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 Post subject: Hickok 540 Fuse Lamp
PostPosted: Feb Thu 07, 2019 7:26 pm 
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Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
Hi, All:

Can anyone tell me what the fuse lamp should be for a Hickok 540 Tube tester?

Thanks!

Mike


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Thu 07, 2019 10:49 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12354
Location: Mpls, Minnesota
Trade Number 81, 6.6 Watts Miniature Incandescent Bulb, G6, Single Contact Bayonet (BA15s)
Try to get an american made bulb, the imported ones sometimes do not work properly.
Dave


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Thu 07, 2019 11:05 pm 
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Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
Hi, Dave:

Just in case you are a Hickok guy, I just bought this tester with a collection from a guy in Mississippi. Apparently someone tried an incorrect lamp and the line adjust pot is fried. Looking like a $40 pot and I am not sure where to get one. Is this tube tester even worth working on? If so, do you have any idea where I might find this pot? It is 200 ohm, .358 amp, which comes out to 25 Watts, I think.

Thanks for the lamp info. Might order some, or not, depending what you have to say.

Mike


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 08, 2019 4:43 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12354
Location: Mpls, Minnesota
This is a good tester for pre-war tubes, if you are going to be working on newer radios you will need a different tester. You can find rheostats for $16 shipped,

Dave


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 08, 2019 12:44 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3493
Location: Sunbury, Ohio 43074
Mike, it's unlikely bordering on impossible that the wrong 81 bulb contributed to the fried line adjust rheostat. I'd look for another issue that caused this, although a mechanical problem with the rheostat is certainly possible. Are you quite sure it's fried? Not a common happening......

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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 08, 2019 1:35 pm 
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Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
Hi, Barry:

Yep. Melted windings, the whole bit. C1 had wax running out the end of it which I presumed was from storage in a hot place. One wire running to the pot from line was also burned. I found the pot for 23 bucks and ordered it, but I'm wondering now if I have a shorted primary winding. All I have is the schematic in the owner's manual. I'll try today to figure it out from that. Any idea where I might obtain service literature?

I mostly work on pre-war, but I have a Triplett 3444 that catches anything newer. As I said in a previous post, this came with a collection I bought. The collection also had 5000 ish tubes, mostly untested pulls, and a couple of tube testers. I was hoping to fix these up and train a couple of friends to use them to help me get through those, and then sell the other 2 tube testers.

Thanks for the help. I'll be back in a few days when the parts arrive.

Mike


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 08, 2019 1:54 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3493
Location: Sunbury, Ohio 43074
Check out the manual for the 550, or navy model OZ-1. I cannot find anything on the 540 but the 550 looks very close. I've got the 550 manual but it's just an ops manual with schematic, no other information on troubleshooting or calibration.

If the line adjust rheostat is cooked, it almost has to be a bad transformer, although I suppose a dead short rectifier could do it too if someone bypassed the fuse lamp. You could possibly substitute a 100 watt light bulb for the rheostat and plug it in ... not likely you can harm anything else at this point. Bring the unit up on a variac. If the bulb starts to glow even halfway bright, something is drawing way too much load. I cannot locate the rated wattage of the 540 or 550 but I'd think 50 watts should be way more than enough. You could probably come close in estimating by calculating the filament load of all the tubes when warm. Then add a fudge factor ... but with no tube under test, the unit should not be drawing much current other than the filaments plus a little bit.

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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 08, 2019 2:37 pm 
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Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
The schematic says right on it that the schematic for the 540 and 550 are the same, except you need an additional sheet for the 550. Couldn't find any service manuals online with a quick search, but this will be a moot point if the transformer is fried.


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 08, 2019 8:28 pm 
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Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
Hi, Barry:

Well, I think I am the victim of what one of my former employers called work-on-it-itis. On my schematic neutral is shown going to the normally open side of the line test switch and the wiper of the rheostat. In my set it goes straight to the center pin of the fuse lamp socket. Hopefully it is safe to assume the schematic is correct, so I am going to rewire that. The primary winding doesn't seem to be dead shorted. If I am following the incorrect wiring correctly, I think I am reading 13 ohms. Does that seem like a reasonable reading?

Haven't tried to rig up your light bulb test yet, but after I get the wiring to what I think is correct, I will give it a try.

Thanks!

Mike


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Sat 09, 2019 4:52 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3493
Location: Sunbury, Ohio 43074
Let's hope the schematic is correct. In this era of equipment, that cannot always be counted on. If it looks like someone may have "adjusted" the wiring however, that could explain the melted rheostat. Is it by any chance hooked up across the AC line at the moment? (never hurts to ask)

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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Sat 09, 2019 6:27 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12354
Location: Mpls, Minnesota
Here is a clip from the 540 schematic. The 540 has a voltmeter in addition to the merit meter. R-14 is the line adjust pot.
Attachment:
540 line adj.jpg
540 line adj.jpg [ 12.42 KiB | Viewed 264 times ]


Dave


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Sat 09, 2019 4:25 pm 
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Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
For sure the power cord had been replaced. I couldn't be absolutely sure if the rest of it had been molested or not, but it didn't stick out like a sore thumb. Dave's clip of the line adjust ckt is the same as on my schematic. As I worked out the wiring, it appears that in my set the fuse lamp was wired ahead of the line adjust pot instead of after it. I'm beginning to suspect it might have been a production change, but I can't find anything online to verify that. There was no way to just move the wiring around to put it like it is on the schematic. I had to open the lacing on the harness to move the wires around. In any case, I now have it wired like the schematic and I'm waiting for the pot and lamps.

My main question is the same, though. Does either of you think 13 ohms is roughly correct for the resistance of the primary winding?

Thanks!

Mike


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Sat 09, 2019 6:45 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3493
Location: Sunbury, Ohio 43074
Hi mike. Your power transformer resistance measurement......I have no idea. If I remember tomorrow I will check mine. If I can find it lol

However a resistance check probably won’t indicate a shorted turn, which of course can cause massive current draw

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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Sun 10, 2019 1:27 am 
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Joined: Feb Fri 13, 2009 5:09 am
Posts: 508
Location: Santa Clara, CA
If you needed a reason to get it fixed up, one would be the cool back-lit meter face...the plastic meter body was cast such that the background of the meter face was able to be painted with silver light-blocking paint, and the numerals and graduations (and the logo!) were left transparent, to be backed by a red or green filter, depending on location. The numerals have a pleasing white, red or green glow against the opaque silver background, and it almost makes me want to test tubes in a dimly-lit room!


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Sun 10, 2019 2:34 pm 
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Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
Hi, Barry:

Don't go to a lot of trouble. I already ordered the parts. I'll put them in and ramp it up with a variac.

Bob, thanks for the eloquent plea to save the thing. It's really ugly on the outside as the previous owner peeled all the vinyl off, so the pretty meter incentive helped me feel a little better about throwing money at it.

Hopefully parts by Tuesday.

Mike


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Wed 13, 2019 11:45 pm 
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Joined: Feb Fri 13, 2009 5:09 am
Posts: 508
Location: Santa Clara, CA
I dragged my 540 out last night and tried to take some pictures of what I liked about the meter treatment. The "Hickok" logo is red, like the "Replace" indicator, but it washed out a bit in the photo.


Attachments:
HickokDk.jpg
HickokDk.jpg [ 87.46 KiB | Viewed 184 times ]
HickokLt.jpg
HickokLt.jpg [ 52.3 KiB | Viewed 184 times ]
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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Thu 14, 2019 3:17 am 
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Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
Hi, Bob!

Yes, the picture in the dark is indeed very pleasing. I'm excited to fix mine now and test some tubes in the dark:)

So while you have that out, if you would unplug it, turn the power switch on, put an ohmmeter across the 2 pins on the power plug and rotate the line adjust to the lowest ohms you can get, that should pretty much be my primary resistance. (I can easily measure the lamp and subtract that.)

I sure would appreciate it, as I suspect the 13 ohms I am reading on mine is about 1/10 of what it should be. Would you mind doing that for me?

Thanks!

Mike


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Thu 14, 2019 7:44 am 
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Joined: Feb Fri 13, 2009 5:09 am
Posts: 508
Location: Santa Clara, CA
Well, first I'm afraid I need to beg your pardon, when I pulled the Hickok out to perform the test you asked, I noticed it was a 530, and not a 540...at one point, I had two of these testers, and thought they were both 540's. One used the center indication on the meter for Line Test (as seen in the picture), and the other had a small outboard voltmeter mounted at the top-left corner of the case, at the upper end of the storage compartment. Maybe that one was a 540, but I think I sold it a few years ago.

At any rate, figuring that they were probably similar enough, I tried measuring the transformer primary per your instructions, but I couldn't get my multimeter (a trusty Triplett 640) to settle down, so I think I may have had a flaky power cord connection to the plug or something. So I opened it up and connected directly to the primary lugs on the transformer, and did indeed measure 13 ohms. I think your transformer primary is therefore probably good. Hope this helps!


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Thu 14, 2019 3:37 pm 
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Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
Outstanding!!!
Thank you for the extra work! My 540 does, indeed have the outboard meter. Hoping for the pot to arrive today. Still have to figure out why it burned up in the first place.


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Thu 14, 2019 4:21 pm 
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Joined: Feb Fri 13, 2009 5:09 am
Posts: 508
Location: Santa Clara, CA
I forgot to mention, there was a bunch of wax dribbles clinging to the bottom of my transformer, as I think you mentioned was on yours. Mine us still fully functional, no funny smells or anything, so I think it's probably not an issue.


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