NAD Fender PA 100 content

[mapleglo]

Found this on Craigslist today, a complete Fender PA 100. $260.00 for the amp and speakers.

Fender PA 100

• mapleglo
• Sep 10, 2017
• fender pa 100 tube amp vintage

Craigslist buy, a complete Fender PA 100

Fender PA 100

• mapleglo
• Sep 10, 2017
• fender tube amp vintage

Brought the PA 100 home, no room in the music room

Currently nestled in the living room. I have to make some space in the music room.

Couple of questions for those experienced with vintage tube amps. First, it's a little microphonic. Tapping on the case of the amp is heard through the speakers. New pre-amp tubes?

The cord had it's ground plug cut off - I'll have to replace the power cord.

I'll take some more detailed pictures in the next few days. The front "grille" is not original, so I'll change that. I may have a small piece of Fender style grille cloth around here somewhere.

Also, I don't think that terminal strip is original:

It might be jumped off the speaker outputs. I'll open it up to take a closer look.

Here's the tube chart:

Should I just buy all new, or start with the preamp tubes? Heh, which ones are the preamp tubes?

I know a little about amps and their innards. For example, I'd feel comfortable changing the power cord. Or, should I just bring it to a tech for a full once over?

 

[rodl2005]

Very nice. I've used one of these as a bass amp a few times over the yrs. .. they work well. I've never even seen the speaker columns ...in the flesh.
Try tapping each tube with a chopstick or similar to see which are microphonic.
Someone with knowledge of these will be along soon.
Congrats. Great pick up!

 

[coreyfyfe]

I would take it to a tech for a once over. Get the power cord sorted, check caps and supply voltages, see how that terminal strip is wired in and remove it if necessary.

These amps are good platforms for modification. Disconnect the extra channels and add them as extra gain stages for some nice overdrive.

Or leave it alone and have four channels of clean fender sound.

 

[Linnin]

That's how Leo Fender got his start, designing and building PA systems for bands. Those were pretty good little PA's in their day. Like singing through a pair of Twin Reverbs. Also great for plugging in a Fender Rhoades 77 too. Shure also made a similar tube PA called a Vocal Master.

 

[Bill Whitehurst]

Great price!
Those can work well for bass (within the limits of it's power), but not with the PA cabs.
They can be a warm and wonderful PA, but need transformers and XLR inputs for low impedence mikes.

As already pointed out, tap each tube with a wooden chop stick.
Probably only one or two microphonic ones.

 

[JTE]

If ou don't know which are power tubes and which are preamp ones, don't go messing around in the amp. Tube amps retain lethal voltages even after turned off and unplugged. If the "which are preamp tubes" was flippant and you have lots of experience with tube amps, you might be OK, but if it's true, you could kill yourself.

 

[rodl2005]

Great price!
Those can work well for bass (within the limits of it's power), but not with the PA cabs.
They can be a warm and wonderful PA, but need transformers and XLR inputs for low impedence mikes.

As already pointed out, tap each tube with a wooden chop stick.
Probably only one or two microphonic ones.

Absolutely! Whenever I used the Fender PA100 amp, it was with a couple of EV TL6O6 1x15 cabs. Sounded killer!

 

[mapleglo]

Thanks for all the comments and advise. I'll try the chop stick test and see if I can locate the microphonic tube.

 

[Passinwind]

Shure also made a similar tube PA called a Vocal Master.

Link please? Every one I've used or worked on was solid state.

 

[40Hz]

Wow! Blast from the past. Those are pretty sweet sounding heads. Works well with guitar or bass. Probably want to put a clean boost or similar preamp in front since those inputs were meant for mics. It'll be a little quiet if you don't unless they modded it internally. Which I'd guess they have based on that terminal strip acoss the back. I have zero idea what that's all about other than to say be careful around it. God know what voltages are present on those tie points. But I'd predict it's some serious AC.

If you're getting microphonics it's most likely going to one of the 6L6 power tubes. You seldom encounter that with the smaller preamp tubes.

Interesting mix of preamp tubes there. That combination of 12AX7, 12AT7, and 7025s makes me wonder which is assigned to what.

 

[mapleglo]

Interesting mix of preamp tubes there. That combination of 12AX7, 12AT7, and 7025s makes me wonder which is assigned to what.

Yes, I have to imagine that one or two are for the reverb.

 

[coreyfyfe]

Interesting mix of preamp tubes there. That combination of 12AX7, 12AT7, and 7025s makes me wonder which is assigned to what.

schematic here

half a 12AX7/channel, two 12AT7 are reverb driver and PI, half a 12AX7 recovery on the back side of the verb, most of the circuit looks like standard silverface fender fare.

 

[beans-on-toast]

A lot going on in the PA100. Converting inputs is easy, just copy what is used in Fender instrument amps. The same goes for tuning up the tone stage. As Corey said, these amps are good platforms for whatever Fender you want to make them into.

The microphonics that you are hearing could be from the reverb pan.

Invalid Link Removed

For the power cord, you can use an 18-3 rubber jacketed cord if you need a new one. Sometimes the old ones are worn out. They sell this type of cord as well as plugs at hardware stores.

 

[Linnin]

Link please? Every one I've used or worked on was solid state.

I don't have link. I remember a tube Shure Vocal Master many years ago.

 

[40Hz]

Yes, I have to imagine that one or two are for the reverb.

Yes. Those tubes are basically are all the same in function except for their gain. It's the 12AX7 that has me puzzled. The 7025s are mostly a more robust and quieter 12AX7. The 12AT7s are a lower gain 12AX7 with slightly better high freq response.

I'll have to see if a schematic is available. I'm not an electronics wonk. But I can usually at least figure out what's what with a schematic.

 

[Passinwind]

I don't have link. I remember a tube Shure Vocal Master many years ago.

You see them advertised as being all-tube fairly often. If you're thinking of one like this from the 60s or early 70s, they aren't:

 

[Linnin]

You see them advertised as being all-tube fairly often. If you're thinking of one like this from the 60s or early 70s, they aren't:

View attachment 2751099

Were there any from the 50's that pre-dated transistors?

 

[beans-on-toast]

Were there any from the 50's that pre-dated transistors?

Not that I am aware of.

Shure Vocal Master for manual and schematics.

 

[Passinwind]

Were there any from the 50's that pre-dated transistors?

As far as I can tell the first one was made in 1967. You'll also see them incorrectly attributed as being in the FOH rig at the Shea Stadium, which was in 1965: Invalid Link Removed

We had one in my old jam space in VT for quite a few years. From the back it was very easy to assume it had tubes in it, given the big silver vertical can caps and the extensive grill openings. It was actually a pretty darned advanced piece of engineering for the time in any case.

I've let a few of those PA 100 amps slip through my grasp over the years. That's a fab modding platform, IMHO.

 

[Linnin]

Thanks @Passinwind. For knowing nothing you Shure are knowledgeable.