It is currently Tue Mar 17, 2020 2:13 am

All times are UTC - 7 hours



Post new topic Reply to topic  [ 16 posts ]  Go to page 1, 2  Next
Go to page 1, 2  Next
Author Message
Post subject: Sudden abnormal hum from HotRod Deluxe
Posted: Tue Dec 15, 2009 8:47 am
Offline
Hobbyist
Hobbyist

Joined: Mon Dec 01, 2008 12:15 pm
Posts: 9
Location: Port St Lucie, FL
Have a sudden hum problem with HotRod Deluxe... started after transporting amp from rehearsal to home (normal transporting - nothing out of ordinary, ie. no large bumps, amp didn't fall over, etc). Was working fine at rehearsal and started immediately when turned on the next time at home plugged into the same 110 outlet it always is. All HotRods have some hum I realize, but this is very loud and uncharacteristic of this amp after bought new and almost 4 years of ownership. Here are the symptoms:

- Goes away if nothing plugged into input jack
- Present on all 3 channels, loudest on "more drive"
- Affected by volume, goes away if turned all the way down

I tried bypassing all pedals one by one - no change. Tried plugging in multiple guitars directly with multiple cables - no change. Seemed to change once when I wiggled the cable from the main speaker output to the speaker, but has not affected it since. Goes away when middle prong of tip-sleeve external speaker jack isn't touching either prong surrounding it - I assume because this creates an open circuit producing no power at all to the main speaker output. I'm embarrassed to say 1) I didn't think to check the 2nd input to see if the problem existed there until now, and 2) the tubes have never been changed since new (even though amp has had very limited usage until the last 9 months).

I realize the amp is still under warranty, but I have a gig tomorrow night and am looking for any advice on connectors, soldering joints, etc to look for that may be a common or quick fix to get me through until I can drop it off at the repair shop after the gig. Any help would be greatly appreciated.


Top
Profile
Fender Play Winter Sale 2020
Post subject:
Posted: Tue Dec 15, 2009 9:57 am
Offline
Hobbyist
Hobbyist

Joined: Thu Dec 10, 2009 9:48 am
Posts: 32
A hunch is that there is a bad connection or open ground to the input jack, although does it behave differently if you use input 2 instead of input 1? You could also try swapping the two tubes in the foam block to see if anything changes.

The latter thing you mentioned about the speaker jack is normal, and also a no-no, don't have the amp running without a speaker plugged in, it's hard on the power tubes. There was no hum because the speaker was effectively disconnected if it's only partially inserted.


Top
Profile
Post subject:
Posted: Tue Dec 15, 2009 10:05 am
Offline
Hobbyist
Hobbyist

Joined: Mon Dec 01, 2008 12:15 pm
Posts: 9
Location: Port St Lucie, FL
Thanks for the advice, Sparkydave. To ease your mind about the external speaker jack, it was only momentary while doing a gentle wiggle test. I can't believe I didn't test the 2nd input last night & I'm going to check it as soon as I get home and also look for a ground problem on input 1. Will post my findings later tonight.

If anyone else has any other ideas to try, they're still welcome as I hope to resolve this issue tonight when I get home from work.


Top
Profile
Post subject:
Posted: Tue Dec 15, 2009 10:13 am
Offline
Hobbyist
Hobbyist

Joined: Thu Dec 10, 2009 9:48 am
Posts: 32
You're welcome, and I'm sure the brief wiggle test didn't kill the tubes. Do check input 2 and see if the hum is still there. Also try to gauge if your sound is at the same level using input 2 alone; if it's at the same level that further points to a bad ground connection, since input 2 forms a resistor divider with input 1 when input 1 is unplugged. If it seems to be playing at the same level, then the ground connection input 1 uses to ground its grid resistor is probably open.


Top
Profile
Post subject:
Posted: Tue Dec 15, 2009 4:42 pm
Offline
Hobbyist
Hobbyist

Joined: Mon Dec 01, 2008 12:15 pm
Posts: 9
Location: Port St Lucie, FL
Unfortunately, the hum is there on both inputs 1 & 2. To answer your question Sparkydave, input 2 is quieter (sounds like standard 6db approx) than input 1 when input 1 is unplugged.

I also tried turning all the knobs down and doing the pencil test on the output tubes - the same sound was not duplicated. I tried the same thing but with the preamp tubes and the volume up - obviously the noise was there because the volume was turned up, but the preamp tubes did not seem to be microphonic.

Any other ideas out there?


Top
Profile
Post subject:
Posted: Tue Dec 15, 2009 5:09 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Sun Oct 21, 2007 1:44 pm
Posts: 521
Location: Memphis, TN
Are there any other devices plugged in around the room, like a Playstation perhaps? My PS3 makes a terrible ground loop with anything else on the same circuit. I have to use an adaptor plug to the wall outlet to get rid of the awful hum.
Have you tried an outlet on another circuit, like say in the kitchen?

_________________
2010 American Deluxe Strat Sunset Metallic - Lindy Fralin Blues Specials in the neck and middle, Dimarzio AT-1 humbucker in the bridge.
PRS Custom 22 with solid rosewood neck
Mesa/Boogie Electra Dyne 1x12 combo
DRRI


Top
Profile
Post subject:
Posted: Tue Dec 15, 2009 5:19 pm
Offline
Hobbyist
Hobbyist

Joined: Mon Dec 01, 2008 12:15 pm
Posts: 9
Location: Port St Lucie, FL
Yes, have tried 3 different circuits in the house. Yes there are other devices plugged in the same room - Roland Fantom G6, Fantom X8, Mackie 1604, 2 Mackie HR824s, my computer, but no PS3 (That's downstairs on a Monster power conditioner). However the outlet I'm currently plugged into is the same outlet I plug into every time I record or practice and have never had this problem before. I have yet to check the tube solder joints for cracks, but headed there next.


Top
Profile
Post subject:
Posted: Tue Dec 15, 2009 6:21 pm
Offline
Hobbyist
Hobbyist

Joined: Thu Dec 10, 2009 9:48 am
Posts: 32
Just another thought, have you tried a different cable? If input 2 was lower, then I'm guessing the input jacks are OK. Failing that, is there another source (another guitar) that you can try?

_________________
My gear:

Hot Rod Deluxe
1975 Vibro Champ
G-DEC 3 Thirty
Kramer XL III
Standard Stratocaster
Oscar Schmidt acoustic


Top
Profile
Post subject:
Posted: Tue Dec 15, 2009 7:40 pm
Offline
Hobbyist
Hobbyist

Joined: Mon Dec 01, 2008 12:15 pm
Posts: 9
Location: Port St Lucie, FL
Yes, I've tried multiple cables (Roadhog, Monster, Shure, Rapco) with multiple guitars (Fender, Ibanez, Guild)... All do the same thing.


Top
Profile
Post subject:
Posted: Tue Dec 15, 2009 7:51 pm
Offline
Hobbyist
Hobbyist

Joined: Mon Dec 01, 2008 12:15 pm
Posts: 9
Location: Port St Lucie, FL
Have just completed switching the preamp tubes to see if it changed... it didn't. (Was thinking preamp due to the face it changes with the volume control). I agree about having a ground problem, but I'm pretty sure it's inside the amp, not the house circiut, cables or guitar due to the fact I've tried 4 different cables I continually use without a problem with 3 different guitars I use without a problem in 3 different house circuits. I think I'm gonna' have to bite the bullet and lose it to a repair shop for a couple weeks...


Top
Profile
Post subject:
Posted: Tue Dec 15, 2009 8:02 pm
Offline
Professional Musician
Professional Musician

Joined: Fri Jun 26, 2009 6:53 pm
Posts: 2252
Location: Harvard IL
Don't the power tubes and phase inverter need to be swapped out, before assuming an internal problem? Art

_________________
None of Us are free, if One of Us is chained !


Top
Profile
Post subject:
Posted: Tue Dec 15, 2009 8:16 pm
Offline
Hobbyist
Hobbyist

Joined: Mon Dec 01, 2008 12:15 pm
Posts: 9
Location: Port St Lucie, FL
You're probably right, Art. However short of replacing the power tubes (which I'm going to do anyway), it's going to have to go to a repair shop as that's about all I'm willing to attempt on my own. As stated before, this suddenly happened with no change in equipment or settings that have all worked flawlessly for the past 4 years and most frequently the last 9 months. I agree it's probably a simple ground problem and not necessarily internal, but I'm not confident enough soldering this circuit board (my cutoff is custom patch cables). I appreciate all the advice, but I don't believe it's going to be a simple fix. Will post when I do have it resolved.


Top
Profile
Post subject:
Posted: Wed Dec 16, 2009 6:37 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Sun Oct 21, 2007 1:44 pm
Posts: 521
Location: Memphis, TN
Good luck. Let us know what it was.

_________________
2010 American Deluxe Strat Sunset Metallic - Lindy Fralin Blues Specials in the neck and middle, Dimarzio AT-1 humbucker in the bridge.
PRS Custom 22 with solid rosewood neck
Mesa/Boogie Electra Dyne 1x12 combo
DRRI


Top
Profile
Post subject:
Posted: Tue Jan 19, 2010 12:31 pm
Offline
Hobbyist
Hobbyist

Joined: Mon Dec 01, 2008 12:15 pm
Posts: 9
Location: Port St Lucie, FL
Congratulations to Art! It ended up being a bad preamp tube after all. Swapped out all 5 tubes with some JJ's and she's back to sounding great! Thanks to all for your help!!!

_________________
- Hosh

______________________________________

2007 Fender American Strat Highway One HSS

Fender HotRod Deluxe

BOSS NS-2>Crybaby Wah>TU-2>GE-7>DD-7


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 16 posts ]  Go to page 1, 2  Next
Go to page 1, 2  Next

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: