Every bench should have one

[AE1PT]

An AC line ammeter and a variac.

Back in the bad old days when I owned the TV and comm shop, I had a couple of these--one for 0-5 ACA, and another for 0-25 ACA. This is when Simpson meters were easy to find and fairly cheap. Any set or rig with PS issues was always hooked up to this and brought up slowly to observe the draw. Amazing how many fuses, regulators, transformers and other components this saved... :-D

I had wanted another for years. When I was at Dayton in 2008, there was a seller that was dumping NIB Simpson panel meters for $5 each. Jesus... I picked up a half dozen voltage and current varieties in values that I felt would come in handy later--including a 0-5 A for this particular project. Seems that it just takes a bit of time to get to things.

Anyway, all of the parts came together in the last month. A nice Budd aluminum enclosure, the meter, a couple 2 3/4" rack handles, a grounded extension cord, and a couple Heyco 7P-2 strain relief's. So here it is, and a good diagnostic tool for bringing old gear slowly back to life--or making sure that something is not drawing too much current if it has had some issues. Works with both vacuum tube and solid state gear.

I still need to add some low profile feet, and about 6-8 ounces of lead sheet on the inside bottom to give it real solidity.

Note the step bit in the picture. The people who make these things believe that they are made of precious metal given the cost they sell them for. This one, which goes up to 7/8" was $45 with tax. But they sure make a better hole than a regular drill bit, and covers about everything encountered for plugs, jacks, pots, switches, etcetera for panel and chassis builders--with a clean hole. Get one. For bigger stuff that you don't want to fiddle all day with a nibbler--bite for a couple common Greenlee large diameter knockout punches. These really seem to be made of gold these days... However, good tools are important. Spend wisely--but get the best and widest variety you can get across time. Such amenities (and essentials) add greatly to the overall bench experience. :heart:

Be sure and write down what you spend and what things are worth so that your widow doesn't get screwed when the clowns show up to buy your estate.:omg:

http://ae1pt.com/photos/imh/acammeter.jpg

[K7SGJ]

I'm taking all my stuff with me.

[kb2vxa]

A grounded extension cord? Looks more like a computer power cord with a meter in the middle. (;->) All well and good for restoration projects but an indispensable protection device when diagnosing equipment with possible shorts (electrolytics, transistors, etc.) is a series current limiting ballast, that is a simple light bulb. I really didn't care how many amps were drawn so instead of the meter was a common ceramic fixture on a 4" square box with either a 25, 60 or 100W bulb in it depending on the anticipated normal current draw. If it did the normal inrush and settle down thing OK, if the bulb went to full brilliance and stayed there it was time to look for a short, or open transistor depending on forward or reverse bias in a DC coupled chain. When the light comes on I get up with feet moving so fast they look like a blur. Betty watches in wonderment as I build my next Rube Goldberg device to locate the transistor the magic smoke leaked out of.

[AE1PT]

It is a grounded extension cord with an ammeter in the middle. Never said it was anything else. The critical part is the variac that it plugs into.

You got me to thinking, Warren. I remember one of those light bulb thingies. IIRC, it was in Emmett Clark's Fix-It Shop down on Main Street in Mayberry...

Seriously though, I have never seen one outside of a hamshack--and few of those. As far as bench service of equipment goes, most shops I worked at had one at every station. When I was certified to do warranty work in my own shop for RCA, Sony, and Hitachi--having one and a variac was part of the mandatory equipment that one had to have in the shop.

Never in a million years (even drunk) would I consider trying the light bulb trick with a Trinitron set...

[N8YX]

Don't forget the light-bulb dummy load. Comes in handy for setting your rig's power fold back adjustments. Also comes in handy in making 'DSG wonder why in the hell I'm attaching one of her bulbs to my HF set. :snicker:

[AE1PT]

Don't forget the light-bulb dummy load. Comes in handy for setting your rig's power fold back adjustments. Also comes in handy in making 'DSG wonder why in the hell I'm attaching one of her bulbs to my HF set. :snicker:

I suppose that it could--with an SWR meter inline. The only time I have needed to do this I used a tuner to present a mismatch into a dummy load and monitored the effect of adjustment at specific SWR ratios. Same thing I suppose, but instantaneous switching recovery back to nominal impedance.

Back in the old days of three letter calls, stations would put bulbs of one sort or another on their lines to observe the keying of the transmitter...

[X-Rated]

http://www.walmart.com/ip/14282370?wmlspartner=wlpa&adid=22222222227000000000&wl0=&wl1=g&wl2=&wl3=21486607510&wl4=&wl5=pla&veh=sem

WalMart has ammeters and they don't have all that added cord on them. No variac's though.

[AE1PT]

http://www.walmart.com/ip/14282370?wmlspartner=wlpa&adid=22222222227000000000&wl0=&wl1=g&wl2=&wl3=21486607510&wl4=&wl5=pla&veh=sem

WalMart has ammeters and they don't have all that added cord on them. No variac's though.

That's pretty neat because it will monitor not only amperage, but voltage as well.

One would still have to put a short extension cord between it and the variac in order to plug it in--but that would not be an issue. I do wonder though if it will run with only about 25-30VAC into it as the variac is brought up.

Good catch Jerry!

[X-Rated]

I have a cheapie Kill-a Watt at home. It is a great thing to have and check the power usage.

[kb2vxa]

"It is a grounded extension cord with an ammeter in the middle. Never said it was anything else."
Either you didn't notice my winkie or you enjoy sticking pins in my coax. (;->)

"The critical part is the variac that it plugs into."
Variac being a brand name of Staco, had quite a few different types of variable autotransformers for single and three phase power. One fairly common on the bench was an 8A single phase unit with an ammeter as a knob and the newer model has one on the front with the switch, fuse and outlet. Uh oh, the infamous Sony Trinitron. Not only the first to use phosphor stripes and a slotted shadow mask but one of the first to use an active power supply. If the AC mains dropped below 90V it stopped oscillating rendering both the variable autotransformer and lamp ballast useless. It was one of those take your best guess which component(s) to replace and pray you don't blow it up worse than it was when it came in.

Of course Emmet's shop had a light bulb ballast, Redneck engineering is tinkering together what you need out of junk on hand. They're not dumb, their motto is "if you don't have it and can't buy it, build it". He must have been awfully smart, he converted an Eico 720 into a VHF FM transceiver that worked without a mic or speaker and rigged it to communicate with Andy in the patrol car that didn't have a radio in it. Just one question, since Mayberry is in North Carolina and so is Lizard Lick why was Andy the only one with a southern accent when everyone in Lizard Lick has one? OH SNAP!

Oh yeah that light bulb that's more load than dummy. Once upon a time I was talking to a friend about 10 miles away for several minutes until he asked why my signal was lower than usual, I looked things over only to discover the "illuminated dummy load" I was testing with earlier.

I don't need a China Mart ammeter to Kill A Watt, that's what the power switch is for.

[AE1PT]

Don't scratch too deeply into the social metaphor that is Mayberry and its inhabitants. It will bleed and leave a nasty scab on the fantasy that many Americans believe post-WW II society to have been...

My "variac" is indeed a Staco--one of the old hammered green paint jewels that proudly bears the cursive inscription 'Adjust-A-Volt." It's a little 7.5A (1.05KVA) job of the 500B flavor. Just about right for whatever crosses the bench. Some times I wish I had the 10 or 15A version. The digital readouts on the new ones are pretty nice. Don't want to think about it too much--as when I get a liking stuck in my head whatever it is magically appears via the postman or UPS. :hittingself::dance:

Sony's never liked power sags. We would get sets in that nothing was wrong with except the line supply to or inside a house. But rest assured, if there was an SCR problem in the PS that did not show up as a low ohm condition under unpowered troubleshooting--it would rear it's head at about 50VAC showing ~1/4 amp draw. Change it out and all would be good. Sony and Hitachi were two of my favorites--as many issues were consistent and predictable--and complex enough that many shops would not fool with them. Having to actually repair the circuitry instead of just swapping a board did not bode well for repair production quotas. For most TV places, the idea of matching the bias on the HOT was lost. And if you did not do it, the set would be back in your hands within a week. I made a lot of money handling "dogs" in the form of high priced Japanese sets for other dealers. For a while they were my main customers...

I have heard more than a few stories from "the golden years" hams about light bulb and dummy load contacts. The best one was the old ham that showed me a burnt spot on the carpet--and how a disconnected transmitter cable loaded the rug and worked California--from Florida!

[XE1/N5AL]

Nice little ammeter project! Also, thanks for the tip on using step bits for leaving cleaner holes. The regular twist bits almost always leave a burr around the drilled hole.

I have a Variac that I bought on the cheap from eBay. It's nothing pretty: the thing looks like it pulled duty on a battlefield. But, it works great!