All things LA2a related

[AnalogPackrat]

[quote author="erland"]The capacitors that came with my kit don't match up with the parts list.

Do I use...

20 µF 500 V instead of 10 µF 450 V

33 µF 450 V instead of 30 µF 450 V

47 µF 450 V instead of 40 µF 450 V ?
[/quote]
Yes on all.

715P400V 223J 0505 - Small orange

0.022uF

715P400V 104J 0513 - Bigger orange

0.1uF

560G 100V - Small black

Probably 560pF silver mica, but you should eMail Mr. Scenaria to find out where he intends you to use it. Do you have more than one of these?

A P

 

[erland]

Thanks a lot.

[quote author="AnalogPackrat"][quote author="erland"]

560G 100V - Small black

Do you have more than one of these?

A P[/quote]

There's only one.

 

[rove]

I need to troubleshoot my bloo t4b. I am getting distortion on compression, really nasty. I ran signal thru the comp without the t4b and there was no distortion, then tried another t4b (jbl tent sale) and have been getting what I consider to be proper reaction from the comp. The questionable t4b also showed more compression on the meter ie going into compression faster, releasing more slowly. I have taken it apart and looked it over for a bad solder joint, etc and plan to go over it with the iron as my soldering skills have gotten a bit better since I built it... Any suggestions on other ways to troubleshoot it or common things that could cause such a reaction?
Thanks

 

[Greg]

hi erland:

I think 560G is 56p, not 560p. The first two digits are the value and the last is the multiplier.

56p X 10^0 = 56p

56 x 10^1 = 560p.

For my Bloo I used a 470p and a 510p Mica, exactly where they're stated in the schematic.

Here's the datasheet:
http://www.cde.com/catalogs/STD-DIPPED.pdf

And the Mouser part numbers:
470p - 5982-15-500V470
510p - 5982-15-500V510

IIRC, Steve sent me the same thing.

 

[erland]

Hey Greg,

I e-mailed Scenario and he said it was 560p. I don't think there's a 56p in the kit. Thanks though.

Can someone tell me what either V1 or V2 is? I only saw mention of V3 and V4 in the manual.

Thank you

 

[CJ]

rove, check ldr off resistance by leaving can on, measuring pins that correspond to the ldr's.

tell me how many k ohms.

maybe he had just gotten back from SxSW that day. :razz:

 

[AnalogPackrat]

[quote author="erland"]Hey Greg,

I e-mailed Scenario and he said it was 560p. I don't think there's a 56p in the kit. Thanks though.

Can someone tell me what either V1 or V2 is? I only saw mention of V3 and V4 in the manual.

Thank you[/quote]

Greg may be right on that cap value. You should measure it before installing it as an order of magnitude difference in value will be bad. Which cap did Scenaria say was 560p?

V1 is valve (tube) 1. Look at the schematic and you'll see them labelled. Three of the tubes are dual triodes so you'll see V1a and V1b for the two halves of V1. The 6AQ5 is a single pentode.

A P

 

[erland]

[quote author="AnalogPackrat"]
Which cap did Scenaria say was 560p? [/quote]

The small black one labeled "560G 100V"

[quote author="AnalogPackrat"]
V1 is valve (tube) 1. Look at the schematic and you'll see them labelled. Three of the tubes are dual triodes so you'll see V1a and V1b for the two halves of V1. The 6AQ5 is a single pentode.

A P[/quote]

Sorry. That's a little confusing for me. I'm pretty new at this. It said something like "hook up the component to pin 3 of V1".

I don't think I got a schematic. Is it separate from the manual?

Thanks,

 

[Greg]

Guess what...

I just checked my 510p and 470p and they're labeled 510 and 470 on the cap itself, respectively. So I'd assume the 560 is 560p, but I that doesn't seem like standard cap marking to me. Maybe I need to brush up on my cap reading skills. :roll:

 

[AnalogPackrat]

I've seen both ways and always measure before soldering. Standards :roll:

 

[erland]

When you measure a cap do you have to worry about it being charged afterwards?

 

[rove]

not getting any K between any pins right now. still have to run over it with the iron, looks a little sketchy in spots. Busy with work at the moment, hopefully have time to mess with it soon...
thanks.

 

[AnalogPackrat]

[quote author="erland"]When you measure a cap do you have to worry about it being charged afterwards?[/quote]

Nope. We're assuming it has not already been soldered in place. If it has, lift one leg (to isolate it from the rest of the circuit) and then measure it.

On your questions about the tube sockets...I think you need to brush up on your schematic reading skills a bit. Don't take this the wrong way--everyone has to start somewhere. Read the metas and google around for some examples. If you look carefully at the bottoms of the tube sockets you will see embossed numbers beside each pin (you may need a flashlight and/or magnifier to read them).

A P

 

[AnalogPackrat]

[quote author="rove"]not getting any K between any pins right now. still have to run over it with the iron, looks a little sketchy in spots. Busy with work at the moment, hopefully have time to mess with it soon...
thanks.[/quote]

You mean it's open (infinite resistance) or shorted (near 0 ohms on your meter)? When you made the thing did you really soak the solder into the base pins? I takes a fair amount (and a lot of heat) to get the buss wire bonded well to the hollow pin--easy to have a cold joint in there.

A P

 

[erland]

[quote author="AnalogPackrat"][quote author="erland"]When you measure a cap do you have to worry about it being charged afterwards?[/quote]

Nope. We're assuming it has not already been soldered in place. If it has, lift one leg (to isolate it from the rest of the circuit) and then measure it.

On your questions about the tube sockets...I think you need to brush up on your schematic reading skills a bit. Don't take this the wrong way--everyone has to start somewhere. Read the metas and google around for some examples. If you look carefully at the bottoms of the tube sockets you will see embossed numbers beside each pin (you may need a flashlight and/or magnifier to read them).

A P[/quote]

I agree. I don't really know how to read schematics too well.

I just didn't know if the bloo used a different schematic. I downloaded the LA-2A 1968 version and think I got the info I needed.

Thanks for your help.

 

[rove]

[quote author="AnalogPackrat"]

You mean it's open (infinite resistance) or shorted (near 0 ohms on your meter)? When you made the thing did you really soak the solder into the base pins? I takes a fair amount (and a lot of heat) to get the buss wire bonded well to the hollow pin--easy to have a cold joint in there.

A P[/quote]
It appears to be infinite. I think that will be the first thing I try is really heating up those pins and soaking them. thanks.

 

[raysolinski]

I am having a problem with my LA2 and this thread seems to be a little more active than the "new la2" thread...My unit stopped passing audio..I did all the usual checking..grounds all appear to be good (visual and meter tested for breaks)....all the tube voltages are in the ballpark except pin 5 on my 6aq which is around 130 volts tube in, I expect 100 or so) my neon lamp lights and I can zero my meter in gr mode..My voltage at pin 5 of the t4b is 8 volts...when I switch to gain mode with the meter switch the voltage at pin 5 jumps to 29 volts...I will check voltages again but I am stumped! With no input or output cables hooked up the meter will jump to the end when I turn the gain up..This guy was working great on Thursday night..compressing beautifully , meter working fine in both modes..the 6aq tube seems to be running a little hot (way hotter than the other tubes) so I only turn it on briefly for testing purposes...any insights would be greatly appreciated!

Cheers,
Ray

 

[CJ]

AP, you need to get out that house Now!

I would book a Holiday in Gatos for a week and let things drain.
OK, call me a wimp, but if you wake up in cold mud, don't say I didn't warn ya!
cj


Did you ohm out R14? :shock:

 

[AnalogPackrat]

Naah. Just 2.75" in the last 24 hours. Not that big a deal. Wind was pretty strong early this morning, though. My house is on top of the mud, so we'll just ride it down to Santa Cuz, see? We have had a good bit of rain this year--my records show 60.5" since October 1, 2005. Juicy! 45-50" is about normal up here (Oct-May). El Nino can bring 80+.

A P

 

[AnalogPackrat]

[quote author="raysolinski"]I am having a problem with my LA2 and this thread seems to be a little more active than the "new la2" thread...My unit stopped passing audio..I did all the usual checking..grounds all appear to be good (visual and meter tested for breaks)....all the tube voltages are in the ballpark except pin 5 on my 6aq which is around 130 volts tube in, I expect 100 or so) my neon lamp lights and I can zero my meter in gr mode..My voltage at pin 5 of the t4b is 8 volts...when I switch to gain mode with the meter switch the voltage at pin 5 jumps to 29 volts...I will check voltages again but I am stumped! With no input or output cables hooked up the meter will jump to the end when I turn the gain up..This guy was working great on Thursday night..compressing beautifully , meter working fine in both modes..the 6aq tube seems to be running a little hot (way hotter than the other tubes) so I only turn it on briefly for testing purposes...any insights would be greatly appreciated!

Cheers,
Ray[/quote]

Seems normal to me. Sketch out the meter circuit (R24-28, Neon, meter, etc) for both conditions of meter reading GR and meter reading output. It should become clear why the voltage at Pin 5 changes like that. The 6aq5 is working a bit, so it will get warmer than the rest. Now go smush some audio!

A P