Hot rod Deluxe

[Valvehead]

Working on a Hot Rod Deluxe Series 1 .

Went thru the usual repairing solder joints , thats all done , and I have 2 problems =

when turning up the reverb pot i just get a squeal and no reverb. I searched on here and U2 seems to be a common tlo72 that goes bad in these. Test point 22 calls for 3.4v and i have 0v. I do have some new tlo72 chips here....so i can start there if i need to . Tank tests good .


Other problem is , the amp switches channels just fine , but with the footswitch plugged in , it only switches the "drive/more drive" feature---not the channels. Ive checked the fsw / cable / solder joints on fsw jack in amp. Whats the common part failure for this Hotrod deluxe issue ? I will do another search but thought I would post this too .
R78,79 test good and have 16v / 48v .

[nevetslab]

On the Hot Rod Deluxe, take a look at the solder joints of the Footswitch jack itself. Your Channel Switch and Drive/More Drive on the control panel work, but not with the foot switch. I have also seen the diodes in the foot switch fail as well. Since you're already going to drop the main PCB down to get at U2, have a look at/de-solder & re-solder the FS jack. And, just in case, on the HR Deluxe schematic, you have all the voltages for each switch position & footswitch position to aid in finding the problem.

[Valvehead]

Im fairly certain i checked all joints--but I will look again--which diodes should i check in this case ? Cr20 / 23/ 24 /27 all test ok in circuit.

[Enzo]

All those diodes are in the amp circuit, but you already reported the amp itself switches fine. It only acts wrong using the footswitch. Is that not correct?

Some amps require the panel switches to be set a certain way for the footswitch to work, but these Fender are not like that. When you plug in the pedal, the panel switches are disconnected.

SInce your pedal does work for one function, I have to think the FS jack on the amp is OK.

The pedal schematic is on the next page with the layout drawing of the amp. Since the gain switches, look at the channel circuit. It is a diode, an LED, and a switch. Not a lot to troubleshoot.

Does the light go off and on on that button? Prolly not. So does the switch open and close when you stomp it? Are the two diode acting like diodes? Not much else.

And finally, Fender added a WHOLE slew of notes on the schematic right next to the channel switching circuit - all those test points. They even tell you how the voltages are a little different when using the pedal. Follow those and see where yours goes astray.

[Valvehead]

ok--ill try and look tonight--thanks

[Valvehead]

All those diodes are in the amp circuit, but you already reported the amp itself switches fine. It only acts wrong using the footswitch. Is that not correct?

Some amps require the panel switches to be set a certain way for the footswitch to work, but these Fender are not like that. When you plug in the pedal, the panel switches are disconnected.

SInce your pedal does work for one function, I have to think the FS jack on the amp is OK.

The pedal schematic is on the next page with the layout drawing of the amp. Since the gain switches, look at the channel circuit. It is a diode, an LED, and a switch. Not a lot to troubleshoot.

Does the light go off and on on that button? Prolly not. So does the switch open and close when you stomp it? Are the two diode acting like diodes? Not much else.

And finally, Fender added a WHOLE slew of notes on the schematic right next to the channel switching circuit - all those test points. They even tell you how the voltages are a little different when using the pedal. Follow those and see where yours goes astray.

the pedal diodes/ switches test ok--both LED work on it.

i tested at all the test points---i do see some problems and ill try to list them here =

TP31 = ALL OK

TP32 = SHOULD BE .527V --I HAVE 9.3V WITH FSW.

TP33 = ALL OK

TP34 = ALL OK

TP35 = W/ FSW...GETTING 9V WITH AND W/O FSW --WAY TOO HIGH, THE 2.6V AND .5V ARE OK

TP36 = ALL OK

hope that makes sense--ill attach the scem

http://www.thetubestore.com/lib/thet...-Schematic.pdf

[nevetslab]

Are you using the Fender unshielded molded F/S cable? I think you have an open ground. With ground, the AC input thru the 1.2k dropping resistor passes thru the 1N4148 diode and the LED in series to ground, which accounts for the 2.53VDC stated in their chart. You're getting 9.3VDC with the F/S. There's an open ground on the F/S.

On TP35.....do you get -9V or +9V? If +9V, it sounds like CR24 and CR26 are installed backwards. But....you 've already stated you ARE getting Drive/More Drive with the F/S, so you must be getting ground from that path in the F/S

Usually with the Fender F/S for the Hot Rod Series, I find the phone jack having a solder fracture, so Ground or Tip isn't getting back to the amp.

[Valvehead]

no--ive tried a different cable (a shielded guitar cable ) for the fsw.....and the Fender cable .

the solder joints look good--but i can re flow them. I dont see any cracks.

TP35= i get -9v

fsw jack might be bad?

[Enzo]

The jacks have no idea what button you push, since one of your functions works, the jacks must be working.

[Valvehead]

ok...reverb works great after replacing U2.

i had the owner drop off a different foot switch today...just to check and be sure... The one I had was labeled = Channel and Reverb. I "assumed" since its a 2 button Fender pedal with a mono plug, that it would function the same. I was wrong.

The pedal I got today switches the amp just fine. They must be different inside ???

[Enzo]

Yes, very different, look at the schematic for th pedal on your layout page.

Not only the label is different, so is the circuit. Note the different part numbers upper right on their faces.

[Valvehead]

Yes , the 1st pedal only had 2 diodes inside