I have an Oliver Amp

[JustMike]

 The owner said it's been sitting in a barn for 10-15 years. And I believe it. I sat it on my bench a few days ago and a little pile of wood dust(?) appeared next to it-TERMITES?  I had never heard of Oliver amps before, but I now know that Oliver was the guy at Ampeg and he started his own company in the '60's. This amp has no markings on it. It looks to be a dual channel bass amp and I'll let the pics explain the rest. Then you'll know as much or more than I do about this amp.
 Due to the condition, I'm tempted to just replace ALL of the components sans Iron, Jacks & pots. What say you?

[JustMike]

The face.

[acheld]

I'm by far no expert, but if this amp has value as an original -- and I would bet it does -- I'd change only what is needed to make it work. 

This old gal has a soul!  LOL, at least it looks like she does.

[PRR]

> -TERMITES?  ..... I'm tempted to just replace ALL of the components sans Iron, Jacks & pots. What say you?

Do NOT wholesale "sans Jacks and pots"!! Jacks and pots are most likely to be feeling their age. Then you really may as well start from scratch.

I do not see much there which I would call "sick". Dirty, rusty, dusty, sure. But that often works fine. Good odds something has died; that's how things end up in barns. But it may be anything, or even nothing (it was really a bad cord and the owner never did figure it out).

Out in the driveway on a long cord. Big bottles out. Start your videocam. Plug in. Smoke? Fire? Post the movie. Nothing? Do the preamp tubes light? Add rectifier, plug in again. Now you may have exploding capacitors. Still OK? Try the power tubes and a guitar.

I don't know where you live. IMHO termites are unlikely but we had a dozen types of beetles which frassed both trees and house-joists. Most soon die in a heated building. Or at least they take >>160 years to chew-up a log.

[Latole]

Amp may need new filter caps.

[sluckey]

I sat it on my bench a few days ago and a little pile of wood dust(?) appeared next to it-TERMITES?

More likely powderpost beetles.

[JustMike]

The barn is in central FL (Lakeland).

[acheld]

Cool.

But, nuttin that 350VAC won't take care of . . .

or some gas.   

[thetragichero]

i feel like i saw one of these on craigslist in sebastien and just never pulled the trigger

[Willabe]

Cool.

But, nuttin that 350VAC won't take care of . . .

or some gas.

 

[JustMike]

i feel like i saw one of these on craigslist in sebastien and just never pulled the trigger

 Probably not the same one. I'm originally from Melbourne BTW. This guy has been in Lakeland a long time and he said it's been sitting in his barn for many years. Looks like rats got to one of the caps too.

[JustMike]

 I haven't been able to find a schematic that matches this amp-at least based on the 60u filter caps I have that I believe to be original. I think the model is an Oliver B-150. These blue caps need to be replaced judging by the little bumps on the positive side of all 4 of them. I found some Sprague atoms that are roughly the same FF, but man, are they proud of them! Also, the aluminum can cap in this thing appears to be a 80u@450/2u (!!)@350/20u@450...2u? I'm relatively new at this, but this value seems very odd to me.

[thetragichero]

may have to do a bit of tracing in the power supply. i avoid the atoms because besides being quite spendy, they're much larger than they need to be. i've been using some of the mod electronics caps from antique electronic supply because they're decently-priced and in values that aren't as common anymore (multiples of 10). plus they've got a clear label over the bare metal can so they just *look* vintage

this has a lot of information but doesn't look like a schematic for your particular amp: http://www.tubebooks.org/file_downloads/oliver_amps.pdf

[sluckey]

May be your amp...

     https://el34world.com/charts/Schematics/files/Ampeg/Ampeg_oliver_b_122.pdf

[Latole]

Oliver amps story;

https://www.vintageguitar.com/1906/oliver-sound-inc/

Some more schematic here; scroll down to see Oliver

https://www.vintage-blue.com/schematics.html

[Latole]

Some more pictures of Oliver amp with new filters caps and more ?

[JustMike]

I wonder how the "anti hum" switch is used in that one, since it was originally a polarity switch with the death cap (which is that .047 on the little bias board). Looks like they added a trim pot to the fixed bias ckt too.

[HotBluePlates]

... I'm tempted to just replace ALL of the components ...

Check out Mr Calson's Lab on YouTube.  He typically calls the red "Tiny Chief" caps "Tiny Grief" because they are generally found to be leaking d.c.  Much like Yellow Astron or non-Difilm Sprague Bumblebee caps are generally found to be leaking d.c.

You might get lucky and have some that are good, but assume you need to check at least all the coupling caps (though we generally assume that all electrolytics need checking/replacing).

[JustMike]

I replaced all of the .1 caps and checked the Tiny Chiefs as I did so. They were all reading at least .125µ. I used orange drops. I also ordered some Sprague Atom replacements for the 60u's. The can cap is an enigma to me. 80/20u is what's being used and it looks like an original (soldering looks original) but the value doesn't make sense to me. 80u right off the 5AR4,  Isn't that too much? Also, the rectifier wiring has my cackles up. The HV sec windings go to pins 8&2, but the B+ comes off of pin 2 (red wire going to 1k10w resistor). Shouldn't it come from pin 8? It looks like original wiring.

[JustMike]

After studying the circuit a little more, it's making more sense to me. BUT the 80/20 cap doesn't. These values are for the PI and the final preamp nodes. All of the Oliver schematics I've looked at that are tube rectified show these nodes as 40u each. But there is no exact schemo for this one that I can find. I believe it is the B150 "Piggyback head". Can someone explain why 80/20u values are used here? I have the proper value can cap to replace, but I just want to know why these values were used.

[thetragichero]

that's what someone had kicking about in their drawer?

[PRR]

Agree that "stock part" may be compelling in production. A 80+20u cap might be the whole filter in a dual-6V6 record player, and thus be a common and competitively-priced part.

The 60+20 (=15u) as first cap is more curious. However we see similar stacks in Ampegs. Why ask why? There was probably a whole sheet of scratch-paper with caps, series values, and distributor prices, figuring the cheapest way to get a minimum uFd and 500V or 500V rating from only <450V parts.

[JustMike]

 Update- She's recapped, retubed, rebiased and up and running. But there's a substantial background hiss-not ridiculous, but I think it's more prominent that it should be. And I wouldn't describe it as snap crackle pop. It's more like a smooth white noise. Is this the plate resistors? or just all of the CC resistors in general?

[thetragichero]

could be sum-of-all parts thing. swapping out every resistor before the input stage grid should provide the biggest improvement i would think