Crate V5 mods... anyone?

[timmer114]

Thanks Jim, I'll take a look at it tonight and try the jumpers. You have been a wealth of V5 info, and I really appreciate the help =)

[timmer114]

I managed to jumper off the existing traces to the cap in C24. I have sound now, but it's very distorted and loud. The volume control is very sensitive, and it sound as if there's a boss DS-1 cranked in front of the amp now. Hrmmm i'll keep at it, thinking the op amp is the culprit here though.

[jim p]

I have been bothered by the fact one of the last mods I do to an amp is to add reverb and when I do I get the 60 Hz noise back that I have been beating down. So looking into where this is coming from figure it is pickup on the reverb tank output. One of the bad things is that the output signal from the tank should connected to the recovery amplifier with a twisted pair inside of a shielded cable with the shield only tied to the recovery amplifier side. But even then the output of the reverb tank is a 1mV to 5mV signal at maximum and relatively high impedance. In all the tank installations I have isolated the input leaving the ground of the reverb tank through the reverb output shield. So a quick fix for that is to isolate the output RCA connector and run a ground wire to the chassis of the reverb tank. You still have a high impedance output from the tank so I thought of the FET buffer I have made for the guitar pickups but do to the reverb output coil floating you can even do better then that.

The buffer for the reverb tank produces a differential signal with a possible gain of up to 20 depending on the JFET used for the buffer. What this requires is to install three resistors and one to two capacitors in the reverb tank or right at the RCA jack. The remaining components are part of the recovery amplifier circuit. The circuit I built used a 2N6550 in the reverb tank but they are sold by only a few distributors and darn expensive. What you want is a JFET with low noise and high transconductance which is equal to low source impedance for the 2N6550 this is 25 to 40 mmho for 40 to 25 ohms source impedance. Instead of the 2N6550 in order of best to OK is 2SK170, BF862, BF861B and J309 the two BF fets only come in SOT23 package. What is unique about the circuit due to the fact you float the coil across the source to gate connection of the JFET you can get gain at both the source and drain side of the JFET. About the parts at the reverb tank the capacitor across the reverb output coil will cause frequency peaking so if you like twangy 2nF will do that I have no capacitor across the coil I did try from 100pF to 3nf something you can play with. R13 is to reduce the gain variation from JFET to JFET for maximum gain you can make it zero ohms. R1 is to set the current at between 1mA to 2mA if the current is high increase this if low lower it. R4 the 100k resistor could be increased to possibly increase the bandwidth of the reverb output or lowered to load down the tank for a darker sound say 50k to 25k ohms. So the source side of the JFET is connected to the outer connector of the RCA jack this is the low impedance side of the JFET while the drain is connected to the center conductor.

The recovery amplifier is a differential amplifier the gain of 10 from the JFET would be doubled if this amplifier was just unity gain but the amp has a gain of 10 so total gain is 200. So the circuit to the JFET is completed by the parts at the recovery amplifier R3, R2 R12 and R11. C1 and C2 along with R9 and R10 provide a high pass filter to help keep the low frequencies out of the recovery signal. C6 across the input will limit the high frequency input to prevent hearing your local AM radio station (because some of the JFETs are RF FETs). The first op amp U1 is to provide equal gain and high input impedance for the negative input to U2. The op amp can be an NE5532 dual op amp it has good low noise numbers and will work well for this application.

To sum it up I have a little hum but the power supplies in the Peavey Windsor I added this too are not great on the low ripple side I should add regulators.

Remember if you have both the input and output of the reverb tank isolate you will need to connect a ground wire to the reverb chassis. Also if you have a painted tank like a Ruby need to break the paint where the four springs that suspend the reverb assembly are attached to complete the grounding.

I want to correct one thing above the Jfet buffer is acting as a current source at both the source and drain so the impedance at the source and drain is the same 1 k ohms in the circuit as shown.

[timmer114]

I can't fix the thing, not sure what went wrong, but I went from having great headroom, to horrid gain at any volume position. Would burning up the op amp cause this? Something tripped the fuses in the amp, I replaced the fuses, and it powers on, but the sound is just beyond horrid with any tubes I use. It's pure distortion now. I can't seem to find which component failed that would cause me to lose all of my clean headroom. It's gotta be a cap after that op amp, maybe C25-or 26 or 21? I was able to jumper C24 to deal with the pulled up trace in that socket, but it doesn't matter at this point, it's all distortion.

Would a damaged op amp chip make the amp behave this way? I know I bumped an op amp leg with the soldering iron, but would that moment of heat burn up the op amp?

My gut tells me, that one of the components that shape the sound fried. The volume works, but the amp behaves like it's cranked wide open at the lowest volume, and only goes higher from there to a point of just chaos hehe.

Thanks for any tips, but I might need to try and locate a new circuit board. Loud doesn't have any in stock anymore =(

Hate to buy an amp just for the board, but I think I might end up having to do that.

[jim p]

You could consider just getting rid of the op amp look at post #160 and #168. An op amp can take quite a bit of heat so I doubt you hurt it that way. If you have not replaced the op amp that would be a start. Without a scope and signal generator there are only a few things you can check. You should check the DC levels of the output pins of the op amp at pin 1 and pin 7 they should be close to zero volts. Also check the voltages at pin 8 and pin 4 pin 8 should be approx 15 volts and pin 4 should be approx -15 volts. If you get bad voltages at pin 4 or 8 check to see if R19 or R20 have not been damaged or changed value due to high current when shorted. Also check the voltages at R19 and R20.

[SciHi]

... but I went from having great headroom, to horrid gain at any volume position.

So does the volume pot actually work? Crate pots have a high failure rate, my master volume on my v18 broke near the ground, so there was no signal sent to ground, just a variable resistor in line, it was loud, ugly, and noisy. Use your vom to test make sure the pot has continuity to ground and is working correctly.

[timmer114]

Hi,

The voume pot does work, it's just the signal that comes out the amp sounds cranked and loud at the lowest volume. As I turn it up, it gets louder and louder to a point where the amp just then buzzes oddly.

Thinking back, I blew 2 fuses on the board. What caused this, I am not sure. But since then, it sounds horrid after replacing the fuses. I am guessing some component failed, I just don't know which component failed.

Symptoms :
Went from pure lovely clean headroom all the way nearly to full on distortion at lowest volume that only get's louder as I increase the volume. Even at lowest volume, it sounds nearly cranked sound wise.

Lots of crackling going on when I touch the volume pot. Hmm. Perhaps that is the issue now that I think of it. Okay that makes sense to me, volume sounds cranked because well.. it is! but then would the volume pot still turn the amp up even more?

What pot would I need to replace it if I can't locate one from Crate. Let's say I had to buy one from Radio Shack, what am I lookin for, just a 250k linear pot?

Thanks,

[jim p]

Just to ask did you check the voltages on the op amp pins as I posted before the negative supply is on pin 4 and should be approx -15 volts. Then there is the positive supply on pin 8 which should be approx +15 volts. With no signal in to the amp the output pins of the op amp should be approx zero volts so pin 1 and 7 should be very close to zero volts. You should be able to check the pot with an ohmmeter to see if it is OK. It is an audio taper pot. There is an advantage to having a capacitor between the two stages of the op amp if there is some DC offset into the amplifier so when I posted to jumper pin 1 to R14 this was meant more as a test and not necessarily a final configuration.

[timmer114]

The Op amp seems to be fine, I replaced it even and same thing, mega distortion and a really sensitive flaky volume pot.

Starting to wonder if it's the volume pot...if I tap the volume pot lightly, the sound cuts in and out, it always stays massively distorted, but the sound cuts in and out just by touching either the volume or tone pots lightly.. hrmm.

[jim p]

Maybe the pot is bad or there is a bad solder joint going to one of the leads on the pot. I would look at the connections to the PC board and maybe just reflow them with a soldering iron and a little solder to make sure the joints are good. Also if you flexed the leads to much taking the board in and out one of the leads could have broken off from the pot. You could clean the pot it should not need it be being nearly new I use a little spritz of WD40 inside of the pot for that. Some people think WD40 is not a good thing to use so you can decide that for yourself. Also look to see if something near the pots might be shorting to the chassis.

[jfelser]

When I originally received the amp from AMS, I was thinking of sending it right back. But I bought it quite cheaply, so I figured at worse, I just got myself a reasonably priced 10" extension speaker cabinet. After googling mods for this amp, I stumbled onto this site. I immediately found a wealth of info provided within all the posts for the Crate V5. It helped me to make the decision of what direction to go. Thank you all!

Well, I just received back the PCB from my Crate V5 amp that I had Mark (deafelectromark) modify and I'm very impressed with his changes. These mods make this a very good small tube amp, with an excellent clean tone. I installed a Jensen P10Q speaker I bought cheaply on eBay a while back. Before reinstalling the head back into the cabinet, I tried several brands of EL84s and 12AX7s, a 5751 Sovtek and a couple of 12AU7s. I settled on a JJ EL84 and a Groove Tubes 12AU7, to keep the gain structure usable with my pedals. My Teles and Strats sound incredible, almost as good as through my Dr Z Maz 38 Sr, but at a fraction of the cost.

Now if I can only add some reverb . . . We'll be talking Jim :-)

[schenkadere]

I'd like to get mine modded. I was in contact with someone here, but soon after lost the email and I can't recall his username. He had a mod for about 40 bucks...send him the head and shipping. Can't believe I lost that!!! This post just reminded me.

[larryx]

Hello fellow fretters, well I wanted to thank one of our members named deaflectomarc. I just sold my v5 that was modded by him last winter. I got $350 for it! So thanks for not only making me money ,but taking a bad soundidng amp and making it really rock. All I had to do was throw a JJEL84 and a JJ12AX7 in it along with a speaker that I pulled out of my Marshall AVT20 and it sounds like a British Beast. Was the easiest sale I've ever made.


Thanks Mark!

[schenkadere]

Hello fellow fretters, well I wanted to thank one of our members named deaflectomarc. I just sold my v5 that was modded by him last winter. I got $350 for it! So thanks for not only making me money ,but taking a bad soundidng amp and making it really rock. All I had to do was throw a JJEL84 and a JJ12AX7 in it along with a speaker that I pulled out of my Marshall AVT20 and it sounds like a British Beast. Was the easiest sale I've ever made.


Thanks Mark!

Wow! I just put mine up on ebay...I won't get anything near that!

I did a quick demo that will either help or hinder the sale.

http://www.youtube.com/watch?v=8JQCkiDjRvw

[deafelectromark]

[QUOTE=schenkadere]Wow! I just put mine up on ebay...I won't get anything near that!

If you had sent it to me like you said that you were going to do, you wouldn't want to sell it, and when you were ready, you would get the extra money out of it. Loud industries took a good little platform and had 'too many cooks' work on it. Too bad they can't hear what they are doing- and I am the DEAF one!
I am still doing mods for $45.00 including return shipping for just the circuit board. If you want to send the whole chassis, it will cost you more in shipping both ways, but is less technical and more of a 'turn-key' operation. I add $5.00 to disassemble and reassemble the chassis from the circuit board and of course your shipping will be calculated to your home and shipping method. If you send me the weight of the chassis and zip code, I can get you a ballpark figure to help you decide if that is the best way for you to go.
Contact me via manoteal@cox.net
Mark

[SEDUK]

This is my first post to the forum, but I really want to recommend Deafelectormark and his mod. I had been playing my V5 through an old combo amp I have with an original Celestion G12-80 in it and it sounded barely tolerable with none of the feel of a real tube amp. After following this string for awhile, I decided I did not want to deal with doing a mod myself, but I really wanted to make the amp useful. So I contacted Deafelectromark and he walked me through the removal of the PCB (no desoldering needed on mine), which I sent out for mod. Meanwhile, I ordered and installed an Eminence Legend 1058 (highly recommended in The Tonequest Report and only $49.95 with shipping included). Mark turned it around within a week or so and I installed it with new JJ tubes ($12 apiece).

What a difference! It is not even the same amp. The bass is incredible, it is very touch sensitive and seems to sing with harmonic complexity. My Highway One Tele with a Glendale "twang" set of brass and aluminum compensated bridges sounds fantastic and depending on the volume, can do clean country all the way up to early Led Zeppelin. Surprisingly, I am not even missing reverb, as the complexity of the tone fills out the sound.

My reissue 1959 Les Paul Standard (Epiphone version, which is a very nice guitar for few $s; I compared it with many Gibson Les Pauls and it holds up well) with Burstbucker 2 in the neck and Burstbucker 3 in the bridge just screams. I can get a great Cream "woman tone" by cranking the volume on the V5 with the tone control at 5 (max treble) and the guitar tones rolled off, middle position with neck on 10 and bridge on 6. Fabulous overtones!

Last, but not least, my Jimmie Vaughan Strat loves this amp. If you set volume at 7, use the bridge or middle pickup and guitar volume between 5 and 7, it has a fantastic Texas blues sound. I can play it all night and never get tired of the interplay between the amp and guitar. Oh---and I can do this in the basement without complaint from the family, as the amp volume is reasonable. Having a total of $175 in the amp, it is a steal; and I didn't even have to heat a soldering iron. This a great way to go for someone who doesn't have time or inclination to get into the mods themselves. Thanks, Deafelectromark!

Update August 23, 2010: I now use a ElectorHarmonix Holy Grail reverb with the modified Crate and it is great!

[raja7052]

I sent my pcb board to mark to get the mod done, he turned it around in a week. what a difference, love the sound of it now. I highly recommend the mod to everyone and Mark is a real professional.

[Tarin]

Wow! i started this thread... my V5 is long gone and this thread's still busy.
Guess i'll have to start one on the Vox Tonelab ST pedal... one fine piece of equipment.

[deafelectromark]

Wow! i started this thread... my V5 is long gone and this thread's still busy.
Guess i'll have to start one on the Vox Tonelab ST pedal... one fine piece of equipment.

Tarin,
P.s Why didn't you let me have a go at yours when you still had it?? Good iron, good chassis, good cabinet, just needs a better speaker and some sand kicked out of it. There are thousands out there- anyone want to sell me theirs?? I will fix em up.
Mark