Fender Hot Rod Deluxe Drive/More Drive switching problem

[kenda47]

You are welcome ehouck. I agree with 52 Bill stick with 470 ohm 5W as lowering value will current stress the zenners. The jewel bulb and filament circuit are both powered by the low voltage secondary from power transformer. The fact that you get both dimming and loss of volume suggests that the problem is nothing to do with the bulb itself. I reckon the likely culprit is where the twisted green wires attatch to the board. From power transformer the spades shake loose. If that is the case crimp gently with pliers so fit tightly. Also the actual terminal posts crack at the solder joints. Even a hairline crack will give symptoms you describe. If you need more help let me know.

[52 Bill]

I can't find a schematic for a new HRD III, to verify the 330 ohm value, so I will stick with my recommended value of 470 ohms for now. Fender did use the 330 ohm value for some of the Devilles maybe. But this was due to the fact that the incoming supply voltage was lower than that of the HRD's.

I've seen a few pilot lamps have similar issues, usually caused by bad contacts at the lamp socket. Remove the jewel and press down on the bulb in the socket. Does it flicker or change brightness? If it does service the socket and bulb contacts.

[ehouck]

Right on. Good thing I bought extra resistors. I'll elevate the 470s and see what happens. And try touching up solder joints. Also this might sound like a weird question but what kind of iron would you guys recommend. I have two $15 cheapos that I've used in the past. They work but then end up forming a nasty black film on the tip and stop working after a while.

[52 Bill]

When you install the new resistors, you can extend the wire leads along the path of the pc traces to add some additional mass to help in the heat dissipation process. If you do this, scrape away the green solder mask to expose the copper trace and solder the wire lead to the bare trace.

As for your iron, you need to keep the tip clean. Use a small sponge moistened with a little water to wipe the black off just before you go to make a joint. If the black does not come off with a simple wipe, the tip may not be tinned correctly. If the tip has not been ruined you need to "tin" the tip with some fresh solder and rosin. The idea is to keep a thin coating of solder on the tip that can oxidize with the heat to protect the metal of the tip itself. Keeping the tip "tinned", will make it last longer and will also help to make better solder joints. I'm sure that you can find better instructions somewhere on the web, but at least that's the basic idea.

[ehouck]

That sounds like a plan. I'll try it out. Thanks Bill 52.

[ehouck]

Well, I took the bad boy apart, which was a pain in my ass trying to gingerly remove the pcb... whew... Replaced the 5w resistors and re-flowed some solder joints that looked iffy. Put it all back together and put to through some tests. Been jamming with it all week. Even was confident enough to take it to a gig on saturday. Havn't had a single problem at all except the jewel light still flickers on and off but it's not effecting the sound at all as I had originally thought. Things are looking good here.

[CraigW]

For the jewel light you will likely need to solder jumper wires from the solder tabs to the socket directly to make it work 100%

I tried doing just the center lead once and then had to take the cover back off to jumper the base as well. After that It worked perfectly.

[Jazz P Bass]

Just add a small ball of solder to the center base pin of the bulb.

[Prairie Dawg]

Well, I took the bad boy apart, which was a pain in my ass trying to gingerly remove the pcb... whew... Replaced the 5w resistors and re-flowed some solder joints that looked iffy. Put it all back together and put to through some tests. Been jamming with it all week. Even was confident enough to take it to a gig on saturday. Havn't had a single problem at all except the jewel light still flickers on and off but it's not effecting the sound at all as I had originally thought. Things are looking good here.

See, that wasn't so bad, was it?

[blueshead1]

WHAT?

See, that wasn't so bad, was it?

New here but have been a tech for many years. As for the Deville, if R78 and R79 were bad you would have more problems than you described. Just measure the resistance of them and if good go on to the next most likely cause. These resistors feed +/-16V to all of the IC's not just the Channel and More Drive circuit. Chances are that you partially solved your problem by reflowing the solder joints. The circuit boards in these amps are not good quality and very prone to failure due to heat. Also, most of the problems I see here need to be referred to a good tech immediately! Good techs can have nervious breakdowns trying to solve these problems. Remember, if you can't determine WHAT made it explode you should not be attempting to fix it yourself.

Just the opinion of an old man.

[g3misa]

Guys i need help. I tried cleaning the pots of my '96 Hotrod De Ville 410 with this Radioshack Control/Contact Cleaner and Lubricant.

Now when i switch the More Drive button to ON, it switches to the Clean channel. The Channel Select works fine and i'm able to see the green square light for the overdrive. But when I press the More Drive, the square light goes off and I get to the Clean channel.

Other than this issue, everything is perfectly normal.

Thanks

[Prairie Dawg]

If the cleaner is what triggered the problem, get yourself some CRC contact cleaner (not the electric motor stuff or the brake cleaner) and clean out what you put in there.

[Enzo]

Or while you were cleaning pots, you bent something or knocked something off the board. I could be wrong, but I tend to think the pots won;t affect the switching circuits.

I suspect the dual color LED itself is bad. Or broken free of the board. The LED has red and green aspects. red and green together makes yellow. On this amp there is no green condition. You have yellow for drive, red for more drive, and dark for clean. You get green, which means red is not working, because it should be one WITH the green to make yellow. When you go to more drive, the red LED stays on and the green one goes off. That is how they change from yellow to red. But your red is not working, so instead of going from yellow to red, yours goes from green to nothing.

Check the solder on the part.

The current for the channel switching relays runs THROUGH the LEDs, so if they are open, the relay will not pull in.

R104 could be open, but I doubt it.

[Mick Bailey]

Every modern Fender seems to have the same resistor problems. I don't want amps coming back so I install aluminium resistors on the chassis and connect them with flying leads. Permanent fix. Once the resistor has become overheated it weakens the bond between the pad and PCB. Raising it off the board puts more strain on the joint and I think silicone impedes heat dissipation from the resitor body, causing more heat to travel down the legs.

When they're burned up like this one I fixed a few months ago the tracks become detached as well;



Eden amps suffer a similar problem and here's the fix I developed for the WT800;

[g3misa]

Hi Enzo,

I checked the LED and its connected to the board. What's weird is that I sprayed CRC QD Electronic cleaner all over the board and when I turned the amp on, I saw the RED flickering for a while, stayed on for about 30 seconds, then went out and never came back. I tried spraying the board again and the RED started flickering and went out again. I'm really not sure what's wrong with this. All solder joints seem to be intact.

Thanks