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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 15, 2019 2:08 am 
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Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
Hi, all:

Got the parts installed today and the news isn't good. When I turn it on with the line set fully ccw the ballast lamp is on dim all the time. Line volts read about 30 with the line pot ccw. When I try to ramp the line up to the "set" point the ballast light gets really bright, the dial gets really bright, the line pot gets fairly hot and the "R" pot gets smoking hot. For a laugh, I pulled both tubes. No help. There has to be a short on the secondary side somewhere, but troubleshooting this thing is like tracing out a bowl of spaghetti.

With nothing but a bare schematic to work from it is impossible to troubleshoot it. Need some simplified diagrams of some sort. I'm thinking this one is looking like it is time to cut my losses. With the condition of the cabinet it is probably a $100 item even if it was working. The good news is I now have 10 brake light bulbs for my 1951 GMC Pickup.

Sure did appreciate the help, guys.

Best

Mike


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 15, 2019 4:13 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3434
Location: Sunbury, Ohio 43074
Well, bummer. My schematic is crystal clear, but drawn by someone with an evil intent. It's the devil to follow, and I do not believe there was ever anything better.

Sounds like possibly the transformer could still be bad on one of the secondaries. Or a wire has a low resistance leak to something somewhere. I assumed you replaced all capacitors? When you say the "R" pot gets hot, which one is that?

As you guessed, with both tubes pulled, there's really not too much in the way of discrete components left to cause such an overload. Don't overlook a possible short due to dirt or foreign substance, or a stray screw, somewhere in there either.

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Preserving the history of electronics, one boat anchor at a time! :)
www.bbtvtestequipment.com


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 15, 2019 4:33 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 706
Location: Opelika, AL
For what it's worth, there are many commonalities to these hickok testers. I ended up with an I-177-B that had that unobtainium wirewound pot with the non-linear taper fried, and scrounged the pot out of a 530-B (I think that's what it is/was). dropped right in and everything worked perfectly. The biggest differences that I've seen are the number of different socket types, and some other fine points, like the tv7-d/u being able to check high mu tubes like 12ax7. otherwise the basic circuit is pretty similar.

If you have one with a nice looking case that looks worth salvaging, be on the lookout for other similar models that are beat up and buy them for parts. I ended up getting that 530-B paid for and shipped for less than the cost of the wirewound pot elsewhere. I was thinking I should get some resistance wire and re-wind the burnt up pot so that I'll have a spare, but I have too many other irons in the fire at the moment.

good luck!

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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 15, 2019 6:40 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 12338
Location: Mpls, Minnesota
R-7 the 3000 ohm "R" pot does not have any current across it with the 5W4 removed. If the "R" pot gets hot with the 5W4 removed the socket must be shorted connecting the plate terminals to the filament terminals. This would put R-6 and R-7 across the 160 volt plate winding.

Dave


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 15, 2019 3:59 pm 
Member

Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
Hi, All:
The "R" pot isn't bad (yet) although the wiper may need to be burnished. I put a tiny amount of oil on the rim of it so I see smoke if it gets hot, and it does indeed get hot with both tubes pulled. The problem is there is no diagram I can find of the pins on the transformer. If there was, I could do resistance measurements/unhook windings until I isolated the short. There is no sensible way to troubleshoot it without something like that to work from. The fact that it makes no difference what position the "A" "B" or "filament" switches are in makes me think it probably isn't the transformer, but more likely a wiring error by a previous servicer.

There is no one alive who dislikes being a quitter more than me. I routinely put 100 hours of labor into restoring $250 antique radios. But at least there, you can trace out wires and transformer windings. There is just no sensible way to do that here.

Maybe I'll throw it on a shelf for a while, but I have 60 radios stacked up waiting to be restored, so probably won't ever work on this again. If I do, I'll post something to this thread. Massive neck surgery next Wednesday will put me out of commission for at least 8 weeks.

Again, thanks to all who tried to help with this.

Mike


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 15, 2019 4:27 pm 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3434
Location: Sunbury, Ohio 43074
I actually have a 540 somewhere in the vastness of the shelves in the warehouse. I'll take some close up hi rez photos for you Sunday or Monday and put them up on my website. Remind me Tuesday if I forget (likely)

Barry

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Preserving the history of electronics, one boat anchor at a time! :)
www.bbtvtestequipment.com


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 Post subject: Re: Hickok 540 Fuse Lamp
PostPosted: Feb Fri 15, 2019 11:06 pm 
Member

Joined: Feb Tue 15, 2011 12:33 am
Posts: 162
Location: Columbia, MO 65202
Hi, Barry!

Thanks for the kind offer, but that is going to be like taking a photo of a bowl of black spaghetti. I'm sure it won't do me any good. Please don't go to all that trouble. I can't see where the wires go even with a bright flashlight at point blank range, and you absolutely can't get at 70% of them to do a test anyhow. I'm pretty sure this is not going to be worth the effort.

Did see a pretty nice one in working order on ebay for $275.

Thanks again.

Mike


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