Crate 5212 Tube Amp Picking up 90.7 FM

[Joe "JJ"]

I recently purchased a Crate 5212 Tube Amp used. Supposedly it worked
fine before I purchased it. But when I plugged it in, I picked up
90.7 FM radio station. It had some other issues as well, so the first
step was to replace all the tubes.

I replaced the power tubes with a matched set of 4 JJ EL-84's (Like
the originals); and a matched set of 4 12AX7's. Pretty much all the
other issues went away, but I am still picking up the radio station.
Sometimes it is so clear I might as well have my radio turned on.

Any suggestions?

Thanks,
Joe

[woodw...@aol.com]

Does it now play any blues songs?What kind of songs does it play now that the radio comes thru it?

I recently purchased a Crate 5212 Tube Amp used.  Supposedly it worked
fine before I purchased it.  But when I plugged it in, I picked up
90.7 FM radio station.  It had some other issues as well, so the first
step was to replace all the tubes.

I replaced the power tubes with a matched set of  4 JJ EL-84's (Like
the originals); and a matched set of 4 12AX7's.  Pretty much all the
other issues went away, but I am still picking up the radio station.
Sometimes it is so clear I might as well have my radio turned on.

Any suggestions?

Thanks,
Joe

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[Sacca, Robert]

Check inside. Maybe someone left an old transistor radio in there.

Seriously, I had a Fender Vibrolux Reverb back in the sixties & it occasionally would pick up radio stations.

I had it checked out & it was suggested that I replace the power transformer.

Sure enough, the problem went away.

I would recommend you take it to an amp tech & get it checked out before you replace anything.

 

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	Robert Sacca Associate
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[Joe's Mail]

No just christian music.  the only station i can get is 90.7 FM which is a local christian station.  Sorry about that!

[Joe's Mail]

Thanks Robert,
I have actually been suspecting the PT, but felt I needed a little more input before doing that.  I have checked the input and the output voltages of the PT, and the output is a bit low, but I wasn't sure it was low enough to merit replacement.
Joe

[woodw...@aol.com]

I was just teasing. I'm glad you get some Christian music.

[GBrag]

I don't doubt what you are hearing, but you are likely to be hearing
some sort of rebroadcast or and AM station partner to the FM station.
FM is much more complex than AM and it is very unlikely the stars
could line up, even in a defective amp circuit, to pick off that kind
of radio station. It would take virtually two different and perfect
failures. AM however is cake to detect, ... happens all the time.
(along with CB and HAM radio signals.) My guess it is most likely a
tube, and most likely a non power tube ... the weak radio signal has
to be amplified and would take some gain stages. I suggest you swap
some like-for-like tubes around (like a two different 12ax7s, etc.) If
it is not a tube you can probably isolate which circuit it is by
selecting different channels or plugging in things in the effects loop
to eliminate the early preamp stages, That is if the amp has an
effects loop or aux/preamp input, I did not check. Also, I have had
this happen with pedals or active circuits in guitars. Do you have
pedals attached, or a battery powered guitar? Take them out if you do
and see what happens. The combination of the new amp and the other
device could be just right to demodulate the signal.

On the other hand, if you like the music, consider it a "feature".

[Clay Smith]

Joe;

   This is either your guitar cord, or poor shielding in the input section of the amp. Never heard of it being in the PT.

       C.K.

 

From: the-am...@googlegroups.com [mailto:the-am...@googlegroups.com] On Behalf Of woodw...@aol.com

Sent: Thursday, December 08, 2011 1:14 PM
To: the-am...@googlegroups.com

[Dave King]

Agree with that it has to be like a broken shield on a wire but will be somewhere in front of the preamp section.
Tubes have internal shields to ground so they won't cause this but a wire connection or solder joint or bad
sockets or even the jack can and will.

Dave

[Joe's Mail]

Hi Clay,
Thanks for your input.  It must be shielding then, because I have ruled out the cord.   When you say the input section, are you referring to the 1/4" plug, or the circuitry driving the input?

I sincerely appreciate your help.

Joe

[Garry McNab]

Move the amp to a different room in the house. Try a different guitar. The
first suspect should be a bad cord, then a bad guitar jack, then a bad amp
input jack. I doubt it's anything after the input jack.

----- Original Message -----
From: "Joe "JJ"" <ifcta...@gmail.com>
To: "The Amp Guide" <the-am...@googlegroups.com>
Sent: Thursday, December 08, 2011 11:08 AM
Subject: [The Amp Guide] Crate 5212 Tube Amp Picking up 90.7 FM

[Buzzwazz]

Is it possibly coming from unshielded guitar electronics? Obviously amp picking up stray RF somewhere...is he close to a transmitter?

I was playing a high gain amp once at rehesrsal studio not far from airport towr and would pick up pilot tramsmissions now and then...

-Sent using 100% recycled electrons

[Clay Smith]

The input jack`s wire isn`t always shielded( like a guitar cable) with the shield soldered to ground, goes to the grid #1 pin on a 12ax7.

There wouldn`t be this cable on a PC built amp.

My amps at times will pickup RF when I use a high gain pedal. I have to use two cables.(antenna)

Move the amp to another location. See if it still happens.

But again this is in the first stage ,or second stage of the amp. That always leaves your guitar.

Do you have another to switch out?

Try it.

          C.K.

P.S. Antennas are tuned for RF by the length of a wire.

[Joe's Mail]

Hi Clay,
When I completely unplug the guitar and cable from the amp I still get the radio station.  In fact this AM it was so clear you'd have thought it was a radio.

Moving it around in the room does have some effect but not much (Room is 14'x15').  I have moved it all around the room, plugged it into different plugs,  swapped cables, swapped guitars, all to minimal avail.  No change with guitar swap, but there does seem to be some improvement with a cable change, but it is so negligible that it may just be  my imagination. 

You may be on to something though with the input jack, because I notice when I unplug the cable from the amp, I get a louder than normal hum/buzz/static through the speakers.  I have also noticed a lot of static noise when I touch the amp.  (I have two other tube amps and I do not get a noise when I unplug them, or touch them; nor do I get the annoying radio station.)  That tells me there is probably a grounding problem somewhere in the input circuit, but as of yet I haven't found it. 

Are you suggesting I run another ground from chassis to pin #1 on the 12AX7?  Please tell me more.

I actually thought when I first got the amp and connected my pedals that they were the problem, but lo they are not.

Again, thanks for all your help, I really appreciate you taking the time to assist.
Joe

[Joe's Mail]

Hi Gary,
Thanks for your response! I have done all the things you suggest,
except replace the input jack on the amp. Someone else suggested it
might be a grounding problem in the input circuit and suggested adding a
ground wire from pin #1 of the 12AX7 to chassis ground. What's your
thought on that?

Thanks again,
Joe

[Mike Satterlee]

Hey, Re the Crate amp radio issue. I have 3 of the Crate Stealth tube amps, that all would mysteriosly lose power after a short duration, bought new tubes(JJs) ,but the problem remained. I found a link that suggested running a cable in the effects loop(1/4" from input to output), tried it and it eliminated the problem. Apparently, the effects loop is the last circuit adjoining the speaker output on Crate amps, might have oxidation or intermittent connection of the circuit at that point or could be a receiver of RFI. Just a thought. Mike

---

From: Joe's Mail <ifcta...@gmail.com>

To: the-am...@googlegroups.com
Sent: Fri, December 9, 2011 9:05:35 AM

[Garry McNab]

Good one Mike.

[Joe's Mail]

The 5212 only has an effects loop input, no output.  Plugging my guitar into the effects loop does however solve the problem.  The moment I unplug from the effects loop input, the radio station comes back.  So is is a safe bet to think that the effects loop is the problem?
Joe

[Clay Smith]

Joe;

   The shield on any input cable goes to ground, not pin#1.That`s the conductor. Do not connect the shield to pin#1.

You may need to replace the input jack.

I`ll see if I can find a  schematic for the crate.

C.K.

[Joe's Mail]

Hi Clay,  thanks for the advice.  I actually have the schematics.  Crate sent them to me a week or so ago.  Took so coaxing, but they did it.

I discovered that the effects loop ties into the rest of the circuitry through a 4 wire jumper, which was completely unshielded, so I took some electrical tape and wrapped both ends of the jumper good.  That helped.  I then wrapped electrical tape over the input jack and the effects loop jack.  By doing that, now, the only time I hear the radio station is if I turn the volume all the way up , which I don't do because of the size of the room.  So, although the problem is still there, I have quietened it to the point that it is now tolerable for me.

Since this amp is old and obviously somewhat abused it is very possible the input jack needs replacing, probably the effects loop as well, but I suspect I will sell it before I do those things.

Thanks again for all your help.
Joe

[Mike Satterlee]

Thanks, Crate Stealth was an all tube(4-6V6s, 3-12AX7s) designed by Lee Jackson(Rivera, Metaltronics, Ampeg)50 watts, made in USA,great amp for low bucks. Try one, if you like high gain, distortion channel mix type circuits. I'm a drummer, got about 22 tube amps, mostly Fenders, one Traynor YGM 3, Mesa, Peavey Delta Blues- old black tolex- 2-10s and the Crates. I dig 'em all. Mike

---

From: Garry McNab <ggm...@telus.net>
To: the-am...@googlegroups.com
Sent: Fri, December 9, 2011 9:39:17 AM

[Clay Smith]

Joe ;

   You can purchase 1”copper foil with glue on one side , and if you can solder a wire to it, you can ground shield the wires you taped. The end of the wire can be secured behind any jack, thus grounding it.

[Joe's Mail]

Thanks Clay, I will try that.