knob 
doesn't line up with '0' when it's turned all the way down. SECONDARILY, 
actual Voltage output will depend on what you put into it.  Some people 
have NO CLUE. . .
******************************

NOW TO SEE ABOUT FIXING THAT WOBBLE!
Having determined the unit is working correctly, no obvious electrical 
problems, I pulled the knob and examined the "Wiper assembly" to see why 
it wobbled (the shaft goes all the way through the unit and is visible 
from the bottom.  Appears to have a lower bearing OK.

The "wiper" is on a husky piece of plastic (think it's white Nylon).  
There are two metal inserts on that plastic thingy, and two setscrews 
that are threaded into he metal inserts.  NOT easy to get a screwdriver 
in to check their tightness.
***********************************

HERE'S HOW I FIXED THE SHAFT WOBBLE. . .

1.  I found that taking two screws out of the front panel that holds the 
meter, switch and outlet there is a nice large hole that allows access 
to the setscrews and upper shaft.  I checked, one setscrew was loose, 
the other one not as tight to the shaft as it could have been.

2.  I loosened the second screw, pushed DOWN on the wiper assembly and 
tightened the set screws.  This alone took most of the wobble out of the 
shaft, still had a little bit as it doesn't have a true bearing at the top.

3.  Examination showed that I could probably make it better though. I 
found a round piece of phenolic about 2.75 inches in diameter and 1/8 
inch thick.  I drilled a hole in the center and slid it down over the 
shaft.  This was to act as a washer or "rubbing surface" for the knob 
(there are three screws in the top, under the knob that would otherwise 
rub).

4.  I then drilled the knob shaft hole ALL the way through the knob.  
This allowed pushing the knob further down the shaft so that it was 
actually lightly rubbing on the phenolic washer. In this position the 
shaft protrudes out the top of the knob maybe 1/16th inch, perfectly 
tolerable!

5.  Checked ALL my work, VOILA!  Almost NO shaft wobble at all. 
Remounted the front meter panel with it's two screws.  While it was off 
I checked the Chinese soldering, ALL soldering looked VERY good for 
Chinese workmanship!

6.  I then checked to make SURE that there were no Voltage glitches or 
dropouts throughout the knob range, there weren't!
*********************************

OK, if I were giving this a "star rating" (5 star scale), how would I 
rate it?????????????????

As it came from the factory with the shaft wobble etc I would rate it a 
'3' as I feel that would probably affect long term reliability.

AS IT IS NOW AFTER THE MODS, IF THE FACTORY SHIPPED IT LIKE THIS I WOULD 
RATE IT A FULL '5 STARS'. . .

-- 
73 From "The Beaconeer's Lair"
Phil, KO6BB
http://www.qsl.net/ko6bb/  (Web Page)

PRESENT HF/LF RADIOS:
Grundigs: S-350 (~2006), G6 (2011) & S450DLX (2014).
HOMEBREW: 7 Tube+Rect 1v3 Regenerative RX for LF (built 2015)
Icom:    IC-735 Transceiver (~1990).
Icom:    R-75, Cascaded 250/125Hz CW-Filt, Panadapter. (~2009)
Icom:    IC-7200 Transceiver (~2015).
R-Shack: DX-380 digital portable (~1990).
SDR:     Softrock Ensemble II LF (built from a kit 2015).
Zenith:  Royal-7000 Transoceanic Portable (~1968).

ACCESSORIES: HOMEBREW LF-MF Pre-Amp, MFJ-993B HF Auto-Tuner.
              HOMEBREW 8 Hz Audio Filter.

ANTENNAS:  88 foot Long Ladder-line fed dipole, 35 feet AGL for MW/SW.
            Active Mini-Whip, 36 Feet AGL for LF/MW/SW.
            37 foot "Low Noise Vertical", 11 feet AGL for LF/MW/SW.

Merced, Central California, 37, 18, 37N   120, 30, 6W CM97rh