Hot Rod Deluxe issue

[g1]

Now that the -16V line is there, go back to TP31 thru TP36 and post any discrepancies like you did in post #3.

[Valvehead]

A lot of it changed....here goes...


TP 31 - ok

TP32 all ok

tp33 normal mode ok
drive mode should be -13.5v ---i have -.08v
more drive sh be -13.9v , i have -.08v


tp34
normal -13v , i have -3v
drive -5.4v , i have -8v
more drive -4.3v , i have -8v


tp35 all ok

tp36
normal ok
drive ok
more drive +16v , i have +4v

[Jazz P Bass]

Check Q4.

It sounds like it is bad.

[52 Bill]

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

I don't understand what you did here. Where did you run jumpers to?

Remove the board and fix the power supply problem. It will probably cure all of your problems.

[Valvehead]

nope---changed Q4. same thing. i notice also, the drive pot has no effect.... amp acts like its switching channels,,,yet the clean volume is still working when in drive mode (ch 2 ) . Something is letting the 2 channels "connect"

[g1]

If you do not have the correct voltages from the switching circuit you can not expect the channels or volume controls to behave normally, so you have to sort out the switching first.
You say you have correct voltages at TP31 and TP32 but incorrect voltages at TP33. That seems to narrow it down to defective U3 (assuming it is still getting correct supply voltages). Replace it.

Edit: Even before this you should check what 52Bill said, find the faulty trace in the -16V line and repair it. It's possible there could be burnt traces along that line in more than 1 location. The bottom of C41, C47, and anode of CR17 all need the -16V line for the switching circuit to work correctly.

[Enzo]

You must have the LEDs working or the switching won;t work. The LED is in series with the relays, so if it is open, they won;t switch.

LD1 is a two color LED, red and green. When you are on more drive, only the red is lit. When both red and green are lit, it makes yellow. So for more drive, it basically turns off the green side of the LED. The signal at TP36 turns off Q3 which kills the green LED, and at the same time it turns on the JFETs to add bypass cathode caps.

The circuit controls two relays, the coils in parallel. K1 and K2. K1a selects which pre control is active, volume or drive. K1b either enables the normal channel brite switch or it adds C3 tone shaping to the drive channel. K2b enables the input to the extra drive channel gain stage V2b, while K2a selects the Master post control when in drive.

The relays coils are in parallel, so both should act together, but that doesn't mean they do.

SO if the clean volume keeps working and the drive does nothing, then K1 is not energizing. Or at least its contacts do not transfer. If the mqaster control works while in drive, then K2 is functioning.

If TP33 is not right then TP34 and TP36 cannot be right. And of course if TP34 is not right, then TP35 cannot be right. Without those being right, the switching circuits they control cannot be right. SO we need to get them all working.

The 4560 ICs or you could use 4580s, do come in various shapes, you want the "package" to be DIP8 or just DIP. The flat looking ones are SOIC (small outline integrated circuit) or other surface mount stuff. Package will be one of the filter parameters in the search box.

[Valvehead]

i just ordered some 4560 chips. I will pull the pcb up and repair / check those traces . Thanks guys .

[Valvehead]

checked all traces--all test good.

replaced U3 .

no change at all.

details :
on drive ch, the led is yellow. pushing in the more drive button the led goes to red, and adds more drive.
on clean ch, led is off .
the clean channel volume still works in either mode----it shouldnt in drive ch.

the Drive level control (gain for drive ch.) doesnt do anything , on either channel

also--i have several new led's here , but they are all 2 leg, where the amp has 3 leg. i didnt see that when i ordered them. would they work somehow to try ? or a waste of time since they arent 3 leg


EDIT--- TESTING THE LED---EACH LEG TO GND.

CLEAN CH. 16V / 15V 16V

DRIVE CH. 0.8V / -1.6V / 380MV

[g1]

Sounds like the LED voltages are good as you are getting the right colours. Is the master working right (no effect on clean ch., works on drive and more drive) ? If so, sounds like relay K1 is bad.

[Valvehead]

yes--master only works on drive ch.

ill swap out K1 next

[Valvehead]

K1 replaced = no change

[g1]

K1 and K2 are energized from the same source. K2 sounds like it is working as the master is switching in and out of circuit.
K1 is not working as the clean volume is always in circuit. Somehow K1 does not seem to be getting it's switching voltage, maybe a cracked trace or something. The K1 contacts labelled as 1 and 16 on the schematic should measure the same voltage as the equivalent K2 contacts. Check in clean and drive postitions.

[Valvehead]

did some testing--

with pcb flipped over, testing K1 and K2 , the 2 end pins =

One thing--i cant hear K1 click, but i CAN hear K2 click.

so the 2 end legs on K2 test 15v / 8v in drive, in clean they are 16v / 16v


K1 2 end legs tests 15v / 8v in drive , 16v / 16v in clean

so they look the same ??

[Jazz P Bass]

The voltages on the relays appears normal.

Clean is a normally closed contact, when the relay is Not energized. 16 volts on both ends of the coil.

Check that the contacts of K1 are switching.

Use an ohmeter.

With the Clean channel ON, the wiper of the Clean volume pot should connect to the junction of R41 & R44.

When you engage Drive, this connection should no longer be true.

The wiper of the Drive pot should now connect to R41/44.