12 volt AC box Pal Buddy with 8950 tube *pics*

[pumphouse]

Digging thru my storage and found this Pal buddy. Fired her up and it works well. Have any of you ever owned one of these? What are its most common problems like parts going bad? Can this baby ac box be upgraded? How much do they sell for? Heres some pics:

Where is the tuning coil that supposed to be inside the box?

Any help/comments/tips would be appreciated.

Thanks!

 

[fnkycoldmedina]

the tune coil is right on the face of the thing .appears there is no load coil .
its in good shape .you gonna sell it?
should be good for about 120 peak or so.

 

[paws264]

Digging thru my storage and found this Pal buddy. Fired her up and it works well. Have any of you ever owned one of these? What are its most common problems like parts going bad? Can this baby ac box be upgraded? How much do they sell for? Heres some pics:

Where is the tuning coil that supposed to be inside the box?

Any help/comments/tips would be appreciated.

Thanks!

The parts most likely to fail are the power transistors located on the rear of the amp, they are PNP switching transistors used to supply the transformer mounted next to the tube.

The variable capacitor marked "TUNE" appears to be your Antenna Load and the Plate Tune is located on the bottom of the copper coil mounted front right.

The only "Upgrade" possible for that amp is a 2057 tube which might increase your output 50 watts or so.

That amp was designed for 4 watts AM input and it would deliver about 15db of gain to your transmitted signal.

As far as the price goes, eBay sets the going price now-adays but, the tube is probably worth $75 bucks itself.

.

 

[pumphouse]

Thanks for all the above posters help. In response to the above, its not for sale at this time. Maybe when i get her running good and get bored of her ill let her go. Meanwhile, still cant find the plate tune. Im looking inside the box and i do see that big red colored coil. its mounted to a pole that bolts to the bottom of the chassis. Does this pole slide up and down? Is this the way to tune?

Sorry dont know much about this ac stuff.....

 

[linearone]

I have always thought this little tube mobile amps were awesome. i always wanted one and still do. From what I was told you can hear the HV when you key, kinda like my big boy box. Awesome pumphouse, just plain cool
if it ever goes for sale call me.

 

[pumphouse]

I have always thought this little tube mobile amps were awesome. i always wanted one and still do. From what I was told you can hear the HV when you key, kinda like my big boy box. Awesome pumphouse, just plain cool
if it ever goes for sale call me.

Thanks for the kind words. My mini 12 volt AC box does make this very high pitch sound when keyed.....but it doesnt come thru (on air) when you are keying. Its damn neat! Radio reports come back as very clean audio. When i go barefooted, then turn it on, no difference in audio. Just in db's. If i do decide to sell, ill post here.


Now when I turn on my dave made 1x2, vs the tube, there is a big audio gain. Why is that?
Hmmmmmmm

Dave made class C dirty.....? Tube fcc type accepted box class ab-1 clean...?

Someone tell me why there is more audio gain with my dave made 1x2 vs the little tube box i have. Or is it just my imagination?

Thanks!

 

[HiDef]

Thanks for the kind words. My mini 12 volt AC box does make this very high pitch sound when keyed.....but it doesnt come thru (on air) when you are keying. Its damn neat! Radio reports come back as very clean audio. When i go barefooted, then turn it on, no difference in audio. Just in db's. If i do decide to sell, ill post here.


Now when I turn on my dave made 1x2, vs the tube, there is a big audio gain. Why is that?
Hmmmmmmm

Dave made class C dirty.....? Tube fcc type accepted box class ab-1 clean...?

Someone tell me why there is more audio gain with my dave made 1x2 vs the little tube box i have. Or is it just my imagination?

Thanks!

How are you loading the tOOb amp? It needs to be loaded for capability of max power during audio peaks.

 

[pumphouse]

How are you loading the tOOb amp? It needs to be loaded for capability of max power during audio peaks.

HiDef,

Thats what im tryin to find out....how to load and balance this amp. It looks like its set up for "automatic" use if there is such a thing.....Just one tuner and nothing to turn inside is where I stand.

Still wondering where is the internal tuner......

 

[HiDef]

Maybe you are looking for a tuned input. I don't see one. You don't always have to have one.

Are you familiar with normal tuning procedure for a linear amplifier used on AM?

 

[pumphouse]

Maybe you are looking for a tuned input. I don't see one. You don't always have to have one.

Are you familiar with normal tuning procedure for a linear amplifier used on AM?

I didnt know that you dont always have to have a tuned input. Maybe it was built this way. If so, easier to tune with one knob.

I read the tutorial here on how to tune a ac amp. Im following those instructions but only with one tuner. Is there another way to tune this one knob amp?

 

[HiDef]

Sorry. I was not looking carefully at the pictures!

There is no loading control. It's using fixed loading which is most likely done by that fat little disc ceramic cap in the pix.

Schlock design. It there's too much cap the amp will be underloaded. You could try ever so slightly compressing or stretching the coil while retuning for maximum peak power. Don't touch it when the amp is on. The plate cap on the tube should always be shorted to ground whenever you put your hands in this thing.

 

[Old Goat]

PAL BUDDY amp

ey Pumphouse GO to CB tricks that one is in plus others Schematics also RAY old goat (525)