Tube Noob with a few questions

jjski78 · 13th March 2012, 01:12 AM

Hello from Arkansas. For some reason beyond my comprehension, the tube bug bit me. I don't know why, all I know is I'm infected. So being the rational person I am, having never touched anything with a vacuum tube, I bought this:

eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices

I figured "it can't be that hard, it's not a lot of money, and if I can't get it to work I guess it's heavy enough to use as a boat anchor". I know it's a mono 10 watt amp but other than that I have no idea about it. I can't even find a schematic for it. I find the LJ2, 3, and 5, but no LJ4. I'm hoping, if I can get this one up and running, to buy another one and get a pair of Fostex full range speakers and have a nice little hifi rig to play my turntable through in the garage. So that said..hi, I'm Joe, I've never touched a tube amp in my life, and can't find a schematic for the one I just bought. Anyone have anywhere I should look?

Chris Daly · 13th March 2012, 01:36 AM

Hi jjski78
And you didn't see my lovely LDR preamps on eBay ! , The tubes are 5Y3GT, 6V6GT x2 and 12AX7 x2
revealed thankfully from the images, So there is your starting point to hunt down those tubes. A full restoration looks to be needed.

Cheers / Chris

Chris Hornbeck · 13th March 2012, 01:40 AM

Hello from Little Rock (which is just like Arkansas, but with bad traffic). This little guy isn't complicated enough to need a schematic, but can't hurt if you can find one. I'd recommend getting an RCA tube manual (reprints are common) and getting familiar with the type 5Y3 and 6V6 (probably the octal based tubes missing) and the 9 pin dual triodes like type 12AX7 (probably the other missing tubes).

Before firing it up, you'll want to learn about SAFETY, reforming the electrolytic capacitors, and especially SAFETY.

All good fortune, and write with more questions,
Chris

jjski78 · 13th March 2012, 01:41 AM

I already had the tube number written down, but will I have to bias the amplifier when I install the power tubes, or should I be ok as long as I get a matched set? I'm going to replace all the caps in it because I've been reading horror stories about them exploding when they get old. Don't feel like making my wife a widow just yet.

Chris Hornbeck · 13th March 2012, 01:45 AM

Quote:

Originally Posted by Chris Daly

revealed thankfully from the images

Wow. You've got a golden future in spy satellite analysis. I can't see that to save my life. Very impressed!

Thanks,
Chris

Bibliophile · 13th March 2012, 01:45 AM

Hi jjski78
Just to add to Chris' post, if you can recognise the components and with the tube data on hand, it shouldn't be too hard to trace out the schematic. It would also be a good learning experience for you.
Best of luck on your journey.

astouffer · 13th March 2012, 01:46 AM

Congrats on your first tube purchase

Don't even bother reforming caps. They're gonna go eventually so spend the extra $5 and install new ones. Its not a question of "if" they go bad its "when".

jjski78 · 13th March 2012, 01:57 AM

Quote:

Originally Posted by Chris Hornbeck

Hello from Little Rock (which is just like Arkansas, but with bad traffic). This little guy isn't complicated enough to need a schematic, but can't hurt if you can find one. I'd recommend getting an RCA tube manual (reprints are common) and getting familiar with the type 5Y3 and 6V6 (probably the octal based tubes missing) and the 9 pin dual triodes like type 12AX7 (probably the other missing tubes).

Before firing it up, you'll want to learn about SAFETY, reforming the electrolytic capacitors, and especially SAFETY.

All good fortune, and write with more questions,
Chris

LOL, I'm just north of you, I know all about the traffic. I was skimming through the RCA manual in the sticky, but it looks to be a bit too old for the tubes in this amp. Still some good info though. I do have experience with some pretty ancient technology, I'm a crew chief on the C-130 and my first bird was a '62 model. I plan on just replacing all the caps in it, just to be on the safe side. Pretty sure I can get those at Radio Shack, right?

Chris Hornbeck · 13th March 2012, 02:20 AM

Quote:

Originally Posted by jjski78

LOL, I'm just north of you, I know all about the traffic. I was skimming through the RCA manual in the sticky, but it looks to be a bit too old for the tubes in this amp. Still some good info though. I do have experience with some pretty ancient technology, I'm a crew chief on the C-130 and my first bird was a '62 model. I plan on just replacing all the caps in it, just to be on the safe side. Pretty sure I can get those at Radio Shack, right?

You're a Zoomy! Thank you for your service.

First plane I ever rode in was a C130, and it was old in 1968. We AFROTC kids were riding up to Griffiss AFB for the day, hanging in the straps on the sides. Pilot walks back, says he can't get the blankety-blank landing gear down, we're low on fuel, yada yada. He opens a door in the floor, climbs down, there's a sound of banging, he climbs up, we land. Most fun I had in the 60's.

Thanks,
Chris

Eli Duttman · 13th March 2012, 03:07 AM

Tracing out the schematic is definitely a good idea. You rate to find the O/P tubes are self (cathode) biased and no adjustment is needed.

13th March 2012, 01:12 AM	#1
jjski78 diyAudio Member Join Date: Mar 2012 Location: Austin, AR	Tube Noob with a few questions Hello from Arkansas. For some reason beyond my comprehension, the tube bug bit me. I don't know why, all I know is I'm infected. So being the rational person I am, having never touched anything with a vacuum tube, I bought this: eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices I figured "it can't be that hard, it's not a lot of money, and if I can't get it to work I guess it's heavy enough to use as a boat anchor". I know it's a mono 10 watt amp but other than that I have no idea about it. I can't even find a schematic for it. I find the LJ2, 3, and 5, but no LJ4. I'm hoping, if I can get this one up and running, to buy another one and get a pair of Fostex full range speakers and have a nice little hifi rig to play my turntable through in the garage. So that said..hi, I'm Joe, I've never touched a tube amp in my life, and can't find a schematic for the one I just bought. Anyone have anywhere I should look?

13th March 2012, 03:07 AM	#10
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	Tracing out the schematic is definitely a good idea. You rate to find the O/P tubes are self (cathode) biased and no adjustment is needed. __________________ Eli D.

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13th March 2012, 01:36 AM	#2
Chris Daly diyAudio Member Join Date: Sep 2004 Location: hobart tasmania	Hi jjski78 And you didn't see my lovely LDR preamps on eBay ! , The tubes are 5Y3GT, 6V6GT x2 and 12AX7 x2 revealed thankfully from the images, So there is your starting point to hunt down those tubes. A full restoration looks to be needed. Cheers / Chris

13th March 2012, 01:40 AM	#3
Chris Hornbeck diyAudio Member Join Date: May 2011 Location: Little Rock	Hello from Little Rock (which is just like Arkansas, but with bad traffic). This little guy isn't complicated enough to need a schematic, but can't hurt if you can find one. I'd recommend getting an RCA tube manual (reprints are common) and getting familiar with the type 5Y3 and 6V6 (probably the octal based tubes missing) and the 9 pin dual triodes like type 12AX7 (probably the other missing tubes). Before firing it up, you'll want to learn about SAFETY, reforming the electrolytic capacitors, and especially SAFETY. All good fortune, and write with more questions, Chris

13th March 2012, 01:41 AM	#4
jjski78 diyAudio Member Join Date: Mar 2012 Location: Austin, AR	I already had the tube number written down, but will I have to bias the amplifier when I install the power tubes, or should I be ok as long as I get a matched set? I'm going to replace all the caps in it because I've been reading horror stories about them exploding when they get old. Don't feel like making my wife a widow just yet.

13th March 2012, 01:45 AM	#6
Bibliophile diyAudio Member Join Date: Nov 2011	Hi jjski78 Just to add to Chris' post, if you can recognise the components and with the tube data on hand, it shouldn't be too hard to trace out the schematic. It would also be a good learning experience for you. Best of luck on your journey.

13th March 2012, 01:46 AM	#7
astouffer diyAudio Member Join Date: Jun 2004 Location: Pittsburgh, crumbling wasteland	Congrats on your first tube purchase Don't even bother reforming caps. They're gonna go eventually so spend the extra $5 and install new ones. Its not a question of "if" they go bad its "when".