Fender Hot Rod deluxe 2009 - drive channel low volume / output compared to clean channel

[spunko]

Hello,
I purchased a really cheap 2009 fender hot rod deluxe with a lot of problems that I have solved except for the one in the tittle. (When purchased it had a leaky C36, bad R78/79 with broken traces, V5 socket broken traces and that 6L6 was over heated, broken ribbon cables).
I changed C36, the resistors, the ribbon cables, repaired the broken traces, tested for voltages and installed new tubes, and now the amp sounds great. I have another '09 hot rod to compare, both sound the excatly the same on the clean channel or direct into the Power Amp IN.
Like the tittle says, the drive channel has lower output than the clean channel. If I set the clean channel volume at 2, the drive channel master must be at 6 to match the output (EQ, Gain, and Presence pots at 50%). I know that is not ok because I have my other amp were both channels match the output.

This is the schematic I used.
What should I check to solve this problem?

https://www.thetubestore.com/lib/the...-Schematic.pdf

Sorry for my bad english.
Thank you in advance.

[mikeydee77]

Are the pre amp valves all the same type? maybe someone tried a lower gain one in the low level one?

Can you exchange them with your reference working amp? That might confirm if the fault is valve or pcb based

[Helmholtz]

I see only one channel.

Drive mode is achieved by overdriving the gain stage around V2-B. In clean mode this stage is bypassed via relais K2.

Please measure V2-B cathode voltage and make sure the relais are working fine.

[spunko]

Thank you for the replies.

All the tubes are new, but also I already swapped between the amps and the same result.

V2-B pin8 reads 1.69 VDC, the schematic says 1.93 VDC.
I can hear a relay, or both, go on and off when I swicth between clean and drive modes, but I can't tell if both are working or just one. I tried pressing my finger on them but I can't feel them altho I can hear them.
I also tried presing one side of a plastic stick on them and the other side direct to my ear and couldn't feel them working. How can I check both relays?

[Enzo]

Follow the signal path with a scope or a signal tracer.

[spunko]

I don't have either of them. I have a tone generator app for my phone and my multimeter, will that work?

[Helmholtz]

Thank you for the replies.

How can I check both relays?

Use your Ohmmeter to verify the switching function. E.g. in drive mode K2-B pin 11 and pin 13 should be shorted, same with K2-A pins 4 and 6. Also K1-A, pins 4 and 8.

Does the drive volume R7 have any effect?
Does the more drive function work?

[glebert]

I don't have either of them. I have a tone generator app for my phone and my multimeter, will that work?

You can set up a test with a sine input from your phone and measure AC magnitudes at the various test points (TP1, 2, etc) as shown on the schematic in ovals. If you read in the notes it will tell you where to set the knobs, and the AC magnitudes are for drive mode (yellow). Assuming your multimeter can do an OK measurement of AC voltages you should be able to see if and where it deviates from expected.

[Enzo]

Do you have some other amp? A signal tracer is nothing more than a probe plugged into an amp. So you can listen to what is at each point in a circuit. Google signal tracer.

[Mick Bailey]

My first check would be the preamp tube DC voltages as per the schematic, then check the AC voltages given on the schematic as per glebert's suggestion. A DMM is perfectly fine for this. Silence the amp by plugging a shorting plug into the power amp in socket.

My check for relay coil operation is a little encapsulated compass glued onto a plastic chopstick when the coil energises the needle deflects considerably. Contact operation and resistance can be checked with a DMM with the amp in standby, though you have to locate appropriate points to measure between on the topside of the board. A easy check with a signal that's switched is just to measure the level either side of the contacts. Any reduction means high resistance.