Finding the voltage of a light bulb

  • Thread starter Thread starter sweetbeats
  • Start date Start date
sweetbeats

sweetbeats

Reel deep thoughts...
How can you do this?

I'm thinking about chumping up and buying a full set of new meter lamp bulbs for my M-520. They are available from Parts Express in 6, 8 and 12 volt, but I don't know which ones to get for the ones in the M-520 that are driven by 6VAC. :confused:
 
It really depends on how bright you want the meters. 6 or 8-volt will work. I know a lot of people use 8v. The last ones I got from Tascam to fit the 246 Portastudio are VLL0021, MATSUSHITA LAMP 5V, 140 mA.

I don’t know of anything Tascam/TEAC that uses the 12V.

Another option is to convert the circuit to use “Super Bright” LEDs. You’ll never have to change them again. I did this on one of my M-200 series mixers and plan to do it with all my Tascam products… someday… when I have time.

The way I did it was to convert the supply to the VU lamps to DC with a small bridge rectifier from Radio Shack, and then use a separate series resistor for each LED. The resistor value will depend on the specs of the LED.
 
Last edited:
Okay...You're funny...I kinda figured they would be 6 volt but I didn't know for sure. :)

I've thought about coverting to LED's, but I am really partial to the incandescent glow, and it certainly makes sense to keep the M-520 stock sine its going to be up for sale.

Maybe I'll do it someday to the M-___ which will be easier to do since the lamps already run on DC current.

Been dealing with the LED retrofit issue for the power indicator on my Ampex 440-8...the stock incandescent power lamp is a harder to find bayonet style bulb that runs direct off the 120VAC. :eek: People have had their fuses blow big time if the filament breaks and drops across the poles in the lamp. The transport control box in which the power lamp resides along with the power cord connection has a step-down transformer and bridge rectifier for the transport electronics (24VDC) which would be a great pick-off point for an LED retrofit but the 24V rail is protected by a safety switch actuated by the takeup tension arm so when tape isn't moaded the power lamp would be off...Found a decent source for the lamps so I'm going to stay stock there too but build in some protection at the bulb holder.

LED's are to lighting as digital is to recorded audio...
 
Sweet...if the power indicator lamp on the 440-8 is the same as the one on my 440-2 machines (Part reference DS-601), I seem to recall that is actually a neon bulb. I've replaced mine before. There is a local place here that sells only light bulbs (lamps they call 'em) and batteries. Every freakin type you could imagine. Lemme know if you need a power lamp. They also have the small low voltage ones that go in the VU meters.....
 
They have the meter lamps????? Those have been unobtanium for years. I suspect they are Sylvania 24PC lamps which are a replacement for the stock lamp but have a longer body and shorter glass on them so they don't illuminate the same as the stock lamp. Not a big deal to me except that I've got a mic of good and bad bulbs and I want the meter illumnation to be consistent at least...if you have a chance can you get a reference number and price on them? 'A' and 'B' electronics used the same bulb I believe but the 'C' electronics used a different bulb...

On the power lamp, a semi-popular upgrade for the 440 transports for true production machines was a neon retrofit. I do not believe that is stock. Stock bulb is a 120MB incandescent...
 
I'll check it all when I get home tonight. I have the receipt for the bulbs stuck in a drawer here somewhere. The lamps were physically exactly the same as the ones I replaced, but that doesnt mean much on 33 year old machines.


Can you quantify the difference between the 440 A/B and 440 C lamps?
Is it voltage or size or both?

I recall having a problem with one pair of the 440-C electronics, in that the meters looked different internally. I noted the lamp housing was a bit heat distorted (melted). When I relamped both machines, one was fine but this particular machines bulbs were BRIGHT and HOT. I immediately pulled them. Some sort of voltage difference. It my #2 Ampex, so I have not jacked with it yet.
 
Looks like they're all different (the lamps) and the meters were different on the 'C' electronics compared to the A/B electronics.

A: 12v .12amp bi-pin lamps in series and then in series again with a 250ohm 5w resistor across the 39v rail source
B: 24V .073amp lamps in series across the 39v rail source
C: sylvania 1828 lamps in series with 150ohm 1/2w resistor across the 39v rail source

So I don't know off-hand at the moment what the physical differences are with the bulbs...dunno the part reference on the 'A' bulbs, can't find the part reference on the 'B' bulbs at the moment...but clearly there are amperage and voltage differences with how the electronics were setup for each version. Somebody probably put the wrong lamps in there. Duh.
 
Ok,so I checked my 440 C

The power lamp IS incandescent...a bayonet base flat top lamp. I dont know the mfg, but the base is marked 130MB

The meter lamps I have are 11/16" long, of which 1/4" is the glass portion.
I did have a note in the bag I have the spare bulbs in about 24V/ 37V but I did not remember it....

The meter bulbs are marked 327 on the base.

>> I did not find the paperwork I had on these lamps, but I will run over to the suppler at lunch and see what they want for them. Like I said before, they have like every lamp you could imagine, so if there is something esle you are looking for, or want me to send ou some lamps, PM me.

I still have the problem with my two 440 C units being different. i wonder if one is a transtional unit with 440 B meters????
 
I've heard of operators that liked the bigger 'A'/'B' meters and would retrofit them to their 'C' electronics. Maybe that's what happened to yours. Yours have the push-button monitor select switches right rather than the slide toggle-select switches of the 'A'/'B' electronics?

Those bulbs you have sound like the 24PC replacement bulbs...the metal body is longer and the glass is shorter so they illuminate differently...but wait...you said the were bayonet-base...the original lamps as well as the replacements are a bi-pin lamp...:confused:

I'm trying to figure out your issue with lamp glowing brighter in light of (pun intended) a suspected meter retrofit.
 
I've heard of operators that liked the bigger 'A'/'B' meters and would retrofit them to their 'C' electronics. Maybe that's what happened to yours. Yours have the push-button monitor select switches right rather than the slide toggle-select switches of the 'A'/'B' electronics?

>>>>Yes they are C models with the pushbutton switches. The meters look essentially the from the faceplate. They are only different from the backside

Those bulbs you have sound like the 24PC replacement bulbs...the metal body is longer and the glass is shorter so they illuminate differently...but wait...you said the were bayonet-base...the original lamps as well as the replacements are a bi-pin lamp...

>>>> The POWER LIGHT on the console is a bayonet base .
The METER LAMPS kind of look like a bullit cartridge on the bottom, with a raised rim around the edge and a contatct button in the center of the bottom. Not Bi pin....

I'm trying to figure out your issue with lamp glowing brighter in light of (pun intended) a suspected meter retrofit.

>>>> i dont think it was a retrofit...looks factory

(trying to attach a picture)
 
So, does this mean it takes three analog-heads to change a lightbulb? :p
 
Looks like this...meters are the same on both units

And yes, it takes AT LEAST three A-Heads to change a light bulb!!!
 

Attachments

  • 440c.webp
    440c.webp
    44.3 KB · Views: 87
Techno...those look SWEET!!!!! :eek:

Okay...yeah those are definitely stock 'C' electronics and meters. So maybe there is something different about the bulbs between the different levels of luminescence with yours, or maybe there is a bad series resistor...you know the drill...you could check the voltage at the lamp socket and it should be about 24VDC.

Regarding the power lamp...OHHHHkay...sorry...missed that you were talking about the power lamp when you mentioned the bayonet base. Yeah, that's the one except the part ereference should be 120MB AKAIK...maybe the 130MB is the same thing just an updated reference. So I'd be curious as to the price on one of those power indicator lamps...Allied has them in a 10-pack for about $10.

And if you're checking into that might you ask them if they have a Sylvania 24PC? That's the one for the 'B' electronics...24V with a bi-pin base...

Thanks in advance. Now I'm going to hit "Submit Reply" so I can look at that pic of your 440's again...:p:cool:
 
Techno...yer a jeanyuss!

That 130MB bulb is the same housing and amperage rating as the stock bulb, which is indeed the 120MB...difference? The 130MB is a 130v bulb, and the 120MB is a (drum roll please)..................................120v bulb! :eek::D

So I was thinking that the 130MB might actually be better because it would run a bit more dim at 120v so it wouldn't generate as much heat, plus I'm planning on putting a series resistor in there to create a little ramp-up for the bulb and further cut the power seen by the bulb bay another 20v or so...then I was noticing that both the 130MB and 120MB bulbs they got are 10,000hr. rated! :cool: That's double the life rating of the OEM spec'ed bulb...and they're basically the same price as Allied but I don't have to get 10 of them!

THEN...I stumbled on the 120MB neon bulb...you said yours were neon. I was under the impression that there was monkey-work to do to get the neon bulbs to work...but...but...its a drop in replacement? And it runs cooler? AND IT IS ONLY $0.50 MORE THAN THE INCANDESCENT??? I'll PM you.

You gotta cool bulb place in your neighborhood...

Yes that 24PC bulb is THE one...granted its a shorter glass area and some say it makes more shadows on the meter face...I'd probably like to get a couple of those and try them but that is price dependent...my current source shows they ain't cheap...looks like Bulb Town doesn't carry them?
 
I had THOUGHT mine were neon (maybe the one that I replaced was) but I do actually use the 130MB incandescent.

Those bi pin bulb are pricey. Ifit twas me ( and actually YOU are more likely to do this) I'd fabricate a replacement using an led. Since its a bi-pin base it would seem to be fairly easy to fab the pins out of the correct gauge copper wire. A cool look might be to try some different color leds....cool blue or yellow. In fact, i have seen a 440 with factory yellow lens on the VU meters...looked kinda neat.

Ok... so get one of the two phase leds....ya know the one that can produce Two colors depending how you power them...and use those. then set up the circuit so that if the channel is in Play mode, the meter is one color, and if it is in record mode, the meter is a different color.....


hehehehehehehe
 
You must log in or register to reply here.

Similar threads

B
Tascam TSR-8 set up (bias...) + Tascam 58 tension arm rollers
2
Replies
24
Views
3K
ecc83
E
P
My Tascam M-35 Restoration Project
Replies
10
Views
2K
peccary
P
RedStone
  • Sticky
A Quick Guide to Before Getting Started with Audio Production
Replies
0
Views
11K
RedStone
RedStone
sweetbeats
Tascam 238 Story #2…
2
Replies
23
Views
4K
Tape2
T
sweetbeats
Cassette Pinch Roller Carnage…
Replies
10
Views
3K
sweetbeats
sweetbeats
Back
Top