Hot Rod Deluxe issue

[Valvehead]

Have a hot rod deluxe that is stuck on clean ch.

Ive replaced relay K2.

all points around the LED circuit area have 16v. the 3 legs of the Led have 16v

tested cr18 / cr19 out of circuit

R84 / 84 / 88 / 104 ok

Q3 has 16v at all 3 legs

Using the fsw doesnt help.

The led will switch from red to "more" red (gain boost) , but has no light for clean . So the led is changing but not the channels.


Could it be relay K1 ? Q3 transistor? or the LED itself ?

http://support.fender.com/schematics..._schematic.pdf

[Enzo]

LED should switch from red to yellow. Does it?

Look at the schematic. On the left it has notes on footswitch operation. read them. Note the five test points on the schematic. The operation notes refer to them. COmpare your amp to what is supposed top be happening there.

[Valvehead]

no--Led goes from red to dark.

i went through all the test points tonight. Most are way off.

Ill try to list them all (the BAD readings)-

TP31 , more drive is 0.7v - should be 1.07v


TP32-
ch select off = is 100mv , should be +.5v
ch sel ON is 1.3v , should be 2.5v



TP33 = all ok

TP34-
normal mode is -3v , should be -13v
drive mode is -2v , should be -5,4v
more drive is -1v , should be -4,3v


TP35
with fsw , yellow mode is -1v , should be -3.3v
more drive is -1v , should be -6.5v

without fsw , more drive off is -100mv , should be -.54v
more drive on is -1v , should be -10v


TP36 -- all ok

i hope this makes sense

also--- the fsw led for ch. select does not work at all . I think it should go from red to yellow ??

[g1]

For now, focus on TP32 and TP35. Hopefully if you get them sorted the rest of the circuit will follow.
Have you checked CR23.24,26,28 ?
Do you have the 39VAC at the top of R97 ?

[Valvehead]

yes --those diodes test good on my meter (in circuit)

yes--40V ac at r97

[Valvehead]

I just got some new LED's in the mail , if we need to try and change either the amp or pedal light

[g1]

The LED's can't work right if they don't get the correct voltages. You have incorrect voltages all the way back to the input of the IC. As you have tested the diodes at the IC inputs and they seem ok, I suggest you replace it (U3).

[Valvehead]

ok--thanks. ill see if i have one. if not i will order one tonight

i have some Tlo71 and tl082 here.... are they compatible ?

[Valvehead]

Looking for that chip a 4560, i have many options---most do NOT look like the chip.

The chip looks like a normal op amp chip with the long legs... if i look up 4560 at Mouser, it shows a chip with "flat" legs.

before i spend "another" $8 to ship a weightless part..... i want to make sure im getting what i need.

how about this one ? ----

NJM4560D IC ECG NTE 891M Dual Op Amp | eBay

[g1]

That's ridiculously expensive. Mouser has them, the key is the package you want is the D or P suffix. It is for through hole mounting, the flat leg ones are m suffix for surface mount boards.
RC4560IP Texas Instruments | Mouser

TL082 is the same pin out and should work. For test purposes I might try it but I would stick with the proper part for a permanent fix, TL082 is jfet input type op amp, 4560 is not.

[Valvehead]

I tested U3 just to be sure ---here are the results :
clean mode

pin 1 16v

2. 5mv

3, 3v

4. 0.6v

5. 1.4v

6. 0.5v

7. 16v

8. 16v

DRIVE mode

1. 16v

2. 2.3v

3. 2.3v

4. 0.5v

5. 1.4v

6. 9.4v

7. 13v

8. 16v

[g1]

It appears you are missing your -16V supply (pin 4).
The power resistors R78 and R79 often overheat their solder connections and need to be resoldered.
Once you get the -16V supply going, it will hopefully solve it (IC and LED's may all be fine).

[Valvehead]

i re-flowed those previously. i also checked all the traces under those and all have continuity

[g1]

What voltage do you measure on each side of R79? Have you checked R79 resistance? CR14?
Does U3 (or any other IC) feel hot?

[Valvehead]

i found i dont have the -16v from r79 to the end of cr14. without pulling the pcb out , i ran a jumper to each--i now have -16v at pin 4 U3, yet still no yellow LED and something weird - the amp acts like its switching channels...but on ch.2 drive , the clean ch. 1 volume AND the drive ch volume both work----the clean ch, volume should not work at all in drive mode