Crate V5 mods... anyone?

[Tarin]

Nop, not a licensed tech or anything... i consider myself a good tinkerer and good with a soldering iron, but i could never come up with the slightest idea on how to mod a tube amp.
That's why i'm waiting for some mod-kit to come up (with instructions), that i can manage. BTW, i'm aware of the dangers involved in tube amps, and know the right proceedures for a proper drain.

Schematics i don't have but i'll start working on getting those (never dealt with Crate people).

As of now, i only have some pics of the amp's board (if that gives any help).

[Tarin]

A few more pic's of the Crate V5...


Sovtek tubes...


And here, the 99 dollar cab and crappy speaker...

[tunghaichuan***]

The good news is that it looks like there are no SMDs on the board.

One thing I would check is the bias. If the schematic I have is correct, the cathode bias resistor is only 100 ohms. It seems like it should be bigger.

You will want to check the plate voltage as well.

What are you trying to accomplish by modding your amp?

tung

[Tarin]

The amp lacks of bass tones, and the overdirve is kinda fuzzy. the volume range jumps drastically when dialed between 6-7... cleans are ok.

The tone knob is really wierd... seems to be a -10/0/10 kinda knob where turning it from one end to the other (0 to 10) the tone at 0 seems be down, then go up at the middle (5) then down again when reached 10 (dunno if i explained myself).

I've read a few other reviews were changing the speaker and tubes helped for some, but others claim that not even that helped (i don't have extra speakers nor tubes to try this out).

So basically the mods consist in providing some bass to the amp and making the tone knob work correctly.

[tunghaichuan***]

Just to make sure I'm looking at the same schematic, what value do you have for R17? On my schematic, it is a 100 ohm, 5 watt resistor.

The circuit should have plenty of bass. I would guess that it is a combination of the 10" speaker and a small output transformer. I wouldn't know what to recommend for a replacement, it depends on how much real estate is on the chassis, and how the OT is connected into the circuit.

The volume control is kind of weird. On my schematic, it is a 10k linear pot. On most circuits this control is 470k to 1 meg ohms and would be an audio/log pot.

The tone control looks like a modified Baxandall to me, but I could be wrong. It definitely isn't the treble cut tweed type that I'm familiar with.

The input gain stages is a cascaded opamp. A TL072. Any of the replacements will give you slightly differing results. I would pull the stock opamp and put in a socket so you can swap them out easy. I believe the TL072 is pin-compatible with the Tube Screamer types. You might even want to spring for a spendy Burr-Brown type.

tung

The amp lacks of bass tones, and the overdirve is kinda fuzzy. the volume range jumps drastically when dialed between 6-7... cleans are ok.

The tone knob is really wierd... seems to be a -10/0/10 kinda knob where turning it from one end to the other (0 to 10) the tone at 0 seems be down, then go up at the middle (5) then down again when reached 10 (dunno if i explained myself).

I've read a few other reviews were changing the speaker and tubes helped for some, but others claim that not even that helped (i don't have extra speakers nor tubes to try this out).

So basically the mods consist in providing some bass to the amp and making the tone knob work correctly.

[Tarin]

I got in touch with LOUD Technologies and they kindly sent me the schematics, PCB assembly and parts chart promptly. (i can email them if needed).
Tung, i really appreciate your interest on helping out making this little amp something worth the 99 bucks...

R17 is: WR 330 5% 5W

As for the volume pot, it's a 250K 05A 15mm single unit.
Tone pot 250KB 15mm single unit.
R12 reads 43K .25W

[Tele-Dave]

Can you please post this at a higher resolution, or maybe link as a pdf. When
trying to magnify, all it does is blur.

Thanx,--- Dave

[chris2002rock]

The good news is that it looks like there are no SMDs on the board.

One thing I would check is the bias. If the schematic I have is correct, the cathode bias resistor is only 100 ohms. It seems like it should be bigger.

You will want to check the plate voltage as well.

What are you trying to accomplish by modding your amp?

tung

Where did you find a schematic for this amp?

FWIW, I am getting to the point where I might just replace the whole schematic with a hand-wired replacement. If possible, I wanted to just replace the tone stack (I doubt the solid state components are entirely to blame)...but I also believe the guy who said he replaced the entire circuit (save the tubes and transformers).

I was hoping for a glance at the schematic before I rip the guts out).

Thanks in advance for any help on this.

[SciHi]

Where did you find a schematic for this amp?

Right here: http://www.thefret.net/showpost.php?...2&postcount=28