1953 alamo help needed-where to get caps? or even find the same ones?

Igneous

Silver Supporting Member
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1,962
Okay, my alamo sounds so insanely good but now, some of those beautifully bubbly caps are making a lot of noise. I think the filter cap should go first. Can anyone help me find out what caps I need for this baby?

Thanks for your time-Chris
 

RiftAmps

Member
Messages
207
OK, I can't find a schematic so you'll have to do it the old fashioned way and pull the chassis from the cabinet and take some detailed photos.

It looks like it has a dual-section capacitor can which would be the main filter cap/s. Other than that those turquoise caps are probably .022uf, .047uf and .100uf in varying quantities. All of those values are readily available.
 

Bruce Gerard

Member
Messages
136
Be sure to check every resistor for tolerance - check them when you have the cap associated with it (if there is one) removed from the circuit. If any of the brown bodied carbon composition resistors have a "crusty" appearance, (like the finish on them is failing) then replacing them is a good idea. IRC made resistors that get "crusty" looking, and they can significantly drift in value due to age.
 

Igneous

Silver Supporting Member
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1,962
60 cycle like mad! I tap the big filter cap(safely) and it crackles. But the amp sounds stellar once played. Just crazy hum. I actually replaced the power cable with a three pronged one, hum was the same but tone was off. I put the dangerous one back on. lol Anyway, here are some shots of my actual amp. Its a mess but she sure sounds purdy...
 

Bruce Gerard

Member
Messages
136
I can pretty much assure you of 2 things -

1) All of the capacitors in that amp are leaking and about 55 years past their prime

2) Changing the power cable to a grounded one has nothing to do with the voicing of the amplifier.


Not sure you are aware of it, but there is a twist lock can that contains the 3 primary filter capacitors for the power supply. If there is a nasty hum ( even if the volume is turned all the way down) then it's likely that this cap has dried out.
 

Igneous

Silver Supporting Member
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1,962
lol yup. Thats exactly the hum when the volume is down too. Twist lock can?
 

Igneous

Silver Supporting Member
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1,962
Oh, it must be on the other side. Im going to open it up and get in the other side. Be back with photos. It's a good place to start.
Thanks!'
 

Bruce Gerard

Member
Messages
136
The can has 3 separate capacitors wound inside it. The case of the can is a common negative connection for all 3 caps. The caps positive terminals are clustered on the base of the can. They are usually identified by little geometric shapes cut into the phenolic wafer that insulates the terminals from the can body. The phenolic wafer is crimped into the base of the can. Shapes will be triangle, square, crescent, or blank (not cut) to designate what each terminal does. The small cans had 3 metal mounting tabs on the base, and the larger cans had 4 mounting tabs. The tabs fit into thin slots punched directly into the chassis metal, or into an adapter plate (like yours) riveted or screwed to the chassis. After the can was inserted into position the tabs of the can were twisted with pliers to lock the can into place. ( hence the name twist-lock ) They were fast & easy to install, space saving, and much more rugged than axial designs. They were also expensive - so manufacturers eventually got away from them. Also, if one section goes bad, you either have to replace the entire can, or jimmy up a substitute capacitor somewhere else in the chassis (if there is room) Cans are difficult to find now, and they are costly. the smaller cans like yours has are extinct. You will likely be better off getting some terminal strips and hanging axials between them to make up the can. You could also opt to drill out the rivets on the adapter plate, remove the can, and install a newer "LCR" type can and clamp. All of the caps in your amp are larger physically than the new offerings from manufacturers today, so don't be alarmed if the new replacements don't look the same size. For replacements of the coupling caps, just get the yellow axial mylar or poly capacitors that are available everywhere. You can replace the coupling caps with ones of a high voltage rating, but not of a lower rating. Anymore, I just buy caps rated for 630 volts unless there is not room for them to be used . I like to get them from Justradios.com - great prices. Don't worry about exotic capacitors, they are a complete waster of money in an amp like this one (and in most cases a wast of money - period ) Also - try to find some fiberglass sleeving for the leads of new parts. Old timers called it "spaghetti" - motor rewind shops have all sorts of fiberglass sleeving - just call one and see if they will sell you a few feet of it. The size would be for 22 gauge wire.
 
Last edited:

zenas

Member
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8,866
You might try www.tubesandmore.com They sell new cap cans if you're lucky they'll have the one need or close enough.
If not and your cap is the larger diameter one you can stuff new small caps inside. That's a pain to do though.
On that amp I'd probably just put a board on the back side of the chassis like a Fender.

The nonelectrolytics might still be fine but I wouldn't to suprised to find a few of those leaking.
 

damian1

Member
Messages
615
I wouldn't touch any of the non electrolytic caps until you've replaced the electrolytic caps and listened to it
 

Igneous

Silver Supporting Member
Messages
1,962
Ok, I got to the can. I need to find a twist lock that is 10/10/10 450vdc but can only find 20/20/20 . You're right! Anyway, I also just got new tubes and a cap to replace that big yellow one as well as reinstall the 3 pronged cord.

I'll get back to ya to let you know if anything changes without getting to that can and changing that. If anyone has any vintage can superpowers and can assist in locating one by all means please!
Cheers-
 

Igneous

Silver Supporting Member
Messages
1,962
eureka! I replaced the big yellow cap for a Mallory- (still waiting on the cans, I found a couple used ones on ebay) BUT HOLYCOW! I have NEVER had such a quiet amp. And all from just making the one swap. It is DEAD quiet and working like it just rolled off the line. I lost my phone but I can take video later and show you. Thanks for all the help. Oh, and I put the 3 pronged cord and attached the ground to the transformer. woohoo! Cant wait to go home and play it again!
 






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