Hot Rod Deluxe bailout needed

[Oldmactech]

96 HR Deluxe Rev A

Replaced the filter caps and a few others from a Fromel kit. Went well but-everything functions but the tone was terrible, sustain resulted in brittleness and distortion. Swapped speakers etc, no change.

Went through an lightly resoldered lots of areas including the tube connections. No big globs I assure you.
Turned it on and now so sound. preamp tube closest to OT’s doesn’t appear to light up. If I touch the volume pot I get a harsh, hideous sound similar to plugging in a GTR cable while on.

I’m going to test voltages later this week but given the symptoms, anyone have a good starting point.

Thanks.

[Leo_Gnardo]

How about those ribbon cables that connect the main board to the output board, they all had to endure some flexing back 'n forth while you hauled the main board out for its mods. Those ribbons love to break! Sometimes in places that are hard to see, like just above the board they're soldered into. The solder connection can look good, but the wire's broken just a couple millimeters away. They've long been recognized as a problem spot in this series of amps. Keep in mind, Fender designed the amp to be built, not to have people haul out the boards & repair/modify them.

[Mick Bailey]

Also, plug your guitar into the 'Power amp in' socket and see if you get a clean sound. The controls won't work, but you're looking at this point to see if the power amp section is working as it should.

[glebert]

I have a similar era HR Deville and had no sound either from preamp or poweramp. What I found was that pads on the V2 and PI tubes had broken from the PCB trace. They looked fine, but they were not making any connection at all.

[Oldmactech]

Thanks. I resoldered v3 pins and v3 now lights up. Not sure the voltages are correct at the pins but will verify. Still no sound but when I flip the power switch off standby there is a slight reverb “ping.”

I will check continuity at the cable connectors, visual inspection is good. I may end up removing the PCBs from the chassis so I can get a better look at the connections.

[The Dude]

Also, plug your guitar into the 'Power amp in' socket and see if you get a clean sound. The controls won't work, but you're looking at this point to see if the power amp section is working as it should.

^^^^^^^ That first. No sense removing boards and potentially causing more problems until you verify where the problem is.

[Oldmactech]

^^^^^^^ That first. No sense removing boards and potentially causing more problems until you verify where the problem is.

Great tip, I do get GTR through Power Amp input. What does that tell me?

[The Dude]

That tells you that your problem is in the preamp section. Using that jack is a good way to verify that the power amp section works as it should.

[TomCarlos]

One other thing to add to the must check list - pull the preamp tubes and check the plate resistors. I have worked on two Hot Rod Deluxe amps and found plate resistors that were way out of tolerance or burned up.

[The Dude]

Not to pick nits, but it's not necessary to pull tubes to check the plate resistors. The plate is just a tube element hanging in space with the amp off. There's nothing physically connected to it. I do agree that it is a good thing to check.

[Oldmactech]

Not to pick nits, but it's not necessary to pull tubes to check the plate resistors. The plate is just a tube element hanging in space with the amp off. There's nothing physically connected to it. I do agree that it is a good thing to check.

With the tubes installed, power off, caps drained and my multimeter set to 20k on Ohms scale both resistors read .48. This was read from the resistor legs. I then read from the solder connections on the PCB backside and the meter jumped a lot but seemed to have the same reading as it settled down.

Should be 1000k,right?

[eschertron]

With the tubes installed, power off, caps drained and my multimeter set to 20k on Ohms scale both resistors read .48. This was read from the resistor legs. I then read from the solder connections on the PCB backside and the meter jumped a lot but seemed to have the same reading as it settled down.

Should be 1000k,right?

I would expect 100k, but the issue I see is that you've set the scale to 20k. I'd think you're seeing whatever passes for over-range on the meter, set like that.

[Oldmactech]

Ok, so with different meter settings I get these:

2000k 001 than flips to 0 after 2 seconds (both)
200k .5
20k .48
2000 first is 481, second is 498


Sorry, my meter skills are amateurish

[eschertron]

Ok, so with different meter settings I get these:

2000k 001 than flips to 0 after 2 seconds (both)
200k .5
20k .48
2000 first is 481, second is 498


Sorry, my meter skills are amateurish

Are these resistors discrete components? Do they have color-band markings? Write down the (4 or 5) color values and post. If you're reading 480..500 Ohms, I suspect that you have some other resistors instead of the plate resistors attached to the meter.

[Justin Thomas]

Plate resistors should be 100k throughout on 12AX7s, except one 82k on V3. Either way, something seems wonky there. 200k scale on meter, try to get a solid reading. But the jumping around leads me to think definitely a bad resistor, pad, or trace on V3.

Justin