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The Dim Bulb Tester says "No"

chadbang

chadbang

Well-Known Member
Oh well, there goes my dream of the easy life with my new Fisher 500-B. After the prerequiste clean up, a little baking (thanks, Larry) and building my first Dim Bulb Tester the moment of truth arrived last night. I put a 30 watt bulb in the Dim Bulb Tester and flicked on the 500-B --- very bright bulb that stayed on for the five seconds before I turned it off again. RATS! It would have been great for a little gas to be left in the tank, but no luck.

The only replacement part I had purchased was to get rid of the selenium rect. which I replaced. My soldering skills are rudimentary at best, and its a pretty big part -- easy to remove and replace (it has to be my soldering iron that sucks -- a $20 Weller -- why do I have such a struggle soldering?). So out went the selenium rect. and in when the Radio Shack silicon.

Still the bulb says: "No."

That little bast__d bulb!

I did have fun building the tester. But now I'm depressed because those kinds of things are my previous electronics masterpieces. I look at all the caps and transistors under that Fisher cabinet and throw up my hands.

Any suggestions for my next step? My tools include a very large magnifying glass, a digital multimeter and a tongue prone to cursing. I do want to repair it, though. DIY is important to me, since money is not in abundance. And finding this amp was a gift, as with the price of gear this Fisher seems like my best bet for getting into the tube sound.

Thanks!
 
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30W??? TOO SMALL! You want a bulb of a size at least 50-60% of the total current draw printed on the back (in watts). So if it's 250W on the back of the unit, use between a 100W and a 150W bulb! You want the bulb to almost flash at 1st and then dim down within a couple seconds. The 30W bulb might as well be connected directly to the wall socket. a 30W is good for a flea amp, that draws 50-80W. But not the 500B.
 
larryderouin said:
30W??? TOO SMALL! You want a bulb of a size at least 50-60% of the total current draw printed on the back (in watts). So if it's 250W on the back of the unit, use between a 100W and a 150W bulb! You want the bulb to almost flash at 1st and then dim down within a couple seconds. The 30W bulb might as well be connected directly to the wall socket. a 30W is good for a flea amp, that draws 50-80W. But not the 500B.
Click to expand...

Really?! Maybe there's hope yet! Let me go check!
 
Bummer. I went up to a hundred watt bulb and it flashed on brightly then went down only slightly in brightness. Nothing really dimmed about it. Almost as if it was plugged in regularly. Must be a short.
 
As long as it dimmed some, means you need a larger bulb. Go down to a hardware store "Ace", True value, etc. anything but Home Depot or one of the big box stores and get a 150w bulb. I get mine at the Supermarket, believe it or not. You may end up having to go to a 200W. What's the back of the 800-B say. (It should be right around the serial # on the top of the chassis. 110-120V @50/60Hz XXXWatts. It may be as high as 275-300.
 
chadbang said:
Bummer. I went up to a hundred watt bulb and it flashed on brightly then went down only slightly in brightness. Nothing really dimmed about it. Almost as if it was plugged in regularly. Must be a short.
Click to expand...

That's a good sign! Looking like a police search light after 10 seconds is a short, you're good.
 
larryderouin said:
As long as it dimmed some, means you need a larger bulb. Go down to a hardware store "Ace", True value, etc. anything but Home Depot or one of the big box stores and get a 150w bulb. I get mine at the Supermarket, believe it or not. You may end up having to go to a 200W. What's the back of the 800-B say. (It should be right around the serial # on the top of the chassis. 110-120V @50/60Hz XXXWatts. It may be as high as 275-300.
Click to expand...

Hi Larry! :banana:
The old numbers are almost impossible to find now thanks to the new gubment rules and "we know what's best for you" regulations. So now, a 60 watt bulb is a 57 watter and a 100 watt bulb is a 97 watter if I remember correctly; it's been a while since I bought any 100 watters. At least that's the way it is around here. It changes from week to week, who they get them from, but I just stocked up on some name brand (General Electric) bulbs at the .99 Cent Store. 4 bulbs for just .99 cents plus tax!
I'm starting to hoard them a bit; our local ACE does have bulbs labeled 100 watts but they cost like blue smoke! (more than a dollar EACH!) Only difference between the bulbs at ACE and the ones at the .99 cent store is the paper packaging. The one dollar each bulbs have more descriptive language on them and prettier graphics with a bunch of lifetime data and charts and other mumbo jumbo.
They're all made in Mexico.
The best bulbs we were getting at the .99 Cent Store were Sylvanias and Tungsrams made in Hungary. That was a while back and those still had the more traditional ratings, 25 - 40 - 60 - 100 etc. Interesting too to note that the Tungsram bulbs were labeled Tungsram U.S.A. a division of General Electric, Made in Hungary. Guess G.E. bought what was left of that company. They are well made and last a long long time. Sad that that is probably all that's left of the once great company that made all those vacuum tubes! :no:
We tried those crappy "green" fluorescent squiggly bulbs that have to warm up. The local power company was pushing them and selling them for only .49 cents each, a taxpayer subsidized discount price to help push people into making the switch, again available at the .99 Cent Store.
So we gave them a try and installed 8 of them in our bathrooms.
They really really sucked. Took for ever to warm up and throw off any kind of light and 2 out of 4 of them over my vanity failed within a couple of months.
That was all I needed; I'm all for the incandescent scene baby, for life! :banana:
Plus I did some research and unless you buy the really expensive ones, those squiggly bulbs seem to be causing quit a few house fires! And they're all made in china! :no: Plus, to add insult to injury, you are supposed to dispose of them at a recycle! I think they contain mercury.
The ones we bought were from an "approved" brand? :saywhat:
After that waste of time and money, I bought 8 globe type bulbs for both our bathrooms about 4 years ago. There are 4 bulbs per fixture. They get heavy use every day. They are 60 watt bulbs and made in Canada. They were expensive and all that our store had left. The date on the packaging was 2004. They are still going strong with no fade or dimming.
https://www.acehomecenters.net/products/bulb-glb-60g25-w-ace|3020070.html
I bet you they are made in china now.
I still want to know how these are any less good for Mother Earth than those mercury filed pieces of crap we had to throw away after just 2 months. The squigglys DID have some sort of ridiculously good "warrantee" but I would have had to box them up and MAIL THEM to some address in California for a "free" replacement.
What a joke! :bs:
With the incandescent bulbs I'm DONE with what I have to do, the lights in the bathroom have been switched off and I'm on my way in about the same time it took those ridiculous "green" bulbs" just to warm up.........and then you still can't see anything!
Nuts!

Phyllis
:)
 
Turn off the lights. If it drops ever so slightly, you're good.

My father-in-law dropped by a while back while I was working on one of my 800-c's. He was a master electrician in the navy and he said he used to use DBT's all the time. I was testing my unit and I really didn't see anything change of any significance and he told me to turn off the lights. If it went from bright to even slightly dim and stayed there, he said it was good: no shorts.

I wouldn't worry about it .
 
Only in the "PEOPLES REPUBLIK of KALIFORNICKA" where every aspect of life is regulated to death! Speaking of, I heard you have to apply for a "LAST Breath and Sinus rhythm" before you allowed to kick the bucket. There's no fee, but the Excise taxes to bury you in YUCCA Mtn set you back $10,000. And the casket has to be of Natural materials with no products known to the PRK to cause cancer or birth defects.

Back here in "The land of Pleasant Living" we can still get honest to (what ever sentient being floats your ARK! Wouldn't want to offend the sensibilities of some) GE, Sylvania, and Tungsram bulbs. But you have to know where they are! Hehehehe!

Notdigital. The slight dimming is ok for gross shorts, but you need a larger wattage bulb to get more voltage to do some testing that requires more than 60-70V (which is about what you probably had at the primary on the 800C. And there is some testing that needs to be done on a dbt before doing it on the wall to "tease the dragon" so to speak. for example, Adjusting the bias pots while under a DBT to check response is safer it than on the wall. When done "teasing the dragon" put the pot(s) back where they were or all the way down. (NEW POTS REPLACEMENT or circuit modifications mainly). Then fire up on the wall and you can bring up the bias to the correct point assured that it will respond correctly. I you left the pot at the "correct on the DBT" spot, when you switched to wall voltage, the bias would be too hot and blow the tube or turn on the output transistors hard and blow them. So you back them all the way down and then fire it up.

A gross drop that is easily noticed is better for a new guy who has no experience. As he gains experience, sure, he can go to a smaller bulb for primary shorts testing as long as he understands the premise and function of the DBT.

Larry
 
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Thanks again for your tips, guys. You're right. I didn't see a single 150 or 200 watt bulb at the store yesterday. I can't believe the day has come that lightbulbs are becoming unobtanium! The good thing about this is that the more I poke under the hood, the less strange and frightening it looks. I went in with my camera today and starting taking some snaps. Okay, now this can't be right! Are these the elephant man components?!

P11108024_zpse3a3a989.jpg
 
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Thats part of the Multiplexer. Leave alone or you WILL have definate problems with FM STEREO!
 
You're right L. I gross test during the initial fire up then rarely do after that. I stare at a mod for as long as it took to wire it up making absolutely certain everything is on the up and up. I guess once you develop that "mechanics touch" you're comfortable shortcutting. :yes:
 
Cheater way for getting around not being able to get a big bulb is to either run multiple sockets in parallel and just screw in more bulbs as needed, or find yourself an outdoor floodlight. Most of those can be found up to 150w. Heat lamps also are high wattage. The cheap way is multiple sockets with 60w bulbs though. High power lamps aren't cheap.
 
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