T4B for the LA-2A, JBLpro e-sale for $89.66

[MrZpliff]

Thank's alot Charlie !

I need one shipped to Sweden, Europe.
I'll pay in advance through paypal for the T4b then
I can make another payment when you know the shipment.
i think it'll be something around 12 $, but I'm not shure.

 

[guavatone]

lets say $12 for shipping. you should receive it 4-6 days after sending item. If it ends up being less $ I will send it back to your paypal act. There will also be a small charge from JBL's shipping. We could start with a $90.00 paypal deposit per unit and handle the mailing charge when they arrive at my door.

We should use PM for the rest of these transactions to save people from viewing our conversation

PM how many you want.

 

[Bluzzi]

I just got mine here and noticed the potting around and below the edge of the casing.

Does anyone know if the potting is also all over the inside cavity?

I want to open it without ruining anything.

Jim

 

[CJ]

It might be a good idea if someone ccarefully opened one up to make sure that it isn't a vactrol switcheroo in there. I doubt it, but ehn I do not think that potting a EL panel would be asmart idea. It might be to keep light out.

 

[mesmer]

I get about five good ones for every eight I buy. JBL has really gone down hill.
Peter

 

[CJ]

Whats wrong with the rejects? Bad sound or no work at all?

 

[hejsan]

Hey, this has made me worried. I just bought a pair of NOS over ebay. The guy said he guaranteed them to work, but that it would be to much trouble for him to test them or match, so I could just get back if they had a problem or were really badly matched.

Thing is that I don't have a clue on how to test them until I have built the units, and even then it would take me a looong time to find out if it was the t4b or my soldering skills or wotnot since I have nothing to compare to...

Can anyone give instructions on how to test these, and even match them, without having a guaranteed functional la2a to put them in?

Thanks,
hejsan

 

[CJ]

Power the EL panel pins with a variac and take resistance readings off the two LDR cells.
Use 250 ma fuse.

 

[NewYorkDave]

90 bucks is still a lot of money. Is it really such a pain to make them yourself? After all, CJ created a webpage with detailed instructions.

When our local Ames was going out of business, before I even came to "Group DIY", I scapped a package of EL nightlights specifically with a homemade T4B in mind :grin:. I hope to get around to it sometime this decade...

 

[Nele]

here's some info on the packaging.
the t4b's come in boxes measuring approx. 143 mm * 86 mm * 84 mm and weigh about 140gr..

adios,
corneel

 

[hejsan]

[quote author="CJ"]Power the EL panel pins with a variac and take resistance readings off the two LDR cells.
Use 250 ma fuse.[/quote]

Thanks a bunch. Actually might I ask you to explain in a bit more detail, idiot proof style .

How do I power the pins with a variac? (I've never ever used a variac, would a signal generator work?) how much voltage? Do I open the can to do this? What should I expect to read if its ok? Is this also the way to match them?

Should I simply set my powersupply to some voltage and touch it to the leads of the El panel?

Thanks a million and sorry for all the stupid question,
Bjarni

 

[CJ]

Not stupid question, just a question, No questions = no forum.
Just wasted knowledge

The EL panel inside the case needs ac as it is kind of like a cap in construction.
If no variac, you can use wall power but be careful. Use insulated jumpers and a low amp fuse. 120 only.

You should read close to infinite ohms with no power, and maybe around 10 K ohms with power applied. Readings should be about the same if the cells are halfway matched.

 

[MrZpliff]

:?:
Is there any chance we could buy a few matched LDR's and maybe a panel & pcb from CJ ?
I'd gladly pay a few bucks for the job ! :guinness:

 

[Butterylicious]

[quote author="Nele"]here's some info on the packaging.
the t4b's come in boxes measuring approx. 143 mm * 86 mm * 84 mm and weigh about 140gr..

adios,
corneel[/quote]

So they say Urei on them. I keep seeing the same fella on evilBay selling NOS Urei T4B's for about 1.4 clams. I wonder ........ :roll:

 

[hejsan]

[quote author="CJ"]... 120 only. See if pins 2, 4, 6 and 8 are tied together using ohm meter...[/quote]
1) So, pins 2, 4, 6 and 8 _should_ be tied together?
2) Also, I have 220V in the walls, would it destroy the t4b?
3) Oh, I actually also have a step down transformer I use to power a reeltoreel I bought from the US, I guess using it's output would be a safer choise right?
4) So I just take one phase of the trafo through a fuse then to pin3 and the other phase straight to pin 6?

Thank's a bunch, beautiful illustration :grin:

 

[CJ]

thanks for reminding me!
pins 2,4, 6, and 8 get tied together on the octal socket.
they will not ohm out as a short, so don't expect it.

hold on....

ok, pins 2 and 3 are where power gets applied

read ohms off of 5 and 6,
and 7 and 8

220 could be used, i would put a 0.001 cap in series at proper voltage if using 220

 

[Bluzzi]

I need help with a final decision.

I almost have all the parts (except for the silly things I forgot like standoffs and the octal plug for T4B).

I am looking at Cayacosta's drawing and I don't need stereo strapping so my question is what wiring can I leave out? I will be wiring to XLR connectors only and not the terminals.

To me it looks like I can leave the following connections and parts out:

A10 pins 2,3,4 and 5 which go to TB1 terminal and have no other connection (not even XLR).

A24 pins 3 and 4 terminate at TB2 with no other connection.

C14, R30 and C6 that go to TB2

R3 stereo adjust pot and C13.

The above look to me to be only used by the stereo adjust circuitry. Are my assumptions correct?

I have the parts but I would rather only solder pertinent parts in the circuit.

Just double checking with you Gurus first.

Thanks.

Jim

 

[CJ]

try 0.01 insteag of .001.
.001 won't give enough current.

here:

 

[CJ]

Jim, I did this unproven schematic,

features:

1) no stereo pot and wiring

2) simplified meter sw

3)xfmr taps gone

4) no de-emphasis pot


cj

 

[Bluzzi]

CJ - (everytime I get used to your Avatar I need to re-route my brain cells again)

Thanks for posting that. Looks like the transformer wiring is what I have.
I am going to stick mostly to the original LA2A for my first venture.

You are still using a 1 meg resistor where the stereo adjust R3 was. Do I still need that? (because I noticed you removed R37 Limiter response pot as well and its a 1 mg). I want to leave that one in.

You left R30 and C6. Are they not part of the Stereo circuit?

C13 and C14 is in the Cayacosta drawing but not the schematics (yours or original).

So the transformer to XLR wiring I am confident on but I want to be sure removing the other components doesn't affect the circuit negatively.

I guess I should start to compare the various schematics and Cayacosta's wiring layout.

Jim