Ebay is your friend! 
All things LA2a related
- Thread starter Scenaria
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Kingston
Well-known member
Sredna said:Ebay is your friend!
yes, ebay indeed. There must be dozens of (usually Russian or Ukrainian) surplus stores, very good reliable stores all of them. Just beware of US resellers. You'll quickly find them, selling 3X the usual price, so you know to avoid them.
Kingston
Well-known member
pH said:
I used the standard chrome/silver PIO's for C2/C3/C4 (K40Y or something like that, the green ones are K42-something), and some very large brown "tub" type for the output, could have been KBG or MBG (some odd paper/PIO/aluminum hybrid).
As soon as I discovered just what these do I went nuts and modded most of my gear for them. Yes, I now have far too large caps dangerously dangling around in even in PCB's where there shouldn't be one.
PS. PIO's are no good for any "historically accurate vintage lofi" LA2A. They are a different sound and some may not even like it.
ruckus328
Well-known member
So almost done picking the parts for my build. Ordered a F&T 10uF lytics for the output, Orange Drop for the 22nF and Solen Fasts for the two .1uF's (seems that's what everyone is putting there). Curious why everyone seems to be going with those as opposed to using Orange Drops there as well though?
Think I'm gonna give 1/4W carbon comps a try on this one.
Think I'm gonna give 1/4W carbon comps a try on this one.
jyrki3101
Active member
Hi, I have to use 2 yellow leds in series for my HB VU meter backlight because I couldn't find a 6V lamp which fits in( there's only a 6.3VAC source on the Drip la2a pcb).Heater CT is connected in a DC reference circuit. So, to avoid the flickering effect on the meter backlight >
My questions are : 1. Do I have to connect the rect.diode and current limiting resistor in series or parallel with the led string?->heaterA(led+)>1N4007>R 220ohm>heaterB(led-)?
2. Is the diode connected in reverse or forward with the leds(If connected parallel with leds)?
3. Is there something else that I may have misunderstood on this?
I'd like to apologise my poor knowledge in electronics but I'd VERY much appreciate your help!!!
With Kind Regards , jyrki3101
My questions are : 1. Do I have to connect the rect.diode and current limiting resistor in series or parallel with the led string?->heaterA(led+)>1N4007>R 220ohm>heaterB(led-)?
2. Is the diode connected in reverse or forward with the leds(If connected parallel with leds)?
3. Is there something else that I may have misunderstood on this?
I'd like to apologise my poor knowledge in electronics but I'd VERY much appreciate your help!!!
With Kind Regards , jyrki3101
jyrki3101
Active member
Hi, I'm soorryy for my STUPID question if someone even understood it?.
I have asked help on this meter light problem with Drip la2a ver3 a few times,( how to power the LEDS from the 6.3VAC heater supply without a strobo effect which might happen with AC supply)
and the answer was : put a resistor and a diode across the led string!
OK, but I just wanted to have more detailed instructions 'cause I'm not a pro, and on my earlier DIY projects I have always put the diode(diodes)&resistor in series between the load&AC supply. Perhaps I just have to jump into the river and learn to swim....or trial by error!
jyrki3101
I have asked help on this meter light problem with Drip la2a ver3 a few times,( how to power the LEDS from the 6.3VAC heater supply without a strobo effect which might happen with AC supply)
and the answer was : put a resistor and a diode across the led string!
OK, but I just wanted to have more detailed instructions 'cause I'm not a pro, and on my earlier DIY projects I have always put the diode(diodes)&resistor in series between the load&AC supply. Perhaps I just have to jump into the river and learn to swim....or trial by error!
jyrki3101
ruckus328
Well-known member
OK, striking out on what to use for a power transformer for Volker's D-LA2A board. Wondering if someone can point me in the right direction?
ruckus328
Well-known member
Thanks, yea you're right I'll move it over there.
dukasound
Well-known member
Hi
As many of you know I was out of DIY pretty long time. Too, I finished my LA-2A before a 4-5 year.
After long staying I tried yesterday to test it, signal goes but I havent any compression.
Visually everything was OK but when I measured voltages I saw.
On 6AQ5:
pin 5 - 296V instead 135V
pin 6 - 5V instead 100V
pin 2 - 0V instedad 7V
I replaced tube but nothing changed.
On 12AX7 voltages are pretty OK.
Thanks in advance
Duka
As many of you know I was out of DIY pretty long time. Too, I finished my LA-2A before a 4-5 year.
After long staying I tried yesterday to test it, signal goes but I havent any compression.
Visually everything was OK but when I measured voltages I saw.
On 6AQ5:
pin 5 - 296V instead 135V
pin 6 - 5V instead 100V
pin 2 - 0V instedad 7V
I replaced tube but nothing changed.
On 12AX7 voltages are pretty OK.
Thanks in advance
Duka
dukasound
Well-known member
Nobody knows what can be problem??????dukasound said:
hi, i have a question about the 12bh7 stage:
it is said to be a cathode follower circuit, but it seems to me a little different from the classic example of cathode follower you can find in theory books or blogs, and i don't understand the role of C3..
i ask you this because i have built a bloo la2a 3 years ago with sowter iron and it worked perfectly since the first time i turned it on, no hum no fuzz and no oscillation. then i recently built another unit with jensen trafo and jensen mod and it oscillated awfully. when i compared the two units i found that in the first one i omitted to wire C3 to pin6 of 12bh7! and when i closed the defectant contact guess what happened... oscillation...
then i removed the contact between pin6 and c3 in the second unit and oscillation ceased.
finally i decided to leave the first unit without the c4 connection since it functioned perfectly for years, and to leave the connection in the second unit putting 1k grid stoppers to eliminate oscillation..
now everything works perfectly both ways, hence my former question:
what is the wiring between the anode of v2b section to the grid of v2a section supposed to do and what really does?
or in other words: the output signal to the transformer is taken from the cathode of v2b or from the anode of v2a?
i am really lost
thank you for helping me understand
paolo
it is said to be a cathode follower circuit, but it seems to me a little different from the classic example of cathode follower you can find in theory books or blogs, and i don't understand the role of C3..
i ask you this because i have built a bloo la2a 3 years ago with sowter iron and it worked perfectly since the first time i turned it on, no hum no fuzz and no oscillation. then i recently built another unit with jensen trafo and jensen mod and it oscillated awfully. when i compared the two units i found that in the first one i omitted to wire C3 to pin6 of 12bh7! and when i closed the defectant contact guess what happened... oscillation...
then i removed the contact between pin6 and c3 in the second unit and oscillation ceased.
finally i decided to leave the first unit without the c4 connection since it functioned perfectly for years, and to leave the connection in the second unit putting 1k grid stoppers to eliminate oscillation..
now everything works perfectly both ways, hence my former question:
what is the wiring between the anode of v2b section to the grid of v2a section supposed to do and what really does?
or in other words: the output signal to the transformer is taken from the cathode of v2b or from the anode of v2a?
i am really lost
thank you for helping me understand
paolo
