69 Fender deluxe,Problem

[ampmike]

I have a silverface deluxe that after its on 10 minutes it gets crackle and static.The caps were changed,95 %of the board caps were changed,I checked all the tubes.Taping the board,cant find this.Ill try to meter all the resisters,found one 100k that was off.When the amp get hot its does it.Its not the speaker,any help to trouble shoot.Thanks Mikey

[xtian]

Carbon comp plate resistors can cause "bacon frying" sounds. So can intermittent connections, and this can become a problem as the circuit heats up. You can divide and conquer by pulling preamp tubes to see if the problem goes away.

[Gibsonman63]

Try changing the 470ohm resistors on the power tube sockets. Those get pretty cooked over time.

[ampmike]

Thank guys,I just changed some plate resisters and Im letting things heat up.Perfect description "bacon frying" thats the sound.I got this amp on ebay when I had some money many moons ago.Its got a JBL 120.It used to sound great.It got me into the classic fender sound.Be back shortly,Mikey

[Milkmansound]

I usually go through coupling caps one by one right to left to track down this noise. Short em to ground on the low voltage AC side (not the B+ side!) until the noise stops.

I've seen this noise caused by bad contacts, bad components, bad tubes, bad lead dress... It's a common noise so you gotta narrow it down to the exact gain stage to fix it

[ampmike]

I thank you Guys for your time and advice,I may have fixed it.No problems for an hour or so.One of the tiny grounds to the brass plate off the board was out.This board flexed pretty bad over the years and may have pulled itself loose.Im going to get things back together and give it a good run,Hopfully we got it ,Thanks Mikey

[Firestorm]

I thank you Guys for your time and advice,I may have fixed it.No problems for an hour or so.One of the tiny grounds to the brass plate off the board was out.This board flexed pretty bad over the years and may have pulled itself loose.Im going to get things back together and give it a good run,Hopfully we got it ,Thanks Mikey

I saw that once on a DR. The board had warped so much it pulled the PI ground loose. That forces the PI to ground itself through the feedback resistor and the speaker. Not a lot current, but a lot of it is DC and it seems to have killed the speaker, too. Not right away, but after months and it was a good speaker.

[ampmike]

Well I got it all put back together and dragged up out of the basement.It was sounding perfect and I was in my Glory "another amp fixed" And back it comes the crappy popping and noise.My buddy is sending me some 470ohm resisters and Ill change them out and keep noodling around with this amp.
Would you guys suggest blackfacing this silverface.I have never really got to do any side by side comparison.Winter coming and I got some time on my hands and would go that route if it made a big diff in sound.I think my Gerald Webber book has a chapter on changing over to blackface specs.This amp is a 68 or 69 silverface I got off of ebay.It does have a JBL which sound pretty nice.Ive already changed a lot on the board.I dont care about resale.I would just like to get this amp sounding steller!!

[Randy Magee]

You mentioned "the basement". Would your basement be a humid environment? If so that "fish paper" board might be absorbing moisture and becoming slightly conductive subjecting the components to voltage creep on the board. I experienced this with a relatively new Victoria amp not long ago.

[ampmike]

Thanks Randy,Its a good dry finished basement,The amps are all upstairs just my bench is downstairs,I think its time to take some pictures.I have not done any resisters on the power tubes yet.It seems to be heat related after she is going a bit it craps out.I may also try what Tim said and try grounding out the orange drops and see if I can find something.I got a nice magnifying light yesterday.helps me see well.This amp is like the car you take to the shop and it works fine when your with the mechanic,you get home and Bam!
Its starts acting up Ill keep poking at it.Keeps me out of trouble.Mikey

[mhartman]

I had big pops and cracks intermittently coming from my Pro Reverb. I re-flowed the solder connections to the rectifier tube socket and it solved the problem.

[Milkmansound]

The problem with that sound is that it can be almost anything - gotta isolate it to one of the gain stages or the power supply. Once you know what neighborhood it lives in, you can hunt it down and destroy it.

Otherwise you are just firing into the dark

Get it to make the noise on the bench and start shunting those coupling caps to ground! (On the low voltage side always)

[rp]

Don't mod till you getting it working right, biased nice, with good (NOS) tubes if you got, and repairs like new filter caps have had a good while to break in. Some silver faces sound just fine, even excellent in their own right, not all but some. The Deluxes were changed the least by CBS, especially the early ones, not much to change. They went to the 5U4G I'm guessing because Mullard was shutting down and 5AR4s where going to get rare. You can't really change that either as the voltage is already high for the 6V6s, and it's just not a big deal sound wise. If yours has a lot of CBS oscillation control crap, disc caps on the output stage, nasty coils for shielding wrapped around wires etc, I would definitely try removing the crap one at a time and see if it's stable, very good chance it will be. The amp will perk up too. If there are problems you can try cleaning up the lead dress to BF style using the old Fender layout diagrams - the wire layout on those is meant to be followed and not just casually drawn. If still not happy the last thing I would hack are the post CBS brown or blue turds. There's really nothing wrong w/ them IMO. Bet you loose sweetness shotgunning with modern caps.

Again, if your SF sounds like a proper old Fender leave it alone.

[ampgeek]

Yep! Divide and conquor as the wise Milkman suggests.

Consider whipping up an amp stethoscope (I highly recommend adding a volume control right from the git-go) and putting it to good use here.

I had an old Silvertone (1400 something or other) on the bench doing just what you described. The stethoscope took me to the right stage in 10 seconds!

Ended up being something funky with the socket (old phenolic material IIRC) but I am sure that I would still be dicking around with it without that sound probe!

Cheers,
Dave O.

[ic-racer]

Looks like a lot of good suggestions. You might want to check out my success story on fixing a crackle like you are experiencing.

https://tubeamparchive.com/viewtopic.php?t=5822&start=9