Hot Rod Deluxe Reverb inop, What are these wires for?

[tmlesko]

Hi, this is my first post. Today I got a Fender Hot Rod Deluxe amp, first time using one. The reverb does not work. Inside, there are two wires, one shorter than the other, with 1/4" plugs. Are these supposed to be plugged in? What are they for?

Thanks,
Tom L.

[oc disorder]

That looks like the original cable that comes with the footswitch.
Are you sure its not mechanically trapped under the reverb tank?
Maybe the previous owner removed the tank to get it working and
inadvertently screwed down the reverb tank on the f/s cable.
There could be a number of reasons why the reverb is not working.
Firstly there should be 2 shielded wires coming down from the chassis to
the reverb tank which is inside a vinyl bag at the bottom of the amp.
These wires should terminate with RCA plugs that plug into the reverb tank.
One carries the signal to "wriggle" the spring ie acts like a tiny speaker and sends the sound down the reverb spring.
The other carries a very minute signal (springy reverberated sound)from the pick up transducer like a microphone back to the amplifier where it ends up going into the reverberation control.
That lead should hum when the tip of the rca is touched also if the amp is rocked the springs can be heard rattling or crashing around in the tank.

The main fault that develops with these mechanical devices is the fine wires
breaking inside the tank that connect the transducers to the RCA socket.

They just need reterminating if you are lucky and they break off near the socket.
In not so lucky circumstances the tank will have to be replaced.

Check the forum for other instances of faulty reverbs.

If all the above is ok the fault could be on the main pcb which has been covered before on this forum.

Hope thats useful information....
P.S.
oh although I'm just a visitor "Welcome to the forum" I'm sure
Enzo will welcome you officially USA time ..its a sunny afternoon in Australia here while most of the tech's are getting their beauty sleep !

[tmlesko]

Thanks, that was helpful. You are correct, I was being cautious and did not pull the wire, it was hung up underneath and does look like the foot switch wire ( I did not get the foot switch with the amp.) Wondering what the empty jack on the chassis next to the output tube is for though?

[oc disorder]

Its for an extension speaker.
It may be a good idea to get the schematic diagram and the User manual
from Fender
http://www.fender.com/support/amp_sc..._Schematic.pdf
User Manual
http://www.fender.com/support/manual...Rod_Deluxe.pdf

Actually it wouldn't be to hard to build a f/s for the amp.
Attached the schematic which is also in the above.

[tmlesko]

Thanks again, you have been very helpful.

I spent 4 years in the Air Force fixing sophisticated tube equipment but that was almost 40 years ago so I think I will defer to a good tech in Boston at the Berklee school shop.

I wonder if there is there a way to use headphones with this amp?

Tom L.

[oc disorder]

Well you could build an attenuation network with resistors or purchase a power attenuator that caters for headphones but If it were me I'de invest in one of those little amps (solid state) or even a Pod type device (more expensive) designed for personal listening.

It would work but the noise floor would be more noticable and often I find
these extras often seem to cause problems in the heat of the moment.

[Enzo]

Hey welcome. But I am not the official, I am just a visitor here myself. tboy owns the place and has to empty the ash trays after each night. I like to welcome people just as I welcome visitors to my shop.

[tmlesko]

Reverb Troubleshooting Procedure

After doing what was suggested in post #2 above, I am wondering what else to do regarding the reverb. I can hear the spring boing with the amp on if I bounce the amp a bit. Is there a troubleshooting procedure somewhere? I have searched this forum and others and only found bits of information. I will visually check the reverb pan internals and the connections tonight, then look at the PC board and the two resistors for visual signs of overheating and/or cold solder joints. After that I am not sure where to go. Any thoughts would be appreciated.

Tom L.
Hingham, MA usa

[tubeswell]

When you say 'spring boing' do you mean you can hear it real loud through the speaker? If so, that reverb isn't not working altogether. You could just have an intermittently loose solder connection somewhere

If you hear the spring boing but it isn't coming through the speaker, there could be several possible causes. The reverb pan is fed from either a tube output transformer (driven by a tube), or a transistor (if SS driven), which in turn is tapped from the signal path in the pre-amp. After it leaves the pan the signal returns through another tube stage or transistor and then back into the main pre-amp signal path. So it could be:

1) a bad tube (or reverb transformer) or transistor feeding or receiving the reverb pan. Quick check is to swap the tube itself, or the IC chip if it is a little op-amp that can be clipped in and out. It could also be a bad connection to the one or more of the heater or electrode pins on the tube socket. If it is a kaput reverb tranny, then you will need a new one

2) a bad wire going to or from the pan. These wires are typically shielded cables with plugs at each end. The wires could be broken or shorting to the shields, in which case they need replacing. Check them with your meter

3) or a bad pan itself - The springs in the pan have little transducers at each end - which convert the electrical impulses from the circuit into mechnical impulses in the spring , and back again. These are dainty little things, and one of them could be broken, and while I have read stories of guys fixing them by unwinding and rewinding the tiny coils if the break is near one end of the coil, that sounds like a real mission, so its probably easier to replace the pan.

[oc disorder]

Well if you can hear the boing (sound a kangaroo makes..heh heh) through the speaker ,(ie you can make it louder or softer with the reverb control) if it can get loud ! we can assume the return path from the reverb pan is working
thus no need for the hum test ("That lead should hum when the tip of the rca is touched ").
So for some reason the "send" signal is not making it to the input of the reverb so working backwards
1.Check the fine wires in the pan and measure the resistance of the transducer. It will be very low less than 200ohms.
This page lists the impedence and the D.C. resistance which is what is measured using a multimeter.
http://www.accutronicsreverb.com/ioic.htm

They explain their numbering system and example http://www.accutronicsreverb.com/Type4.htm

Their example 4EB2C1B has a shorter decay time 2 = Medium (1.75 - 3.0)

So if it is a 4EB3C1B Reverb Tank
4 = 17" 2 Spring
E = 600ohms 58 ohms DC resistance
B = 2250ohms 200 ohms DC resistance
3 = Long (2.75 - 4.0)
C = Input Insulated - Output Grounded
1 = No Lock
B = Horizontal, open side down

So if the reverb unit tranducers and connections are ok have to check the
shielded wire that leads back to the reverb send unit which is basically a TLO72 IC.
Faultfinding this area will entail dismantling the amplifier to get at the other side of the PCB.

This may be useful
The Unofficial Fender Hot Rod Deluxe Owner's Guide
http://studentweb.eku.edu/justin_holton/

Lets hope its just the wires to the input transducer.

[tmlesko]

With the amp on, if i lift the amp and set it down, I hear the reverb spring crash sound through the speaker. If I turn the reverb knob to zero, then I can't hear the crash sound. It does not vary in volume much by rotating the reverb knob to max, just goes away when the knob is at zero. Also the crash sound does not vary with the volume knob.

I have the spring pan out and found that one of the little holding-springs that suspend the reverb-spring unit in mid air was broken causing the reverb-spring assembly to sag and touch the floor of the amp case. I also did the touch-hum test, it hums.

The output transducer (on the end that had the broken holding-spring) appears to be open, the input transducer measures around 105 ohms. I assume that the output transducer has a broken wire and the spring pan should be replaced?? Sound correct?

It is a 4EB3C1B, stock, long type, Should I replace it with a medium decay unit 4EB2C1B?

Also, the amp has a hum, not loud but noticeable, can I assume that is normal?

Thanks again for the help.

Tom L.
Hingham, MA usa

[Enzo]

If either end transducer is open, replace the pan

www.tubesandmore.com has a selection at reasonable price.

AS to whether or not you want the longer or shorter delay - that is up to you. The difference is not large. And if the seller only has one or the other, there is the decision made for you.

Your hum may or may not be related. It could be anything from a loose ground to mismatched power tubes to... the reverb.

[tmlesko]

"Tanks" Enzo,
Not having ever messed with a guitar amp, I am a little cautious, plus it has been 40 years since my electronics days and I am afraid I have forgotten much of what I once new. Although, most of the equipment I worked on in the Air Force was tube equipment - because the newer solid state stuff didn't break much.

Thanks again, I will report back on the progress but I have to order the tank so that will take a while.

Tom L.

[tmlesko]

Received the reverb tank, installed it (took about 30 seconds) and I am happy to say it works fine! I ordered the medium delay/decay 4EB2C1B. Happy with it. $38 including shipping.

Thanks for everyone's help!

Tom L.