Fender Hotrod Deville crackling at turn on

[ogeecheeman]

Boy these things are a mess. In addition to the laundry list of items to correct like- plate resistors,power recap,broken solder joints,broken ribbon connectors,bad relays,faulty jacks etc...this guy had one screw holding on the back panel.it fell backwards,the panel pushed into the output tubes breaking the guide pins and knocking them out of the sockets.the guy tried re-using the tubes.put them in misaligned(remember the broken guides).fuse pops.he puts in a 10A fuse. goodbye screen resistors,a few foil traces and a burned hole thru the board.and if that's not enough it looks like a drink has been spilled into it.
1)corrected foil,broken solder joints,ribbon conns,jacks,
2)replaced tubes-returned to customer with understanding that he will return with caps.
amp is back.still crackling
3)faulty power switch, new tubes with....you guessed it, broken guide pins again.
4)replaced ALL plate resistors
5)recap of power supply- 47uf...22uf....100uf
so far...maybe

[nevetslab]

Sounds like you still have some solder joints acting up to find. The last Hot Rod series amp I had with crackling was found on the staked-in fast-on terminals over on the primary/secondary side....where I usually DON'T find the trouble. My biggest complaint on this series is the really poor quality PCB material used. The adhesive under the foil breaks down under re-heating of solder pads while changing parts with the greatest of ease. It doesn't help that Fender folds the leads over prior to flow-soldering the board, so you can't use a Pace Desoldering tool directly. (At least you can on the IC's and relays).

You may still have further damage that you didn't find on the tube PCB's down below. Sounds like you're well aware of the normal solder fractures that plague the Hot Rod Series (input jacks, foot switch/pre out/pwr amp in jacks, pots & their support brackets, the tiny solder-masked pads for the power supply caps (I hate how Fender thought it wise to reduce those tinned pads to be so tiny, and NOT use all of the pad dia as should have be done!). I work on Hot Rod series all the time, as there's at least 20 in the rental inventory where my shop is, as well as with other clients. They do come back together and work fine again. And, there's an easy mod to reduce the excessive gain in the More Drive mode.

If you haven't already done so, I'd scrub the PCB wherever you see evidence of the drink being spilled into it, as that also coul dbe your source of the crackling.

[xtian]

The Hot Rod series is to amp techs what Microsoft Windows is to IT techs—a constant and reliable stream of income.

[Mick Bailey]

Yes - the gift that keeps on giving.

[Tone Meister]

Don't overlook the tube sockets either if they're the old black phenolic ones. And I mean the sockets themselves, not just the solder joints. I've seen the old black sockets that lose their grip to where tightening the pins wouldn't help because the metal was compromised by heat over time.

[ogeecheeman]

sorry this post took so long.i did solve it. faulty off/on and standby switch.thanks

[Perkinsman]

sorry this post took so long.i did solve it. faulty off/on and standby switch.thanks

Thx for closing your thread with the solution, I have a HR Deville on the bench right now with intermittent weird crackling and popping noises. Sometimes redplates too. I can't find any bad solder joints and considered the toggle switches but could you tell me how to test them?

[ogeecheeman]

if it redplates your switches are working.
disclaimer- these amps have voltages that can kill you.if you are not experienced and qualified I do not recommend you servicing this amp.

red plating is the result of no bias or improper bias voltage.can be a bad tube,failed solder joint, open bias or cracked circuit board. if it is on just one output tube,swap tubes.if problem moves you have a bad tube.if it does not move you have a bias issue on that socket. check for -54vdc at pin 5. check for 60 mv at TP30 or R66. my guess and experience tells me a bad solder joint.re-flow output tube socket pins and test again.
once you solve that problem you can isolate cracking sounds.put a cable in (power amp in) jack. if noise stops the problem is in the preamp stage. likely causes;bad preamp tube,bad input jack,also susceptible to cold solder joints or crosstalk or carbon tracking between pin 1 and grid of V2.if you have a steady hand and are good with a DC voltmeter you can check for carbon tracking but amp must be on and you must be extremely careful.set meter to 200v scale or higher. ground - probe to chassis.place + probe on pin 1 of V2. You should see about 100 vdc.slowly move probe , without losing contact, away from pin 1 towards neutral non-conductive area of circuit board. if you are still reading any more than a few volts here then you are probably getting bleedover to the grid. noise! turn off amp.take a rag with component cleaner on it,clean board around tube socket pins thoroughly.retest.I finally had to cut a channel in my board with an exacto knife to stop it.hope this helps.good luck.stay safe.
added- fender went thru several boards. I think they finally got it right on number 4.seems to me the green boards are the worst of the lot.

[Perkinsman]

if it redplates your switches are working.
disclaimer- these amps have voltages that can kill you.if you are not experienced and qualified I do not recommend you servicing this amp.

red plating is the result of no bias or improper bias voltage.can be a bad tube,failed solder joint, open bias or cracked circuit board. if it is on just one output tube,swap tubes.if problem moves you have a bad tube.if it does not move you have a bias issue on that socket. check for -54vdc at pin 5. check for 60 mv at TP30 or R66. my guess and experience tells me a bad solder joint.re-flow output tube socket pins and test again.
once you solve that problem you can isolate cracking sounds.put a cable in (power amp in) jack. if noise stops the problem is in the preamp stage. likely causes;bad preamp tube,bad input jack,also susceptible to cold solder joints or crosstalk or carbon tracking between pin 1 and grid of V2.if you have a steady hand and are good with a DC voltmeter you can check for carbon tracking but amp must be on and you must be extremely careful.set meter to 200v scale or higher. ground - probe to chassis.place + probe on pin 1 of V2. You should see about 100 vdc.slowly move probe , without losing contact, away from pin 1 towards neutral non-conductive area of circuit board. if you are still reading any more than a few volts here then you are probably getting bleedover to the grid. noise! turn off amp.take a rag with component cleaner on it,clean board around tube socket pins thoroughly.retest.I finally had to cut a channel in my board with an exacto knife to stop it.hope this helps.good luck.stay safe.
added- fender went thru several boards. I think they finally got it right on number 4.seems to me the green boards are the worst of the lot.

Of course this is the green board...turns out V3, the PI pins were the problem with the crackling. I had lots of help here making good suggestions until we nailed it down.

[ogeecheeman]

Of course this is the green board...turns out V3, the PI pins were the problem with the crackling. I had lots of help here making good suggestions until we nailed it down.

nice.glad you solved it.