Fender Hot Rod Deville Amp

[g1]

Also, if memory serves the heater grounding resistors or hum balance pots can also get damaged when power tubes get put in wrong due to broken pin base keys. So check those as well.

[52 Bill]

When power tubes are inserted the wrong way into a socket, the tubes can be damaged and the amp can be damaged. If you only have a burned screen grid resistor, consider yourself lucky.

If you were to use an oscilloscope to look at the audio output that is across either the speaker or a dummy load, you would probably see one side of the signal was weak or completely missing.

Broken center pins on octal tubes are really common, and I think they are caused more by pushing the tube from side to side, leveraging the pin to break off in the socket. Instead of pulling a tube straight out some folks like to rock them back and forth to wiggle them out.

[mozz]

6 pin savers for $20.
https://reverb.com/item/2465597-6-pi...key-fix-repair

Years ago i don't remember indexing pins breaking off. I say it happens today because a: of inexperienced people swapping tubes, and b: cheaper materials.

[g1]

Broken center pins on octal tubes are really common, and I think they are caused more by pushing the tube from side to side, leveraging the pin to break off in the socket. Instead of pulling a tube straight out some folks like to rock them back and forth to wiggle them out.

Especially when they have bear trap style retainers ala Fender, and people don't want to use both hands.

[bob p]

I hate it when people bring in tubes with broken indexing pins. I like the idea of putting an index mark next to Pin 1 on the tube and the Pin 1 socket on the chassis.

[TwinBeech]

I found R61 and R62 both burned. I replaced them and re flowed the 6L6 socket pins. The amp now has lots of volume and sounds clean except for a lot of popping and crackling. I have seen some threads on that subject so I will read those before I look into the noises. Thanks for all the replies.

[mac dillard]

"I have a Fender DeVille with 4x10's in it that has new tubes but is distorted"

First post says the amp has new tubes. What happened?

[TwinBeech]

I think the tubes had been inserted wrong and burned the two screen grid resistors. Replaced them and had good sound but lots of popping and crackling when cold. Less when hot. Sprayed a lot of coolant but no change. The V1 tube has a lot of sound when tapped so I will re flow the pins tomorrow. At the pre amp output there is no noise. So I guess it is between there and the output. With V3 out there is no noise. None of the controls effect the noise so maybe I should look at the power supply?

[g1]

The plate resistors on the phase splitter in those amps are notorious for going bad. That would be after the preamp out. You can give them a shot of your freeze spray and see if you get a reaction. (R57 & R58 at V3A on schematic you posted)

[Chuck H]

Not sure why a tube inserted incorrectly would burn BOTH screen resistors. I think testing voltages (including the bias supply) is in order. Make sure the amp is operating as it should be. Not just "lots of volume and sounds clean". If there's still something wrong with how the amp is operating it's only a matter of time before you lose the new tubes too. Perhaps worse. It's easy to check voltages on all tube pins and compare them to the schematic.

EDIT: Check that. You may not want to use the schematic from this thread. Anyone else see something fishy about the tube voltages on that schem?!? It looks like most are AC signal voltages. DC voltages (indicated by a + or - symbol I assume) aren't given for reference to many HV operating voltages.

TwinBeech, if you post the DC voltages at idle on all the tube pins we should be able to interpret them from context

[Tone Meister]

Chuck, that schematic is for the earliest USA-made HRDeville. Not sure what revision of the amp TwinBeech is working on. The schematics did evolve over time, of course

[TwinBeech]

I will post voltages today. I have the schematic that I got from the Fender site. The revision says B 24 May, 1996.

[Tone Meister]

Do you know the revision of your amp? Was it made in USA or Mexico?

[TwinBeech]

I see a date inside of 6/27/1996 and "Made In U.S.A."

[52 Bill]

Not sure why a tube inserted incorrectly would burn BOTH screen resistors.

Probably because both tubes were inserted incorrectly.