Crate V3112 - Clean Channel Noise Distortion

[TomCarlos]

Hello Friends...

I am trying to save a Crate V3112 combo from the landfill. This amp belongs to a young starving guitar student so I decided to take it on as a "Let me see what I can do project."

When I first turned on the amp, I disregarded the lamo Celestion Seventy 80 speaker. I heard some noise and distortion coming out of the clean channel. So I removed the EL84 power tubes and using the Line Out to drive a clean amp and good speaker. Yup, the distortion and noise are still there. I also notice an occasional "tick" sound coming through the amp. So I need to clean up the input stage (and maybe the power supplies).

I found a VC3112 schematic but it does not look right. The components do not seem to match what I have on-hand. Does anyone know if these (V3112 and VC3112) are similar?

I saw a very old post on this board but the source file for the schematics must have been removed. And yes, I saw the posts regarding the 60 ohm, 10 watt cathode resistor that needs to be swapped out for an aluminum mounted on the case. I will get to that, eventually.

For now, I want to start with a clean schematic if I can find one and measure up the power supplies and look at ripple levels.

Thanks in advance,

Tom

[pontiacpete]

Here's what i have

[TomCarlos]

Hi Pete...

Thanks for posting the schematics. Unfortunately, that is what I already have and they are not the right ones for the V30 V3112. I did a spot check in the Power Supply section and it's not the same.

The search continues.... and if I find the right schematic, I will post it. There was a very old post on this site but it looks like the source files were removed. I will see if I can contact the original post author.

Tom

[g1]

There was a very old post on this site but it looks like the source files were removed. I will see if I can contact the original post author.

Please link us to that post. If we see the exact original filename, one of us may have it.

[TomCarlos]

Here is the old post - http://music-electronics-forum.com/t21578/

I sent a message to the group member asking if he still has the files. I will keep searching. Thanks G-one.

Tom

[Pedro Vecino]

The photo of the PCB is not of the old model 3112 Vintage Club series. It is the modern version called V32.

[TomCarlos]

Here are pics of the cabinet and rear of the chassis.

Tom

[g1]

The photo of the PCB is not of the old model 3112 Vintage Club series. It is the modern version called V32.

Pedro, do you mean V30 ? V32 (palomino) schematic is easily found on internet but I think he needs V30 for V3112, and it is not same as VC3112.

[TomCarlos]

That is correct G-one... Thank you.

[Pedro Vecino]

Yes, V32 Palomino. If that amp has two channels with boost and presence switches is a V32 (same circuit, I mean)

[Pedro Vecino]

The PCB image that you put is identical to some that I keep of the V32 (components and distribution).
Check if this scheme represents your model.
CRATE PALOMINO V32 Service Manual free download, schematics, eeprom, repair info for electronics
Since preamp tubes suffer much heat in that amp is possible that you may have a faulty 12AX7.

[Jazz P Bass]

Crate V3112 Schematic

Here is the schematic set that The Doctor originally posted.
Thanks for the nudge G-One.

[TomCarlos]

Thank you Jazz P Bass and Pedro....

I found a schematic for the V32 Palomino, board 07-677 which appears to be close (if not the same) as the V30. Looks like the one JPB was able to dig up from that old post.

The first thing I checked was the supply voltages on the 12AX7 and EL84 tubes- they seem off. The tubes appear to be ok when I look at them on my Tube Checker but I will swap them out to see changes on Pins 1 and 6 of the 12AX7s.

Pete- if you are still monitoring this thread, please delete your schematic. It might confuse readers. Thanks!

Tom

[TomCarlos]

Ok... some prelim voltage checks.... Just to see if this matches the schematics...

Standby Switch - Schematic - 320vdc
I measure 348vdc

Tube 1A
Pin 1 schematic - 185v
I measure 208v
Pin 3 schematic - 1.6v
I measure 1.76v
Pin 6 schematic - 140v
I measure 155v
Pin 8 schematic - 1.3v
I measure 1.42v

R34 -
Schematic High side - 260v
I measure 285v
Schematic Low side - 252v
I measure 273v

As I swapped out the 12AX7 tubes, that changes the voltage readings on the various tubes. So it must be about tube variation and current draw? But it looks like B+ is too high.

Tom

[g1]

They are showing a 115VAC tap for incoming power from the wall. I'm not sure if their voltages are based on that, but line voltage will affect all your readings. What do you measure for 6.3V heaters?