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Deluxe Reverb Clone crackling

GOLDENSTRAT

Member
Messages
966
Have a used Mojo kit deluxe reverb clone amp for almost a year now, it has been working pretty well, have been through some tubes. Don't know about the bias setting.

Just the past 2 weeks have been getting crackling on the amp at loud volume as I hit E or D chords - crackling starts when strings are hit, goes away quickly until next "strum".

Don't have a amp tech anymore so trying hard myself.

Did a bunch o' research today about "crackling" on the TGP, so I bought some Deoxit D5 at radio shack, did that dance, retensioned the rectifier and power tube sockets per BillM's website, then resoldered the V2, power and rectifier tube sockets (don't use V1 tube).
Tried different cords, guitars, speakers, hit the speaker plug with Deoxit, tried the chop stick poke around deal.

No progress, still crackles.

Any other suggestions other than do it all again?

thanks a bunch, Fred
 
Messages
42
If you don't have a wooden dowel about a foot long for troubleshooting by all means get one. Great for tapping around the circuit to induce sounds so you can find the source of pops, crackles, etc.
 

GOLDENSTRAT

Member
Messages
966
Thanks Ht, Did that, tried different power tubes, did a musical chairs with pre amp tubes......
I will keep poking I guess.
 
Messages
42
Thanks Ht, Did that, tried different power tubes, did a musical chairs with pre amp tubes......
I will keep poking I guess.
If you have a bad component or poor solder joint, a good tap should get it to respond. I'd focus first on dc supply voltage stuff first. Plate load resistors, etc.
 

GOLDENSTRAT

Member
Messages
966
Ok, amp is outta chassis, plugged in , turned on, guitar plugged in, etc.

By poking with stick, I can get a small ungrounded type of sound out of pin# 7 on V2 and V4. sound goes away once I move stick away. Kinda like letting go of guitar strings makes a bit more hum through amp.

On the first power tube pin#1 moves up and down slightly but makes no noise.

The amp so far has not crackled either, so the crackle might be speaker induced vibration.

Put it back together, crackles right away.
 
Last edited:

GOLDENSTRAT

Member
Messages
966
If i wiggle power tube #2 (next to rectifier) when it is running, it glows more red as does power tube #1 at that moment and crackles more.

Pin 5 moves the most 9but just a bit) when i wiggle the tube but nothing looks like it
moves enough to touch or short or break contact - does the wiggle indicate a faulty tube socket?

The screen resistors across pins 4 and 6 are white plastic blocks marked 471 ohm 5 watt, do people use those typically or the the smaller regular looking resistors?

Thanks a bunch, Fred
 

hank57

Platinum Supporting Member
Messages
8,642
Tighten all the nuts for the inputs and outputs. including the RCA jacks for reverb, and reverb/term and pedal.

Try different cords and check the solder joint in the speaker cable. The input jack could also need to be cleaned where the tips connection is.
 

GOLDENSTRAT

Member
Messages
966
Well, both screen resistors measured 465K or so. Connections are good on tube sockets.

sanded and tightened reverb RCA cable connections on back of amp.

Amp will make crackling noise if I smack the cabinet, wiggling reverb cables does not induce crackle.

Amp will make crackling noise Normal or Vibrato channel if volume is over 6 or so, it seems to get a bit worse as reverb is turned up.

Could not find 470K 2watt resistors in town today to buy.....

If the screen resistors are bad, would they measure ok but when hot do something else??? It does not take but 3 minutes for the crackling to start.

Thanks for the suggestions so far!

fred
 

GOLDENSTRAT

Member
Messages
966
thanks, the grid resistors measured ok, re deox-it'ed the pre amp tubes.

Could the screen resistors be bad if they measure ok?

Really crackles if I jump the channels - they are out of phase.

A few solder joints on the fiber board do make the speaker make a small sound if i touch them.



Crackles if reverb cables are hooked up or not.
 

GOLDENSTRAT

Member
Messages
966
Hi again.

Put in new screen resistors, no difference in crackling.



Poking with chop stick tonight, I was able to make some popping sounds by touching the turret board (the black sheet that lots of resistors and capacitors are hooked up to) . Then then it would not make the noises when poking the board. I put it back together and after 5 minutes started making crackling noises at high volumes again.

no solder joints I poked seemed to generate a crackling noise.

Any suggestions?
 

GOLDENSTRAT

Member
Messages
966
Ha, thanks for asking, haven't looked at this forum for a long time!
Found a great new tech (to me) last spring.
He went thru it and found a bunch of loose joints and a couple wrong value parts that he replaced.
It now rocks and i have used it at every gig since.
Still a mystery to me how he found "lots of loose connections" and i could not with my chopstick.
Score one for the professional!
 




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