Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on October 26, 2012, 08:41:47 am
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HRD crackling. Well i have an HRD that was saltwater abused. Worst case senario. The amp is crackling with no guitar input. This tells me it is in the power section of the amp to my memory. I have already replaced the PI plate,grid and screen resistors with metal film. I didnt change the LT resistors. I have changed the preamp plates to carbon comps. What else is there in the power section that i may be over looking? Im going to test the pwer supply caps next. If i recall there was a thread on here a few years ago about bad PS caps causing crackling. Does this sound right? Generally speaking the plate resistor have always been the main crackling problem with the HRD amps for me. This ones being a D**k
The amps tone controls were so badly rusted i had to use my dremel to cut one side of 3 pot nuts off to replace the pots
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Tube sockets. I had one that was doing the same thing. Came down to the sockets. If the pots were that corroded the sockets are probably the same. Good Luck.
Bruce
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Thanks Bruce* I already cleaned the sockets and resoldered all tube pins on the board. I remember a PS cap a long time ago that did the same thing on a Bassman. I checked all the PS node resistors and they read there values. They are metal oxide so i doubt they are the problem. Working on the PS caps now
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You've probably already covered this but----have you tried a different preamp tube in v1?
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You've probably already covered this but----have you tried a different preamp tube in v1?
Yes i tried other preamp tubes in V1 position. The crackling i think is isolated to the power section.
I have changed the PI plate,grid,screen resistors. I did not change the 1Meg PI grids,470r cathode or 6.8K tail resistor
Looks like im going back in! Anyone got a plunger to hang onto?
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Ok let me start over again because i need to ask another question:
With no signal to the input grids i have crackling when i turn the volume knob up
Does this sound like the input jacks could be shot and not making a ground reference?
I shouldnt be getting any preamp volume with no input signal right?
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Use an alligator jumper and ground the input jacks tip to see?
Brad :icon_biggrin:
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Checkout. http://www.justinholton.com/hotrod/plateloads.html (http://www.justinholton.com/hotrod/plateloads.html)
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I did all the Justin mods as usual but still sounds like a deep fryer. Never had one do this before after all the plates were changed. Cleaned all the input and other jacks on the amp. Sounds just like a bad crackly preamp tube but it's not. It looks like im going to have to go through everything from the OP amps to who knows what. :sad2:
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I'm not an expert but from what I have read re: pops and crackles can be from moisture finding it's way into parts such as resistors, capacitors or maybe even the windings on the PT or OT? especially prevelent when the amp has been stored in moist area.
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I'm not an expert but from what I have read re: pops and crackles can be from moisture finding it's way into parts such as resistors, capacitors or maybe even the windings on the PT or OT? especially prevelent when the amp has been stored in moist area.
Good thinking smackoj. That would explain the seriously rusted pot nuts. I think i may have a nightmare on my hands. Time will tell
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Well this amp is driving me insane. I have replaced all the plate load resistors in the power supply and preamp. I have recapped the power supply. I have changed all the preamp amd power tubes. The tube sockets are all retetioned and clean. Pots are all clean and good. I still have hiss and crackling when turning up the volume pot with no guitar input signal. Never seen one do what this one is doing before. Lastest thing that comes to mind is could there possably be moisture in the input jacks? Im out of ideas
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I didn't see anything about cathode resistors? I have an amp that had a hissss (not crackles) and changing the preamp cathode resistor fixed it. You may have already tried this but have you tried plugging the amp in at a different location---any possible electronic devices pugged into the same circuit that could cause interference?
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Have not changed any cathode resistors. Possable. I am going to check the preamp coupling caps today. :sad2: :sad2: :sad2: :sad2: :sad2: :sad2: :sad2: :sad2: :sad2:
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Get some cold spray.You can get a bad component to crackle by spraying it.Spray everything until you find it.
Also a listening amp will help.I have an old tube circuit tracer with a speaker and I use it to help me locate noisy resistors and caps.
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Plexi50, Try using Doug`s listening device to see if you can pin point where the crackling is coming from.
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punkykatt i took your advice and just finished building the listening device. Not a pretty box but i had nothing else laying around that i could find. Red ground clip (will change to black later). Sheilded mini cable soldered to 1/4" jack and to tip of red probe. The cable slid nice and snug through the red probe handle. Soldered center of sheilded cable to metal probe tip and screwed tight to red pencil handle.
Now to go back over the operating instructions. I should have built it years ago as many have told me to. It appears it's the only way im going to find the problem in this amp. Im sure it will make my other troublesome amps that come in much easier to repair
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That`s real perdy. Mine is made from a real old Electro Harmonics Small Stone Phase Shifter chassis from back in the early 70`s. You will find this device to be the best and most useful piece of test gear you have. Thanks Doug!!!!!!!
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Thanks punkykatt! I cant wait to try it out in the morning. Thanks to Doug all things are possable with repairing and learning
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Listening amp = any guitar amp in the house.
Just add special 'test' guitar cord with gator clips or probe on one end.
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OK, that sounds simple enough. Old guitar cord+gator clip+probe+solder+Guitar Amp=crakel Hisss Identified/located! Now I can put my old pignose to work and sniff it out!! Oink Oink!
:laugh:
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Ok now im happy! :laugh: Oink!
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Major source of crackling in an HRD is the power tube PC board.I wiggle the power tubes and look at the solder joints with a BIG magnifying glass.I usually see the cracked solder joints wiggling under pressure.
Also the preamp tube boards,especially V1 does it too.AND....the riboon cables are MAJOR pain in the as when they start fraying,which is almost immediately on the new Deluxe III's. They suck royally!!!!!!!!!!!!!!!!!!!!!
!!!
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Thanks phsyconoodler. I soldered all of the tube pins. But i didnt stop to think that a trace or or solder eyelet of the tubes may be not making contact very well. I have a head set magnifier i will use tommorrow as well as do a continuity trace on all pins throughout the traces.
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Got it. Found the problem within minutes using Dougs Listening O'meter. Wow*
V1 Plate was cracked at the tube pin trace just to the right of the tube pin itself. Could not see it even with my magnifier head set.
I probed V1 tube pin and got an enormous amount of crackling. All other plates were quiet in comparison
I can see an infinate number of uses for this tool and am sorry i didnt build one before last night. Shamalamaampalamadingdong HRD :worthy1:
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Shamalamaampalamadingdong HRD :worthy1:
I'm not sure what that means, but for some reason it made me giggle.
Dave
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That means translated to North Louisiana Red Neck=Yeeeeeeeeeeee Haw!
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Shamalamaampalamadingdong = Three Dog Night right??????
Glad you found the problem source. Was`nt that fun???? Punky
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We want pics of you wearing the hjeadset magnifyers. HeHe
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Yeah that was fun building that listening box. Then i tried what Steve mentioned about just making a special cable with a .1 cap before the probe tip from a test amp mounted under my bench which is used for pedal work. It worked the same as the box. I like the box as it has the 1M pot to set the level without having the crap scared out of you when you hit that noisy spot
The head set lens really works great but you have to have good light on the parts your looking at.
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Glad you found it.
Album cover in the photo; Aerosmith was the first concert I saw at the Aragon Ballroom in Chicago when I was in high school, it was for their 2'nd album and were the headliners. It was general admission so we cut school and got there at about 1:00pm and stood in line all day untill 7:00pm till they opened up the doors so we could get front row seats. :l2:
Every once in a while I listen to that album.
Brad :icon_biggrin:
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Man i have about 300 or more vinyl albums. All the great stuff. I rarely listen to them anymore but on occasion the Bug Light makes me play them.
Fast story:
1970. Skipped school. On the look out for truant officers. Caught 1 block before Pirates World in Dania Beach near Ft.Lauderdale. Talked my way out of getting taken back to school. Said i was sick and on my way home. Dozens of people pushing a gate down to get into Pirates World. I saw this and just fled inside with the crowd. Got lost in the mix. Black Sabbath was playing that day and i had planned this for a while. It amazed me at that time that even the Cops were passing the herb around and smoking it as well. Such a cool time and fantastic concert. Tony was tripping and his eyes were rolling back in his head. He falls to the ground. Ozzy grabs him by his neck. Slaps the piss out of him back handed 3 times. Bends over and get Tonys SG off the stage. Puts it in Tonys hands and they played flawlessly for another 45 minutes or more. Priceless*
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WOW! I'D NEVER FORGET THAT SHOW!
Still want to see you with the glasses on peering inside the HRD! LOL!
In 1970 I was playing hooky riding my dirt bike.I don't think I spent more that 10 days in social studies in all of grade 10.I snuck into the back of the class after not being there for a couple of weeks and I was dumb enough to think he wouldn't notice.Off to the principal's office again!