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HELP! Alamo Scematics

MapleFlame

Well-known member
Joined
Jul 3, 2005
Messages
14,044
I do believe you are right about Lectrolab building my Capitol amp. However, it doesn't match any Lectrolab schematic or tube complement.
The Capitol has six 6EU7 tubes, four 7591 tubes and a GZ34 rectifier. It is a stereo amp with two output transformers. It is cathode biased, has a tube tremolo (cap and resistor network), grid leak bias for the input triodes, and a cathodyne phase inverter. The transformers are labeled "Tranco" and are dated to 1961. It has two Jensen C12R speakers that also date to 1961. My amp cabinet is also made of real wood, not press board like most other Lectrolabs.

Sound Projects Co.
 

j45

Active member
Joined
Jun 14, 2002
Messages
9,081
You really don't need a schematic to work on an amp. :rolleyes: This sounds like a puss-out. I enjoyed your bet of being able to fix it, and personally, I'd like to see what you can do.

Get an RCA handbook and compare voltages to what you find in the amp. Dump a seperate preamp signal into the power section to quickly see if the problem is with that satellite tone section. Prior to digging in, you need to trust most wax caps will be drifted while drop-style caps will probably be OK. Most of the resistors are probably OK. Cap values shouldn't be much of a mystery.

I don't know anything about amps other than how to turn them on a play but this looks pretty intimidating to try and tackle without a schematic. It may not be as bad as it looks to a good tech, maybe it's because it's a lot more stuff crammed in than I'm used to seeing and I don't know what I'm looking at. Let's just say it looks nothing at all like the simple layout in the amp that Diablo1 posted. I still haven't had the chance to get a gut shot pic but will get to it after my weekend work ends.
 

Wally

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Joined
Feb 27, 2003
Messages
3,535
THanks for the 'push' to get j45 to let me work on that amp, Diablo. However, my amp doesn't have its original PT, so I could not be sure that my voltages would be 'correct'. In any case, unless one runs a VAriac or some sort of voltage control, these old amps are not functioning at 'correct' votlages anyway. And....lowering voltages for these vintage amps makes a world of difference in how they sound, ime.
So, j45, my amp's resitors and caps have readble values on them...but that is the extent of my being able to ascertain 'original' specs. The PT that is there is huge and has a homemade bracket supporting it. A different PT might be one thing on the list in putting this one back into action...although it was working when I pulled the speaker for a recone....and a recap for the circuit.
j45, if you have the orignal PT, it would be of great interst to know the specs on that one...or to have it here side by side with my amp in order that both of them could return to 'original' specs.
IF anyone ever takes measurements of the voltage on that PT....without tubes installed., that would be of great interest to me.
 

valcotone

Member
Joined
May 8, 2002
Messages
431
Here's a photo of an Alamo 6 I saved from somewhere a few years ago.... maybe it will help while J45 gets some shots of his. I almost bought one of these and would love a chance to hear one in person some day.


1952-Alamo-model-6-amp.jpg
 

MapleFlame

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Joined
Jul 3, 2005
Messages
14,044
Thanks for posting pics.
#1 Get some electronics cleaner spray and spray the hell out of it or use an air compressor and blow all the dust out. Dust/cat hair etc... in these amps with spaghetti wire mess will be greatly affected.
#2 Far right is the electrolytics, replace them.
#3 All those other caps, diodes, etc.. just need to be checked to see if they are still in spec. Any good amp tech can figure out Power section etc... and do a process of elimination to find where things are at.
 

Brown Recluse

Active member
Joined
Aug 11, 2006
Messages
1,108
Kerry, I just spoke with my friend and amp guy, Skip Simmons. He doesn't have a schematic for the Model 6 Alamo, however, he said that he has worked on a couple of them and did use the term "rat's nest" when describing them. You might contact him about having your amp serviced. He is located here in Northern California.
 

j45

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Jun 14, 2002
Messages
9,081
Kerry, I just spoke with my friend and amp guy, Skip Simmons. He doesn't have a schematic for the Model 6 Alamo, however, he said that he has worked on a couple of them and did use the term "rat's nest" when describing them. You might contact him about having your amp serviced. He is located here in Northern California.

This is awesome...yes I'd love to contact him if you would tell me how. I'll ship them in a heartbeat.
 

j45

Active member
Joined
Jun 14, 2002
Messages
9,081
Here's a photo of an Alamo 6 I saved from somewhere a few years ago.... maybe it will help while J45 gets some shots of his. I almost bought one of these and would love a chance to hear one in person some day.


1952-Alamo-model-6-amp.jpg

!!! This looks like both of my amps. Identical in all ways as far as I can see. If I'm not mistaken the speaker is not a field coil like it appears to be.... I believe that's the output tranny mounted on the side. Anybody know? Thanks for the pic. I almost have to wonder if this may not be one of mine before I got it. Can't be that many around, especially this clean. I recall perfectly that I was in absolute heaven that last day I was playing mine. I was deep in a zone just digging how awesome the sound was when my "good one" failed. These photos really inspire me to get mine going again. These are just killer amps. Thanks again for the pics!
 

cryptozoo

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Joined
Jun 25, 2008
Messages
2,738
Puss-out? Maybe.
If it was my amp, I'd have a go at it for sure. I just think Wally is a safer bet because he has a working amp and knows the cap and resistor values by either measuring or reading the codes/labels. He also can measure the voltages at every socket pin on his working amp, so he can quickly tell where the problems are in the one that needs repair. What if it needs a new PT? Wally can figure out the requirements based on his working amp. How the heck could I possibly guess the right B+ voltage to spec? Sure I could get a transformer that would work, but I couldn't match an unknown B+.

That was sarcasm from the start, sorry it went over your head -- why anyone would blindly ship an amp to a stranger on the internet who bets they can 'fix it' because they got lucky on theirs is beyond me. :ha

http://www.skipsimmonsamps.com/
Skip Simmons Amp Repair
4824 Bevan Road
Loma Rica, CA 95901
530-771-7345 • 707.678.5705
skip@skipsimmonsamps.com
 

Diablo1

New member
Joined
Jan 20, 2008
Messages
597
That was sarcasm from the start, sorry it went over your head -- why anyone would blindly ship an amp to a stranger on the internet who bets they can 'fix it' because they got lucky on theirs is beyond me. :ha

http://www.skipsimmonsamps.com/
Skip Simmons Amp Repair
4824 Bevan Road
Loma Rica, CA 95901
530-771-7345 • 707.678.5705
skip@skipsimmonsamps.com

Sarcasm is hard to pick up on the internet. You don't know me and I don't know you. That's sounds like a good deal for me. You don't know what skills I have or don't have, but you have a business fixing amps, so I'm certain that an amateur like me rubs you the wrong way....good. The only reason I started into amp repairs/building as a hobby is because I have an amp that I took to three professionals, and none of them fixed it, but they did charge me, and tell me, "nothing is wrong". They weren't crooks, just incompetent or too lazy to do the job right. I did my research on the internet, studied the schematic, and learned exactly how every circuit worked on that amp. I also found out the common failure points for the amp. Then I fixed it. I checked the value of every resistor and cap to make certain they were within spec or replaced. The amp sounds good as new, and I've owned it since new 42 years ago. I didn't get lucky, I'm persistent and know that the information is available to fix or build nearly anything if you have some intelligence and can read.....it's an engineer thing.
 

Brown Recluse

Active member
Joined
Aug 11, 2006
Messages
1,108
Sarcasm is hard to pick up on the internet. You don't know me and I don't know you. That's sounds like a good deal for me. You don't know what skills I have or don't have, but you have a business fixing amps, so I'm certain that an amateur like me rubs you the wrong way....good. The only reason I started into amp repairs/building as a hobby is because I have an amp that I took to three professionals, and none of them fixed it, but they did charge me, and tell me, "nothing is wrong". They weren't crooks, just incompetent or too lazy to do the job right. I did my research on the internet, studied the schematic, and learned exactly how every circuit worked on that amp. I also found out the common failure points for the amp. Then I fixed it. I checked the value of every resistor and cap to make certain they were within spec or replaced. The amp sounds good as new, and I've owned it since new 42 years ago. I didn't get lucky, I'm persistent and know that the information is available to fix or build nearly anything if you have some intelligence and can read.....it's an engineer thing.

Diablo1, I don't know if cryptozoo has an amplifier repair business, however, I just wanted to make it clear that he isn't Skip Simmons.
 

MikeSlub

Administrator
Joined
Jul 15, 2001
Messages
15,166
!!! This looks like both of my amps. Identical in all ways as far as I can see. If I'm not mistaken the speaker is not a field coil like it appears to be.... I believe that's the output tranny mounted on the side. Anybody know? Thanks for the pic. I almost have to wonder if this may not be one of mine before I got it. Can't be that many around, especially this clean. I recall perfectly that I was in absolute heaven that last day I was playing mine. I was deep in a zone just digging how awesome the sound was when my "good one" failed. These photos really inspire me to get mine going again. These are just killer amps. Thanks again for the pics!

Yes, that is an output tranny mounted on the speaker. Not a field coil. :2zone
 

Diablo1

New member
Joined
Jan 20, 2008
Messages
597
Diablo1, I don't know if cryptozoo has an amplifier repair business, however, I just wanted to make it clear that he isn't Skip Simmons.

Thanks Brown Recluse. You're right, I thought that was Skip Simmons posting from the ad in the signature. I owe an apology to Skip for my wrong assumption.
 

Patrick Ginnaty

Well-known member
Joined
Dec 15, 2001
Messages
1,498
Sorry to go a wee bit off topic, but I *just* got my Alamo Twin Ten back yesterday. The tech had to draw his own schematic to figure it out.

What a tone monster.
 

latestarter

Well-known member
Joined
Nov 9, 2009
Messages
4,173
wow, looks great with the pine cab. crypto, not everyone is a crook man. chill sometimes.
 
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